Non-contacting apparatus for determining relative rotary position of two elements

Information

  • Patent Grant
  • 6668774
  • Patent Number
    6,668,774
  • Date Filed
    Wednesday, September 4, 2002
    22 years ago
  • Date Issued
    Tuesday, December 30, 2003
    21 years ago
Abstract
An assembly having first and second coaxially-related elements oscillatingly-rotatable about a mean angular relationship therebetween. An axial well in one element is threaded and an axial well in the other element is splined. A pin having threads on a first end and splines on the second end is disposed on both the threads and splines of the two elements. A Hall-effect magnetic field strength sensor is disposed coaxially adjacent to the assembly. A permanent magnet mounted on an end of the pin adjacent the Hall-effect sensor creates a magnetic response therein. As the angular relationship between the two elements changes, the pin turns with the splined element, the threads simultaneously displacing the pin and magnet axially of the assembly, thereby changing the intensity of the field experienced by the sensor and the signal output therefrom in proportion to the relative angular position of the two elements. The invention is especially useful for continuous monitoring and control of the advance and retard timing of an engine cam phaser.
Description




TECHNICAL FIELD




The present invention relates to mechanisms for determining relative angular position between two coaxially-related elements; more particularly, to mechanisms for continuously determining the instantaneous angular relationship between a camshaft pulley and a camshaft in a cam phaser apparatus for an internal combustion engine; and most particularly, to apparatus for making such instantaneous determination without contact between the two coaxially-related elements.




BACKGROUND OF THE INVENTION




In apparatus including first and second elements having coaxial relative rotation therebetween about a mean angular position, the need arises to determine changes in the relative angular position in either direction. An especially demanding application is one in which both elements are being simultaneously rotated on a common shaft. Just such a situation occurs in variable cam phasing systems for internal combustion engines. The angular relationship between the camshaft pulley and the camshaft itself is variable and must be determined at all times, but conveying a signal from the rotating apparatus via prior art means is difficult and cumbersome.




One known approach is to use a conventional position sensor, resistive or otherwise, mounted on the rotating cam phaser, and to convey a signal to an engine control module (ECM) via slip rings. This solution is expensive to implement and is prone to failure.




Another known approach is to use digital Hall-effect proximity sensors to detect the passing of timing features on each of the elements. By measuring the time interval therebetween, the angular relationship can be inferred. This solution, while theoretically sound, is complicated to implement because the angular velocity of the engine can vary within a single revolution of the cam phaser, causing an error in the apparent time phase measurement.




What is needed is a simple, inexpensive, and reliable means for determining the phase relationship of first and second coaxially mounted rotatable elements in an assembly, especially a cam phaser.




It is a principal object of the present invention to provide a simplified and reliable measurement of the phase relationship of such elements.




It is a still further object of the invention to provide such measurement proximately and without electrical connection to the assembly.




SUMMARY OF THE INVENTION




Briefly described, apparatus in accordance with the invention includes a Hall-effect magnetic field strength sensor disposed coaxially adjacent to an assembly having first and second coaxially-related elements oscillatingly-rotatable about a mean angular relationship therebetween. One of the elements is provided with a threaded axial bore or stud, and the other of the elements is provided with a longitudinally-splined axial bore. A pin having threads on a first end and splines on the second end is matingly disposed on both the threads and splines, respectively, of the two coaxially-related elements. A permanent magnet is mounted on an end of the pin adjacent the Hall-effect sensor, creating a magnetic response therein. As the angular relationship between the two elements changes, the pin turns with the splined element. However, the turning pin is simultaneously displaced axially of the assembly by the threads, thus displacing the magnet with respect to the sensor and thereby changing the intensity of the field experienced by the sensor. Thus, the sensor output is a continuous signal representing the intensity of magnetic field which is directly proportional to the relative angular position of the two elements. Because the magnet and sensor are coaxially disposed, rotation of the magnet, as occurs, for example, in a cam phaser application, is irrelevant. In such an application, the sensor signal is provided to an engine control module for continuous monitoring and control of the advance and retard timing of engine intake valve opening and closing.











BRIEF DESCRIPTION OF THE DRAWINGS




The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:





FIG. 1

is a schematic cross-sectional view of a first embodiment of an apparatus in accordance with the invention;





FIG. 2

is a schematic cross-sectional view of a second embodiment of an apparatus in accordance with the invention;





FIG. 3

is a schematic cross-sectional view of a third embodiment of an apparatus in accordance with the invention;





FIG. 4

is a cross-sectional view of a prior art vane-type cam phaser; and





FIG. 5

is a cross-sectional view of a vane type cam phaser in accordance with the invention.











DESCRIPTION OF THE PREFERRED EMBODIMENTS




Referring to

FIGS. 1 through 3

, first element


10


and second element


12


are disposed coaxially on axis


14


. First element


10


is formed of a non-ferromagnetic material, for example, a polymeric resin, aluminum, or certain stainless steels. First element


10


is provided with a first axial well


16


having a thin bottom wall


18


. Second element


12


is provided with a second axial well


20


having a bottom wall


22


. Coaxially disposed closely adjacent well bottom wall


18


but not in contact with element


10


is a ratiometric Hall-effect sensor


24


, a semiconductor device which produces a voltage proportional to the local magnetic field strength. One such device is the A3515LUA, available from Allegro Microsystems, Inc., Worcester, Mass. 01615, USA. Sensor


24


may be connected to a control means


26


, for example, an engine control module.




Extending into both wells


16


and


20


and axially moveable therein is a pin


28


, splined along one end portion and threaded along the opposite end portion. The only differences among the embodiments shown in

FIGS. 1-3

is the male/female relationships of the threads and splines and their placement in either element


10


or element


12


. All are equivalent in function in accordance with the invention.




In first embodiment


30


(FIG.


1


), well


16


is female-splined with longitudinal splines


23


, running parallel to axis


14


and pin


28


is male-splined with longitudinal splines


25


in element


10


, and well


20


is female-threaded with threads


27


and pin


28


is male-threaded with threads


29


in element


12


.




In second embodiment


30


′ (FIG.


2


), well


16


is female-threaded and pin


28


is male threaded, and well


20


is female-splined and pin


28


is male-splined.




In third embodiment


30


″ (FIG.


3


), well


16


is female-splined and pin


28


is male-splined as in embodiment


30


. Pin


28


has a threaded axial bore


32


, and well


20


is provided with a threaded stud


34


axially mounted on wall


22


.




In each of embodiments


30


,


30


′,


30


″, a permanent magnet


36


is disposed in well


16


on the end of pin


28


adjacent sensor


24


. By definition, an angular relationship with respect to axis


14


exists between elements


10


and


12


. At any given angular relationship, sensor


24


is exposed to a magnetic field produced by magnet


36


and sends a signal to control means


26


proportional to the field strength. If elements


10


,


12


are rotated with respect to each other about axis


14


to assume a different angular relationship, pin


28


must rotate with the longitudinal splined element. The rotation causes pin


28


to turn along threads


27


,


29


in the threaded element by an amount equal to the angular change between elements


10


,


12


. Magnet


36


is thereby axially displaced, according to the pitch of the threads, either toward or away from sensor


24


, depending upon the direction of relative rotation; the field experienced by sensor


24


is either increased or decreased, and the signal sent to control means


26


is either increased or decreased proportionally. The device may be readily calibrated in known fashion to relate relative angular position to signal strength. Note that, because all motions are relative to axis


14


and the magnetic field is symmetrical about axis


14


, combined rotation of elements


10


,


12


about axis


14


is irrelevant and does not affect the signal even when the sensor is stationary.




Referring to

FIG. 4

, a prior art vane-type cam phaser


50


is well known in the automotive arts for controllably altering the phase relationship between the crankshaft (not shown) and the camshaft


52


of an internal combustion engine


54


, the motion and phase of the crankshaft being transmitted to the phaser via a crankshaft pulley


56


. Phaser


50


is rotatably mounted on an end


53


of camshaft


52


. Pulley


56


is integrally assembled with phaser hub


58


, body


60


, and cover


62


which therefore rotate as a crankshaft subassembly


61


in phase according to pulley


56


. A rotor hub


64


is pressed into a recess in the end of camshaft


52


, supporting a multi-vaned rotor


66


connected to hub


64


via a hollow bolt


68


threaded into hub


64


, forming a camshaft subassembly


67


having an angular relationship to crankshaft subassembly


61


. Control hydraulic fluid in the form of pressurized engine oil flows from ports in the camshaft (not shown) axially through bolt


68


, into gallery


70


, and thence into galleries formed between vanes


72


and stator lobes (not visible in this elevational cross-sectional view) to urge rotor subassembly to a different angular position with respect to crankshaft subassembly


61


. Other mechanisms, which need not be addressed here but are well known in the art, act to urge the rotor assembly in the opposite direction as required. Thus, in normal operation of the cam phaser, there is relative rotational motion between cover


62


and bolt


64


, in both rotational directions, about a mean angular position.




Referring to

FIG. 5

, an improved cam phaser


50


′ is shown, substantially identical in all respects to prior art phaser


50


except as shown and discussed below. A non-contacting apparatus is included in phaser


50


′ for sensing and signaling changes in the relative angular position of subassembly


61


with respect to subassembly


67


. The embodiment shown is equivalent to embodiment


30


′ shown in FIG.


2


. Well


20


formed in the head of bolt


68


is female-splined, and pin


28


is male splined. A new well


16


is formed in cover


62


and is female-threaded. Pin


28


is male threaded. Threads may be either right-or left-handed. A permanent magnet


36


is mounted on the outer end of pin


28


. A Hall-effect sensor


24


is mounted closely adjacent cover


62


but preferably not in contact with cover


62


, which in operation may be rotated at several hundreds or thousands of revolutions per minute. Sensor


24


is connected to engine control module


26


. Pin


28


, being spline-mounted in bolt


68


, rotates with camshaft subassembly


67


and is driven axially by threads


27


in well


16


toward and away from sensor


24


.




Thus, the invention provides a simple, inexpensive, reliable, non-contacting means for determining and measuring changes in angular position between first and second coaxially disposed elements.




While the embodiment described in

FIG. 5

is shown as being equivalent to embodiment


30


′ shown in

FIG. 2

, it is understood that improved cam phase


50


′ may be shown as being equivalent to embodiment


30


′ or


30


″ and fall within the scope of the invention.




While the invention has been described by reference to various specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiments, but will have full scope defined by the language of the following claims.



Claims
  • 1. Apparatus for determining and measuring changes in relative rotational position, comprising:a) a first element having a first axial well formed therein; b) a second element having a second axial well formed therein, said first and second wells having a common axis, and said first and second elements having a variable relative angular relationship therebetween about said axis; c) splines formed in one of said first and second wells; d) threads formed in the other of said first and second wells; e) a pin disposed in said apparatus and extending into each of said wells and having mating splines on a pin portion extending into said splined well and having mating threads on a pin portion extending into said threaded well; f) a magnet disposed axially disposed on an end of said pin extending into said first well; and g) a Hall-effect sensor disposed adjacent said magnet outside of said first element for providing signals proportional to the axial position of said magnet in said first well, said signals representating the angular position of said first element with respect to said second element.
  • 2. An apparatus in accordance with claim 1 wherein said other of said first and second wells is provided with an axial stud attached to a bottom of said well and wherein said threads are formed on said stud.
  • 3. An apparatus in accordance with claim 1 wherein said first element is a cam phaser crankshaft subassembly and said second element is a cam phaser camshaft subassembly.
  • 4. An apparatus in accordance with claim 3 further comprising an engine control module receivable of said signals from said sensor.
  • 5. A multiple-cylinder internal combustion engine comprising a cam phaser, includinga cam phaser crankshaft subassembly having a first axial well formed therein, a cam phaser camshaft subassembly having a second axial well formed therein, said first and second wells having a common axis, and said first and second subassemblies having a variable relative angular relationship therebetween about said axis, splines formed in one of said first and second wells, threads formed in the other of said first and second wells, a pin disposed in said cam phaser and extending into each of said wells and having mating splines on a pin portion extending into said splined well and having mating threads on a pin portion extending into said threaded well, a magnet disposed axially disposed on an end of said pin extending into said first well, and a Hall-effect sensor disposed adjacent said magnet outside of said cam phaser crankshaft subassembly for providing signals to an engine control module proportional to the axial position of said magnet in said first well, said signals representating the angular position of said cam phaser crankshaft subassembly with respect to said cam phaser camshaft subassembly.
US Referenced Citations (3)
Number Name Date Kind
5522352 Adachi et al. Jun 1996 A
6429647 Nicholson Aug 2002 B1
6588404 Mathews Jul 2003 B1
Non-Patent Literature Citations (1)
Entry
Mathews et al., Target Wheel Tooth Detection, US patent application Publication, US 2003/0000498A1, Jan. 2, 2003.