DE102004057462B4 - Method for the evaluation of measured data - Google Patents

Abstract

Method for evaluating measured data of cylindrical components, in which the deviation of the measured contour from the circular shape is determined, the measured data being recorded by means of a measuring device having the following construction: - at least three sensors arranged equidistantly within the cylinder, - the sensors are arranged relative to one another firmly on a sensor carrier, - the sensors measure the distance against the inner wall of the cylindrical components, characterized in that by means of the sensors (4) at least two distance measurements (m1i, m2i) take place in the same plane of the cylindrical component, the sensor carrier (3) with the sensors (4) arranged thereon is rotated between the distance measurements (m1i, m2i) by an angle alpha about the longitudinal axis of the cylindrical component, the angle alpha being an integer multiple of the quotient 360 ° by the number (k ) of the sensors (4) is.

Description

The invention relates to a method for evaluating measured data according to the preamble of patent claim 1.

The measurement of cylindrical parts is particularly important for the design and manufacture of internal combustion engines. In the classic reciprocating engine, the working space of the engine is formed by a cylinder tube, which is delimited by the cylinder head and piston. The arranged inside the cylinder piston is sealed by means of piston rings against the cylinder wall. The piston ring fills the gap between the cylinder and the piston, and its filling capacity during operation of the engine has a significant influence on the operating behavior of the engine. The blow-through losses, the oil consumption and the friction losses depend significantly on the sealing surfaces of the piston rings to the cylinder. During operation of the engine, in addition to the lifting movement, so-called secondary piston movements occur during the movement of the piston, in which case the piston displaces horizontally within the cylinder eccentrically or tilts within the cylinder bore. Furthermore, the cylinder liners are not ideal circular cylindrical due to the manufacturing tolerances and the thermal deformations occurring during operation. There are deviations from the circular shape, which are referred to as cylinder distortion. Low-distortion cylinder tubes are advantageous in terms of sealing behavior, friction values and wear. For a good seal between the piston and cylinder wall, a cylinder contour is sought, which can be compensated as well as possible by the shape filling capacity of the piston rings. With regard to this shape-filling capacity and the geometric boundary conditions in the engine, circularity deviations of the 2nd, 3rd and 4th order are particularly relevant.

For the construction and production of low-distortion cylinder tubes, it is therefore necessary to determine the cylinder distortion preferably during operation of the internal combustion engine.

In the prior art, various devices and measuring methods for this purpose are previously known. A summary of the prior art devices and methods can be found in the series Progress Reports VDI Series 12, No. 469 by Olaf Josef. In particular, the internal measuring method (starting from page 26 of said report), in which sensors are introduced into the piston and measure the distance between the piston and the running surface during operation of the engine are suitable for measuring the distortion in dynamic engine operation. Various types of sensors are described, such as styli, optical sensors, and Hall sensors. Advantageously, a plurality of sensors are arranged circumferentially distributed. The recorded distance values can thus be distinguished in a subsequent evaluation method in distance changes due to the secondary piston movement and changes in distance due to the cylinder distortion. The problem with all measuring methods is that for measuring the cylinder distortion a very high accuracy of the measuring device and the evaluation must be given, since the cylinder distortion in the range of a few microns (typical measuring range <50 microns) must be detected. Among other things, the specimen-specific scattering of the sensors and the deviations caused by the deformation of the sensor carrier (piston or piston ring or separate carrier element) influence the measurement.

If only one sensor element is used for the measurement (see Progress Report p. 29), then the specimen-specific scattering between sensors is not given, but it must be assumed for the successive, different measurements that the superimposed second piston movement in the same operating states of the Motor remains the same over the course of the measurement. The device can scan through the rotating piston upper part with a sensor a large part of the cylinder surface, but the measurements must be performed sequentially. The device has by the rotating piston upper part on a high construction costs.

The use of multiple circumferentially distributed sensors simplifies the process of synthesis of cylinder distortion and secondary piston motion from the distance measurements. For this purpose, various evaluation methods are known in the prior art. For example, the assumption of a circular reference contour is described. This is advantageously within the cylinder contour near the bottom dead center, since the influence of the screw connections neglected and the cylinder distortion can be simplified to temperature-proportional diameter enlargement. The description of the deviation from the circular shape is generally described by means of a Fourier analysis, as in Dunaevsky, V. V .: Analysis of distortions and conformability of piston rings. Tribology Transactions Vol. 33 (1990) No. 1, pp. 33-40. The contour determined by the measured data is simulated by means of a Fourier analysis and, based on an order analysis of the Fourier series, the piston secondary motion can be isolated from the measured data since this corresponds to the first order of the function obtained by the Fourier analysis. The first-order function components are subtracted from the measurement data, and the cylinder contour can then be synthesized from the coefficients of Fourier higher-order analysis.

From Fujimoto, H., et al.: Measurement of Cylinder Bore Deformation by Means of a Turning Piston with a Gap Sensor during Engine Operation, JSME International Journal, Series 2, Vol. 3, 1991, pages 391-396 and the publications DE 44 06 132 A1 and DE 100 52 360 A1 are devices for measuring cylinder deformations known.

The problem with the evaluation method described in the prior art is the high accuracy required for the distortion measurement, which must be measured on the basis of the low distortion values. In particular, the sample-specific deviations of the individual sensors and their transmission chain significantly influence the measurement result. It is therefore necessary to increase the measurement data acquisition and its evaluation, in particular with regard to accuracy, while largely avoiding or compensating for measurement errors.

The invention is therefore based on the object to provide a method for evaluating measurement data of cylindrical components, which determines the delay of the cylinder contour, in particular the 2nd, 3rd and 4th default with high accuracy.

This object is achieved according to the invention in the generic method for measured value detection by the characterizing features of claim 1.

According to the invention, a measurement is advantageously carried out within the cylinder with at least three sensors which are arranged fixedly relative to one another in their relative position, at least two measurements being made in a measuring plane of the cylinder. For each measurement, the distance values of all sensors arranged on the carrier are recorded. At least one further measurement is subsequently carried out, the advantage of the invention being that the measurement takes place by a defined angle value offset from the first measurement in the same plane of the cylinder. The angle value by which the measurements are offset is an integer multiple of the quotient 360 ° by the number k of the sensors. It is thus achieved that the same cylinder position is measured by a second sensor with respect to the distance to the sensor, wherein in the second measurement, another sensor at the same position of the cylinder inner wall takes the distance to this. Based on the second measurement, it is possible to determine the absolute sensor errors relative to each other. This offers the possibility, in particular for the determination of the cylinder distortion greater than the first order, with the knowledge of the relative errors of the sensors to each other to obtain a highly accurate measurement result.

Advantageously according to the invention, the cylinder distortion is described as a deformation value which, starting from the center position of the cylinder, is composed of the sum of the distance measurement value from the center, the measurement error and a component from the eccentricity of the sensor carrier to the center. Based on the distance measurement data, the secondary movement of the piston and the sensor carrier arranged thereon is mathematically eliminated from the measurement data by describing the contour and its deviation from the circular shape by means of a Fourier analysis and the first-order fraction in which the piston secondary motion is reflected the contour description is removed and the further processing of the data is carried out by means of a contour synthesized from the higher-order components.

Advantageously, according to the invention, the data are recorded in the dynamic operation of the internal combustion engine, wherein the distance values of all sensors are recorded in different planes of the cylinder and subsequently the sensor carrier is rotated by the angle alpha and another measurement series of distance measurement values is recorded in the same planes of the cylinder.

Further details of the invention are described in the drawing with reference to schematically illustrated embodiments.

Hereby show:

1 a schematic representation of a measuring device for determining the distance measured values for the cylinder distortion measurement;

2 a model representation of the cylinder distortion starting from the measured values of a sensor carrier equipped with 8 sensors;

3 (Page 1 illustration new method) a model representation of the cylinder distortion with the distance measured values and the description according to the invention of the eccentricity, measured value and systematic sensor errors;

4 a representation of the measured values of the distortion measurements with rotation of the sensor carrier by the angle alpha.

1 shows a schematic representation of a measuring device for determining the distance measured values for the cylinder distortion measurement. In a cylinder 1 is relatively movable to this a piston 2 arranged. On the piston 2 is a sensor carrier 3 , which is formed in the form of a ring, arranged in which circumferentially distributed 8th sensors 4 are attached. The sensors 4 measure the distance to the opposite inner wall of the cylinder 1 and the measurement signal is transmitted to an evaluation unit (not shown). The transmission can be done telemetrically, optically or by wire. The sensors 4 can be on both optical, inductive or mechanical principle working distance sensors. Advantageously, the sensor carrier 3 made of a nearly rigid and less thermally deformable material, to minimize the influence of the displacement of the sensors to each other during the measurements.

2 shows a model representation of the cylinder distortion of a equipped with 8 sensors sensor carrier. From the data obtained by the distance measurement, a contour can be reproduced by means of the Fourier analysis. Schematically represented is a section through a cylinder with an ideal circular contour 1a and a cylinder contour 1b with a cloverleaf-shaped cylinder distortion of the fourth order, which is represented in the order analysis, the Fourier series describing the contour, as a fourth-order fraction. The delay of the cylinder contour 1b is shown greatly enlarged. The higher-order components are particularly important for the distortion measurement, since these deviations from the circular shape can not be filled by the mold filling capacity of piston rings. The fourth-order cloverleaf distortion is a typical deformation phenomenon for a 4-bolt cylinder.

3 shows a model representation of the cylinder distortion with the deformations v _i . The deformation v _i is based on the distance measurement values m _i by the description according to the invention by means of the eccentricities e _y ; e _x and the systematic sensor error f _{x of} the respective distance measured value m _i described. Starting from the sensor carrier 3 measure the sensors 4 against the cylinder wall. For the distance measured values m _i still the radius of the sensor carrier 3 be added to determine the distance from the center and thus the deformation v _i . If the sensor carrier has no deviation from its reference position and the distance measurement values are ideally not affected by errors, then the sum of distance measurement values m _i and the radius of the sensor carrier correspond to the deformation v _i . If there is no cylinder distortion, the deformations v _{i are} all the same size. The cylinder distortion can thus be described by the deviations of the deformations v _i from the circular reference contour. The sensor errors f _{i are} superimposed on the distance measurement value m _i and according to the invention are included in the description of the deformation in order to compensate them as described below by another measurement offset by an integer multiple of the quotient 360 ° / number of sensors.

4 shows a description of the deformations v _i , wherein two measurements per plane are performed and the deformation is thus measured twice at one point of the measuring plane, but with different sensors. The indexing of the measured values is thereby extended by an index n, which indicates the number of the measurements. The left-hand representation shows measured values for the first measurement, wherein the distance measurement values m _{ni are} recorded with n = 1. According to the invention, the sensor carrier is rotated by an integer multiple of the quotient 360 ° / number of sensors for a second measurement. The right-hand illustration therefore shows a measurement with a sensor rotated by 45 ° with respect to the first measurement. For example, sensor number 2 now measures the piston-cylinder distance measured by sensor number one in the previous measurement. The deformations and the eccentricity can thus be described by means of the following equations.

für die Messung n = 2 v₁ = m₂₂ + f₂ – e_2x v₂ = m₂₃ + f₃ + e₂·sin45° – e_2y·cos45° v₃ = m₂₄ + f₄ + e_2y v₄ = m₂₅ + f₅ + e_2x·cos45° + e_2y·sin45° v_s = m₂₆ + f₆ + e_2x v₆ = m₂₇ + f₇ + e_2x·sin45° – e_2y·cos45° v₇ = m₂₈ + f₈ – e_2y v₈ = m₂₁ + f₁ – e_2x·cos45° – e_2y·sin45°

For the measurement n = 1 arise v ₁ = m ₁₁ + f ₁ -e _1x v ₂ = m ₁₂ + f ₂ + e _1x · sin45 ° - e _1y · cos45 ° v ₃ = m ₁₃ + f ₃ + e _1y v ₄ = m ₁₄ + f ₄ + e _1x · cos45 ° + e _1y · sin45 ° v ₅ = m ₁₅ + f ₅ + e _1x v ₆ = m ₁₆ + f ₆ + e _1x · sin45 ° - e _1y · cos45 ° v ₇ = m ₁₇ + f ₇ - e _1y v ₈ = m ₁₈ + f ₈ - e _1x · cos45 ° - e _1y · sin45 °

for the measurement n = 2 v ₁ = m ₂₂ + f ₂ - e _2x v ₂ = m ₂₃ + f ₃ + e ₂ · sin45 ° - e _2y · cos45 ° v ₃ = m ₂₄ + f ₄ + e _2y v ₄ = m ₂₅ + f ₅ + e _2x · cos45 ° + e _2y · sin45 ° v _s = m ₂₆ + f ₆ + e _2x v ₆ = m ₂₇ + f ₇ + e _2x · sin45 ° - e _2y · cos45 ° v ₇ = m ₂₈ + f ₈ - e _2y v ₈ = m ₂₁ + f ₁ - e _2x · cos45 ° - e _2y · sin45 °

The equation system is over-determined in itself. The relative sensor errors can thus be determined analytically. The cylinder distortion, in particular greater than the first order, can be determined with high accuracy by knowing the absolute measurement error of the sensors relative to one another. The deformations v and the eccentricity e describe the cylinder distortion very accurately, whereby the absolute measurement errors of the sensors relative to each other can be compensated by the second measurement.

The measurements continue to be carried out in different measuring levels in order to record three-dimensional cylinder distortion.

In a development of the invention, the determination of the absolute measurement errors of the sensors takes place relative to one another by a second measurement offset by the angle α, where α is an integer multiple of the quotient 360 ° by the number (k) of the sensors ( 4 ). After the sensor errors have been determined, further intermediate values can be measured, for which purpose the sensor carrier can be swiveled by any angle value. These measurements are now possible with high accuracy, since from the two previous measurements, the absolute errors of the sensors are known relative to each other.

LIST OF REFERENCE NUMBERS

1

cylinder

1a

Cylindrical contour circular

1b

Cylinder contour with fourth order distortion

2

piston

3

sensor support

4

sensors

v

deformation

f

sensor error

e

eccentricity

i

Numbering of the sensors

y

Proportion in y-direction of the eccentricity

x

Proportion in the x direction of the eccentricity

n

Number of the measurement

m

distance measurement

k

Number of sensors

Claims (6)

Method for evaluating measured data of cylindrical components, in which the deviation of the measured contour from the circular shape is determined, the measured data being recorded by means of a measuring device having the following construction: - at least three sensors arranged equidistantly within the cylinder, - the sensors are arranged relative to each other firmly on a sensor carrier, - the sensors measure the distance against the inner wall of the cylindrical components, characterized in that by means of the sensors ( 4 ) at least two distance measurements (m _1i , m _2i ) take place in the same plane of the cylindrical component, wherein the sensor carrier ( 3 ) with the sensors ( 4 ) between the distance measurements (m _1i , m _2i ) is _rotated by an angle alpha about the longitudinal axis of the cylindrical component, wherein the angle alpha is an integer multiple of the quotient 360 ° by the number (k) of the sensors ( 4 ) is. Method according to claim 1, characterized in that the distance measurements (m _i ) within a cylinder ( 1 ) of an internal combustion engine, wherein the sensor carrier ( 3 ) in the cylinder ( 1 ) movable piston ( 2 ) or one on the piston ( 2 ) rotatably arranged piston ring and the sensors ( 4 ) between the distance measurements (m _1i , m _2i ) within the cylinder ( 1 ) are rotated about its longitudinal axis by the sensor carrier ( 3 ) is rotated by the angle alpha and subsequently the relative sensor errors (f _i ) are computationally compensated by a second measurement. Method according to Claim 1 or 2, characterized in that the distance measurement values (m _ni ) recorded in one plane per measurement (n = 1, 2,...) Are evaluated by evaluating the measured distance values by means of a Fourier analysis, by the cylinder contour is reproduced by means of a Fourier series and the secondary movement of the sensor carrier is eliminated by removing the first-order function parts of the Fourier series, wherein for each measurement in the same plane of the cylinder distance measurements (m _ni ) present, which characterize the cylinder distortion in the respective plane. Method according to one of the preceding claims, characterized in that the cylinder distortion over a deformation (v _i ) based on the eccentricity (e _x , e _y ) and the measured distance values (m _i ) and the sensor error (f _i ) of the respective sensor defined becomes. Method according to one of the preceding claims, characterized in that for the distance measurement values (m _i ) of each sensor on the basis of the at least two (n = 1, 2, ...) offset by the angle alpha distance measurements (m _ni ) an equation system of the deformations (v _i ) and the eccentricities (e _x , e _y ) are set up and solved for the calculation of the deformations v _i and the cylinder distortion is described on the basis of the deformations. Method according to one of the preceding claims, characterized in that the measurements take place in different planes of the cylinder, wherein only in a fixed position of the sensor carrier to the piston, the distance measured values (m _1i ) are recorded for different levels of the cylinder and recording further measured values (m _ni ) which are offset by the angle alpha, after taking the distance measurement _values (m _1i ) in the desired cylinder _planes .

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