A variable reluctance sensor is disclosed as adapted for sensing the rate of revolution of a toothed wheel of magnetic material. The sensor has at least two magnets disposed side by side. One of the magnet has a first pole (e.g. S pole) disposed opposite the toothed wheel, and the other magnet has a second pole (e.g. N pole) disposed opposite the toothed wheel. The second pole of the first mentioned magnet and the first pole of the second magnet are both held against a magnetic core around which a coil is wound. As the teeth of the magnetic wheel successively travel past the magnets, they create magnetic fluxes oriented in opposite directions, which counteract each other in the core. Consequently, the total magnetic flux in the magnetic member varies more greatly than heretofore depending upon whether each magnet is opposed to any one tooth, or to the space between any two neighboring teeth, of the magnetic wheel. Such great variations in magnetic flux are translated into a correspondingly large amplitude signal as by the coil around the core.
A target wheel sensor includes a sensing structure (112) disposed within a hollow sensor housing (102). The sensing structure (112) has a T-shaped spool (114) that includes a pole piece holder (116) that terminates in a magnet holder (118). Moreover, a pole piece (120) and a magnet (122) are slidably engaged within the pole piece holder (16) and the magnet holder (118) respectively. The magnet (122) and the pole piece (120) are magnetically coupled so that the pole piece (120) is magnetized by the magnet. Also, the magnet (122) and the pole piece (120) are physically coupled so that they move in unison within the sensing structure (112). A metal target wheel (130) having one or more teeth (132) is provided and works in conjunction with the sensor (100). The target wheel (130) is placed in proximity to the sensor (100) and as the target wheel (130) rotates and a tooth (132) passes by the sensor (100) the force of magnetic attraction between the pole piece (120) and the tooth (132) will draw the pole piece (120) toward the target wheel (130) and into the extended position. As the target wheel (130) continues to rotate, the tooth (132) will move away from the pole piece (120) causing the magnetic force to lessen and allowing the pole piece (120) to return to the retracted position under the influence of a spring (128).
A magnetic position detector including a magnetic field generating element and a magnetic field detector that are arranged together so that a field generating element can be longitudinally positioned relative to the detector. The magnetic field generating element includes first, second and third longitudinally axially lined magnets. The second and third magnets are located adjacent the opposed ends of the first magnet and are spaced apart from the first magnet. The magnets are arranged so that the first magnet has a first polarity and the second and third magnets have an opposed polarity. The magnets are spaced apart to define inter-magnet gaps. The magnetic field detector includes a Hall element sensitive to the magnetic flux generated by the magnets. A power supply supplies a small bias voltage to produce an offset Hall effect output signal. The bias voltage is adjusted so that the Hall element output signal switches polarity as the Hall element passes over the inter-magnet gaps.
A magnetic sensor is provided having a pole piece, a housing for receiving and containing the pole piece, a sensing magnet and a cap for mounting the sensing magnet within the housing while retaining cracked magnet portions and either absorbing forces applied by the housing or distributing them over an entire surface of said magnet. In another aspect the invention provides a cap for mounting a sensing magnet in a magnetic sensor housing.
A sensor for detecting the angular velocity of a rotating member. The sensor includes a bobbin having an exterior defining an annular recess and a coil within the recess. The bobbin also has a generally cylindrical aperture and supports a probe and a permanent magnet in the aperture. The housing is secured to the bobbin and the housing and bobbin include tapered inner and outer surfaces, respectively, that are made to form a wedge fit seal between the bobbin and the housing to prevent the introduction of molding material during the overmolding process. The bobbin also includes supports for supporting the lead wires extending between the coil and the terminals.
A weight sensor (10) senses a load applied to a vehicle seat (12). The sensor includes a first mounting member (40; 120) and a second mounting member (42; 122) positioned opposite from and movable relative to the first mounting member (40; 120). A pair of spaced apart and opposed guide elements (44 and 46; 132 and 134) are connected between the first and second mounting members (40 and 42; 120 and 122), respectively. The pair of guide elements (44 and 46; 132 and 134) guide relative movement between the first and second mounting members (40 and 42; 120 and 122). Biasing means (44 and 46; 132 and 134) are provided for urging a spaced apart relationship between the first and second mounting members (40 and 42; 120 and 122). A variable reluctance sensor (90; 150) is operatively positioned between the first and second mounting members (40 and 42; 120 and 122) and has a variable reluctance condition responsive to the relative spacing between the first and second mounting members (40 and 42; 120 and 122) and indicative of the applied load in the seat.
