In machines having a cyclic operation, as in internal combustion engines, certain operations or movements must be controlled or actuated in synchronism with the displacement or rotation of a part such as the camshaft. For example, the occurrence of spark ignition, fuel injection and movement of a valve must be coordinated. To achieve the desired sequential coordination, a signal generator indicates the position of the camshaft.
Known distributors have signal generating apparatus including a fixed magnet with turning vanes which change the intensity of the magnetic field adjacent the magnet. An inductive sensor adjacent the magnet can sense these field fluctuations.
U.S. Pat. No. 4,235,213 to Jellissen teaches an ignition system having a Hall effect sensor with a magnetic circuit positioned to provide magnetic flux through the Hall effect sensor. The magnetic flux through the Hall effect sensor is interruptable by a high permeability vane moving through the air gap in the magnetic circuit, activating the Hall effect sensor to provide timing signals for an automotive ignition distributor system. A housing in an automotive ignition distributor system is mounted on a swing arm pivotal about the axis of a distributor shaft. The housing contains a magnetic circuit and a circuit board having a Hall effect sensor affixed thereto.
Analogously, U.S. Pat. No. 4,150,653 issued to Grancoin teaches a magnetic field source produced by a rotating shaft and a Hall effect sensor positioned within the field.
U.S. Pat. No. 4,223,249 issued to Eschelman teaches a bistable magnetic wire having an electrically conductive wire coil thereabout to form a magnetic wire assembly adjacent the magnet. The ends of the conductive wire are electrically connected to a sensing apparatus. A shield or shutter arrangement operated between the magnetic wire assembly and the magnet serves to cause the magnetic wire to be at times placed under the influence of the magnetic field of the magnet thereby resulting in the magnetic wire changing from one stable state to another state. In so changing states, a voltage is induced into the inductive wire to produce a pulse across the ends of the wire.
Various problems with the known prior art include signal sensitivity not only to position of the rotating element but also to the speed of rotation. Further, the magnitude of the signal indicating a particular position may not be sufficiently different from the magnitude of a signal indicating another position. Such a lack of distinction in magnitudes may be particularly undesirable in environments having high noise such as an automotive engine.
U.S. Pat. No. 4,165,726 issued to Helmer teaches a distributor 10 which is coupled to an engine 28. Extending downwardly from the housing for the distributor is an integrally formed tubular shank or end portion 20 with a stepped mounting flange 22 at its lower end, which is received in an opening and is suitably secured to the engine block. Stem portion 20 includes an upper thrust bearing 23 and a lower sleeve bearing 24 in which is journaled the distributor rotor shaft 26, which is formed of machined steel and is suitably coupled to and rotatably driven from the electrically grounded engine.
Also known are various geared couplings between the engine crankshaft and the shaft of the distributor. Typically, a pinion gear is used to transmit crankshaft rotation to the distributor shaft causing it to rotate.
Such an elaborate connection between a crankshaft and the rotating portion of the distributor providing a signal indicative of crankshaft position is both expensive and prone to various inaccuracies. That is, any looseness in the coupling between the crankshaft and the signal generating device would cause an erroneous indication of crankshaft position. Further, an accurate transmission of crankshaft movement requires relatively close manufacturing tolerances which are typically expensive. A simpler, more direct coupling between the crankshaft and the distributor would be desirable. These are some of the problems this invention overcomes.
In distributor mountings, it is also known to attach a spring to a rotor by the use of an ultrasonically deformed rivet. It would be desirable to eliminate the use of such a rivet to reduce the number of pieces required for assembly and the expensive tooling required to ultrasonically insert the rivet. The elimination of this process would reduce the number of possible ignition system failure areas along with reducing the overall cost of the rotor.