Title of Invention

INSTANTANEOUS SWEPT VOLUME MEASURING DEVICE FOR RECIPROCATING MACHINES

Abstract

This invention relates to a device, which can be used for measurnii^ instantaneous swept volume of reciprocating machines. Sv\cp{ volume measurements are required for plotting PV diagram >! reciprocating machines, such as compressors, automotive engines The object of this invention is to make the measurcmeni ^w instantaneous swept volume simpler, easier and economical The devise consisting of a cam, which is fixed to the crankshaft o( flywheel, possesses a profile, which conforms to the relation between crank angle and swept volume, A dynamic non-contaci displacement sensor, having adequate frequency response t ^ measure the fast rotating cam profile is positioned to measure ihc profile geometry dynamically. The dynamic non- coniaci displacement-measuring sensor gives electrical output proportional to instantaneous swept volume of the reciprocating machine. The cam can be permanently fixed on reciprocating machines and ilie dynamic non-contact displacement sensor can be fixed whenever the measurements are to be performed, to enable the measuremenis to be performed on number of machines with single sensor lo i minimize the errors in measurement the measurement axis ot the dynamic non-contact sensor and the geometric center of the cam should coincide. Further the center of rotation of the cam and liie geometric reference center of the cam should coincide.

Full Text

This invention relates to a device for measuring instantaneous swept volume of reciprocating machines. The reciprocating machines such as compressors and automobiles, employ a slider crank mechanism for t onversion of reciprocating motion of the piston Into rotary motion and vice versa. The swept volume of the reciprocating machine as a function of crank angle is given by the kinematic relationship of that slider crank mechanism. The relationship is given as Whereas *V' is the swept volume corresponding to crank angle *9* ; *r is the length of the connecting rod; 'r* is the radius of the crank; *D' is the diameter of cylinder; *9' is the position of the crank. The swept volume measurement is required for number of applications. One of the important applications is plotting the PV diagram of reciprocating machines. Presently devices such as crank angle encoders are used to measure the instantaneous crank position; the crank angle encoder provides electrical pulses in accordance to incremental rotation of the crank; an auxiliaiy electronic circuit is needed to convert these electrical pulses into analog voltage proportional to tlie swept volume by using kinematic relationship of the slider crank mechanism employed in that machine. The crank angle measuring devices presently used are expensive and delicate. Therefore installation of these devices on reciprocating machines is cumbersome and time consuming. When swept volume measurements are required to be performed on a number of reciprocating machines, using a single crank angle measuring device available, it would be rather difficult and time consuming to fix and dismantle it to individual machines. It is therefore the bject of this invention is to make the measurement of swept volume easier, economical and suitable for perfonning measurements on number of reciprocating machines. The device for measuring the instantaneous swept volume of the reciprocating machines according to this invention, consisting of a cam,, wliose profile conforms the relation between crank angle and swept volume applicable to particular reciprocating machine, is normally fixed on the crank shaft or flywheel; a non-contact dynamic displacement-measuring sensor to measure the profile of the cam in non-contact principle and provides electrical output. Therefore the electrical voltage proportional to instantaneous swept volume is obtained without the use of auxiliary electronic device. The term 'reciprocating machine' in this specification is intended to include reciprocating compressors, automotive engines, reciprocating pimips and such other machines to which this invention is applicable. Invention provides an instantaneous swept volume measuring device for reciprocating machines comprising: a cam whose profile is generated by superimposing a curve conforming the kinematic relationship between the crank angle and swept volume of the reciprocating machine under consideration over a base circle; and a dynamic non-contact displacement sensor capable of measuring the profile of the rotating cam using non-contact principle and provides analogous electrical output. This invention will now be described with reference to the accompanying drawings, which illustrate, by way of example and not by way of limitation, one of possible embodiments of the device proposed here in. Fig. 1 Illustrating the relationship between crank angle and swept volume of reciprocating machine in polar chart. Fig. 2.Illustrating the cam Fig. 3. Illustrating the arrangement of instantaneous swept volume measuring device. The profile G is generated conforming the relationship between crank angle and swept volume, applicable to that particular slider-crank mechanism employed in the reciprocating machine under consideration; The profile of the cam C is generated by imposing the profile G on the base circle B; The physical shape of the cam C will change if the diameter of base circle B is altered O is the geometric reference center of the cam. The cam C is installed on the crankshaft S of the reciprocating machine in such a way that the rotating axis of the crankshaft and reference center O of cam coincides. A non-contact dynamic displacement sensor D is positioned so that its measuring axis X coincide with the cam reference center O. The sensor D measures the distance between its position and nearest point of the cam profile, which is inUne with measuring axis X, and provides proportional electrical output E. When the piston of the reciprocating machine is at its dead center the maximum point M and minimum point N of the cam C should be in line with the measuring axis X to eliminate phase delay in measurements. During the operation of the reciprocating machine, the cam C rotates along with the crank shaft S and the profile of the cam C is dynamically measured by the sensor D and provides proportional electrical signal output E. The signal E may be given directly to an oscilloscope or any indicating / measuring instrument. The holes H are provided on the cam C in appropriate locations, to balance the mass of the cam C with reference to O. The power supply P powers the sensor D. By this arrangement the instantaneous swept volume is measured. The unique advantage of this device is that, being less expensive and rugged, the cam can be permanently fixed on each reciprocating machine. The dynamic displacement sensor being light and portable can be fixed whenever measurements are to be performed. Therefore using a single dynamic non-contact displacement sensor itself instantaneous swept volume measurement can be performed on a number of reciprocating machines. The dynamic non-contact displacement sensor can be included as part of instrumentation that measures the performance of these reciprocating machines by plotting PV diagram. Another advantage of this device is that it does not require auxiliary electronic circuitry for converting crank angle in to voltage proportional to swept volume. In multi cylinder reciprocating machines, a single cam can be used to measure the instantaneous swept volume of any cylinder by fixing the dynamic non-contact displacement sensor in appropriate location to accommodate inherent phase shift in the motion of pistons in each cylinders .Other variations of this device are that the cam can also be made of different types like internal cam , cylindrical cam, wedge cam. The terms and expressions herein are of description and not of limitation, there being no intention of excluding any equivalents of the features herein described and illustrated but it is understood that various other embodiments of the devise proposed herein are possible with out departing from the scope and ambit of this invention. I claim 1. An instantaneous swept volume measuring device for reciprocating machines comprising: a cam whose profile is generated by superimposing a curve conforming the kinematic relationship between the crank angle and swept volume of the reciprocating machine under consideration over a base circle; and a dynamic non-contact displacement sensor capable of measuring the profile of the rotating cam using non-contact principle and provides analogous electrical output. 2. The instantaneous swept volume measuring device for reciprocating machines as claimed in claim 1 wherein the radial dimension of the said curve superimposed on the base circle is scaled up to fit the measuring range of dynamic displacement sensor. 3. The instantaneous swept volume measuring device for reciprocating machines as claimed in claim 1 wherein the said cam is dynamically balanced. 4. The instantaneous swept volume measuring device for reciprocating machines as claimed in claim 1 wherein the said cam is an intemal cam or cylindrical cam or wedge cam. 5. The instantaneous swept volume measuring device for reciprocating machines as claimed in claim 1 wherein the said dynamic non-contact displacement sensor is fixed in such a manner to either provide minimum voltage or maximum voltage when the piston of the reciprocating machine is at its dead center to avoid phase delay in swept volume measurements. 6. The instantaneous swept volume measuring device for reciprocating machines as claimed in claim 1 wherein the said dynamic non-contact displacement sensor is anyone from the group of sensors consisting non contact laser displacement sensor, eddy current displacement sensor and proximity sensor. 7. A instantaneous swept volume measuring device for reciprocating machines substantially as herein described and as illustrated in the accompanying drawings.

Documents:

1057-che-2003-abstract.pdf

1057-che-2003-claims filed.pdf

1057-che-2003-claims granted.pdf

1057-che-2003-correspondnece-others.pdf

1057-che-2003-correspondnece-po.pdf

1057-che-2003-description(complete) filed.pdf

1057-che-2003-description(complete) granted.pdf

1057-che-2003-drawings.pdf

1057-che-2003-form 1.pdf

1057-che-2003-form 19.pdf