Displacement measurement device

An displacement measurement device and associated method where displacement measurements of a movable member are obtained by an electromagnetic field sensor that need not move relative to the magnet or other electromagnetic field source. The electromagnetic field sensor senses disruptions in the electromagnetic field caused by movement of the movable member to provide an output indicative of the position of the actuator.

RELATED APPLICATIONS

This application claims priority of U.S. Provisional Application Nos. 60/799,853 filed May 12, 2006 and 60/808,415 filed May 25, 2006, both of which are hereby incorporated herein by reference.

FIELD OF THE INVENTION

The herein described invention relates generally to electromagnetically actuated devices, such as solenoid-actuated valves, and more particularly to such devices that provide a position output indicative of the position of a position-controlled member of the device. The invention also relates more generally to displacement measurement devices.

BACKGROUND OF THE INVENTION

Heretofore, solenoid actuated valves have used sensors to provide position feedback for control purposes. Linear variable displacement transducers (LVDTs) are well-known and widely used devices that measure the displacement of an armature relative to a coil assembly. One driving coil is used in conjunction with two secondary measurement coils.

Another type of sensor that has been used is a Hall-effect sensor. The Hall-effect sensor is an analog measuring device that provides a varying voltage output in relation to local disruptions of an electromagnetic field. The Hall-effect sensor typically is positioned to interact with a permanent magnet on the armature of the solenoid. The sensor and the magnet move relative to one another in order to vary the voltage output of the sensor thereby provide an indication of position. In a slide-by position sensor arrangement, tight control over the movement path of the armature usually must be maintained to ensure accurate displacement measurement.

SUMMARY OF THE INVENTION

The present invention provides a displacement measurement device and associated method where displacement measurements of a movable member are obtained by an electromagnetic field sensor that need not move relative to the magnet or other electromagnetic field source. The electromagnetic field sensor senses disruptions in the electromagnetic field caused by movement of the movable member to provide an output indicative of the position of the actuator.

Additionally, the present invention provides a novel approach for monitoring the position of a movable member such as an armature of a valve. A coil of the sensing mechanism produces a magnetic field when electrical power is applied to the coil. When electrical power is properly controlled (or fixed at a constant) the flux concentration of the magnetic field is substantially constant, as seen by a field sensor. Movement of the armature through the magnetic field of the coil changes the concentration of magnetic flux seen by the sensor. As a result, the position of the armature (or other movable member) can be determined by monitoring the magnetic field.

According to one aspect of the invention, a valve comprises a body; an armature movable in the body; and a position sensor for determining the position of the armature relative to the body, the position sensor including a source for providing a magnetic field and a member for sensing the magnetic field, the armature changing a value sensed by the member, the value being indicative of the position of the armature relative to the body.

According to another aspect of the invention, a device for measuring displacement of a movable member, comprises a source for providing a magnetic field, a member movable in the magnetic field, and an electromagnetic field sensor for sensing disruptions in the magnetic field at a location in the magnetic field to provide an output indicative of the position of the movable member.

According to another aspect of the invention, a method of measuring the displacement of a movable member, comprises sensing at a location in the an electromagnetic field the disruption in the field caused by movement of the movable member in the field to provide an output indicative of the position of the actuator.

Further features of the invention will become apparent from the following detailed description when considered in conjunction with the drawings.

DETAILED DESCRIPTION

Referring now to the drawings in detail and initially toFIG. 1, an exemplary displacement measurement device according to the invention is indicated generally at10. The device10generally comprises a source for providing a magnetic field, such as a permanent magnet20; a member movable in the magnetic field, such as a plunger or armature30; and one or more electromagnetic field sensors, such as a Hall-effect sensors40, for sensing disruptions in the magnetic field at a location (respective locations) in the magnetic field to provide an output indicative of the position of the movable member. Unlike other displacement measurement devices, the field sensor(s) is intended to remain stationary in the magnetic field produced by the source20. Movement of the member30will disrupt the magnetic field and vary the magnetic flux acting on the field sensor40, whereby the field sensor will output a signal indicative of the position of the member relative to the source. The sensor output can be supplied to a processor (analog and/or digital)50configured, as by suitable programming, to process the output of the sensor and provide a position signal or data corresponding to the sensed position of the member30that can be used, for example, to provide position feedback, position verification, movement feedback, etc., to an overall system controller60that may include the processor50as a component thereof. The device may be used in a variety of systems that use displacement sensors and/or feedback controls, such as steer-by-wire systems.

As will be appreciated, other types of field sensors may be employed, although Hall-effect sensors are preferred. Electromagnetic sensors, such as a Hall-effect sensor, are analog measuring devices that provide varying voltage output in relation to local disruptions of an electromagnetic field produced by a permanent magnet(s) or electromagnet(s). Analog sensors, in particular, provide a signal particularly suited for electrical control and monitoring systems.

The movable member30may be made of any suitable material, such as a ferromagnetic material, that is operative to disrupt the magnetic field when the armature moves through the field, whereupon the field strengths sensed by the field sensor for given positions of the movable member provide respective unique signals from which the respective positions of the movable member can be derived. Reliance may also be had on the change in field strength (or even the rate of change in field strength) as the movable member moves from position to position in order to provide an accurate indication of the position and/or movement property of the movable member.

As will be appreciated, other types of magnetic field sources may be used. By way of example,FIG. 2shows an exemplary displacement measurement device110including an electromagnet120as the magnetic field source. The illustrated exemplary electromagnet120includes a coil121(multiple coils can also be employed) wound on a bobbin122or the like that includes a guide bore123(preferably concentric as shown) for the movable member, such as an armature130. As shown, a field sensor140(e.g. Hall-effect sensor) may be suitably positioned in the magnetic field, such as radially inwardly of the coil121between the coil and the guide bore123. The sensor leads141may be routed along with the coil leads124to a connector170for facilitating connection to other system components such as the processor50and/or system controller60shown inFIG. 1. The leads141and124may be those conventionally associated with the particular sensor and coil (or coils) used in the device110.

InFIG. 3, another exemplary displacement measurement device210is shown. The device210is the same as the device110, except the field sensor240is located radially outwardly of the coil221. Also, the connector270is differently oriented.

InFIG. 4, an exemplary application of a displacement measurement device according to the invention is illustrated. Here the device310is shown embodied in a solenoid-operated spool valve assembly315, in particular a cartridge valve assembly. In this embodiment, the device310comprises two field sensors340aand340b, which may be identical Hall-effect sensors. The sensors340aand340bare located in the magnetic fields produced by axially spaced electromagnets, e.g. coils321aand321b, that act on a movable member (armature)330. Upon differential energization of the coils, the armature330can be proportionally positioned between opposed pole pieces125aand125b. The armature is connected by suitable means to a valve316for controlling the position of the valve. In the illustrated embodiment, the armature is connected by a rod317to a spool valve member318that moves in a valve body for controlling flow between one or more ports of the valve body, as in a conventionally known manner.

As will be appreciated, the coils321aand321badditionally function as sources of the magnetic fields sensed by the sensors340aand340bthat provide signals indicative of the position of the armature. One or both of the sensors may be used to provide position information, such as to a valve controller. As shown, the sensors may have the leads thereof connected to suitable terminals of a connector for convenient connection to a signal processor or system controller. The sensors are also shown conveniently located radially outwardly, and preferably centrally, of the respective coils. As will be appreciated, in the various embodiments the sensor may be located centrally in respect of the longitudinal axis of the magnetic field, although radially offset therefrom. The magnetic field for any given level of energization of the coils will be disrupted by the position of the armature relative to the coils, such that position information can be obtained from the output of the field sensor or sensors by a suitable processor.

In particular embodiments, the sensor may used at standard coil voltage (often 12 or 24 VDC) or a small voltage (could be <5 VDC) with good resolution. Electromagnetic sensors such as Hall-effect and EM sensors can be used for this purpose.

FIG. 5shows another exemplary application of a displacement measurement device410in a different type of valve assembly415. The valve assembly415includes a solenoid coil421wound on a bobbin or the like including a central passage for a movable member, in particular the armature430. Energization and de-energization of the coil will cause the armature to move towards or away from a pole piece425, as is known in the art. The armature functions as an actuator for a valve member416, movement of the armature effecting corresponding movement of the valve member relative to a valve seat418. The armature and/or valve member may be biased by one or more springs to provide a desired operational configuration of the valve, such as a normally closed or normally open valve configuration.

In the valve assembly415, the field sensor440of the device410is located externally of the solenoid housing, but within the magnetic field generated by the solenoid coil (or other magnetic field source). This illustrates how the device can be implemented, for example, to retrofit an existing valve assembly with a displacement measurement device according to the invention. More generally,FIG. 5illustrates one manner by which existing solenoid valves (or other electromagnetically actuated devices) can be fitted with a low-cost, fast-response, accurate, small footprint displacement sensor.

FIG. 6shows a valve assembly515that is the same as the valve assembly415, except the field sensor540is integrated into the connector570of the solenoid. This provides a convenient means for mounting the field sensor relative to the magnetic field source while also facilitating connection to a signal processor and/or system controller.

As can now be appreciated, the present invention enables displacement measurements that can be used as a way to provide closed-loop feedback controls far more effectively than existing devices, because real-time internal valve motion can be accurately measured. This value is realized whether the valve is operated in proportional or on-off modes. A displacement measurement device can be added non-invasively to existing valve assemblies, or it may have other packaging advantages by including the sensors in the original valve construction. Various options have been herein illustrated and described.

Accordingly, one or more features of the present invention may be used to provide one or more advantages, particularly when an actuator device serves as both an actuator and a highly accurate measuring device. Attainable advantages include: 1) low cost, 2) non-contacting and very robust design, 3) subject to fewer failure modes in operation, 4) fast and accurate analog measurement, and 5) small physical space requirements. Additionally, when a device is used in a sensor mode, anomalous system behaviors can be monitored and valve performance characteristics can be adapted and optimized in real time.