Measuring and testing – Test stand – For engine
Reexamination Certificate
2000-10-18
2002-09-10
McCall, Eric S. (Department: 2855)
Measuring and testing
Test stand
For engine
C073S114220
Reexamination Certificate
active
06446497
ABSTRACT:
CROSS-REFERENCES TO RELATED APPLICATIONS
This application claims the benefit of foreign priority Austrian Patent No. GM 723/99, filed Oct. 18, 1999.
BACKGROUND OF THE INVENTION
The invention relates to a reciprocating machine with a friction bearing crank mechanism and a monitoring device for monitoring operating parameters of the friction bearings of the crank mechanism via at least one sensor associated with an evaluation device.
The crank mechanism, and in particular a crankshaft with connecting rods and pertaining bearings, is the mechanical hub of a reciprocating machine, such as a combustion engine or a compressor. The forces generated by all cylinders act on the crankshaft and its connecting rods and bearings, adding up to the total power output of the reciprocating machine. Therefore, diagnostic monitoring of the mechanism is particularly important. The invention is based on the premise that the beginning of a malfunction of individually disposed bearings or cylinders can be detected relatively isolated to a particular area.
It is known in the art that bearing defects can be detected by acoustic emission as the defect begins and increases in severity, particularly with high-frequency sound or ultrasound. See, for example Acoustic Emission Testing (Nondestructive Testing Handbook; Vol. 5) by Ronnie K. Miller, Paul McIntire, American Society for Nondestructive Testing, 1987; Diagnostic of sliding pairings by means of sound emission analysis, by A. Sturm, S. Kuhlemann, Mechanical Engineering Berling 34 (1985) 3, pages 129-132; Method and arrangement for detecting the cause of wearing symptoms in friction bearings, by A. Sturm et al., DE 41 23 576 A1 & DE 40 28 559 A1.
Sensors for structure-borne sound having a piezo-electrical measuring element are usually used for analyzing the effect of sound emission on solid body structures. However, resistive, capacitive, inductive, piezo-magnetic or optical sensors for structure-borne sound can also be used. A comparison is made between “active” sensors, which require no auxiliary energy, and “passive” sensors, which typically have to be supplied with electrical current or a stimulating light. Generally, the sensors are designed to be mountable on the structure surfaces and to receive structure-borne sound signals transmitted by the structure that reach the surface of the structure. There are, however, differences in the directional characteristics and in the modal sensitivity of the sensors. For example, a sensor can be designed to detect sound waves arriving radially versus axially with a longitudinal polarization or with a transversal polarization in a certain direction.
Errors in the operation of individual cylinders of an internal combustion engine, such as spark failure, knocking or differences in performance as compared to the performance of other cylinders, can be detected by a standard indication method based on measured gas pressures in the combustion chamber, and can also be used for individual cylinder control and monitoring.
Disadvantages of known methods and devices include the fact that the monitoring sensors usually have to be mounted on the exterior of the static structures, and therefore they are far removed from the hub of the mechanical action, i.e. the crankshaft and bearings. This results in inferior detection of beginning bearing defects and of errors in individual cylinder behavior.
Typical mounting of sound emission sensors on the exterior of components having structure-borne sound contact with the static exterior of bearing-structures causes a significant weakening in the signal and inferior localized sound source differentiation because of long sound paths relative to the wavelength of the high-frequency sounds. Both of the above effects result in an undesirable strength ratio between the wanted signal and the underground or interfering signal, and therefore in an inferior monitoring capability. Furthermore, such apparatus is only able to monitor the main bearings. The apparatus is not able to monitor the connecting rod bearings because the sound signals generated in the connecting rod bearings are weakened on their way to the sensors by the complex structures, joints and lubricating oil films of the crank mechanism and the housing. In some instances, the sound signals are weakened to the point of being virtually unusable.
Using combustion chamber pressure indicators for indicating the behavior of individual cylinders suffers from the extreme stress to which the sensors are subjected. At least the more cost-effective models typically do not provide adequate operational reliability and life-expectancy for monitoring functions, whereby alternative solutions need to be found.
An objective of the present invention is to overcome one or more of the aforementioned disadvantages of apparatus known in the art.
SUMMARY OF THE INVENTION
At least one sensor is positioned near the friction bearings to be monitored in the crank mechanism that moves relative to the machine's housing, and the sensor's connection with the evaluation device is guided, at least in part, via the crankshaft. The sensor is mounted in close proximity with the event to be monitored whereby it can be reliably located or detected and analyzed. By guiding the sensor signals out via the crankshaft, the structural element, which is mechanically highly stable, can be advantageously utilized and it can also be provided, for example, that individual signal lines are disposed in the lubricant bores, which are usually present in the crankshaft. This provides a fairly simple apparatus for reliably monitoring the friction bearings in addition to various measured variables that affect the crank mechanism.
In another embodiment of the present invention, a non-contact, preferably capacitive, transmission device is provided for feeding the sensor signals in and/or out of the connecting path that runs in or on the crankshaft, and the transmission device preferably operates without any auxiliary energy. In such embodiment, in the proximity of the connecting rod bearings on the connecting rod or the bearings associated therewith, for example, sensors can be provided which, via a capacitive transmission device or other medium transmit respective measuring signals to the crankshaft from where they are led to the outside, for example, via signal lines present in the lubricating oil bores, for example in the area of the toothed rim on the flywheel where, again via a non-contact transmission device, the output to the monitoring device can take place. This allows continuous monitoring of the connecting rod bearing, for example, where the respective measuring signals can be transmitted to the outside quasi continuously.
In another embodiment of the present invention at least one sensor is formed as a sensor for structure-borne sound for high-frequency sound waves which is advantageous for detecting the beginning of bearing damage.
In another embodiment of the invention, at least one sensor is designed for detecting low-frequency mechanical tensions and deformations and it is preferably disposed on the connecting rod bearing, thus allowing the connecting rod stress to be measured so as to provide a measure for the combustion chamber pressure in the pertaining cylinder, and thus allowing an evaluation of the individual cylinders of an internal combustion engine.
In a further embodiment of the invention, at least one sensor is designed for detecting low-frequency hydraulic lubricating oil pressure on at least one friction bearing of the crank mechanism. This allows both the lubricating oil pressure and the bearing play, and thus wear and tear associated therewith, to be monitored.
In another embodiment of the invention, at least one sensor is designed as a combination sensor for detecting various measured variables, both low-frequency and high-frequency, for joint transmission of the combined signal portions to the evaluation device.
It is particularly advantageous to design the monitoring sensor as a combination sensor for sensing ultrasound emission and for sen
Glaser Josef
Harms Klaus-Christoph
Kling Wolfgang
Rasser Michael
Wojik Karl
AVL List GmbH
McCall Eric S.
Sonnenschein Nath & Rosenthal
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