WO2007098455A2

WO2007098455A2 - Non-oriented fluid level sensor

Info

Publication number: WO2007098455A2
Application number: PCT/US2007/062451
Authority: WO
Inventors: Eric C. Mueller; Bradley J. Landmann
Original assignee: Stoneridge Inc
Current assignee: Stoneridge Inc
Priority date: 2006-02-17
Filing date: 2007-02-20
Publication date: 2007-08-30
Anticipated expiration: 2008-08-17
Also published as: EP1987328A2; WO2007098455A3

Abstract

A fluid level sensor (10, 40) comprising a body (19) including an axially extending post (16) configured for insertion into a container comprising a fluid and a float (18) having an opening (17). The post (16) may extend at least partially through the opening (17) in the float (18). A magnetic structure (22) may be coupled to the float (18) and a magnetic field sensor (21) may be coupled to the body (19) at a position axially spaced from and adjacent to an end of the float (18) for sensing magnetic flux imparted thereon by the magnetic structure (22) as the float (18) moves radially with respect to the post (16). Optionally, an annular magnetic shield (42) may be disposed at least partially within the post (16) and may define a cavity (44). The magnetic field sensor (21) may be at least partially disposed within the cavity (44). The annular magnetic shield (42) may optionally comprises an aperture (46) disposed proximate an end face of the annular magnetic shield 42 proximate the float (18).

Description

NON-ORIENTED FLUID LEVEL SENSOR

Cross-Reference to Related Applications

This application claims the benefit of U.S. Provisional Application No. 60/774,581, filed February 17, 2006, the teachings of which are fully incorporated herein by reference.

Technical Field

The present disclosure is generally directed to fluid level sensors, and, in particular, to a non-oriented fluid level sensor which may be suitable for side mounting or horizontal applications.

Background

In certain usages of fluid level sensors it may be desirable for the fluid level sensor to be mounted in a sidewall of a container for fluid whose level is to be sensed. This type of mounting may be desirable for any of a number of various reasons, a typical reason being where mounting in a vertical sense cannot be conveniently accomplished.

A horizontal mounting may involve the creation of an aperture in the sidewall of the container for fluid whose level is to be sensed and fitting of the fluid level sensor into the aperture. With suitable provisions, the switch can be mounted so that fluid does not leak through the aperture.

In certain instances it may be desirable that the aperture be threaded and that the fluid level sensor have a corresponding screw thread which allows the switch to be screwed from outside the container into the aperture. A compressible seal may be disposed between the switch and the aperture and compressed to seal the switch to the aperture when the switch is tightened.

Some types of fluid level sensors utilize a float which is buoyant in the fluid whose level is to be sensed. So long as fluid level remains above a certain minimum, the float may be buoyed upwardly. As the fluid level falls below that minimum, the float assumes a more downwardly position which operates the sensor. Because a fluid level float may depend for operation upon the influence of gravity, proper orientation of the float relative to vertical can be important. For a fluid level switch which is to be mounted horizontally, and particularly when it is to be threaded into a threaded aperture in the sidewall of the container, there may be no assurance that the final tightened position will produce the required orientation for proper operation of the float for its fluid level sensing purpose.

Special measures can be taken to assure that the switch has been properly oriented. However these special measures might involve procedures, such as trial-and-error shimming, before a satisfactory combination of tightness, sealing, and orientation is achieved. Special measures are generally unacceptable in mass production application, such as in an automotive assembly line, because the line may not tolerate use of trial and error procedures, or the like, if it is to be operated cost-effectively.

According there is a need for a fluid level sensor configured so that so that proper orientation of the fluid level sensing float may be automatically attained upon installation.

Brief Description Of The Drawings

FIG. 1 is a schematic view of an embodiment of a sensor consistent with the present disclosure; FIG. 2 is a schematic view of an embodiment of a float and magnetic structure assembly consistent with the present disclosure;

FIG. 2A is a schematic view of another embodiment of a float and magnetic structure assembly consistent with the present disclosure;

FIGS. 3A through 3C show an embodiment of a sensor consistent with the present disclosure with the float in a neutral position, in a low fluid level position and in a high fluid level positions, respectively;

FIG.4 is a schematic view of another embodiment of a sensor consistent with the present disclosure;

FIG. 5 is a schematic view of the magnet and annular magnetic shield consistent with the embodiment shown in FTG.4;

FIG. 6 is another schematic view of the magnet and annular magnetic shield consistent with the embodiment shown in FTG. 4;

FIG. 7 is an illustrative embodiment the magnetic field generated by the magnet and annular magnetic shield consistent with the embodiment shown in FIG. 4; and FIG. 8 is a chart of the normalized flux density as a function of float/magnet displacement for various annular magnetic shield aperture diameters consistent with the present disclosure. Description

The present disclosure is generally directed at a fluid level sensor which may be suitable for side mounting or horizontal applications, such as generally disclosed in U.S. Patent No. 4,609,796, issued September 2, 1986, the entire disclosure of which is incorporated herein by reference.

Referring to the drawings, HG. 1 depicts an embodiment of a sensor 10 consistent with the present disclosure. As shown, the sensor 10 may generally be configured as a longitudinal member. The sensor 10 may include a connector, such as integral connector 12, pigtail connector, etc. The sensor connector may include electrical contact for providing an output indicative of a sensed fluid level. The sensor 10 may extend through an opening and into a reservoir, tank, or other container or body capable of containing a fluid, such as an oil pan, transmission housing, etc.(not shown). The sensor 10 may include mounting threads 14, which may engage cooperating threads associated with the opening for maintaining the sensor 10 in position. The sensor 10 may also include a post 16 extending generally axially. A float 18 may be disposed on the post 16 and may be movable substantially transverse to the axis 11 of the post 16. For example, in an embodiment including a post 16 having a generally round shape, the float 18 may be generally cylindrical and movable radially relative to the post 16. The post 16 may extend at least partially through an opening 17 (FIGS. 2), e.g. a central opening, through the float 18, with the opening 17 though the float 18 being larger than the post 16 in at least one direction. The degree of movement of the float 18 relative to the post 16 may vary depending upon the application. For example, the post 16 may have a diameter of approximately 6 mm and the opening 17 may have a diameter of approximately 9 mm. The post 16 may optionally include an end portion 20 which may be sized to retain the float 18 on the post 16. Various alternative retention arrangements may also suitably be employed. The end portion 20 and the sensor body 19 may generally axially locate the float 18 relative to the post 16.

A magnetic field sensor, such as a Hall Effect device 21, may be coupled to the sensor body 19 at a position spaced from the end of the float 18 but adjacent the float 18. In one embodiment the sensor 21 may be disposed in the sensor body 19 adjacent to the post 16. In other embodiments, the Hall Effect device may be disposed at least partially, or completely, within the post 16. As shown in FIG. 2, the float 18 may have a magnetic structure 22, e.g., a permanent magnet, coupled thereto. The float 18 may be buoyant in the fluid, the level of which is being sensed. Accordingly, the float 18 and the magnetic structure therewith may rise and fall on the post 16 with changes in fluid level. The rising and falling of the float 18 and the magnetic structure 22 may move the magnetic structure 22 relative to the Hall effect device 21, thereby changing the magnetic flux through the Hall effect device 21. The changes in magnetic flux through the Hall Effect device 21 may produce one or more outputs of the Hall Effect device 21 corresponding to fluid levels relative to the sensor 10. For example, as shown in FIGS. 3 A through 3C, when the fluid level is above a threshold level, as in FIG. 3C, the float 18 may be in a rising position placing the magnetic structure 22 adjacent the Hall Effect device 21. When the fluid level is below a threshold level, as in FIG. 3B, the float 18 may be in a sinking position placing the magnetic structure 22 away from the Hall Effect device 21. Various other magnetic sensing elements 21 may be used in connection with the present disclosure, in addition to the described Hall effect device. As shown in FIG. 2, in one embodiment, the float 18 may also include a ballast 24.

The ballast 24 may alter the weight distribution along the length of the float 18 such that the float 18 may obtain a desired orientation relative to the post 16 or sensor body 19. For example, the ballast 24 may allow the float 18 to achieve a generally parallel orientation relative to the post 16 or the body 19. The ballast 24 may therefore, in some embodiments, offset the end weighting of the float 18 resulting from the magnet 22. Various alternative embodiments may be provided for achieving a desired float weight distribution and orientation, e.g., a continuous bar magnet extending along the length of the float as illustrated in HG. 2A, a centrally positioned magnet, etc.

According to one aspect, sensor 10 may be installed in a service position by threadably engaging the mounting threads 14 with cooperating threads in a mounting opening. The float 18 may be a self locating, horizontal float, which may use the mass of the magnetic structure 22 to orient the float 18 with the magnetic structure 22 beneath the post 16. For example, the mass of the magnetic structure 22 may cause the float 18 to rotate about the post 16 such that the magnetic structure 22 is disposed generally beneath the post 16 regardless of the rotational position of the sensor body 19. In this manner, the magnetic structure 22 may align into the sensing region of the Hall Effect device 21. This may allow the use of a planar sensitive hall device in an application where rotation of the main body member 19 is required to install the sensor 10. Additionally, this may eliminate the need to mount the sensor in a particular rotational orientation.

According to another aspect, the center of the Hall Effect device 21 may be disposed approximately on the center axis 11 of the sensor 10. In combination with the bottom seeking character of the magnetic structure 22 weighted float 18, the axial positioning of the Hall Effect device 21 may eliminate the need for particular rotational orientation of the sensor 10 during installation.

According to yet another aspect, the Hall Effect device 21 may be a programmable device. Using a programmable Hall Effect device may eliminate the need for magnet calibration to be performed during the assembly process. Accordingly, it may be possible to reduce the complexity and time necessary for the assembly process.

According to still another aspect, the magnetic structure 22 may include one or more permanent magnets. Additionally, the magnetic structure 22 may include a field concentration which may allow the sensing element to switch within a controlled float travel envelope. Accordingly, the operating characteristics of the fluid level sensor may be varied and/or optimized according to a given application.

Turning now to HG. 4, there is illustrated another exemplary embodiment of a fluid level sensor 40. The fluid level sensor 40 may include a sensor body 19 including at least one magnetic field sensor (such as, but not limited to, a Hall Effect device 21). The float 18 may include at least one magnet 22 which may be movable substantially transverse to the axis 11 of the sensor body 19. As the float 18 moves generally perpendicular to the horizontal installation axis of the fluid level sensor 40, the magnetic field generated by the magnet 22 will vary and actuate the active sensing element 21 when a predetermined position of the float 18 is achieved. According to one embodiment, the sensor body 19 may include a threaded region

14 as described above and a post 16 extending generally axially. The float 18 may be disposed on the post 16 and may be movable substantially transverse to the axis 11 of the post 16. For example, in an embodiment including a post 16 having a generally round shape, the float 18 may be generally cylindrical and movable radially relative to the post 16. The post 16 may extend at least partially through an opening, e.g. a central opening, through the float 18, with the opening though the float 18 being larger than the post 16 in at least one direction. The degree of movement of the float 18 relative to the post 16 may vary depending upon the application. For example, the post 16 may have a diameter of approximately 6 mm and the opening in the float 18 may have a diameter of approximately 9 mm. The post 16 may optionally include an end portion 20 which may be sized to retain the float 18 on the post 16. Various alternative retention arrangements may also suitably be employed. The end portion 20 and the sensor body 19 may generally axially locate the float 18 relative to the post 16.

As described above, the float 18 may also include at least one magnet 22 according to any of the embodiments described above. For example, the float 18 may include a substantially centrally positioned magnet 22a. The mass of the magnet 22 and/or ballast 24 may cause the float 18 to rotate about the post 16 such that the magnet 22 is disposed generally beneath the post 16 regardless of the rotational position of the sensor body 19.

The fluid level sensor 40 according to the present embodiment may also feature an annular magnetic shield 42. The annular magnetic shield 42 facilitates greater control over the establishment of the switch point of the fluid level sensor 40 by providing an additional degree of freedom for title fluid level sensor 40. The annular magnetic shield 42 may include any material that is at least partially reduces the magnetic flux density transmitted through the annular shield 42 generated by the magnet 22.

The annular magnetic shield 42 may be disposed within at least a portion of the sensor body 19. According to one embodiment, the annular magnetic shield 42 may be disposed within at least a portion of the sensor body 19 at a position spaced form the end of the float 18 but substantially adjacent to the float 18. For example, the annular magnetic shield 42 may be disposed in the sensor body 19 adjacent to the post 16. In other embodiments, the annular magnetic shield 42 may be disposed at least partially, or completely, within the post 16. Moreover, the annular magnetic shield 42 may be disposed substantially concentric with the axis 11 of the sensor body 19 or offset from the axis 11 of the sensor body 19.

Referring to FIGS. 5 and 6, the annular magnetic shield 42 and the magnet 22 are shown without sensor body 19 and float 18. The annular magnetic shield 42 may define a cavity 44 sized and shaped to at least partially accept the active sensing element 21 and may also include an aperture 46 disposed about an end face proximate the magnet 22. As can be seen in FIG. 7, the overall dimensions of the annular magnetic shield 42 as well as the diameter of the aperture 46 shape the magnetic field 50 generated by the magnet 22 as well as the magnetic flux level sensed by the magnetic field sensor 21. As a result, the overall dimensions of the annular magnetic shield 42 and the diameter of the aperture 46 will depend upon the intended application for the fluid level sensor 40 and is considered within the knowledge of one of ordinary skill in the art. For example, the annular magnetic shield 42 may have an outer diameter of approximately 10 mm and the cavity 44 may have an inner diameter of approximately 8 mm. The aperture 46 may have a diameter of approximately 3-4 mm.

Since the dimensions of the annular magnetic shield 42 and the diameter of the aperture 46 alter the magnetic flux level sensed by the magnetic field sensor 21, the fluid level sensor 40 according to this embodiment allows for greater design flexibility (e.g., establishing and controlling the switch point) as compared to designs without the annular magnetic shield 42. Referring to FIG. 8, the normalized flux density as a function of float 18/magnet 22 displacement is shown for various diameters of the aperture 46. As can be seen, the annular magnetic shield 42 modifies the magnetic flux level sensed by the magnetic field sensor 21.

Accordingly, the present disclosure features a fluid level sensor comprising a body including an axially extending post configured for insertion into a container comprising a fluid and a float having an opening. The post may extend at least partially through the opening in the float. A magnetic structure may be coupled to the float and a magnetic field sensor may be coupled to the body at a position axially spaced from and adjacent to an end of the float for sensing magnetic flux imparted thereon by the magnetic structure as the float moves radially with respect to the post.

According to another embodiment, the present disclosure features a fluid level sensor comprising a body including an axially extending post configured for insertion into a container comprising a fluid and a float having a central opening wherein the post extends through the central opening. A permanent magnet may be coupled to the float at a position whereby the force of gravity acting on the permanent magnetic results in positioning of the permanent magnetic beneath the post upon horizontal orientation of the body in any rotational position. A Hall Effect sensor may be coupled to the body with a center line of the Hall Effect sensor disposed approximately on a centerline of the body. The Hall Effect sensor may be axially spaced from and adjacent to an end of the float for sensing magnetic flux imparted thereon by the permanent magnet as the float moves radially with respect to the post.

According to a further embodiment, the present disclosure features a fluid level sensor comprising a body including an axially extending post configured for insertion into a container comprising a fluid and a float having a central opening wherein the post extends through the central opening. A magnetic structure may be coupled to the float at a position whereby the force of gravity acting on the magnetic structure results in positioning of the magnetic structure beneath the post upon horizontal orientation of the body in any rotational position. An annular magnetic shield may disposed at least partially within the post and may define a cavity and a magnetic field sensor may be at least partially disposed within the cavity. The annular magnetic shield may optionally comprises an aperture disposed proximate an end face of the annular magnetic shield proximate the float.

The features and aspects described with reference to particular embodiments disclosed herein may be susceptible to combination and/or application in various other embodiments described herein. Such combinations and/or applications of such described features and aspects to such other embodiments are contemplated herein. Additionally, the embodiments disclosed herein are susceptible to numerous variations and modifications without materially departing from the spirit of the disclosed subject matter. Accordingly, the invention herein should not be considered to be limited to the particular embodiments disclosed herein.

Claims

What is claimed is:

1. A fluid level sensor comprising: a body comprising an axially extending post configured for insertion into a container comprising a fluid; a float having an opening, said post extending at least partially through said opening; a magnetic structure coupled to said float; and a magnetic field sensor coupled to said body at a position axially spaced from and adjacent to an end of said float for sensing magnetic flux imparted thereon by said magnetic structure as said float moves radially with respect to said post.

2. A sensor according to claim 1, wherein said float is generally cylindrical.

3. A sensor according to claim 1, wherein said magnetic structure comprises a permanent magnet.

4. A sensor according to claim 1, wherein the force of gravity acting on said magnetic structure results in positioning of said magnetic structure beneath said post upon horizontal orientation of said body in any rotational position.

5. A sensor according to claim 1, wherein the magnetic structure is disposed adjacent a first end of said float, said sensor further comprising a ballast disposed adjacent a second end of said float.

6. A sensor according to claim 1, wherein a center of said magnetic field sensor is positioned approximately on a centerline of said body.

7. A sensor according to claim 1, wherein a center of said magnetic field sensor comprises a Hall Effect sensor.

8. A sensor according to claim 1, wherein said body further comprises an annular magnetic shield at least partially disposed within said post and defining a cavity, wherein said magnetic field sensor is at least partially disposed within said cavity.

9. A sensor according to claim 8, wherein said annular magnetic shield comprises an aperture disposed proximate an end face of said annular magnetic shield proximate said float.

10. A sensor according to claim 9, wherein a center of said magnetic field sensor is positioned approximately on a centerline of said body.

11. A sensor according to claim 10, wherein a center of said magnetic field sensor comprises a Hall Effect sensor.

12. A sensor according to claim 8 wherein said annular magnetic shield at least partially reduces the magnetic flux density transmitted through said annular magnetic shield.

13. A fluid level sensor comprising: a body comprising an axially extending post configured for insertion into a container comprising a fluid; a float having a central opening, said post extending through said central opening; a permanent magnet coupled to said float at a position whereby the force of gravity acting on said permanent magnetic results in positioning of said permanent magnetic beneath said post upon horizontal orientation of said body in any rotational position; and a Hall Effect sensor coupled to said body with a center line of said Hall Effect sensor disposed approximately on a centerline of said body, said Hall Effect sensor being axially spaced from and adjacent to an end of said float for sensing magnetic flux imparted thereon by said permanent magnet as said float moves radially with respect to said post.

14. A sensor according to claim 13, wherein the magnetic structure is disposed adjacent a first end of said float, said sensor further comprising a ballast disposed adjacent a second end of said float.

15. A sensor according to claim 13, wherein said body further comprises an annular magnetic shield at least partially disposed within said post and defining a cavity, wherein said magnetic field sensor is at least partially disposed within said cavity.

16. A sensor according to claim 15, wherein said annular magnetic shield comprises an aperture disposed proximate an end face of said annular magnetic shield proximate said float.

17. A fluid level sensor comprising: a body comprising an axially extending post configured for insertion into a container comprising a fluid; a float having a central opening, said post extending through said central opening; a magnetic structure coupled to said float at a position whereby the force of gravity acting on said magnetic structure results in positioning of said magnetic structure beneath said post upon horizontal orientation of said body in any rotational position; an annular magnetic shield at least partially disposed within said post and defining a cavity; and a magnetic field sensor at least partially disposed within said cavity.

18. The sensor according to claim 17 wherein said magnetic field sensor is axially spaced from and adjacent to an end of said float for sensing magnetic flux imparted thereon by said magnetic structure as said float moves radially with respect to said post.

19. The sensor according to claim 18 wherein said magnetic field sensor comprises a Hall Effect sensor coupled to said body with a center line of said Hall Effect sensor disposed approximately on a centerline of said body, said Hall Effect sensor

20. A sensor according to claim 19, wherein said annular magnetic shield comprises an aperture disposed proximate an end face of said annular magnetic shield proximate said float.