Position sensor

Details Position sensor Position sensor

2000-12-01

2003-07-08

Lefkowitz, Edward (Department: 2862)

Electricity: measuring and testing

Magnetic

Displacement

C324S207240, C324S207250, C073S597000

Reexamination Certificate

active

06590387

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a position sensor, and particularly, to a magneto-strictive sensor for determining a position of a valve in an internal combustion engine.
BACKGROUND OF THE INVENTION
Automotive manufacturers are currently utilizing camless intake and exhaust valve assemblies to control fluid communication in engine cylinders of internal combustion engines. The camless valve assemblies may utilize hydraulic, pneumatic, or electromechanical means to move a valve.
It is further known that varying an engine valve dwell time (i.e., the time interval a valve is open), a valve dwell position (i.e., the amount the valve is open), a valve opening rate, a valve closing rate, and an initial opening time of a valve (i.e., valve phasing) may be used to increase fuel efficiency and lower emissions. Further, the most flexible valve assemblies may be independently actuated/controlled with respect to other valve assemblies in an engine.
Referring to
FIG. 1
, a known engine
10
having an engine head
12
and electromechanical valve assemblies
14
,
16
is shown. The engine head
12
includes an air intake line
18
and an exhaust line
20
. The valve assemblies
14
,
16
control communication between the line
18
,
20
, respectively, with an engine cylinder (not shown).
The valve assembly
14
includes a pair of solenoids
22
,
24
, and a valve
26
. The valve
26
includes a valve stem
28
and a valve head
30
. The solenoids
22
,
24
are utilized to either open or close the valve
26
. In particular, when the solenoid
24
is energized (and solenoid
22
is de-energized), the valve head
30
is moved axially away from a valve seat
32
to allow fluid communication between the intake line
18
and a cylinder (not shown). When the solenoid
22
is energized (and solenoid
24
is de-energized) the valve head
30
engages the valve seat
32
to prevent fluid communication between the intake line
18
and the cylinder. Thus, the known valve assembly
14
has a two-position valve
26
having either a full open state or a full closed state. As such, the valve assembly
14
has several operational disadvantages. In particular, the valve assembly
14
cannot precisely control a valve dwell time duration, a valve dwell position, a valve opening rate, a valve closing rate, valve phasing. Thus, the valve assembly
14
cannot be utilized to effectively increase fuel efficiency and lower emissions in an engine. Further, the valve assembly
14
does not provide for soft seating of the valve head
30
on the valve seat
32
under all operating conditions of the engine
10
—including temperature extremes and control strategy variations. As a result, the valve head
30
generates undesirable noise when contacting the valve seat
32
.
Another known electromechanical valve assembly (not shown) includes an electric motor, a cam, and a poppet valve. The motor selectively rotates an output shaft that is connected to the cam. The cam converts that rotary motion of the output shaft to an axial motion of the poppet valve. This known valve assembly is capable of controlling a valve dwell time, a valve dwell position, a valve opening rate, and a valve closing rate. However, the known valve assembly suffers from several disadvantages. First, the valve assembly requires a separate cam resulting in increased component and manufacturing costs. Further, the valve assembly requires a relatively large package space since a separate cam is utilized for each poppet valve.
Position sensors have been used to determine an axial position of valves in intake and exhaust valve assemblies. Two commonly used types of position sensors include a Hall Effect sensor and a variable reluctance sensor. Each valve assembly may have a corresponding position sensor disposed on top of the valve assembly. As such, the known position sensors have several disadvantages in an automotive vehicle. In particular, the known position sensors have a relatively thick axial profile. Accordingly, the sensors substantially increase the height of intake and exhaust valve assemblies, resulting in an increased height of a vehicle hood to accommodate the valve assemblies. Those skilled in the art will recognize that a higher vehicle hood results in decreased fuel economy and decreased visual aesthetics of the automotive vehicle.
SUMMARY OF THE INVENTION
The present invention provides a magneto-strictive sensor for determining a position of a valve in an electromechanical valve assembly. The electromechanical valve assembly may comprise an intake or exhaust valve assembly in an internal combustion engine.
The magneto-strictive sensor in accordance with the present invention includes two preferred embodiments. The first preferred embodiment of the magneto-strictive sensor is utilized to determine (i) a rotational position of a rotor of an electromechanical valve assembly and (ii) an axial position of a valve of the valve assembly. The rotor includes a sensor magnet attached to the rotor that rotates with the rotor. Accordingly, a rotational position of the sensor magnet is indicative of a rotational position of the rotor. The magneto-strictive sensor includes a sonic conduit extending around a portion of a circumference of the rotor of the valve assembly. The sensor further includes a sonic wave generator generating a sonic wave in the conduit responsive to a transmit signal. The sonic wave propagates to a localized stress boundary in the conduit which is induced by the sensor magnet. The sonic wave is reflected in the conduit from the stress boundary. The sensor further includes a sonic wave receiver receiving the reflected sonic wave from the conduit and generating a received signal responsive to the sonic wave. Finally, the sensor includes a sensor controller configured to generate the transmit signal and to receive the received signal. The controller calculates a position value responsive to a round trip travel time of the sonic wave in the conduit. As previously discussed, the position value represents (i) a rotational position of the rotor and/or (ii) an axial position of the valve.
The second preferred embodiment of the magneto-strictive sensor is utilized to determine an axial position of a valve in a valve assembly. The rotor includes a permanent ring magnet that is stationary along an axial axis of the valve. The magneto-strictive sensor includes a sonic conduit extending generally axially on or integral with the valve. The sensor further includes a sonic wave generator generating a sonic wave in the conduit responsive to a transmit signal. The sonic wave propagates to a localized stress boundary in the conduit. The stress boundary is induced by the ring magnet and the sonic wave is reflected in the conduit from the boundary. The sensor further includes a sonic wave receiver receiving the reflected sonic wave and generating a received signal responsive to the sonic wave. Finally, the sensor includes a sensor controller configured to generate the transmit signal and to receive the received signal. The controller calculates a position value responsive to a round trip travel time of the sonic wave in said conduit. As previously discussed, the position value represents an axial position value of the valve.
The magneto-strictive sensor in accordance with the present invention represents a significant improvement over conventional position sensors. In particular, the inventive sensor has an extremely thin axial profile as compared with conventional sensors. Accordingly, the inventive sensor may be disposed within a valve enclosure without increasing the height of an intake or exhaust valve assembly. Accordingly, the lower valve assemblies allow for a lower vehicle hood profile that results in increased fuel economy of the automotive vehicle.
These and other features and advantages of this invention will become apparent to one skilled in the art from the following detailed description and the accompanying drawings illustrating features of this invention by way of example.


REFERENCES:
patent: 3894433 (1975-07-01), Rieste

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