STEERING SYSTEM POSITION DETECTOR

Abstract: A system for continuously detecting the operational position of an automotive steering gear includes a first sensor element (32) incorporated into a sliding member (24) which is reciprocably mounted within the steering gear (10), with the sliding member (24) being linked with the output members of the steering gear, and a second sensor element (26) for detecting the position of the first sensor element and the sliding member as the steering gear is moved reciprocably, with the second sensor element (26) incorporated into a bearing for supporting the sliding member (24).

Description: This invention relates to a system for detecting the operational position of an automotive steering gear. It is necessary with several types of automotive control systems to know the precise steering location of the road wheels, or in other words, the operational position of the steering gear. For example, systems which control adjustable shock absorbers according to the sensing of steering angles such as the systems illustrated in U.S. Patent 4,621,833, rely upon the sensing of the steering position of the wheels. The '833 patent discloses a system for detecting rotational position of a steering driveshaft which is connected in turn to a steering gear. This system of the '833 patent is not, however, well suited for use with a remote mounted steering gear, unless such steering gear is driven by a mechanical driveshaft originating at the front steering gear. Accordingly, it is an object of the present invention to provide a steering sensing system for detecting the operational position of an automotive steering gear which is suitable for use with a remotely mounted steering gear such as that employed with the rear wheels of four wheel steering systems. U.S. Patent 4,671,523 discloses an externally mounted sensor for detecting the position of the steered rear wheels of a vehicle having a four wheel steering system. Other systems employ additional sensors such as a linear variable differential transformer (LVDT) for the purpose of detecting the rear wheel steering position. Such sensors are subject to maladjustment and generally increase the space requirement for the electronic package mounted within the steering gear. It is a further object of the present invention to provide a steering gear position sensor which minimises the additional space, weight and complexity requirements. U.S. Patent 4,785,901 discloses a rack end signal generating system in which only the extreme left and right steering positions of a steering rack are detected; such a system cannot provide information for controlling a steering gear throughout its full travel. JP-A-62-012457 which corresponds to the preamble of claim 1, discloses a steering angle sensor including a magnetic sensor secured to the gear box of a rack-pinion type steering gear and two magnets of varying thickness secured to the rack shaft. According to the present invention there is provided a system for detecting the operational position of an automotive steering gear, comprising, a magnet attached to a component within said steering gear , with said component and said magnet being subject to movement synchronously with the output members of said steering gear, and detection means for continuously detecting the position of said magnet as the output members of said steering gear are moved reciprocably characterised in that said detection means comprises an inductive pickup coil which is incorporated into a bearing for slidably supporting said components . It is an advantage of the present invention that a detection system embodying this invention is compatible for use not only with remotely mounted rear wheel steering gears but also main steering gears employed at the front wheels of the vehicle. It is an advantage of the system embodying the present invention that the sensor system may be employed for continuously and reliably detecting the position of a steering gear as the steering gear moves the roadwheels from one extreme position to the other extreme of the possible steering positions. The magnet may be attached to the piston rod of a hydraulically powered steering gear. The invention will now be described further, by way of example, with reference to the accompanying drawings, in which : Figure 1 is a perspective view of a rear axle incorporating a steering system with a sensor embodying to the present invention, Figure 2 is a partially broken away view of a steering gear having a sensor system embodying the present invention. Figure 2A is a schematic representation of a hydraulically powered steering gear including a sensing system embodying to the present invention. Figure 3 is a plan view of a portion of the steering gear of Figure 2 showing a sensor system embodying the present invention. Figure 4 is a rear elevation, partially broken away, of a portion of the steering gear Figure 2 showing the sensor system embodying the present invention, and Figure 5 is an end view taken along the line 5-5 of Figure 3. As shown in Figure 1, rear steering gear 10 is coupled to a pair of spindles 16, by means of tierods 14. Accordingly, as the tierods are driven reciprocably by steering gear 10, road wheels 12 will be caused to rotate about the kingpin axes defined by ball joints 18, and as a result road wheels 12 will be steered by steering gear 10. Figure 2 illustrates the internal parts of but one example of a steering gear suitable for use with a system according to the present invention. Those skilled in the art will appreciate that a system according to the present invention would be useful not only with the illustrated rack and pinion gear but also with other types of steering gears employing hydraulic, mechanical or electrical operating systems as prime movers. Figure 2A illustrates a hydraulically powered steering gear in which piston 42, mounted upon piston rod 44, is moved reciprocably by means of hydraulic fluid directed by valves 46. The steering gear of Figure 2A includes a support bearing and coil assembly and moving magnet, which will be fully explained in connection with Figure 2. The steering gear shown in Figure 2 employs motor 20 as a prime mover to drive pinion shaft 22 through a series of gears. Pinion shaft 22 in turn drives rack 24 reciprocably. Note that tierods 14 are connected with the steering racks such that the reciprocal motion of rack 24 is transmitted to the tierods. Accordingly, the tierods comprise the output members of the steering gear. Figure 2 further illustrates magnet 32, which is recessed into rack 24, and rack support bushing and coil assembly 26, which, taken together, comprise first and second sensor elements for detecting the position of rack 24. Details of the sensor assembly according to the present invention are shown in Figures 3, 4 and 5. As best shown in Figure 4, rack 24 is supported on one end by means of rack support block 28 which is maintained in contact with the rack by means of compression spring 30. It is understood that the force imposed by compression spring 30 is opposed by a corresponding force exerted in a downward direction by pinion shaft 22. The opposite end of rack 24 is supported by means of rack support bushing and coil assembly 26. Assembly 26 comprises not only a bearing for supporting the rack but also a sensing coil for determining the position of magnet 32, and hence, the position of rack 24. Magnet 32 is recessed into magnet support 34 which, in turn, is recessed into rack 24. As a result, magnet 32 moves synchronously with rack 24. Magnet support 34 may comprise any suitable material such as aluminium or plastic or other materials known to those skilled in the art and suggested by this disclosure. As shown in the figures, assembly 26 includes winding 36, which is connected with system control module 38 to permit the control module to be advised at all times of the location of magnet 32 and rack 24. Winding 36 comprises an inductive pickup coil. The sensor may be operated by passing an appropriate electrical potential through winding 36 and by measuring the current within the winding. As magnet 32 moves into greater or lesser proximity of winding 36, the current within winding 36 will change accordingly. As a result, system control module 38 will be able to ascertain the position of rack 24 by means of a lookup table or other means incorporated into a microprocessor or other calibrated device contained within the system control module. It is important to note that a system according to the present invention may be employed for the purpose of continuously tracking the location of the steering rack as the rack moves from one extreme of its travel to the other such extreme. Also, as noted above, a system according to this invention will provide an accurate reading of rack position without the necessity of bulky external sensors.

Claims: A system for detecting the operational position of an automotive steering gear, comprising, a magnet (32) attached to a component (24) within said steering gear (10), with said component and said magnet being subject to movement synchronously with the output members of said steering gear, and detection means (26) for continuously detecting the position of said magnet (32) as the output members of said steering gear are moved reciprocably characterised in that said detection means (26) comprises an inductive pickup coil which is incorporated into a bearing for slidably supporting said components (24). A system according to Claim 1, wherein said steering gear comprises a rack and pinion steering gear and said magnet is attached to the rack of the steering gear. A system according to Claim 1 or 2, wherein said inductive pickup coil encircles a portion of said steering rack. A system according to claim 1 wherein said magnet is attached to the piston rod of a hydraulically powered steering gear. A system according to Claim 2, wherein said magnet is recessed into the rack of the rack and pinion steering gear.

Inventors: OSLAPAS, ALGIS
Applicants: FORD FRANCE S. A., FORD MOTOR COMPANY LIMITED, FORD-WERKE AKTIENGESELLSCHAFT
Application year: 1989
Main classification: B62D15
IPC codes: B62D5, B62D7, B62D15