Patent Grant
6999000
1. Field of the Invention
The present invention relates generally to microwave telemetry and, more specifically, to a transponder-based microwave telemetry apparatus for sensing conditions in or on machinery.
2. Description of the Related Art
It is known to sense conditions in machinery such as an internal combustion engine or a torque converter for a motor vehicle. Typically, the engine includes an engine block having a plurality of cylinders and reciprocating pistons disposed in the cylinders. The pistons are reciprocated by a crankshaft via connecting rods.
It is desirable to monitor or sense temperature, pressure, strain, acceleration, proximity, velocity, etc. inside machinery such as the internal combustion engine. However, it becomes difficult to get the sensed conditions off of moving parts and out of enclosed areas of the engine as a reliable, usable signal and in a cost effective manner. For example, it has been proposed to bring signals out of the engine using slip rings and/or mechanical linkages. These have a number of inherent disadvantages. Slip rings are susceptible to electrical noise, which affects reliability. Mechanical linkages are difficult to install, requiring extensive modifications to the engine, and are limited as to the speeds to which they can be exposed, i.e. engine R.P.M.
It is also known to provide a microwave telemetry apparatus for sensing conditions. An example of such an apparatus is disclosed in U.S. Pat. No. 5,555,457 to Campbell et al., the disclosure of which is hereby incorporated by reference. In that patent, an apparatus includes a sensor to sense the interior pressure of a torque converter and generate an electrical signal representative of that pressure. The apparatus also includes a microwave transmitter located within the torque converter, which converts the electrical signal to microwave energy, which is radiated into the interior of the torque converter. The apparatus further includes a stationary receiving microwave antenna exposed to the interior of the torque converter to receive the microwaves and transmit an electrical signal corresponding the microwave energy to a remote receiving device external of the torque converter.
A number of techniques are currently used to measure the temperature of a piston in an internal combustion engine. For example, infrared telemetry transmits information “line-of-sight” as pulses of infrared light from the paths to a stationary photodetector disposed in the crankcase of the engine. Another example is the contact point method, which maintains continuous sliding electrical contact between the piston and the stationary contact on the engine block. Yet another example is the induction coil method that transmits information only at the top or bottom of piston travel when a moving secondary coil on the system is coupled with a stationary primary coil on the engine. Still another example is an “L-Link” or “Grasshopper” linkage, which is designed to support the information carrying wire harness from the piston to outside the engine. A further example is radio frequency telemetry, which transmits information from the piston by way of a radio transmitter mounted on the piston, which transmits waves to an antenna in the crankcase of the engine. Yet a further example is “templugs” which are small threaded plugs made of alloy steel with a special heat treatment. After exposure to elevated temperatures, the plugs will undergo an annealing process and the hardness of the plugs is measured to determine what temperature they were exposed.
It is, therefore, one object of the present invention to provide a transponder-based microwave telemetry apparatus for sensing conditions in or on moving machinery.
It is another object of the present invention to provide a transponder-based microwave telemetry apparatus for sensing temperature, pressure, strain, acceleration, proximity, velocity, etc., in or on moving machinery such as a piston in an internal combustion engine, or a blade element in a torque converter.
To achieve the foregoing objects, the present invention is a transponder-based microwave telemetry apparatus for moving machinery. The transponder-based microwave telemetry apparatus includes a microwave transmitter disposed outside the moving machinery to fill a chamber of the moving machinery with microwave energy. The transponder-based microwave telemetry apparatus also includes a transponder disposed inside the moving machinery for measuring a sensed condition of a part of the moving machinery and providing a modulated microwave signal that contains information on the sensed condition. The transponder-based microwave telemetry apparatus further includes a receiver disposed outside the moving machinery to separate modulated and continuous-wave signal components of the signal and extract information from the modulated component.
One advantage of the present invention is that a transponder-based microwave telemetry apparatus is provided for moving machinery such as an internal combustion engine. Another advantage of the present invention is that the transponder-based microwave telemetry apparatus has a smaller package size, no “line-of-sight” constraint, which allows more freedom in the placement of the transmitter and receiver. Yet another advantage of the present invention is that the transponder-based microwave telemetry apparatus uses an electromagnetic frequency which is relatively unaffected by any other interference in the engine and is actually enhanced by reflection within the confines of a crankcase of an internal combustion engine. Still another advantage of the present invention is that the transponder-based microwave telemetry apparatus has low power consumption, has no wires, is easy to install, supports continuous data transmissions, and experiences very little attenuation by engine oil in a crankcase of an internal combustion engine. A further advantage of the present invention is that the transponder-based microwave telemetry apparatus incorporates a transponder that shrinks the size of conventional transmitters and greatly reduces power consumption.
Other objects, features, and advantages of the present invention will be readily appreciated, as the same becomes better understood, after reading the subsequent description taken in conjunction with the accompanying drawings.
Referring to the drawings and in particular
The transponder-based microwave telemetry apparatus 10 includes a transponder 28 connected to the piston 18 or connecting rod 20 by suitable means. The transponder 28 measures a sensed condition such as temperature of the piston 18 in the internal combustion engine 12 and modulates the signal received from a transceiver 32 to be described to produce a signal that contains information on the sensed condition by varying the scattering efficiency of the transponder antenna. It should be appreciated that the sensed condition may be temperature, pressure, strain, acceleration, proximity, velocity, etc. It should also be appreciated that, although an embodiment illustrating the internal combustion engine 12 is shown, the transponder-based microwave telemetry apparatus 10 may be used for sensing conditions in or on other moving machinery such as a torque converter. It should further be appreciated that the transponder 28 may be mounted anywhere that there is room on a given machine part and packaged to withstand very high g loading, shock, vibration, and temperature.
The transponder-based microwave telemetry apparatus 10 also includes a receiving antenna 30 having one end extending through the crankcase 14 for receiving the modulated microwave signal from the transponder 28. The transponder-based microwave telemetry apparatus 10 includes a transceiver 32 connected to the other end of the receiving antenna 30. The transceiver 32 is of a microwave type for receiving the modulated signal and for transmitting microwave energy. The transponder-based microwave telemetry apparatus 10 also includes a transmitting antenna 34 having one end connected to the transceiver 32 and another end extending through the crankcase 14 to fill the crankcase 14 of the internal combustion engine 12 with microwave energy from the transceiver 32. It should be appreciated that temperature sensitive thermistors (not shown) in the piston 18 are used to sense temperature of the piston 18 and are electrically connected by suitable means such as wires (not shown) to the transponder 28.
Referring to
Referring to
The timer chip 36 is used as the information gathering circuit 28b that biases the diode 38 on and off at a rate determined by the sensed signal. The diode 38 requires a predetermined voltage such as 0.5 V before it fully conducts current. The diode amplitude modulates the incoming carrier from the transmitting antenna 34 and its wire leads reradiate the AM signal to the receiving antenna 30. The signal evolution in time and frequency domains for the transponder 28 is illustrated in
Referring to
In operation, the signal generator of the transceiver 32 transmits a microwave frequency, sinusoidal carrier to the transponder 28. The transponder 28 modulates the carrier's amplitude with the square wave output of its timer chip 36. The AM signal was radiated to two receiving antennas 30 that were each connected to their own mixer 52,54. A local oscillator input for both mixers 52,54 was created by multiplying a stable radio frequency reference from the signal generator 32a of the transceiver 32. The mixers 52,54 subtracted the local oscillation frequency from the received signal frequency. The two resulting radio frequency signals were sent to a receiver 32b of the transceiver 32. The receiver essentially did the same frequency down conversion operation over again. This time its from the radio frequency range to the audio (20 Hz to 20 kHz) range. The only difference was that its local oscillator frequency was adjustable so that the resulting audio signals could be tuned to fall into the “frequency window” generated by a low pass filter. The presence of the AM signal was detected visually with the spectrum analyzer 58 and the audio amplifier 60.
Verification of the operation of the transponder 28 was successfully completed using the above. Presence of the AM signal's upper and lower side band odd harmonics were verified out to the 9th harmonic. Adjusting the receiver's local oscillating frequency made the spectrum of the AM signal slide back and forth in the frequency domain. When one of the AM signal's spectrum components fell into the low pass filter's frequency window, a sharp spike could be observed on the spectrum analyzer 58 and an audible tone could be heard from the audio amplifier 60. When the transponder's 9V battery 40 was disconnected, the spike and tone would disappear except for the case when the carrier was tuned in. The spike and tone did not vanish in this case because the carrier was still being received directly from the signal generator. Turning the signal generator off verified this. It should be appreciated that the results of this test also showed that the transponder 28 is capable of using amplitude modulation by a radio frequency square wave pulse waveform.
Referring to
The present invention has been described in an illustrative manner. It is to be understood that the terminology, which has been used, is intended to be in the nature of words of description rather than of limitation.
Many modifications and variations of the present invention are possible in light of the above teachings. Therefore, within the scope of the appended claims, the present invention may be practiced other than as specifically described.
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| Number | Date | Country | |
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| 20040017299 A1 | Jan 2004 | US |
