GB2317958A - A rotational speed and position sensing system - Google Patents
A rotational speed and position sensing system Download PDFInfo
- Publication number
- GB2317958A GB2317958A GB9702992A GB9702992A GB2317958A GB 2317958 A GB2317958 A GB 2317958A GB 9702992 A GB9702992 A GB 9702992A GB 9702992 A GB9702992 A GB 9702992A GB 2317958 A GB2317958 A GB 2317958A
- Authority
- GB
- United Kingdom
- Prior art keywords
- target
- camshaft
- pole piece
- sensor
- detection system
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P3/00—Measuring linear or angular speed; Measuring differences of linear or angular speeds
- G01P3/42—Devices characterised by the use of electric or magnetic means
- G01P3/44—Devices characterised by the use of electric or magnetic means for measuring angular speed
- G01P3/48—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage
- G01P3/481—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage of pulse signals
- G01P3/488—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage of pulse signals delivered by variable reluctance detectors
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
- G01D5/14—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage
- G01D5/20—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature
- G01D5/2006—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature by influencing the self-induction of one or more coils
- G01D5/2013—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature by influencing the self-induction of one or more coils by a movable ferromagnetic element, e.g. a core
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Valve-Gear Or Valve Arrangements (AREA)
- Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)
Abstract
A rotational speed and rotation sensing system for a shaft such as a camshaft 10 of an i.c. engine comprises a target 11 having a pair of axially spaced elements 11A, 11B projecting from the shaft with an axial gap G therebetween, and a variable reluctance sensor 12 having a protruding pin 16 which extends between the elements and senses the passage of the target 11 in a consistent manner despite variations in radial or axial positioning of the target and censor. As shown the target is in the form of a lobe similar to an operational lobe of the camshaft but divided by the gap G, but a shaft having a pair of axially spaced teeth is also described. The sensor 12 has a coil 15 around the pin 16 which is magnetically linked to a permanent magnet 13 by a pole-piece 14.
Description
A Rotational Speed and Position Sensing Svstem
This invention relates to rotational speed and position sensing systems and in particular to a variable reluctance system for sensing the speed and position of a rotating shaft.
It is known to sense the rotational speed and position of a shaft by placing a variable reluctance sensor in close proximity to a target wheel rotating with the shaft. The sensor detects the presence and absence of ferrous targets by sensing changes in flux linkage between it and the target wheel and generates a varying voltage signal dependant thereon. The maintenance of a controlled air gap between the sensor pole piece and its target is critical in order to obtain a stable sensor output.
It is an object of this invention to provide an improved rotational speed and position sensing system.
According to the invention there is provided a rotational speed and position detection system for a shaft rotatable about a fixed axis the system comprising a variable reluctance sensor held in a fixed relationship with respect to the shaft by means of a sensor mounting means, a sensor target rotatable with the shaft for magnetic interaction with a protruding pole piece of the variable reluctance sensor so as to detect the target passing the pole piece and to supply a signal indicative thereof to an electronic signal processing and control means, wherein the target comprises a pair of spaced apart radially outwardly extending target members defining a gap therebetween into which the protruding pole piece of the reluctance sensor extends during rotation of the target past the pole piece so as to produce a significant radial overlap between the end of the pole piece and the target members.
The sensor may detect the target members substantially at right angles to the centre line of the pole piece as the target members pass the pole piece.
The overlap of the pole piece and the target members may be arranged to provide a sufficient running clearance between the pole piece and the shaft at both extremes of the accumulative radial tolerances of the shaft and of the sensor. The radial tolerances may further include all radial positional variations.
The gap between the target members may be arranged to provide a sufficient bilateral clearance to the pole piece to accommodate both extremes of the accumulative axial tolerances of the shaft and of the sensor.
The axial tolerances may further include all axial positional variations.
The electronic signal processing and control means may comprise part of an engine management system of an internal combustion engine.
The shaft may comprise a camshaft of an internal combustion engine and the target may comprise a target lobe on the camshaft which may be substantially to the same profile as a camshaft lobe of the camshaft.
The invention also provides a camshaft for an internal combustion engine having a sensor target rotatable therewith, the target comprising a pair of spaced apart radially outwardly extending target members defining a gap therebetween.
The target may be arranged for magnetic interaction with a pole piece of a variable reluctance sensor protruding into the gap to detect the target passing the pole piece, the sensor being held in fixed relationship to the camshaft by means of a sensor mounting means and arranged to supply a signal indicative of the target to an engine management system of the engine.
The invention will now be described by way of example with reference to the accompanying drawings in which:
Figure 1 shows part of a rotational speed and position sensing system according to a first embodiment of the invention;
Figure 2 shows a section through part of Figure 1 on the line A to A;
Figure 3 is an isometric vlew of part of the system shown in Figure 1;
Figure 4 is an isometric view of part of a system in accordance with a second embodiment of the invention; and
Figure 5 is a section through part of the system of Figure 4 on the line
B to B.
Referring to Figures 1 to 3, part of a camshaft 10 of an internal combustion engine (not shown further) has a sensor target formed on it which comprises a target lobe 11 of the same profile as the camshaft lobes (none shown). The lobe 11 has a slot in it down to the depth of its base circle BC and provides a pair of radially outwardly extending lobe members 11A, 11B with a gap G defined between them.
A variable reluctance sensor 12 is held by a mounting bracket (not shown) in a fixed position with its centre line CL1 perpendicular to the centre line CL2 of the camshaft 10.
The sensor 12 comprises a permanent magnet 13 with a soft iron pole
piece 14 in abutment and magnetically linked to it. A coil 15 is wound
around a bobbin (not shown separately) which surrounds a pin 16 which is
part of the pole piece 14.
The coil 15 is connected to an electronic signal processing and control means in the form of an engine management system 17 which controls a fuelling system 18 of the engine.
The pin 16 protrudes from the sensor outer body (not shown) and points radially towards the camshaft 10 along its centre line CL1 which lies nominally halfway between the lobe members 11A, 11B. The pin 16 is long enough to overlap the lobe members 11A, 11B in the gap G by a distance L as the shaft 10 rotates and the lobe members 11A, 11B pass the pin 16.
The pin 16 has a diameter D and a clearance to the lobe members 11A, 1 1B set nominally at (G-D)/2. This clearance represents a forward clearance dl to the first lobe member 11A and a rearward clearance d2 to the second lobe member 11B.
As the camshaft 10 rotates, the lobe members 11A, 11B pass the pin 16 and the flux linkage between the sensor 12 and the camshaft 10 increases significantly due to an increase in magnetic flux linkage between the pin 16 and the lobe members 11A, 11B, the presence or absence of which is sensed substantially at right angles to the centre line CL1 of the pin 16.
The continuing rotation of the camshaft 10 causes the cutting of lines of flux which results in the generation of a varying voltage signal in the coil 15 which is connected to the engine management system 17. The signal is used by the engine management system 17 to determine the rotational speed and position of the camshaft 10 and from that to determine information on which cylinder of the engine is on its firing stroke. The engine management system 17 uses the information to vary the injection of fuel into the engine using a fuelling system 18.
The overlap L is set such that variations in radial position will not adversely effect the consistency of the sensor signal and to ensure that the output of the sensor 12 does not vary beyond the upper and lower operating limits of the sensor signal processing circuit of the engine management system 17 throughout the operating speed range of the engine.
The overlap L is also set to provide a running clearance between the tip of the pin 16 and the surface of the camshaft 10 at the base circle BC, while maintaining sufficient overlap L at both extremes of the accumulative radial tolerance stack of the assembly to satisfy the signal strength requirements of the engine management system 17 throughout the operating speed range of the engine.
The clearances dl, d2 are set to accommodate the accumulative axial tolerances of the assembly and still provide a bilateral running clearance between the pin 16 and the lobe members 11A, 11B at either extreme of the axial tolerance stack. By using a pair of lobe members 11 , 11B the effects of axial movement are significantly reduced. As the pin 16 moves towards either lobe member 11A, 11B the flux linkage between the pin 16 and that lobe member 11A, 11B increases. The subsequent increase in signal strength is substantially offset by an equivalent decrease in flux linkage between the pin 16 and the other lobe member 11A, 11B thereby maintaining an acceptably consistent signal output to variations in axial tolerance.
The axial and radial tolerances include, for example, sensor build tolerances, sensor mounting tolerances, engine and camshaft machining and build tolerances, wear, thrust and valve train bounce.
The camshaft 10 is drop forged before the machining of its lobes and bearing surfaces. The profile of the target 11 is made substantially the same as the rest of the camshaft lobes to ease the production process, as the machining tools will already be arranged for machining lobes of that profile.
When the lobes have been machined to the camshaft profile, a slot is machined out of the target lobe 11 to provide the gap G. As the sensor 12 is a non-contact sensor, there is no need to harden the target lobe 11. To enable such a target lobe 11 to operate with a variable reluctance sensor 12, the profile should have little or no peak dwell in order to provide as rapid a change in flux linkage at maximum pin 16 to lobe member 11A, 1 1B overlap L.
The camshaft could also bye made by casting as well as by drop forging techniques. The machining of the slot could occur before or after machining of the lobe surfaces and the slot need not be limited to the depth of the base circle BC, so long as a sufficient radial running clearance between the pin 16 and the bottom of the slot is provided. The camshaft may also be a composite camshaft made, for example, by assembling lobes and a target onto a hollow shaft by shrink fitting.
The target could be a target lobe separated from the other lobes on the camshaft, as shown in the first embodiment of the invention with reference to Figures 1 to 3. It would be also possible to use an existing camshaft lobe and to machine a slot in it to perform the target function, though durability on such a lobe might make it preferable to, for example, extend an existing lobe away from the valve lifting surface and form the slot in the non-contact portion of such an extended lobe.
With reference to Figures 4 and 5, a second embodiment of this invention provides a camshaft 20 having a ferrous target formed on it which comprises a pair of spaced apart outwardly extending target members 21A, 21B defining a gap g between them. The target is fixed to the camshaft 20 and rotates with it. A variable reluctance sensor 22 has a protruding pole piece 26 which extends into the gap g between the target members 21A, 21B and the sensing arrangement operates in similar fashion to the sensing system of the first embodiment.
Claims (21)
1. A rotational speed and position detection system for a shaft
rotatable about a fixed axis the system comprising a variable reluctance
sensor held in a fixed relationship with respect to the shaft by means of
a sensor mounting means, a sensor target rotatable with the shaft for
magnetic interaction with a protruding pole piece of the variable
reluctance sensor so as to detect the target passing the pole piece and to
supply a signal indicative thereof to an electronic signal processing and
control means, wherein the target comprises a pair of spaced apart
radially outwardly extending target members defining a gap
therebetween into which the protruding pole piece of the reluctance
sensor extends during rotation of the target past the pole piece so as to
produce a significant radial overlap between the end of the pole piece
and the target members.
2. A detection system according to Claim 1 wherein the sensor detects
the target members substantially at right angles to the centre line of
the pole piece as the target members pass the pole piece.
3. A detection system according to Claim 1 or Claim 2 wherein the
overlap of the pole piece and the target members is arranged to provide
a sufficient running clearance between the pole piece and the shaft at
both extremes of the accumulative radial tolerances of the shaft and of
the sensor.
4. A detection system according to Claim 3 wherein the radial
tolerances further include all radial positional variations.
5. A detection system according to any preceding claim wherein the
gap between the target members is arranged to provide a sufficient
bilateral clearance to the pole piece to accommodate both extremes of
the accumulative axial tolerances of the shaft and of the sensor.
6. A detection system according to Claim 5 wherein the axial
tolerances further include all axial positional variations.
7. A detection system according to any preceding Claim wherein the
electronic signal processing and control means comprises part of an
engine management system of an internal combustion engine.
8. A detection system according to any preceding Claim wherein the
shaft comprises a camshaft of an internal combustion engine.
9. A detection system according to Claim 8 wherein the target
comprises a target lobe on the camshaft.
10. A detection system according to Claim 8 or Claim 9 wherein the
target lobe is substantially to the same profile as a camshaft lobe of the
camshaft.
11. A camshaft for an internal combustion engine having a sensor target
rotatable therewith, the target comprising a pair of spaced apart
radially outwardly extending target members defining a gap
therebetween.
12. A camshaft according to Claim 11 wherein the target is arranged for
magnetic interaction with a pole piece of a variable reluctance sensor
protruding into the gap to detect the target passing the pole piece, the
sensor being held in fixed relationship to the camshaft by means of a
sensor mounting means and arranged to supply a signal indicative of
the target to an engine management system of the engine.
13. A camshaft according to Claim 11 or Claim 12 wherein the target
comprises a target lobe on the camshaft.
14. A camshaft according to Claim 13 wherein the target lobe is of
substantially the same profile as a camshaft lobe of the camshaft.
15. A camshaft according to any one of Claims 11 to 14 wherein the
sensor detects the target members substantially at right angles to the
centre line of the pole piece as the target members pass the pole piece.
16. A camshaft according to any one of Claims 11 to 15 wherein the
overlap of the pole piece and the target members is arranged to provide
a sufficient running clearance between the pole piece and the camshaft
at both extremes of the accumulative radial tolerances of the camshaft
and of the sensor.
17. A camshaft according to Claim 16 wherein the radial tolerances
further include all radial positional variations.
18. A camshaft according to any one of Claims 11 to 17 wherein the gap
between the target members is arranged to provide a sufficient bilateral
clearance to the pole piece to accommodate both extremes of the
accumulative axial tolerances of the camshaft and of the sensor.
19. A camshaft according to Claim 18 wherein the axial tolerances
further include all axial positional variations.
20. A camshaft for an internal combustion engine substantially as
described herein with reference to the accompanying drawings.
21. A rotational speed and position detection system substantially as
described herein with reference to the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9702992A GB2317958B (en) | 1996-10-03 | 1997-02-13 | A rotational speed and position sensing system |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GBGB9620629.7A GB9620629D0 (en) | 1996-10-03 | 1996-10-03 | A rotational speed and position sensing system |
| GB9702992A GB2317958B (en) | 1996-10-03 | 1997-02-13 | A rotational speed and position sensing system |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB9702992D0 GB9702992D0 (en) | 1997-04-02 |
| GB2317958A true GB2317958A (en) | 1998-04-08 |
| GB2317958B GB2317958B (en) | 2000-06-28 |
Family
ID=26310153
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9702992A Expired - Fee Related GB2317958B (en) | 1996-10-03 | 1997-02-13 | A rotational speed and position sensing system |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2317958B (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1464793A1 (en) | 2003-04-02 | 2004-10-06 | Renault s.a.s. | Camshaft arrangements for engines |
| WO2006105894A1 (en) * | 2005-04-04 | 2006-10-12 | Knorr-Bremse Systeme für Nutzfahrzeuge GmbH | Ride level control device of a vehicle |
| EP3086096A1 (en) * | 2015-04-23 | 2016-10-26 | SKF Canada Limited | Combined radial position and speed sensor assembly |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4166977A (en) * | 1976-09-16 | 1979-09-04 | Robert Bosch Gmbh | Rotary speed and angular position determination system, particularly for the crankshaft of an internal combustion engine |
-
1997
- 1997-02-13 GB GB9702992A patent/GB2317958B/en not_active Expired - Fee Related
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4166977A (en) * | 1976-09-16 | 1979-09-04 | Robert Bosch Gmbh | Rotary speed and angular position determination system, particularly for the crankshaft of an internal combustion engine |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1464793A1 (en) | 2003-04-02 | 2004-10-06 | Renault s.a.s. | Camshaft arrangements for engines |
| WO2006105894A1 (en) * | 2005-04-04 | 2006-10-12 | Knorr-Bremse Systeme für Nutzfahrzeuge GmbH | Ride level control device of a vehicle |
| EP3086096A1 (en) * | 2015-04-23 | 2016-10-26 | SKF Canada Limited | Combined radial position and speed sensor assembly |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2317958B (en) | 2000-06-28 |
| GB9702992D0 (en) | 1997-04-02 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| 732E | Amendments to the register in respect of changes of name or changes affecting rights (sect. 32/1977) | ||
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 20010213 |