Integrated ultrasonic-inductive pulse sensor for wear debris detection

An apparatus for detecting wear particles in a fluid includes an inlet channel and an outlet channel. An ultrasonic transducer creating an acoustic wave that defines an acoustic focal zone is located between the inlet and outlet channels. A flow path located between the inlet and outlet channel is shaped to restrict the flow of the fluid to be within the acoustic focal zone. An inductive pulse sensor includes a plurality of flow channels receiving the fluid and a plurality of planar coils wound around the flow channels. The inductive pulse sensor includes a detection system for the detection of wear particles passing through the flow channels based on a change in an electrical property of the planar coils. A single combined excitation signal is sent to all the planar coils at once and the detection system measures one single output measurement for the plurality of flow channels.

FIELD OF THE INVENTION

The present invention generally relates to an apparatus and a method for detection of wear particles in a lubricant. Some embodiments relate to an apparatus employing an ultrasonic transducer to detect wear particles in a fluid forced to flow through a focal zone of the ultrasonic wave generated by the transducer. Other embodiments relate to an apparatus employing an inductive pulse sensor multiplexed and multichannel detection. More particularly, the present invention relates to an apparatus and method of detecting wear particles in a lubricant which uses both an ultrasonic detection means which employs a multiplexed and multichannel detection means, and an inductive pulse detection means.

BACKGROUND OF THE INVENTION

Machine parts, such as aircraft engines and gear boxes in which components move relative to each other, are often lubricated with a lubricant oil to reduce wear. Over time, small wear particles break off from machine components and build up in the oil. These wear particles generally begin with sizes in the range of 1-10 microns, but, when abnormal wear begins, larger particles, in the range of 10 to 50 microns are generated. The particle population and size of the particles tends to increase over time until eventually, a machine failure can result.

To monitor the change in lubricant wear particles, samples of the oil may be withdrawn from the machine at scheduled times and sent to a laboratory for analysis. A variety of off-line methods exist for measuring properties of lubricating fluids. For example, the suspended particles may be separated from the oil sample (e.g., by using a rotary particle depositor) and then quantified. Another method involves placing the oil sample in a container and creating a magnetic flux field using a sensing electromagnetic coil. The distortion of the flux field caused by the particle burden is then noted as a numerical Particle Quantifying (PQ) value (see U.S. Pat. No. 5,404,100). However, each of these methods takes time to generate wear information. As a result, critical failures of machines may occur even when samples are sent regularly for testing.

There are currently known apparatuses and methods of detecting lubricating oil debris, both ferrous and non-ferrous. The apparatus and method taught in U.S. Pat. No. 8,522,604 uses a single microchannel and an inductive pulse sensor to detect and count all metallic debris based on the inductive Coulter counting principle. However, this apparatus and method of detecting debris has two faults—it cannot detect non-metallic debris and it lacks the ability to incorporate multiple channels for higher throughput of data collection. Wear particle detection apparatus would benefit from the ability to detect non-metallic debris because many modern machine parts have components that are made of a non-metallic material such as plastic. In this context, the art would also benefit from being able to discern between metallic and non-metallic wear particles. The art would also benefit from the ability to use a multiplexed and multichannel inductive sensor because this will allow for a higher throughput of micro scale debris particles. Therefore, there remains a need for an apparatus and method which permits in-situ testing of lubricants that can detect both metallic and non-metallic debris and which has the ability to incorporate a multiplexed and multichannel inductive sensor which will use only one set of detection electronics.

SUMMARY OF THE INVENTION

A first embodiment of this invention provides an apparatus for the detection of wear particles in a fluid comprising of: an inlet channel receiving a fluid having wear particles therein; an outlet channel, wherein said fluid flows from said inlet channel to said outlet channel; an ultrasonic transducer creating an acoustic wave that defines an acoustic focal zone between said inlet channel and said outlet channel; and a flow path between said inlet channel and said outlet channel wherein said flow path is shaped to restrict the flow of said fluid to be wholly within said acoustic focal zone of said ultrasonic transducer.

A second embodiment of this invention provides an apparatus as in the first embodiment, further comprising an inductive pulse sensor comprising a planar coil wound around the inlet channel and a detection system for detecting wear particles passing through the inlet channel based on a change in an electrical property of said planer coil as a wear particle passes said planar coil.

A third embodiment of this invention provides an apparatus as in any either the first or second embodiment further comprising an inductive pulse sensor comprising a planar coil wound around the outlet channel and a detection system for detecting wear particles passing through the inlet channel based on a change in an electrical property of said planer coil as a wear particle passes said planar coil.

A fourth embodiment of this invention provides an apparatus as in the first through third embodiments wherein said ultrasonic transducer is a point focused ultrasonic transducer.

A fifth embodiment of this invention provides an apparatus as in the first through fourth embodiments wherein said ultrasonic transducer is a line focused ultrasonic transducer.

A sixth embodiment of this invention provides an apparatus as in the first through fifth embodiments wherein said ultrasonic transducer is a point focused ultrasonic transducer; wherein said acoustic focal zone is in the shape of an hourglass; and wherein said flow path is in the shape of an hourglass.

A seventh embodiment of this invention provides an apparatus for the detection of wear particles in a fluid comprising of: an inductive pulse sensor comprising of: a plurality of flow channels receiving a fluid having wear particles therein; a plurality of planar coils wound around said plurality of flow channels and wherein said plurality of planar coils are in series with one another; an outlet channel, wherein said fluid flows from said plurality of flow channels to said outlet channel; and a detection system for the detection of wear particles passing through said plurality of flow channels based on a change in an electrical property of said planar coils as a wear particle(s) passes said planar coils and wherein a single combined excitation signal is sent to all of said planar coils at once and said detection system measures one single output measurement for said plurality of flow channels.

A eighth embodiment of this invention provides an apparatus for the detection of wear particles in a fluid comprising of: an inlet channel receiving a fluid having wear particles therein; an outlet channel, wherein said fluid flows from said inlet channel to said outlet channel; an ultrasonic transducer creating an acoustic wave that defines an acoustic focal zone between said inlet channel and said outlet channel; a flow path between said inlet channel and said outlet channel wherein said flow path is shaped to restrict the flow of said fluid to be wholly within said acoustic focal zone of said ultrasonic transducer; and e. an inductive pulse sensor comprising of: a plurality of flow channels receiving the fluid having wear particles therein; a plurality of planar coils wound around said plurality of flow channels and wherein said plurality of planar coils are in series with one another; and iii. a detection system for the detection of wear particles passing through said plurality of flow channels based on a change in an electrical property of said planar coils as a wear particle(s) passes said planar coils and wherein a single combined excitation signal is sent to all of said planar coils at once and said detection system measures one single output measurement for said plurality of flow channels.

A ninth embodiment of this invention provides an apparatus as in the eighth embodiment wherein said inductive pulse sensor is located upstream of said ultrasonic transducer.

A tenth embodiment of this invention provides an apparatus as in either the eighth or ninth embodiments wherein said inductive pulse sensor is located downstream of said ultrasonic transducer.

An eleventh embodiment of this invention provides an apparatus as in the eighth through tenth embodiments wherein said ultrasonic transducer is a point focused ultrasonic transducer.

A twelfth embodiment of this invention provides an apparatus as in the eighth through eleventh embodiments wherein said ultrasonic transducer is a line focused ultrasonic transducer.

A thirteenth embodiment of this invention provides an apparatus as in the eighth through twelfth embodiments wherein said ultrasonic transducer is a point focused ultrasonic transducer; wherein said acoustic focal zone is in the shape of an hourglass; and wherein said flow path is in the shape of an hourglass

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

With reference toFIGS. 1 and 2, a first embodiment of this invention provides an apparatus10for the detection of wear particles in a fluid. The apparatus10includes a housing11having a through bore B that receives an inlet channel12and an outlet channel14with a flow path22defined by a flow path structure23between the inlet channel12and outlet channel14. Fluid F having wear particles therein is fed into the inlet channel12from a source S1and flows from the inlet channel12to the outlet channel14through the flow path22. The housing11further includes a transducer chamber C that receives an ultrasonic transducer16. The transducer chamber C communicates with the through bore B through a wave passage P in a wall W between the through bore B and the transducer chamber C. The ultrasonic transducer16creates an acoustic wave18that defines an acoustic focal zone20at the flow path22. The flow path22is shaped to restrict the flow of the fluid F to be wholly within the acoustic focal zone20of the ultrasonic transducer16. This is the defining characteristic of the flow path22, and it can be defined by any appropriate flow path structure23that confines the flow of fluid F to be wholly within the acoustic focal zone20. The flow path structure23may be a pipe or conduit and can even be an integral part of the inlet channel12and outlet channel14. To facilitate assembly of an apparatus10, the flow path structure23may be defined by separate block structures25,27that together form an appropriately shaped flow path22, as shown inFIG. 2. The flow path structure23has an opening24to allow for the unimpeded entrance of the acoustic waves18forming the acoustic focal zone20at the flow path22. Different sets of blocks could be employed for providing different flow paths22appropriate for a particular amplitude or type of ultrasonic wave18and its concomitant focal zone20.

Fluid F fills the transducer chamber C, inlet channel12, flow path structure23and outlet channel14, and, with the chamber C filled with fluid F, the fluid F in the transducer chamber C serves as a static barrier to urge the flow of fluid F directly from the inlet channel12to the outlet channel14through the flow path22, without diverting into the transducer chamber C. Thus, once the system is filled, further fluid flow is maintained through the flow path22. The acoustic waves18generated by the ultrasonic transducer16are directed at the flow path22such that the fluid F passes through the acoustic focal zone20created by the acoustic waves18, the focal zone20being wholly within the flow path22. Wear particles within the fluid F scatter the acoustic wave18and produce a pulse echo received by the ultrasonic transducer. The amplitude of the echo is analyzed to determine the size of the wear particle. The ultrasonic transducer16has the ability to detect all solid debris, both metallic and non-metallic. This ability to detect all types of solid debris is important because the working components of modern machinery are often formed of or coated with or otherwise present both metallic and non-metallic wear particles into lubricating oil or other fluid.

The flow path22is vital to the operation of the apparatus10because it ensures that the fluid F flows through the acoustic focal zone20of the transducer16. The acoustic focal zone20has a non-uniform hourglass shaped acoustic intensity profile. Acoustic intensity reaches maximum at the center of the acoustic focal zone20, and decreases to zero outside of the acoustic focal zone20. Therefore, large wear particles in the fluid F outside of the acoustic focal zone20may produce a small echo, and may be counted as a small debris or may not generate an echo at all. However, because the flow path22is shaped to restrict the flow of the fluid having wear particles to be wholly within the acoustic focal zone20of the ultrasonic transducer16, there is no worry that a wear particle would not be counted or would not be measured accurately.

FIG. 2, taken along line2-2ofFIG. 1shows the cross section of an embodiment of the flow path22of the apparatus10, while, for comparison,FIG. 3shows a cross section of a flow path of a prior art ultrasonic debris sensor apparatus. The flow path22shown inFIG. 2is defined by a flow path structure23, and the inlet channel12, outlet channel14and flow path structure23are positioned relative to the ultrasonic transducer16so that the flow path22in the flow path structure23restricts the flow of the fluid F to be wholly with the acoustic focal zone20. In the prior art, the flow path22′ shown inFIG. 3is defined by flow path structure23′ in the form of a common circular conduit, and the flow path22′ is much larger than the acoustic focal zone20′ ofFIG. 3. When fluid F flows through the flow path22′, only those wear particles that fall in the acoustic focal zone20′ can be detected, which will lead to an inaccurate measurement of wear particles. When fluid F flows through the flow path22, all particles are forced to flow through the focal zone20, and all wear particles are more accurately detected.

FIG. 2provides a flow path22for a point focused ultrasonic transducer and thus has an hourglass shape. In other embodiments, a line focused ultrasonic transducer is employed and the flow path22has a rectangular shape. In all instances, the flow path22closely matches the size of the focal zone to ensure that particles in the fluid F flow through the focal zone.

The ultrasonic transducer16of the apparatus10can be either a point focused ultrasonic transducer, also known as a spherical focused ultrasonic transducer, or a line focused ultrasonic transducer, also known as a cylindrical focused ultrasonic transducer. As the names suggest, a point focused ultrasonic transducer forms a focal point and a line focused ultrasonic transducer forms focal line. Point focused ultrasonic transducers are commonly used to inspect smaller targets and line focused ultrasonic transducers are typically used to detect targets in a flat plane. Line focused ultrasonic transducers have a larger sensing zone so they have the ability to process more samples. Point focused ultrasonic transducers, on the other hand, have a smaller sensing zone than a line focused ultrasonic transducer, but with the smaller sensing zone comes higher sensitivity, which is important to being able to detect small wear particles. By detecting smaller sized wear particles in the fluid F, the user will be able to detect problems earlier and potentially catch and stop problems before they become a major issue. The actual focal zone of a point focused ultrasonic transducer is an area which surrounds the focal point and is where the most energy is located. The focal zone20of the point focused ultrasonic transducer16is shaped like an hourglass. The acoustic energy within the hourglass region does not vary much, and because of that the flow path22is shaped like an hourglass. The focal zone of a line focused ultrasonic transducer is shaped like two wedges connecting at the tip and, presents a rectangular shaped focal zone cross section at the flow path22.

With reference toFIG. 4, a second embodiment of this invention provides an apparatus110for the detection of wear particles in a fluid F. This apparatus is substantially like that ofFIGS. 1 and 2though an inductive pulse sensor is added upstream of the flow path122at which the ultrasonic transducer116acts to analyze wear particulate data. Thus, the apparatus110includes a housing111having a through bore B that receives an inlet channel112and an outlet channel114, with a flow path122defined by a flow path structure123between the inlet channel112and outlet channel114. Fluid F having wear particles therein is fed into the inlet channel112from a source S2and flows from the inlet channel112to the outlet channel114through the flow path122. The housing111further includes a transducer chamber C that receives an ultrasonic transducer116. The transducer chamber C communicates with the through bore B through a wave passage P in a wall W between the through bore B and the transducer chamber C. The ultrasonic transducer116creates an acoustic wave118that defines an acoustic focal zone120at the flow path122. The flow path122is shaped to restrict the flow of the fluid F to be wholly within the acoustic focal zone120of the ultrasonic transducer116. These elements are as described above though like parts receive like numerals but increased by 100 in the disclosure of the present embodiment. Thus further details of these elements as provided above apply here as well.

In distinction to the embodiment of apparatus10, the apparatus110further includes an inductive pulse sensor124. The inductive pulse sensor124includes a planar coil126wound around the inlet channel112and a detection system (not shown) for detecting metallic wear particles in the fluid as they pass through the inlet channel112. The inductive pulse sensor124can only detect metallic/conductive wear particles and it can differentiate between ferrous and non-ferrous metallic/conductive wear particles. The metallic wear particles are detected based on a change in an electrical property of the planar coil126as metallic wear particles in the fluid F pass the planar coil126.FIG. 5is taken along line5-5ofFIG. 4and shows the cross section of the inductive pulse sensor124. In particular,FIG. 5shows how the planar coil126is wound around the inlet channel112.

The inductive pulse sensor124detects and counts all metallic wear particles in the fluid, both ferrous and non-ferrous particles. An external oscillator, such as an AC source (not shown), supplies an alternating current to the planar coil126. The AC source may be one which is able to provide a frequency of oscillation in the range of about 2 Hz-20 MHz, e.g., 100-600 KHz. The planar coil126may be formed from copper or other conductive metal. As shown inFIG. 5, the planar coil126defines a continuous strip with a plurality of concentric turns. To optimize detection of very small particles, it is desirable for the coil to have as many turns as possible in as small an area as possible. A turn is an entire 360 degree wrapping of the planar coil126around the inlet channel112. While inFIG. 5, the coil is illustrated as being substantially rectangular, in other embodiments, the coil may be circular. As shown inFIG. 5, the turns of the coil126may have a line width of about 2 μm or greater (i.e., sufficient width to carry an electric current for producing a magnetic field) e.g., up to about 50 μm. A spacing in between turns of the coil may be about 2-100 μm, e.g., 5-10 μm.

The inductive pulse sensor124uses the Coulter counting principle to detect the wear particles. The Coulter principle states that as wear particles in the fluid F flow through the inlet channel112and passes the planar coil126; the wear particles produce a change in an electrical property of the planar coil126that is proportional to the size of the wear particle passing the planar coil126. The inductive pulse sensor124relies on the fact that wear particles in the fluid that pass the electric field created by the planar coil126will cause a measurable disturbance in the field and that the magnitude of the disturbance is proportional to the size of the wear particle.

The ultrasonic transducer116of the apparatus110has the ability to detect all solid wear particles, both metallic and non-metallic. The inductive pulse sensor124has the ability to detect only metallic wear particles. By comparing the results from the ultrasonic transducer and the inductive pulse sensor, the apparatus110is advantageously capable of differentiating and detecting the specific amount of both non-metallic and metallic wear particles in the fluid.

With reference toFIG. 6, a third embodiment of this invention provides an apparatus210for the detection of wear particles in a fluid F. This apparatus is substantially like that ofFIGS. 3 and 4, though the inductive pulse sensor224is positioned downstream of the flow path222at which the ultrasonic transducer216acts to analyze wear particulate data. Thus, the apparatus210includes a housing211having a through bore B that receives an inlet channel212and an outlet channel212, with a flow path222defined by a flow path structure223between the inlet channel212and the outlet channel214. Fluid F having wear particles therein is fed into the inlet channel212from a source S3and flows from the inlet channel212to the outlet channel214through the flow path222. The housing211further includes a transducer chamber C that receives an ultrasonic transducer216. The transducer chamber C communicates with the through bore B through a wave passage P in a wall W between the through bore B and the transducer chamber C. The ultrasonic transducer216creates an acoustic wave218that defines an acoustic focal zone220at the flow path222. The flow path222is shaped to restrict the flow of the fluid F to be wholly within the acoustic focal zone220of the ultrasonic transducer216.

The apparatus210further includes an inductive pulse sensor224. The inductive pulse sensor224includes a planar coil226wound around the outlet channel214and a detection system (not shown) for detecting wear particles in the fluid F as they pass through the outlet channel214. The wear particles are detected based on a change in an electrical property of the planar coil226as a wear particle in the fluid passes the planar coil226.FIG. 7is taken along line7-7ofFIG. 6and shows a top down view of the inductive pulse sensor224. In particular,FIG. 7shows how the planar coil226is wound around the outlet channel214.

With reference toFIG. 8, a fourth embodiment of this invention provides an apparatus310for the detection of wear particles in a fluid. The apparatus310includes a multichannel, multiplexed inductive pulse sensor324that interacts with a plurality of flow channels328a,328b,328cand328dthat feed to a common outlet channel314. A fluid F having wear particles therein is fed into the plurality of flow channels328a-dfrom one or more sources (not shown) and flows from the plurality of flow channels328a-dto the outlet channel314. The inductive pulse sensor also includes a plurality of electrically conductive coils, such as planar coils326a,326b,326cand326d, shown inFIG. 8, each of which are respectively wound around one of the plurality of flow channels328a-d. The plurality of planar coils326a-dare connected to a detection system330, and serve to detect metallic wear particles passing through the plurality of flow channels328a-dbased on a change in an electrical property of the coils326a-din a manner to be discussed.

Specifically, as shown clearly inFIG. 9, each of the planar coils326a-dare connected in series with one another, whereby each planar coil326a-dis modeled as an inductance Lsi(i=1, 2, 3, 4) in series with a resistance Rsi(i=1, 2, 3, 4). In addition, an external capacitor Cpi, (i=1, 2, 3, 4) is connected in parallel with each planar coil326a-d, so as to form a plurality of series-coupled parallel LC resonant circuits327a-d.

Continuing, each of the series coupled parallel LC resonant circuits327a-dare connected to a sinusoidal excitation source Vo, that is in series with an internal resistor Ro, as shown inFIG. 9. Next, a specific capacitance Cpiis selected for each LC resonant circuit327a-dthat is associated with each respective flow channel328a-d, so that each LC resonant circuit has a unique resonance frequency. Once each the LC resonant circuits327a-dare tuned so they have different resonance frequencies, a combined excitation signal is applied to the series coupled LC resonant circuits by the excitation source Vo. The combined excitation signal comprises four separate waveforms whose individual frequencies are near or close to each of the tuned resonant frequencies of the LC resonant circuits associated with each of the flow channels328a-d. However, it should be appreciated that the excitation signal may comprise a sine wave, cosine wave, or any other suitable waveform. Upon the application of the combined excitation signal, the detection system330generates a combined response voltage Voutthat can be readily measured across the all of the LC resonant circuits327a-d. In other words, the detection system330applies a single combined excitation signal, which includes the resonant frequency of each of the parallel LC resonant circuits327a-d, to all of the LC resonant circuits at one time, whereupon the detection system330measures one single voltage output Voutfor the plurality of flow channels328a-d. Accordingly, the voltage signals from each flow channel328a-dexhibits a peak amplitude at its resonant frequency, so the signals for each individual flow channel328a-dcan be recovered from the combined response by taking the spectrum components at each resonance frequency with an improved signal-to-noise ratio. As a result, the change in electrical property for each planar coil326a-das identified by the LC resonant circuit327a-dassociated with of each respective flow channel328a-dcan be calculated from individual signals. That is, in the event of the passage of one or more wear particles through the flow channels328a-da change in the expected response of the LC resonant circuits327a-dis be detected by the detection system300.

Thus, the detection system330uses resonant frequency division multiplexing to simultaneously detect wear particles in a fluid passing through the channels328-dwhile using only one set of detection electronics. For example, in the case of the 4-flow channel328a-dsystem shown inFIGS. 8 and 9, a 300% increase in throughput is able to be achieved. AlthoughFIGS. 8 and 9show the use of only 4 flow channels, it is contemplated by those of skill in the art that such concept can be used for a multitude of flow channels and is not limited to just an apparatus employing only 4 flow channels. It should be appreciated that by adjusting the value of the external capacitor Cpi, the resonant frequency of each individual flow channel328a-dcan be regulated differently.

With reference toFIG. 10, a fifth embodiment of this invention provides an apparatus410for the detection of wear particles in a fluid. The apparatus410provides a combination of the above multichannel, multiplexed inductive pulse sensor apparatus (as inFIGS. 8 and 9) with the above concentrated focal zone ultrasonic apparatus (as inFIGS. 1 and 2) to provide an apparatus suitable for handling large flow rates and accurately measuring and discerning both metallic and non-metallic debris in a working fluid. Thus, the apparatus410includes an inductive pulse sensor424including a plurality of flow channels428a,428b,428c, and428dwhich receive a fluid F having wear particles therein. The fluid F (not shown) is fed into the plurality of flow channels428a-dfrom one or more sources (not shown) and flows from the plurality of flow channels428a-dto the inlet channel412, which is like the outlet channel314ofFIG. 8, but termed an inlet channel here because it serves as an inlet to the focal zone of an ultrasonic transducer, as will be described more fully below. The inductive pulse sensor also includes a plurality of planar coils426a,426b,426c, and426dwound around a respective one of the plurality of flow channels428a-d. The plurality of planar coils426a-dare connected in series with one another, as represented inFIG. 10, and a detection system430serves to detect metallic wear particles passing through the plurality of flow channels428a-d. The detection system430detects wear particles based on a change in an electrical property of the plurality of planar coils426. The detection system430sends a single combined excitation signal to all of the planar coils426at one time and the detection system430then measures one single output measurement for the plurality of flow channels428. Each planar coil426is electrically connected in parallel with an external capacitor which is represented by Cpi(i=1, 2, 3, 4).The apparatus410also includes a housing411having a through bore B that receives an inlet channel412and an outlet channel414with a flow path422defined by a flow path structure423between the inlet channel412and the outlet channel414. Fluid F having wear particles therein is fed into the inlet channel412from the plurality of flow channels428and flows from the inlet channel412to the outlet channel414through the flow path22. The housing411further includes a transducer chamber C that receives an ultrasonic transducer416. The transducer chamber C communicates with the through bore B through a wave passage P in a wall W between the through bore and the transducer chamber C. The ultrasonic transducer416creates an acoustic wave418that defines an acoustic focal zone420between the inlet channel412and the outlet channel414. The apparatus410further includes at the flow path422. The flow path422is shaped to restrict the flow of the fluid F to be wholly within the acoustic focal zone420of the ultrasonic transducer416. This is the defining characteristic of the flow path422, and it can be defined by any appropriate flow path structure423that confines the flow of the fluid F to be wholly within the acoustic focal zone420. The flow path structure423may be a pipe of conduit and can even be an integral part of the inlet channel412and outlet channel414.

Fluid F fills the transducer chamber C, inlet channel412, flow path structure423and outlet channel414, and, with the chamber C filled with fluid F, the fluid F in the transducer chamber C serves as a static barrier to urge the flow of fluid F directly from the inlet channel412to the outlet channel414through the flow path422, without diverting into the transducer chamber C. Thus, once the system is filled, further fluid flow is maintained through the flow path422. The acoustic waves418generated by the ultrasonic transducer416are directed at the flow path422such that the fluid F passes through the acoustic focal zone420created by the acoustic waves418, the focal zone420being wholly within the flow path422. Wear particles within the fluid F scatter the acoustic wave418and produce a pulse echo received by the ultrasonic transducer416. The amplitude of the echo is analyzed to determine the size of the wear particle. The ultrasonic transducer416has the ability to detect all solid debris, both metallic and non-metallic. This ability to detect all types of solid debris is important because the working components of modern machinery are often formed of or coated with or otherwise present both metallic and nonmetallic wear particles into a lubricating oil or other fluid.

The flow path422is vital to the operation of the apparatus410because it ensures that the fluid F flows through the acoustic focal zone420of the transducer416. The acoustic focal zone420has a non-uniform hourglass shaped acoustic intensity profile. Acoustic intensity reaches maximum at the center of the acoustic focal zone420, and decreases to zero outside of the acoustic focal zone420. Therefore, large wear particles in the fluid F outside of the acoustic focal zone420may produce a small echo, and may be counted as a small debris or may not generate an echo at all. However, because the flow path422is shaped to restrict the flow of the fluid having wear particles to be wholly within the acoustic focal zone420of the ultrasonic transducer416, there is no worry that a wear particle would not be counted or would not be measured accurately. The detection system430of the apparatus410operates in exactly the same manner as the detection system330of the apparatus310.

The inductive pulse sensor424uses the Coulter counting principle to detect the wear particles. The Coulter principle states that as wear particles in the fluid F flow through the flow channels438a-dand pass the planar coils426a-d; the wear particles produce a change in an electrical property of the planar coils426a-dthat is proportional to the size of the wear particle passing the planar coils426a-d. The inductive pulse sensor424relies on the fact that wear particles in the fluid that pass the electric field created by the planar coils426a-dwill cause a measurable disturbance in the field and that the magnitude of the disturbance is proportional to the size of the wear particle.

The ultrasonic transducer416of the apparatus410has the ability to detect all solid wear particles, both metallic and non-metallic. The inductive pulse sensor424has the ability to detect only metallic wear particles. By comparing the results from the ultrasonic transducer and the inductive pulse sensor, the apparatus410is advantageously capable of differentiating and detecting the specific amount of both non-metallic and metallic wear particles in the fluid.

With reference toFIG. 11, a sixth embodiment of this invention provides an apparatus510for the detection of wear particles in a fluid F (not shown). This apparatus is substantially like that ofFIGS. 10 and 11above but for the fact that the inductive pulse sensor524is downstream of the flow path522at which the ultrasonic transducer516acts to analyze wear particulate data. Thus, the apparatus510includes a housing511having a through bore B that receives an inlet channel512and an outlet channel514, with a flow path522defined by a flow path structure523between the inlet channel512and the outlet channel514. Fluid F having wear particles therein is fed into the inlet channel512from a source (not shown) and flows from the inlet channel512to the outlet channel514through the flow path522. The housing511further includes a transducer chamber C that receives an ultrasonic transducer516. The transducer chamber C communicates with the through bore B through a wave passage P in a wall W between the through bore B and the transducer chamber C. The ultrasonic transducer516creates an acoustic wave518that defines an acoustic focal zone520at the flow path522. The flow path522is shaped to restrict the flow of the fluid F to be wholly within the acoustic focal zone520of the ultrasonic transducer516.

The apparatus510further includes an inductive pulse sensor524. The inductive pulse sensor524includes a plurality of flow channels528a-dthat receives a fluid F having wear particles therein. The fluid F is fed into the plurality of flow channels528a-dfrom the outlet channel514. The inductive pulse sensor also includes a plurality of electrically conductive coils, such as planar coils526a,526b,526c, and526d, each of which are wound around the plurality of flow channels528a-d. The plurality of planar coils526a-dare connected to a detection system330, and serve to detect metallic wear particles passing through the plurality of flow channels528a-dbased on a change in an electrical property of the plurality of planar coils526a-d. The detection system530of the apparatus510operates in exactly the same manner as the detection system530of the apparatus310.

In light of the foregoing, it should be appreciated that the present invention significantly advances the art by providing an integrated ultrasonic-inductive pulse sensor for the detection of wear particles that is structurally and functionally improved in a number of ways. While particular embodiments of the invention have been disclosed in detail herein, it should be appreciated that the invention is not limited thereto or thereby inasmuch as variations on the invention herein will be readily appreciated by those of ordinary skill in the art. The scope of the invention shall be appreciated from the claims that follow.