CN1015740B - Piston ring radial pressure distribution measuring device by local thin wall process and its calibration method - Google Patents

Abstract

The present invention relates to a device for measuring the radial pressure distribution of a piston ring by using a partial thin wall method and a calibration method thereof. The device adopts a cam-chuck type elastic clamping device. A piston ring is firstly placed in a ring gauge and then is tightly clamped by the elastic clamping device, which not only ensures the flexible rotation of the piston ring during measurement without any scratch, but also ensures accurate position fixing so as to obtain an exact value of measurement. The device is calibrated by a method of inflation pressurization or deflation depressurization so as to measure a corresponding value of pressure in the device and the strain of the thinnest position. The functional relationship between radial pressure and the strain of the thinnest position is obtained by treating discrete data in a mathematical mode.

Description

Piston ring radial pressure distribution measuring device by local thin wall process and its calibration method

The present invention relates to the mechanical measurement technique field, is to measure device and the scaling method thereof that radial pressure of piston ring distributes.

Piston ring is the vital part of reciprocating machines such as the internal combustion engine, air compressor in the mechanical engineering.Solving piston ring packs into behind the cylinder and contact pressure distribution P radially between the casing wall _γ=f(θ) problems of measurement, significant on engineering.The free state type line of piston ring is the requirement according to machinery, and selected radial pressure distribution function obtains by CAD.Then, in the processes process, realize such molded lines.Theoretically, the piston ring with this molded lines is packed into after the cylinder, should reproduce original selected radial pressure and distribute, but in fact deviation may occur.The radial pressure that if can measure piston ring exactly distributes, and just can judge the reason that deviation occurs, is process issues or CAD design problem; Realized that as work in-process originally selected radial pressure distributes, then can judge that by bench test whether selected pressure distribution is rationally with effective.This shows that the radial pressure of measuring piston ring distributes, very important to the design of piston ring with production.But, make it become technical in the last hundred years a great problem because it relates to the measurement of contact stress.

Once adopted multiple measuring method in the past, but all because of its in the application that do not put it over of the shortcoming on the principle or on the measuring accuracy.One-point method in these methods and multipoint method only can be measured one or more concentrated stress rather than pressure.The thin strip process that famous West Germany Goetze factory is adopted is fixed the piston hoop during to end-gaps with metal sheet band earlier with piston ring, measure the coordinate figure of 12 points on its profile then, calculates the radial pressure distribution of piston ring again by Calculation Method.This method only is a kind of half Calculation Method of partly measuring, and is not measuring method completely.

The purpose of this invention is to provide a kind of device and the scaling method thereof that can directly measure the radial pressure of piston ring distribution easily and accurately.

Basic thought of the present invention is based on the principle that thin-walled is measured, and promptly cuts one arc and form the ring gauge with local thin wall on the garden tube of certain wall thickness, and its internal diameter is identical with the piston ring nominal diameter, sticks miniature foil gauge at its thinnest part.When piston ring placed ring gauge, its radial pressure that acts on the thin-walled place caused the distortion of foil gauge tension and output and the corresponding microstrain of radial pressure.For measuring the radial pressure at piston ring point place, need this point is rotated to subsides foil gauge place, this just requires piston ring positioning of rotating effectively, and unlikely scratch ring gauge and piston ring; And when measuring radial pressure numerical value, make piston ring be in the normal condition of non-clamping again, to obtain correct measured value.The present invention has adopted the elastic clamp device of cam-chuck formula, has realized purpose of the present invention.

Apparatus structure of the present invention as shown in Figure 1.Form by ring gauge 1, ring-shaped work pieces 2, spring 3, spring supporting spring 4, two offset cams 5, inverted T-shaped part 6, the little axles 7 of cam, on ring gauge 1, cut one arc, make this place form local thin wall (thickness is generally between 0.35～0.65mm), Fig. 2 is that ring gauge 1 cuts the cut-away view after arc.Miniature foil gauge 9 is posted at the thin-walled place.The center pit of ring-shaped work pieces 2 is passed by the stem portion of inverted T-shaped part 6, and 2 top is by the upper surface rest of ring gauge 1, and its underpart is the garden annular, the diameter coupling of its external diameter and ring gauge 1.Inverted T-shaped part 6 bottoms are garden shape dish, and its diameter also is complementary with the diameter of ring gauge 1, and a hole is arranged at the top of its center-pole, pass by the little axle 7 of cam, two offset cams 5 are contained on the little axle 7, are positioned at the both sides of the intermediate bar of inverted T-shaped part 6, interrelate with spring supporting spring 4.Spring 3 is placed between spring supporting spring 4 and the ring-shaped work pieces 2.During measurement, earlier piston ring 8 is placed between the garden dish and ring-shaped work pieces 2 of inverted T-shaped part 6, places then within the ring gauge 1; The little axle of rotating cam 7 is when the outshot of cam 5 is in the below and when being pressed on spring supporting spring 4, spring 3 pressurizeds will push away on the inverted T-shaped part 6, and piston ring is flexibly compressed.At this moment, rotate ring-shaped work pieces 2, can be with piston ring 8, inverted T-shaped part 6 rotates together.When measuring the radial pressure at piston ring 8 certain some place, the measured point is gone to the little axle 7 of rotating cam behind the thinnest part of ring gauge 1, make the outshot of cam turn to the top, spring 3 is loosened, inverted T-shaped part 6 is borrowed deadweight and is descended, piston ring is unclamped, thereby measured the radial pressure that piston ring acts on the ring gauge thinnest part by foil gauge 9.

In order when measuring piston ring 8 correctly to be located, this device has adopted groove to aim at method.Promptly on the upper end of ring gauge 1, be carved with scale mark, for example, on ring-shaped work pieces 2, fix a locating piece 10 every scale mark at 5 ° of quarters.During use, the sideline of locating piece is aimed at the end-gaps of piston ring 8, borrow elastic clamp device to clamp the back then and rotate, when the sideline of locating piece 10 when a certain scale mark on the ring gauge 1 overlaps, certain a bit is in the thinnest part of ring gauge 1 promptly to represent piston ring 8, so just can exactly all measured points of piston ring be transferred to the thinnest part of ring gauge 1.Except that above-mentioned line aligning method, also available angular transducer positions.

What paste at ring gauge 1 thinnest part in the said apparatus is miniature foil gauge, and that directly measure is the microstrain μ ε at this place, and actual needs is the radial pressure value of piston ring.Therefore, also said apparatus is demarcated among the present invention, to set up the corresponding relation of microstrain and radial pressure, concrete scaling method is as follows: add the gland bonnet plate respectively on the both ends of the surface up and down of ring gauge 1, tighten up by nut, tensimeter and the valve that can charge and discharge gas are housed on the gland bonnet of upper end, inflation in the ring gauge 1 is pressurizeed by valve, tensimeter indicates the pressure reading in the ring gauge 1, measures the strain value μ ε of thinnest part foil gauge with statical strain indicator.Corresponding to a series of pressure value P _{γ i}, can record corresponding strain value μ ε _i, i=1,2 ... n, but general n=10; With discrete point (P _{γ i}, μ _{ε i}) carry out mathematics manipulation, as use least square method, promptly get the radial pressure P of this device _γFunctional expression with strain μ ε.For different devices, P _γAlso different with the corresponding relation of μ ε, therefore, each device all will carry out single demarcation with said method.Therefore when the radial pressure at actual measurement piston ring point place,, relend the P of this device as long as record corresponding to this strain value μ ε _γ-μ _εCorresponding relation, the radial pressure value P that promptly obtains at this some place _γ

Use the said method timing signal, valve can adopt the charging valve of bicycle tyre, just can be to ring gauge 1 inflation pressurization with common inflator.The decompression timing signal can be exitted as long as unscrew nut, to reduce the pressure in the ring gauge 1.

The piston ring of corresponding different cylinder diameters, said apparatus should be designed to the different ring gauge of size.Especially for the piston ring of big cylinder diameter, ring-shaped work pieces 2 in the device and inverted T-shaped part 6 can be designed to knockdown respectively, are beneficial to processing, but measuring principle and method and above-mentioned identical.The stem portion of inverted T-shaped part 6 also can be designed to knockdown, is beneficial to the elastic force of regulating spring 3, and feasible clamping force to piston ring is adjustable.

The apparatus structure that the present invention proposes is simple, and it is convenient to demarcate, and can measure the radial pressure at certain some place on the piston ring arbitrarily.Because piston ring and garden ring gauge are Continuous Contact, guaranteed this and its stress identical in cylinder, thereby the degree of accuracy of measured radial pressure distribution is high.For example, once the radial pressure of piston ring distribution value that this device is recorded was carried out numerical integration, tried to achieve radial pressure mean value, compared with the radially mean pressure that records with thin strip process, and the two is very approaching, and this proves absolutely that this device is effectively and reliably.

Fig. 1 is the structure cut-away view of apparatus of the present invention.

Fig. 2 is that apparatus of the present invention ring gauge is at the simple cut-away view that cuts after arc.

Be an embodiment below, when the nominal diameter of piston ring 8=95mm is described, to the resulting P of this device normalization _γWith μ _εThe numerical value corresponding tables:

During pressurization:

Sequence number, i 123456789 10

Pressure, bar, P _γI 0.32 0.60 0.905 1.195 1.50 1.86 2.10 2.40 2.69 2.96

Microstrain, μ ε _i47 91 135 177.2 221 275 308 352 392 430

During decompression:

Sequence number, i 123456789 10

Pressure, bar, P _{γ i}0.295 0.60 0.895 1.195 1.50 1.80 2.10 2.40 2.70 2.96

Microstrain, μ ε _i42 90 131.6 176 220 265 308 352 394.2 430

According to above data, can obtain force value K corresponding to the unit microstrain with least square method _pFor:

$K_P=\frac{\underset{\mathrm{i\; =\; 1}}{\overset{n}{\mathrm{\Σ}}}{\mathrm{(P}}_{\mathrm{r\; i}}{\mathrm{)\; (\; \mu \; \epsilon }}_i)}{\underset{\mathrm{i\; =\; 1}}{\overset{n}{\mathrm{\Σ}}}{\mathrm{(\; \mu \; \epsilon }}_i{)}^2}{\mathrm{=\; 0.683\; \times \; 10}}^2\frac{\mathrm{bar}}{\mathrm{\mu \; \epsilon }}$

Claims (3)

1, a kind of local thin wall method is measured the device that radial pressure of piston ring distributes, by ring gauge 1, ring-shaped work pieces 2, spring 3, spring supporting spring 4, two offset cams 5, inverted T-shaped part 6, the little axle 7 of cam is formed, it is characterized in that on ring gauge 1, cutting one arc, the thickness that makes its thinnest part is between 0.35～0.65mm, post miniature foil gauge herein, the interstitial hole of ring-shaped work pieces 2 is passed by the stem portion of inverted T-shaped part 6, top is by ring gauge 1 upper surface institute rest, the bottom is an annular, its external diameter and ring gauge 1 diameter are complementary, inverted T-shaped part 6 bottoms are the garden dish, diameter and ring gauge 1 diameter are complementary, the top of its stem portion is porose, is passed by the little axle 7 of cam, and two offset cams 5 are contained on the little axle 7, be positioned at the both sides of inverted T-shaped part 6, interrelate with spring supporting spring 4, spring 3 is located between supporting spring 4 and the ring-shaped work pieces 2, thereby has constituted elastic clamp device.During measurement, piston ring 8 is positioned between the garden dish and ring-shaped work pieces 2 of inverted T-shaped part 6, places then within the ring gauge 1, the little axle 7 of rotating cam, by spring 3, make on the part 6 to push away, piston ring elasticity is clamped, rotational parts 2 again, the measured point of piston 8 is gone to the thinnest part of ring gauge 1, releasing spring 3, and unclamp piston ring, can measure.

2, according to the described measurement mechanism of claim 1, it is characterized in that on the upper surface of above-mentioned ring gauge 1, being carved with scale mark, fixing a positioning block 10 on ring-shaped work pieces 2 is used for the aligning location of piston ring at ring gauge 1.

3, a kind of scaling method that is exclusively used in the described radial pressure of piston ring measurement mechanism of claim 1, upper and lower end face at ring gauge 1 seals plate respectively, wherein on the cover plate of upper end tensimeter and the valve that can charge and discharge gas are housed, it is characterized in that by valve inflation pressurization in the ring gauge 1, strain value μ ε i with strain-ga(u)ge measurement ring gauge 1 thinnest part reads a series of pressure value P by tensimeter simultaneously _{γ i}, i=1,2 ... n is with discrete point (P _{γ i}, μ ε _i) handle with least square method, promptly get the radial pressure P that installs _γFuntcional relationship with strain μ ε.

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