BACKGROUND OF THE INVENTION

Field of Invention

The invention is related in general to systems and methods involving the use of magnetic field sensors and magneto-elastic devices for measuring a load and outputting a signal indicative of a load force dynamically applied to an object. The invention is also related to use of the force-sensing apparatus in connection with a vehicle-trailer hitch or tow coupling. The invention is also related to methods for determining a direction and magnitude of the force vector on the hitch or a particular hitch component.

Description of Related Art

Tow coupling devices are popular accessories for owners of passenger automobiles (cars and trucks) who tow trailers. These coupling devices may be purchased and installed in a new automobile, or purchased in the aftermarket and installed by owners after acquiring an automobile. The automotive and tow hitch industries classify trailer hitches according to various criteria. In one aspect, hitches are classified in one of Class 1-5. Each class of hitch includes associated real-world standards such as minimum force load requirements, including at least longitudinal tension, longitudinal compression, transverse thrust, vertical tension, and vertical compression.

In many trailer hitch use cases, strain gauges are used for sensing a force load on a hitch. Strain gauges, however, often require a structural weakening of the load-conducting elements. There is a need for load measurements without compromising the structural stability of the measuring device. This is especially true for tow couplings.

Furthermore, there is a strong demand for smart tow couplings, e.g., for systems providing at least the following: a load weight gauge (measuring the tongue load of a tow coupling), a tow load weight shift alert, an unsafe trailer load distribution alert, a vehicle limit notification, an automated trailer brake control (closed loop), a low/flat trailer tire notification, a check trailer brake notification, a closed loop braking control, a vehicle shift control, an engine control, and a stability control. These and other functions require the measurement of tow loads and/or tongue loads at the tow coupling.

Prior art load measurement devices for tow couplings have significant shortcomings, e.g. the complexity of the measurement and control devices, and the costs of the sensor assembly. Thus, there is a need for a tow coupling apparatus that may be purchased and installed in an automobile that provides the above functions without weakening over time.

In certain towing situations, when towing a trailer with a standard, rear-mounted hitch, a trailer's tongue weight is transferred to the rear axle of the tow vehicle. This can weigh down the vehicle's back end and cause the front end to point upward, especially on vehicles that have a suspension designed for driving comfort. When this happens, the vehicle's rear axle will bear the weight of not only the trailer, but much of the tow vehicle's weight as well. What is more, the lessened weight on the vehicle's front axle can diminish the ability to steer, maintain traction, and use available power for stopping. Moreover, the vehicle may experience increased trailer sway, and the driver's view of the road ahead may be limited due to the upward angle of the vehicle.

One solution to these problems is the use of a weight distribution tow hitch system, which uses spring bars that apply leverage to both sides of the tow hitch system, thereby transferring the load at the rear of the vehicle to all axles of the tow vehicle and trailer. This even distribution of weight results in a smoother, more level ride, as well as the improved ability to tow at the maximum capacity of the tow hitch. What is needed, however, is a way to better monitor the distributed forces acting on a towing vehicle, trailer, and weight distribution tow hitch system and its components using load sensing pins as described below.

BRIEF SUMMARY OF THE INVENTION

In one aspect of the invention, an improved magneto-elastic based sensor assembly is provided to effectively measure stress and strain in systems having a portion, which is subject to a mechanic load. The invention also provides a method of determining a direction of a load vector acting on a magneto-elastic based sensor assembly.

In one aspect of the invention, a tow hitch assembly includes a hitch tube, a first part, a second part, a receiver tube, and first and second load sensor pins8,9connecting the first and second parts. The hitch tube is typically a longitudinally extending, round, oval, square, or other shape member for attaching to a vehicle, typically near the rear bumper of a passenger vehicle. Bolts or other fastening means may be used to attach the hitch tube to the vehicle.

The first part of the tow hitch assembly may be a bracket with two side flange portions having through-holes: first and second through-holes on one flange, and third and fourth through-holes on the other, such that the first and third through-holes are axially aligned with each other and the second and fourth through-holes are also axially aligned with each other.

The second part may include a receiver tube connected to a longitudinally extending middle adapter member that fits between the two flanges of the bracket when the hitch components are in an assembled state. In one aspect, the adapter may be configured to include a front portion that would be positioned in front of the hitch tube, and a back portion that would be positioned in back of the hitch tube, the front and the back portions each having a through-hole axially aligned with the through-holes on the bracket when the first and second parts are in an assembled state. In another aspect, the entirety of the adapter could be in front of the hitch tube, or behind the hitch tube, or in some other configuration.

In another aspect, the first and second load sensor pins8,9are configured to sense forces applied to the receiver tube and other components of the hitch assembly. One of the two load sensor pins8,9extends through the first and third through-holes of the bracket and one of the through-holes of the adapter, and the other pin extends through the second and fourth through-holes of the bracket and a different through-hole of the adapter to secure the first and second parts together.

In another aspect, there is a gap of about 0.5 mm between the top of the middle adapter member and the base portion of the bracket, and the thickness of the base portion of the bracket in the configuration shown is 8 mm. Alternatively, the thickness of the base portion of the bracket is about 10 mm, and the gap is about 5 mm between the top of the middle adapter member and the base portion of the bracket. Press-fit bushings could be used, having a pre-determined radial thickness inserted into the axially-aligned through-holes of the bracket.

In another aspect, during use of the assembled tow hitch, a force is applied to the proximate end of a drawbar and transmitted to the front pin. The output signals from magnetic field sensors associated with the front pin may be received in a suitable software algorithm, for example one that is embedded on a circuit board having a suitable processor located inside the front pin. The receive output signals from the sensors, which may be indicative of the magnetic field/flux exhibited by the front pin magneto-elastic active regions, may be used to determine the forces.

In U.S. Pat. No. 9,347,845, owned by Methode Electronics, which is incorporated herein by reference in its entirety, a magneto-elastic sensor having a longitudinally extending shaft like member with at least one magneto-elastically active region and a magnetic field sensor device is described. The longitudinally extending shaft like member is subject to a load introducing mechanic stress in the member. The at least one magneto-elastically active region is directly or indirectly attached to the shaft like member. However, the at least one magneto-elastically active region may also form a part of the member. The magneto-elastically active region is arranged in such a manner that the mechanic stress is transmitted to the active region. The region includes at least one magnetically polarized region such that the magnetic polarization becomes increasingly helically shaped as the applied stress increases. The magnetic field sensor means or device is arranged proximate the at least one magneto-elastically active region. The magnetic field sensor means/device is further configured for outputting a signal corresponding to a stress-induced magnetic flux, which emanates from the magnetically polarized region. The sensor may be a magnetic sensor device with at least one direction sensitive magnetic field sensor. This direction sensitive magnetic field sensor is configured for determination of a shear stress and/or of a tensile or compressive stress. In particular, the direction sensitive magnetic field sensor is arranged to have a predetermined and fixed spatial coordination with the member.

One object of the invention described herein, which is also described in EP17162429.9, owned by Methode Electronics and incorporated herein by reference in its entirety, is a sensor assembly for force sensing, the force sensor being associated with a vehicle hitch assembly. The improved magneto-elastic based sensor assembly is useful for effectively measuring stress and strain in systems having a portion, which is subject to a mechanic load. The invention provides a method of determining a direction of a load vector acting on a magneto-elastic based sensor assembly.

According to an aspect of the invention, a sensor assembly for force sensing can include a first portion having a first and a second through-hole. The sensor assembly can further include a second portion having a third and a fourth through-hole. The third and the fourth through-hole can be positioned in correspondence to the first and the second through-holes.

The sensor assembly can further include a first pin and a second pin. The first pin can be arranged such that it extends through the first and the third through-hole and the second pin can be arranged such that it extends through the second and the fourth through-hole, so as to couple the first portion to the second portion. At least one out of the first and the second pin can include at least one magneto-elastically active region that may directly or indirectly be attached to or form a part of the pin in such a manner that mechanic stress on the pin is transmitted to the magneto-elastically active region. The magneto-elastically active region can include at least one magnetically polarized region such that a polarization of the magnetically polarized region may become increasingly helically shaped as the applied stress increases.

The sensor assembly can further include a magnetic field sensor means or device which may be arranged proximate the at least one magneto-elastically active region. The magnetic field sensor means/device may be configured to output a signal corresponding to a stress-induced magnetic flux which may emanate from the magnetically polarized region. The magnetic field sensor means/device may comprise at least one direction sensitive magnetic field sensor which may be configured to determine a shear force in at least one direction. The at least one direction sensitive magnetic field sensor may in particular be arranged to have a predetermined and fixed spatial coordination with the pin, wherein this pin may at least be partially hollow. The at least one direction sensitive magnetic field sensor may be arranged inside an interior of this pin.

By means of the sensor assembly, stress which is applied to a pin caused by a mechanic load can effectively be measured. The sensor assembly according to aspects of the invention thus described overcomes the drawback of the prior art solutions. In particular, the sensor assembly does not tend to drift with respect to the measurement values and is less error-prone.

According to another aspect of the invention, at least one out of the first and the second pin of the sensor assembly can comprise at least one X-direction sensitive magnetic field sensor, which can be configured to detect a force component Fx1in a longitudinal direction X, and/or at least one Z-direction sensitive magnetic field sensor, which can be configured to detect a force component Fz1in a vertical direction Z. The longitudinal direction X can be defined by a direction of longitudinal extension of the second portion. The vertical direction Z can be substantially perpendicular to the longitudinal direction X and substantially perpendicular to the transversal direction Y of longitudinal extension of the at least one pin.

According to another aspect of the invention, the first through-hole and the third through-hole of the sensor assembly can be configured such that they encompass the first pin in a positive-fitting manner. A positive-fitting manner of the fitting allows the pin to be substantially rigidly fixed to the first portion and the second portion by the first and the third through-hole. This means that the pin has almost no play inside the first and third through-hole and that the accuracy of the force measurement is advantageously increased compared to a configuration in which the first pin has play inside the first and the third through-hole.

According to another aspect of the invention, the first pin may be cryogenically treated, such as by subjecting the entire first pin to liquefied nitrogen, thereby causing a reduction in the cross-section dimension of the pin. After super-cooling the first pin, it may be positioned in the first and third through-holes and allowed to return to ambient temperature. As the material in the pin warms up to ambient temperature, the cross-section dimension will increase until the first pin is substantially rigidly fixed in the first and third through-holes.

According to another aspect, the second pin of the sensor assembly may be encompassed by the second through-hole in a positive-fitting manner and the fourth through-hole may be configured such that the second pin may have one additional degree of freedom of movement within the fourth through-hole. The additional degree of freedom of movement allows the second pin to be insensitive with respect to shear forces acting in the direction of the additional degree of freedom of movement. This means that the determination of the shear force along this direction can advantageously be simplified since the shear effect occurs exclusively on the first pin.

According to another aspect, the second pin, like the first pin, may be cryogenically treated, such as by subjecting the entire first pin to liquefied nitrogen, thereby causing a reduction in the cross-section dimension of the pin. After super-cooling the second pin, it may be positioned in the second and fourth through-holes and allowed to return to ambient temperature. As the material in the second pin warms up to ambient temperature, the cross-section dimension will increase until the second pin is substantially rigidly fixed in the second and fourth through-holes with the additional degree of freedom of movement noted above.

According to another aspect, the additional degree of freedom of movement may extend in the longitudinal direction X. Since the additional degree of freedom of movement corresponds to the longitudinal direction X, the determination of the shear force along this direction can advantageously be simplified.

According to another aspect, the first and/or the second pin of the sensor assembly can include a first magneto-elastically active region and a second magneto-elastically active region. The first and the second magneto-elastically active regions may be directly or indirectly attached to or form parts of the pin in such a manner that mechanic stress may be transmitted to the magneto-elastically active regions. Each magneto-elastically active region can include a magnetically polarized region. Particularly, the magnetic polarization of the first magneto-elastically active region and the magnetic polarization of the second magneto-elastically active region may be substantially opposite to each other. The magnetic field sensor means/device can include at least one first direction sensitive magnetic field sensor which may be arranged approximate the first magneto-elastically active region. The magnetic field sensor means/device may be configured to output a first signal corresponding to a stress-induced magnetic flux which may emanate from the first magneto-elastically active region. The magnetic field sensor means/device may include at least one second direction sensitive magnetic field sensor which may be arranged approximate the second magneto-elastically active region. The magnetic field sensor means/device may be configured to output a second signal corresponding to a stress-induced magnetic flux which may emanate from the second magneto-elastically active region. This way, the shear force can advantageously be determined in two opposing directions thereby improving the quality of the determination of the shear force. This “vice versa” configuration of the magnetic field sensors enables the shear directions to be determined by the magneto-elastically active regions. For example, the directions may be distinguishable, if the measurement data, which is acquired from the first direction sensitive magnetic field sensor and the second direction sensitive magnetic field sensor, is differentially processed.

The differential evaluation of the signals advantageously doubles the signal, which is correlated with the applied stress. Because the polarization of the first and second magneto-elastically active region is opposite to each other, theoretically possible external fields may be compensated. The sensor assembly according to this embodiment may be more sensitive and less susceptible to errors.

According to another aspect of the invention, the first and/or the second pin of the sensor assembly can include at least one first X-direction sensitive magnetic field sensor and/or at least one second X-direction sensitive magnetic field sensor and/or at least one Z-direction sensitive magnetic field sensor and/or at least one second Z-direction sensitive magnetic field sensor. The at least one X-direction sensitive magnetic field sensor may be configured to detect a force component Fx1in the first magneto-elastically active region in the longitudinal direction X of the second portion. The at least one second X-direction sensitive magnetic field sensor may be configured to detect a force component Fx2in the second magneto-elastically active region in the longitudinal direction X of the second portion. The at least one Z-direction sensitive magnetic field sensor may be configured to detect a force component Fz1in the first magneto-elastically active region in the vertical direction Z. The at least one second Z-direction sensitive magnetic field sensor may be configured to detect a force component Fz2in the second magneto-elastically active region in the vertical direction Z. Advantageously, the shear force can be determined in different directions being perpendicularly aligned with respect to each other.

According to another aspect, the first pin of the sensor assembly can include the at least one Z-direction sensitive magnetic field sensor and the at least one second Z-direction sensitive magnetic field sensor. Advantageously, the first pin can be configured to exclusively react on a shear force acting along the Z-direction.

According to still another aspect of the above invention, the first pin of the sensor assembly can include the at least one first X-direction sensitive magnetic field sensor, the at least one second X-direction sensitive magnetic field sensor, the at least one first Z-direction sensitive magnetic field sensor and the at least one second Z-direction sensitive magnetic field sensor and the second pin of the sensor assembly can comprise the at least one Z-direction sensitive magnetic field sensor and the at least one second Z-direction magnetic field sensor. Advantageously, the first pin can be configured to exclusively react on the shear effect along the X-direction which simplifies the shear force evaluation, wherein the shear force along the vertical Z-direction is acting on both load sensor pins8,9.

According to another aspect, the first pin of the sensor assembly can include the at least one first X-direction sensitive magnetic field sensor, the at least one second X-direction sensitive magnetic field sensor, the at least one first Z-direction sensitive magnetic field sensor and the at least one second Z-direction sensitive magnetic field sensor, and the second pin of the sensor assembly can include the at least one first X-direction sensitive magnetic field sensor, the at least one second X-direction sensitive magnetic field sensor, the at least one first Z-direction sensitive magnetic field sensor and the at least one second Z-direction sensitive magnetic field sensor. This way, both load sensor pins8,9are sensitive to all shear forces along the vertical Z-direction as well as along the longitudinal X-direction. The first and the second pin advantageously can detect the different components of the shear force at different positions of the system.

The magnetic field sensor means/device may be configured for determination of a first component and a second component of the load, which is applied to the pin. In particular, the at least one first X-direction sensitive magnetic field sensor and the at least one second X-direction sensitive magnetic field sensor can form a first group of sensors and the at least one first Z-direction sensitive magnetic field sensor and the at least one second Z-direction sensitive magnetic field sensor can form a second group of sensors. The first group of sensors is suitable for determination of a load component, which is directed along the X-axis. The second group of sensors senses a component of the load, which is substantially perpendicular to the first component along the Z-direction. Consequently, the direction and the value of the stress or force, which is applied to the load sensor pins8,9, may be determined from said components in this coordinate system.

According to another aspect, the second portion of the sensor assembly can comprise a center wall which may extend in the longitudinal direction X and the vertical direction Z. The third and the fourth through-hole may also extend through the center wall. Advantageously, the center wall allows the first portion to be effectively affected by the shear force at an additional point of action.

According to another aspect, the first and/or the second pin of the sensor assembly may be fixedly attached in a predetermined manner to the first portion. The first and/or the second pin can advantageously be fixedly attached in all six degrees of freedom. This way, the determination of the shear forces is effectively possible since the load sensor pins8,9do not have play inside the through-holes of the first portion.

According to another aspect, the first portion of the sensor assembly can have a yoke-like shape. The yoke legs of the first portion can comprise the first and the second through-holes. The second portion of the sensor assembly can have a tubular shape. The side walls of the second portion can comprise the third and fourth through-holes. The direction sensitive magnetic field sensor(s) may be configured to detect force components of shear forces introduced into the load sensor pins8,9by the first portion and the second portion. Advantageously, a yoke-like shape of the first portion and a tubular shape of the second portion allow the sensor assembly to be implemented in an elongated joint connection of two objects, whereas the load sensor pins8,9are arranged in the through-holes and connect both objects.

According to another aspect, the first portion of the sensor assembly can have a yoke-like shape. The yoke legs of the first portion can comprise the first and the second through-holes. The center wall can comprise the third and fourth through-holes. The direction sensitive magnetic field sensor(s) may be configured to detect force components of shear forces introduced into the load sensor pins8,9by the first portion and the second portion. In particular, the side walls of the second portion can comprise through-holes which may be larger than the third and the fourth through-holes such that the shear forces may be introduced into the load sensor load sensor pins8,9by abutment surfaces of the first and the second through-holes in the yoke legs and abutment surfaces of the third and the fourth through-holes in the center wall. The abutment surfaces allow the transmission of power between the first portion and the second portion to be configured in an advantageous manner.

According to another aspect, a tow coupling can comprise a sensor assembly wherein the first portion is a hitch assembly that may be configured to be attached to a car chassis and wherein the second portion may be a receiving tube which may be configured to receive a drawbar, alternatively a hitch bar or a ball mount of the tow coupling. Advantageously, the sensor assembly is configured to detect the forces of a tow coupling of an automobile, which may be part of a land based on-road or off-road vehicle.

According to another aspect, the first portion of the sensor assembly may be a supporting yoke having two yoke legs. The yoke legs may comprise recesses which are aligned in correspondence to each other and which represent the first and the second through-holes of the first portion.

According to another aspect, the first portion of the sensor assembly may be a supporting yoke having four yoke legs. The yoke legs may comprise recesses which are aligned in correspondence to each other and which represent the first and the second through-holes of the first portion.

According to another aspect, the sensor assembly dispenses with a mechanical linkage or connection between the magnetic field sensor means and the second portion. This eliminates sources of error, which result from mechanic failure of this connection. The sensor assembly reliably operates even under extreme operating conditions. The drift of the measurement values during long term measurement is reduced. The sensor assembly according to aspects of the invention is versatile in that it may be applied to or integrated in nearly every tubular shaped portion, which may be for example a part of a hydraulic unit of a land-, marine-, rail- or air transport vehicle.

According to another aspect, the forces which are detectable by the sensor assembly are not exclusively restricted to shear forces which originate from shear stress but may also originate due to tensile or compressive stress acting on the magneto-elastically active region(s) of the first pin and/or the second pin of the sensor assembly. In other words, shear stress and normal stress may both induce a variation of the polarization of the magnetically polarized region emanating from the magneto-elastically active region(s). This polarization may be detectable by the magnetic field sensor means which may output a signal corresponding to a stress-induced magnetic flux towards the polarization direction sensitive magnetic field sensor that may be configured to determine the acting force. Consequently, the magneto-elastically active region may be sensitive to all stress types. The embodiment may particularly be suitable, if the pin is exposed to only one single type of stress.

According to another aspect, the direction sensitive magnetic field sensors L may be one of a Hall-effect, magneto-resistance, magneto-transistor, magneto-diode, MAGFET field sensors or fluxgate magnetometer. These aspects advantageously apply to all embodiments of the invention.

According to another aspect, any hydraulic piston, crane application, car and other various applications incorporating bolts and load sensor pins8,9, where shear forces may be applied, may be equipped with the sensor assembly according to aspects of the invention. Traditionally, shear force sensors using strain-gauges are designed in that they get intentionally weaken to provide enough deformation so as to allow a measurement of the applied loads. The magneto-elastically active region of the sensor assembly, however, provides the possibility to design the bolt without weaken locations and significantly higher overload capability. The load pin having the integrated magneto-elastically active region provides the possibility to detect shear forces in load sensor pins8,9, screws, bolts etc.

According to another aspect, a method of determining a direction of a load vector is provided. Within said method, a sensor assembly according to aspects of the invention is provided. In other words, a sensor assembly is provided which can comprise a first portion having a first and a second through-hole. The sensor assembly can further comprise a second portion having a third and a fourth through-hole. The third and the fourth through-hole can be positioned in correspondence to the first and the second through-hole. The sensor assembly can further comprise a first pin and a second pin. The first pin can be arranged such that it extends through the first and the third through-hole and the second pin can be arranged such that it extends through the second and the fourth through-hole, so as to couple the first portion to the second portion. At least one out of the first and the second pin can comprise at least one magneto-elastically active region that may directly or indirectly be attached to or form a part of the pin in such a manner that mechanic stress on the pin is transmitted to the magneto-elastically active region. The magneto-elastically active region can comprise at least one magnetically polarized region such that a polarization of the magnetically polarized region may become increasingly helically shaped as the applied stress increases. The sensor assembly can further comprise a magnetic field sensor means which may be arranged approximate the at least one magneto-elastically active region. The magnetic field sensor means may be configured to output a signal corresponding to a stress-induced magnetic flux which may emanate from the magnetically polarized region. The magnetic field sensor means may comprise at least one direction sensitive magnetic field sensor which may be configured to determine a shear force in at least one direction. The at least one direction sensitive magnetic field sensor may in particular be arranged to have a predetermined and fixed spatial coordination with the pin, wherein this pin may at least be partially hollow. The at least one direction sensitive magnetic field sensor may be arranged inside an interior of this pin.

Furthermore, within the method according to another aspect, the first pin and the second pin may be exposed to a load. Measurement data of the at least one direction sensitive magnetic field sensor may be processed so as to determine a shear stress and/or a tensile or compressive stress that is applied by the second portion and the first portion to the first and/or second load sensor pins8,9.

In particular, a direction of a force F may be determined from the measurement data on the one hand and the predetermined and known spatial coordination between the direction sensitive magnetic field sensor(s), the first pin, the second pin and the point of load. The force F is applied to the sensor assembly via the second portion.

Same or similar advantages which have been already mentioned with respect to the sensor assembly having a magneto-elastically active region according to aspects of the invention apply in a same or similar way to the method of determining a direction of the load vector and will be not repeated.

Devices and methods related to magnetizing a cylindrical shaft, pin, or similar shaped object, and using magnetic field sensors positioned proximate to the same for detecting a magnetic flux emanating from the object and other magnetic fields, are disclosed in one or more of the following patents owned by Methode Electronics, the entire contents and disclosures of which are incorporated herein by reference: U.S. Pat. No. 6,490,934 (“Circularly magnetized non-contact torque sensor and method for measuring torque sing the same”); U.S. Pat. No. 6,553,847 (“Collarless circularly magnetized torque transducer and method for measuring torque using the same”); U.S. Pat. No. 6,904,814 (“Magnetic torque sensor system”); U.S. Pat. No. 7,140,258 (“Magnetic-based force/torque sensor”); U.S. Pat. No. 8,087,304 (“Magneto-elastic torque sensor with ambient field rejection”); U.S. Pat. No. 8,578,794; (“Magneto-elastic torque sensor with ambient field rejection”); and U.S. Pat. No. 8,893,562 (“System and method for detecting magnetic noise by applying a switching function”).

In many of the above references, a magneto-elastic torque sensor is described, in which an output signal indicative of a force applied to a member is provided. The sensor includes a first magneto-elastically active region in the member, the region being ferromagnetic, magnetostrictive magnetically polarized in a single circumferential direction and possessing sufficient magnetic anisotropy to return the magnetization in the region to the single circumferential direction when the applied torque is reduced to zero, whereby the ferromagnetic, magnetostrictive region produces a magnetic field varying with the torque. Magnetic field sensors are mounted proximate to the ferromagnetic, magnetostrictive region to sense the magnetic field at the sensors and provide the output signal in response thereto.

Apparatus and methods related to strain-induced magnetic anisotropy to measure the tension or compression present in a plate-like object are described in US20150204737 (“Magneto-elastic sensor”), owned by Methode Electronics, the entire content and disclosure of which are incorporated herein by reference. The device includes an annular region of a plate is magnetized with a circumferential magnetization. Magnetic field sensors are then placed near this magnetized band at locations where the magnetization direction is non-parallel and non-perpendicular to the axis of tension. The strain-induced magnetic anisotropy caused by tension or compression then produces a shift in the magnetization direction in the plate regions near the field sensors, thereby causing magnetic field changes which are detected by the magnetic field sensors. The magnetic field sensors are connected to an electronic circuit which outputs a voltage signal which indicates the tension or compression in the plate.

According to another aspect, an embedded software program is used to receive signals from various sensors and output a signal containing information useful in determining or assessing a load weight gauge (measuring the tongue load of a tow coupling), a tow load weight shift alert, an unsafe trailer load distribution alert, a vehicle limit notification, an automated trailer brake control (closed loop), a low/flat trailer tire notification, a check trailer brake notification, a closed loop braking control, a vehicle shift control, an engine control, and a stability control.

According to another aspect, shielding material or a shielding device or multiple shielding devices may be used to shield the load sensor pins8,9from the effects of external magnetic sources, such as nearby permanent magnets. In one embodiment, a flux directly may be used to direct external magnetic fields to minimize or reduce their effect on the load sensor pins8,9and the output signal from the load sensor pins8,9.

According to another aspect, the load sensor pins8,9output one or more signals to one or more microcontroller units. The microcontrollers are adapted to processing the signals and providing processed signals to a vehicle onboard control system via the vehicle's bus network. The processed signal may include information related to a comparison of the load pin forces to one or more threshold forces and instructional data for corrective actions to be taken by one or more vehicle control systems in response thereto.

In another aspect, the load sensor pins8,9and other components of the tow coupling apparatus may be used to measure a sprung weight of a towing or towed vehicle by measuring the sheer forces on the load sensor pins8,9caused by the weight on the vehicle producing a force on the load sensor pins8,9.

In still another aspect, the load sensor pins8,9and other components of the tow coupling apparatus may be used in connection with a weight distribution-type tow hitch and algorithms utilizing individual load sensor pin output signals may be employed to assess a tongue load and other sheer forces on a hitch caused by a trailer attached to a tow vehicle.

The present invention provides additional advantageous features related to magneto-elastic sensors for measuring forces, especially loads applied to one or more components of a vehicle hitch assembly.

