PROCESS AND APPARATUS FOR CONTACTLESS AND ACCURATE GAUGING OF MACHINE PARTS

Abstract: A process and an apparatus for contactless, accurate gauging of machine parts such as crankshafts (Av) and the like, comprises photoelectric gauging of bearing surfaces and other finely finished surfaces. After a machine part is inserted into a frame the radially directed surfaces of the machine part are scanned by a laser scanner included in a measuring device (30) which can be moved axially and operates in a radially extending plane (33), and further, the position of the axially directed surfaces of the machine part is determined with a measuring device (44) that can be moved both axially (x) and radially (y). During measuring the machine part can be rotated and its rotational position is determined by an angle gauge (28).

Description: PROCESS AND APPARATUS FOR CONTACTLESS AND ACCURATE GAUGING OF MACHINE PARTS Technical Field The present invention relates to a process for contactlessly and accurately gauging serially mass produced machine parts which have a rotational axis defined in their design along which there are situated finely finished surfaces that are distinct from one another, which method comprises irradiating the surfaces with light that gives rise to electic signals from which a measure¬ ment number for the surfaces is determined. The invention also relates to an apparatus by means of which such a method is practiced. A type of machine part with which the invention is particularly but not exclusively concerned is shafts that have beari^π sur¬ faces finished to accurate dimensions and which must b suged before they are assembled. Examples of such shafts are crank- shafts and camshafts that are used in combustion engines and which are now often produced in prolonged series on automatic machines. Here there are included in the finished machine part on the one hand a number of bearing surfaces concentric to the rotational axis that will fit in the main bearings of an engine block, and on the other hand one or several bearing surfaces situated between the main bearing surfaces and eccentric to them, for the engine connecting rod or connecting rods. Usually sur¬ faces like those just mentioned are bounded in the axial direc¬ tion by ring-shaped bearing surfaces situated at right angles to the axis of rotation. The motor manufacturer places a high demand for dimensional and form accuracy on mashine parts with such bearing surfaces, so that for every produced unit it is desired to set forth absolute values for all existing diameter dimensions and shaft radii as well as the angle position for crankshaft surfaces. Gauging thus has as its object to establish that tolerances prescribed in the design are maintained with respect to the roundness of the sur¬ face, its conicity and straightness, as well as with respect to whether the centerline of the main bearing coincides with the rotational axis of the shaft. Also, other checking items can exist, based upon those obtained absolute values. It is thus an accurate geometrical total picture of the measured object that one desires to obtain. State of the Art Such a total picture could heretofore only be measured up with three coordinate machines, but these operate too slowly to be used in a production which is set up according to the assembly line principle, for example automobile engine production. In such applications gauging has therefore usually been carried out manually, with conventional mechanical or electromechanical measuring devices, or alternatively by means of specially con- structed measuring machines which also take for granted contact with the surfaces that are to be gauged. These heretofore known measuring methods are often dependent upon expensive fixtures that must be rebuilt every time a change is made in a drawing dimension for the machine parts that are to be gauged. A wholly manual gauging of the type of measured object with which the in¬ vention is particularly concerned is very time consuπύng and therefore makes overall gauging impossible, and it is also diffi¬ cult to obtain from all of the measurement data, without waste of time, a total picture of the geometry of the measured object that precedes the decision to approve or reject an object. Summary of the Invention It is therefore an object of the present invention to bring forward a method and an apparatus that facilitates an accurate gauging of serially mass produced machine parts and which takes place according to the principle of contactless photoelectric measuring. The intent in this is to eliminate the inconveniences that are associated with heretofore known measuring methods and apparatus and in this way to endeavor to carry out gauging of machine parts quickly and with the least possible manual contri¬ bution without neglecting the requirement for a high quality in the measuring. A particular object of the invention is to provide a process and apparatus that is well adapted for the gauging of crankshafts, camshafts and the like and which in this way solves the problem of accurately and contactlessly gauging both bearing surfaces that are concentric or eccentric relative to the rotational axis and bearing surfaces that extend in the axial direction. In this respect it is a desire that the process shall be suitable for being carried out in the apparatus in a predetermined, pref¬ erably programmable and wholly automatic procedure which takes its start from a machine part being carrid forward in a given manner to the apparatus, after which the latter carries out all of the measuring operations in a sequence and produces the required measurement data for the machine part in suitable form, and which procedure is repetitive so that it can be applied to an automatic production system. This object and intent is realized according to the invention through the process and apparatus obtained with the characte¬ rizing features set forth hereinafter in the claims. Description of Drawings The invention will now be explained with reference to the accompanying drawings, wherein: Figs. 1 and 2 are side views of a crankshaft and of a crankshaft, respectively; Fig. 3 is a view in perspective of apparatus according to the invention; Fig. 4 is a view partly in section showing means for coupling a shaft end to the apparatus; Figs. 5 and 6 show in perspective a measuring device of the apparatus for radial measurement and axial measurement, respec¬ tively; Fig. 7 is a diagram showing a measuring signal that is obtained in measuring of a radial measurement; and Fig. 8 illustrates a compensating procedure for measuring of a crankshaft bearing surface. Application The process and apparatus of the invention is described herein¬ after in an application which particularly relates to production of engine shafts and similar machine parts, which can here be considered to be produced in long series on an automated pro¬ duction line. At its end the machine parts will be given a final inspection wherein all functionally important measurements will be checked, which, according to the invention, takes place con¬ tactlessly and at a rate that can be matched to that of the production line. Two typical examples of measured objects that are current in such applications- are illustrated in Figs. 1 and 2, respectively showing schematically a crankshaft A and a camshaft A. for a four-cylinder automobile engine. The shafts have a center or rotational axis defined in their design which is represented in the finished shaft by a dowel hole c made in each end of the shaft. At separate places along the rotational axis there are on both shafts a plurality of finely finished surfaces which should be accurately gauged, namely the radially directed surfaces r which are provided for the bearings of the respective shafts and which should be concentric to the rotation axis £, the similarly radially directed but eccentrically disposed surfaces r that respectively form crank bearing and cam surfaces, as well as the axially directed surfaces which bound the bearing surfaces just mentioned. Usually such surfaces are ground to accurate dimensions, and high tolerance requirements apply to correctness in both dimensions and form. Also, since the invention arises from the desire for a process and an apparatus for accurate, contactless gauging of machine parts with such a complicated geometry as that here described, where the advantages of the invention are greatest as compared with known technique, it is obvious that the invention can also be applied for machine parts with simpler configuration and having a lesser number of finely finished surfaces. Frame In the embodiment of the invention that is illustrated in Fig. 3 the apparatus comprises a frame that is generally designated by 1 and is constructed of steel sections, of which a pair of lengthwise and transversely extending beams 2 and 3, respecti¬ vely, are shown at the top of the figure, as well as two inwardly directed brackets 4. There are similarly corresponding brackets on the other longitudinal side of the frame, supported on the lengthwise extending beams 2 and in turn supporting a stiff parallelepiped part 5 forming a downwardly turned horizontal plane 6 with pilot bearing (not shown). By this means there is accurately defined a horizontal coordinate direction x. designa¬ ted by the arrow at 6. The frame 1 further has in its ends located in front of the block 5 two downwardly hanging consoles 7, 8 forming the attach¬ ment for two tailstocks 9, 10 located in the lower part of the apparatus. The console 8 also supports a positioning motor 11 which is set up to rotate a feed screw 12 that extends in the _ direction under the plane 6 and the rotational movement of which can be accurately determined with the aid of an optical angle transmitter (eπcorder) 13. The Measuring Zone The tailstocks 9, 10 are provided in a known manner with opposite mutually displaceable conical dowels 14 of which the dowel that is comprised in the tailstock 9 distinctly appears in Fig. 4. A straight line 15 that connects the tips of the dowels and extends horizontally and parallel to the coordinate direction x. defines the measuring axis of the apparatus which in the present embodiment for engine shafts can have an effective length on the order of 0.5-1 m. Around the measuring axis there is a space that forms a three-dimensional measuring zone 16 that is large enough so that the machine parts to be gauged in the apparatus can be introduced between the dowels and rotated around the measuring axis. In the drawing is shown a crankshaft A , corres¬ ponding in principle to Fig. 1, which has been introduced into the measuring zone and which for gauging is so fixed to the tailstocks 9, 10 that the centerline of the crankshaft coin¬ cides at least in the main with the measuring axis 15. A linear optical transmitter 17 detects the position of the tailstock 9. For fixing a machine part in the measuring zone each tail- stock cooperates with a remotely controlled operating device secured in the consoles 7, 8, suitably a hydraulically damped pneumatic actuating cylinder. Such an operating device, designated by 18, can translate the dowel in the tailstock 10 in the forward direction along the line 15, suitably towards and from a prede- ter ined end position. The second tailstock 9 has a similar operating device 19, partly hidden in the drawing, which can move that tailstock in the same directions, and the operating device is suitably so designed that when the tailstock meets the end of a machine part installed in the measuring zone, that part is gripped with a certain axial force that produces a stable engagement between the machine part and the tailstocks. In connection with two tailstocks there are devices whereby the installed machine part is coupled with the measuring system of the apparatus mechanically and according to the techniques of measurement. The tailstock 9 thus has, farthest forward, a gauge 20 which, as appears from Fig. 4, comprises two measuring tips 21, each having its segments 22 facing in opposite directions and which project out parallel each from its plate 23 supported on the dowel 14. The plates are mutually biased laterally, and provided that the machine part A has in that end of it a keyway j< fitting the measuring tips, oriented at a predetermined angular position relative to the measuring axis 15, the gauge 20 with the segment 22 will feel the sides of the keyway during forward movement. In this there is produced from a measurement instrumentality 24, which determines the breadth of the spring 25 between the plates, an electrical signal which in part indi- cates the presence of the keyway and in part provides a measure¬ ment of its width and its angular position relative to the main bearings of the crankshaft. The same tailstock further comprises a carrier formed with an arm 26 projecting outwardly in the same angulr position as the measuring tips. It is made so that it can get into the keyway < like a key so that the crankshaft A is thereby nonrotatably coupled to a drive motor connected with the carrier. The second tailstock 10 has a mechanism that will accompany the rotational movement of the crankshaft and comprises a pin 27 that projects out parallel to the dowel 14. It is biased in the axial direction and is so arranged that when rotational move¬ ment begins it snaps into one of the holes in a circle of holes in the flange f of the crankshaft. Through the coupling of the mechanism with the crankshaft an angle gauge 28 arranged on a prolongation of the measuring line 15 will produce a pulse train representing the turning movement that is processed in a computer. The latter can be zeroed by a signal which is produced when the measurement procedure is started and which represents an initial position of the keyway, for example straight up, so that the contents of the calculator will thereafter continuously denote the existing position of rotation of the crankshaft. Measuring Device for Radial Measurement A dimension that is essential for the measurement process of the invention is determination of diameters and radii for the vital surfaces of a machine part, exemplified in Fig. 1 by the main bearing surface r and the crank bearing surface r . For this purpose the apparatus has a measuring device 30 which at its exterior has the form of a yoke that stranddles transversely across the measuring zone 16 and is suspended by a first measur¬ ing table 31. The latter is accurately controlled relative to the fixed frame part 5 so that it can be displaced along its plane 6 in the ^ direction. By means of a nut in the table cooperating with the feed screw 12, the table, and with it the measuring device 30, can be brought to occupy any arbitrary position along the measuring line 15 by means of the positioning motor 11, angle transmitter 13 and a servo circuit. The measuring device is photoelectric and works with laser light that is emitted by a scanning system jhich, in a known manner, can consist of a laser transmitter that emits laser light in the form of a narrow beam, a rotating mirror which deflects the laser beam, and a lens that directs the light parallel and from which the beam 32, as illustrated in Fig. 5, is sent out towards the measuring zone 16 in a plane 33 that extends at right angles to the measuring axis 15. The parts just mentioned are contained in one leg 34 of the measuring device, that left one in Figs. 3 and 5, while in the other leg 35 there is an optical arrangement that directs and focuses tha laser light received from the measuring zone onto a photodetector from which an electric measuring signal is emitted. The system can operate in principle like the apparatus shown in Fig. 1 of our Swedish patent appli- cation 8602110-2. Owing to the movement of the rotating mirror, the laser beam 32 that has passed through the lens is caused to be quickly and cyclically translated parallel to itself in the plane 33, each time from an initial position, for example down in the lower part at 36, to a final position 37, and in this the displacement is somewhat greater than the effective height of the measuring zone. In this manner the laser beam will scan an object that is in the measuring zone and is intersected by the plane 33. Assum¬ ing that the object is a part of the crankshaft A in Fig. 3 that is bounded by the main bearing surface r , the scanning pattern will be obtained that is illustrated in Fig. 5 and which is characterized in that the bearing surface blacks out the laser light within a field corresponding to the diameter £ of the surface, or, more precisely expressed: the distance in the direction of translation j of the laser beam that is indicated by the two tangents 38, 29 to the bearing surface. This distance, which in principle corresponds to the interval in which the electrical measuring signal from the above mentioned photo¬ detector does not appear, is represented by a corresponding rotational angle of the rotating mirror of the laser scanner, and by letting the measuring signal give; rise to an accurate determination of this angle there is obtained a diamter measure¬ ment D_ seen in the direction y_. Out of the measurement the calcu¬ lator unit of the apparatus determines a corresponding measure- ment number, which can be obtained with an accuracy as high as cm. That the measurement is taken in the mentioned direction on the main bearing surface is at the same time recorded with the help of the signal from the angle gauge 28. The rotational angle of the mirror can be determined by the method described in our Swedish patent application 8602111-0 (= PCT/SE87/00229) . In the case of the application of the invention here under con¬ sideration the requirement for correctness of dimensions and form is not satisfied by an individual diameter measurement for the bearing surface, the above procedure is repeated at the same time that the crankshaft is rotated, suitably through one revolution, either continuously or in steps, and each time a measurement is taken. In this manner there is obtained a series of measurement values, for example ten, that are taken in dif- ferent directions on the bearing surface and at equal angular divisions. A comparison between these measurement numbers, which are of course equivalent from a measuring technology standpoint with those an inspector gets with a micrometer he holds in different angular positions, shows whether maximum and minimum tolerances have been maintained and whether the surface has any ovalness, but no more than in this manual measuring method is it possible to calculate roundness out of these measurement numbers since they are not space oriented. The straightness and existing coπicity of the bearing surface are important criteria in the inspection of crankshafts and similar machine parts. According to a special characteristic of the invention, the scanning system is therefore arranged so that it emits three simultaneous laser beams, each of which sweeps its plane, and with the position of the plane in the x ^ direction so selected that it intersects the bearing surface at a repre¬ sentative location. In Fig. 5 those that are compared with the above described scanning plane are designated 33' and 33". These three beams now sweep cyclically in their plane in analogy with what was stated for the laser beam 32, and when the crankshaft simultaneously rotates the measuring device forms three series of measurement values that issue in parallel channels and are taken at points that are evenly distributed in the axial and peripheral direction over the surface of the inspected part of the crankshaft. Provided that the measurement values are space oriented, they can be used for determining whether the surface satisfies the above mentioned criteria. How a radially directed surface can be gauged by means of a measuring device 30 in accordance with the preferred embodiment of the invention, to check its roundness, straightness and coni- city, will now be briefly described with reference to Fig. 5 and 7. The latter figure shows the amplitude of the detected measure ¬ ment signal as a function of the position of the laser beam 32 in the sweep direction y. Through the first part of the sweep movement when the laser beam unimpededly passes the bearing surface r the signal has a largely constant maximum value V.. In the instant when the beam passes the point of tangency 38 the signal falls steeply but with a certain slope by reason of light diffusion, after which the signal has its minimum value V ? during the interval when the bearing surface blacks out the light. When the beam passes the other tangency location 39, the singal rises and quickly re¬ turns to its high value V 1 . It maintains this until, just before the final position 37, the beam reaches a reference position 40 which is defined by a sharp-edged screen 41. This is arranged like a knife in the fixed structure of the measuring device 30 so that during measuring its inwardly directed edge transverse to the plane 33 has a constant known position in the coordinate direction _. This occurs because for every time that the beam sweeps over the plane 33 the measuring signal amplitude will have exactly the same y_ value just before the final position 37 is reached, and in an unambiguous manner falls from the value V 1 to the value V_, and this naturally independently of the measured object. The said _ value can therefore be seen as an extremely accurate reference or a fixed point in the plane 33. For the reason that the measuring signal does not fall or rise vertically at the points 38-40, the signal can not be directly employed for determining a measurement without its first being processed in a circuit that compares the signal with a threshold value V f which is suitably £ (V.. - V„). The circuit produces a square wave (depicted at the bottom of the diagram) during the time the measuring signal exceeds the threshold value and for every scanning cycle three discrete y_ values are thus obtained which represent points 38-40 in Fig. 7. Out of them the appa¬ ratus can now calculate two related, space oriented measurement values Y - Y τ 3 τ 1 Y - Y T 3 2 which represent the distance from the "reference knife" y, to the lowest and the highest points, respectively, on the bearing surface. Through an earlier conducted calibration measurement and compensation for nonunifor ities that occur in the intensity of the laser light within the scanned field, which procedure is described in our above mentioned Swedish patent application 8602110-2, the two values can finally be translated to exact measurement numbers, expressed in applicable measuring units. These measurement numbers, which together with a related angle measure¬ ment from the angle gauge 28 are generated, measuring cycle for measuring cycle, while the bearing surface r rotates through a revolution, make it possible to determine unambiguously the form of the bearing surface in the plane 33 and to thus determine whether the pertinent demands concerning roundness are satisfied. By arranging a "reference knife" 41* and 41" in each of the two other planes, and in the above explained manner processing the measuring signals in all three channels, the bearing surface can be further checked as to whether it is satisfactorily straight, that is, whether the three points on the surface that in an arbitrary angular position form its generatrix, lie in a straight line, and whether the surface has any conicity, that is, whether the line is inclined in relation to the measuring axis 15. In the description of the function of the measuring device 30 it has heretofore been assumed that the scanned surface is concentric to the measuring axis 15 and thus changes position unmeasurably by reason of the rotation of the machine part. In practice, such precision in manufacture is often unattainable, and a function in the measurement checking of the crankshaft A can therefore be to calculate how great the actually existing eccentricity of a certain bearing surface r is, expressed as a lateral translation of its geometrical center in relation to the center of another such bearing surface or to the centerline £ defined by the dowel holes d_. This function is solved by ana¬ lyzing in a special calculating program the above mentioned space related measurement numbers and angle measurements, and one can thus also obtain information about the angular position, calculated, for example, from the keyway k_, at which the center of the bearing surface is displaced. The same measuring method and analysis of obtained measuring data can in principle be employed for all other curved surfaces such as the eccentric surfaces r on the shafts in Figs. 1 and e 2 which constitute the main bearing surfaces and cam surfaces, respectively. When such surfaces are "plotted" it is of special importance, insofar as measurement values are taken while the measured object rotates continuously, that consideration be ' given to the turning motion. This is made clear in Fig. 8 which shows in cross-section a main bearing part of a crankshaft A . During gauging of the bearing surface r the shaft rotates in t_ * the direction of the arrow 42, and by reason of this the bearing surface manages to shift a small distance transverse to the laser beam, which is taken to be horizontal, while it sweeps over the bearing surface. This measurement , which is obtained from the detector unit, will thus be too large if the beam is assumed to sweep upward and downward, and the calculator unit is there¬ fore so programmed that it calculates, from the angular posi¬ tions^.. and C 2 which exist when the laser light is broken off and resumed, respectively, a sum corresponding to Δ D and auto- matically corrects the measuring number for by subtracting that sum. With diameter measurement corrected in this manner and radial measurement taken in different rotational positions of the crankshaft or camshaft, an accurate check of measurements and form can be made, taking into account all of the above men- tioned criteria. A measurement important for main crankshaft bearing surfaces that can also be checked with the measurement values taken with the measuring device 30 is the crank radius R ^ , and if that measurement is taken at three axial positions with the use of three parallel beams, according to Fig. 5, inspection can also be made of the main bearing surface or the parallelism of its central axis with the measurement axis 15 or the center £ of the shaft axis. Measuring Device for Axial Measurement In the preferred embodiment of the invention shown in the drawings the gauging of the diameter and radius measurements of machine parts is shown coordinated with a checking of axial measurement, in the example of the crankshaft directed to the ring-shaped shoulder surfaces that bound the main bearing and cam bearing surfaces r and r and one of which, designated by a is shown in broken lines in Fig. 8. This gauging is taken care of by a measuring device 44, the operative parts of which are enclosed in a fork-shaped frame 45 opening downward toward the measuring axis 15 on one side of the measuring device 30. In its upper portion the axial measuring device is united with a second measuring table 46 which is suspended beside the first measuring table 31 and is moveable in the x ^ direction in two alternative ways, one involving its being locked relative to the table 31 for following along with it during positioning of the measuring device 30, while in the second alternative an indepen¬ dent movement in the x_ direction can be carried out relative to the first table 31. This relative movement, which can take place only in a zone bounded by the table 31 and is produced by a second positioning motor 47, has for its function to permit the axial measuring device 44, after the table 31 and the measur¬ ing device 30 have come into a suitable position for diameter measuring, to alone carry out the movements which, in dependence upon the design of the machine part, are necessary for being able to gauge the axial surfaces . In this way time is saved and it is only the smaller and lighter axial measuring device that needs to be moved for the last mentioned gauging moment. The relative motion is measured by a linear transmitter 48 or the like. The axial measuring device is also adjustable in the y_ direction by means of the second measuring table 46, which goes in that direction and is enclosed in at third measuring table 49 inte¬ grated with the frame 45. The movement in the vertical direction is obtained from a third positioning motor 50 and one of the driven screws 51 and the movement is measured by an angle en¬ coder 52. The frame 45 has in two box-shaped housings 53, 54, seen in Fig. 3 on the farther and nearer sides, respectively, of the measuring zone, two systems of light sources 56, 57 and, cooperating with them, light detectors 55 and 58, respectively, working in oblique ray paths across the measuring zone that are mirror-imaged relative to one another. The light from the light sources, which is preferably infrared, is emitted from openings 59, 60 so that it is focused at two axially distinct points that can be sup- posed to be located in the middle of the measuring zone, like the point P_ in Fig. 8, and towards which the light detectors are also focused. The arrangement is best seen in Fig. 6 which illustrates the optical function when length measurement is taken between two opposite shoulder surfaces a,, and ~ „ . The focal point P 1 for the system 57, 55 is, as shown, located to the right along the measuring axis 15, and the point P_ for the other system to the left, nearer the keyway end. Through a preprogrammed vertical movement of the third measur¬ ing table 49, suited to the design, the axial measuring device is so preadjusted that the light from the light source 57 will be able to meet the shoulder surface a 1 that is turned toward it in the figure, and at the same vertical position of the measuring device the light from the other light source 56 will be able to meet the shoulder surface a n facing forward in the figure. For the length measuring moment there remains now to displace the axial measuring device 44 in the x. direction with the use of the positioning motor 47, past the position in which the point P. falls on the surface a. and the light from the trans¬ mitter 57 is reflected by that surface to the receiver 55, as well as the position where the receiver of the second system receives light from its transmitter after reflection at the point ?m . These positions are registered by signals from the receivers 55 and 58 and from the calculator unit is received corresponding length measurements for the shoulder surfaces related to the reference plane defined in the design. Measuring Sequence It is assumed that an apparatus according to the invention, in the embodiment here described, is installed at the end of a production line on which finished crankshafts or similar machine parts are transported towards the apparatus in close succession on a band. The apparatus has its measuring axis 15 oriented above the transport band and parallel with the centerline £ for a crankshaft that comes along in a waiting position under the appa- ratus and which waits its turn to be gauged. The procedure begins with said crankshaft being brought up by a lifter 61 into the measuring zone, where it is briefly held by the lifter while it is fixed between the dowels 14. When the keyway j< is checked, the driver motor is started and the angle gauge 28 has entered into function, gauging can begin. In this the two measuring devices 30 and 44 are at the one end of the measuring axis 15, for example the right one in Fig. 3. The measuring device 30 is now positioned in a position selected according to the design right under the main bearing surface r located nearest the end of the crankshaft, after which it is inspected, which is carried out while the shaft is rotated one revolution. The measuring device is now moved in the x_ direc¬ tion to a new position suitable for the first crank bearing surface r . At the same time that the latter is inspected the axial measuring device 44 now carries out the relative movements in the __ direction and the jx direction that make possible the determination of the position of the first axially directed surface , which can be regarded as facing toward the end of the crankshaft, like the surface a_ in Fig. 6. When the measuring device has taken these measurements, a new mutual movement takes place such that the diameter for another main bearing surface as well as an axial measurement for the previously mentioned main bearing can be determined. The measur- * ing device thus continues, in a constrained, preprogrammed move¬ ment scheme, to gauge surface after surface on the crankshaft all while it is rotated. When all ot the surfaces have been gauged, the measuring device returns to its initial position, a remover (not shown), which is located behind the lifter 61 in the transporting direction, now goes up under the crankshaft and takes it away when the dowels 14 spread apart, after which the released crankshaft is placed upon the transport band. At the same time the lifter has again stepped into function to bring up a new crankshaft in the posi¬ tion for gauging. The whole procedure takes only about half a minute. During the measuring sequence all obtained measuring data are processed in the calculator unit of the apparatus, and through the analysis described generally above it becomes possible shortly after the gauging of a machine part to classify it as acceptable or not acceptable. In the gauging of a cam shaft A. or other machine part on which critical axial measurements for shoulder surfaces or the like do not exist, the measuring device 44 does not perform any function. In such circumstances it is therefore possible to simplify the process and the apparatus according to the inven¬ tion as compared with the herein described embodiment.

Claims: 19 Claims 1. Process for contactlessly and accurately gauging serially mass produced machine parts which have a structurally defined rotational axis (c) along which there are finely finished sur- 5 faces (r, a) that are located separately from one another, which process involves lighting the surfaces with light that gives rise to electrical signals from which measurement numbers for the surfaces are determined, characterized by process steps of introducing the machine part (A) into a measuring frame (1) that 10 has a threedimensional measuring zone (16) through which there ? is a well defined measuring axis the length of which exceeds the length of the rotational axis (£) and a carrier (26) rotatable relative to the frame, so that the rotational axis coincides with the measuring axis, after which the machine part is secured 15 to the carrier in an unambiguous angular position relative to it, that the machine part (A) is brought into rotation around the measuring axis (£) by means of the carrier (26), that a radial measuring device (30) which can move through the measuring zone (16) in a direction parallel to the measuring axis 20 and has a laser scanner operating in a plane (33) at right angles to the measuring axis is adjusted to a position in which a first radially facing surface (τ is intersected by said plane, after which the surface is scanned by a laser beam (32) which is rapid¬ ly translated parallel to itself in the plane (33) so that the 25 laser light that passes the surface is detected, that there are recorded mutually connected values relating to thό measurement " corresponding to the radial extension (D) of the surface in the direction of translation (y_) of the laser beam at which the laser beam is blacked out by the surface, the momentary 30 rotational position of the machine part (A) and the position of adjustment of the radial measuring device (30), so that measure¬ ment numbers for the surface and its axial position can be cal¬ culated and compared with tolerance values given in the design, that the radial measuring device (30) is adjusted to a new posi- tion suitable for a second radially facing surface (r) which is gauged in an analogous manner, that the process is repeated so that all surfaces that are to be checked have been gauged in a sequence, after which the machine part (A) is released from the carrier and taken out of the measuring frame (1) so that a new machine part can be introduced into the measuring zone and gauged during a repetition of said sequence. 2. Process according to claim 1 for gauging of crankshafts (A ) and similar machine parts (A. ) that have bearing surfaces (r ) which are eccentrically positioned relative to the rotational axis (£) and extend parallel to it, characterized in that every value which relates to such a surface and is obtained from the radial measuring device (30) in the form of said measurement (D) while the machine part rotates is corrected by increasing or decreasing the measurement by a sum (ΔD) that corresponds to the movement, calculated in the direction of displacement of the laser beam, that the bearing surface (r ) carries out by reason of the rotation while the measurement is taken. 3. Process according to claim 1 or 2, characterized in that the machine part (A) is rotated one revolution for every radially facing surface (τ), that during this the radial measuring device (30), through a cyclical function of the laser scanner, produces a plurality of values at uniform intervals for said measurement of the surface and that these values individually are combined with the corresponding momentary rotational positions of the mac ine part, for determination of the roundness of the bearing surface. 4. Process according to claim 1, 2 or 3 characterized in that the radially facing surface (τ) is irradiated by three parallel laser beams (32) mutually displaced in the direction of the measuring axis (15), each of which gives rise to its measurement, through which the conicity of the surface together with its parallelism with the rotational axis can be determined. 5. Process according to any of claims 1 - 4, characterized in that said measurement is determined in such a manner that a measuring signal is emitted in the two instants during the scan¬ ning of the surface (r) when the detected laser light has a predetermined level (V _), preferably the mean value of the two levels (V., V„) that are respectively obtained when the laser beam (32) passes by and is blacked out by the surface, and which predetermined level is permitted to represent an imaginary point (38, 39) in the displacement direction (4) of the laser beam where a light radiation is tangent to the surface, and that each point is related to a reference (40) that is obtained by means of a sharp-edged screen (41) located in a known position in the outer portion of the scanning plane (33) which the laser beam scans each time a diametral or radial measurement is determined. 6. Process according to claim 1 for gauging of machine parts (A ) that have bearings with shoulder surfaces (a) facing in the direction of the axis of rotation (£) , characterized by the further process step that an axial measuring device (44) which, in carrying out said sequence, can be moved partly axially, part- ly radially relative to the measuring axis (15), at opposite sides of the same respectively emits and receives light in oblique directions relative to the measuring axis, which direc¬ tions intersect one another at a point (P) at the measuring axis, that the axial measuring device (44) is adjusted to a radial position in which, according to the design of the machine part, the light can be reflected from a shoulder surface (a) on the machine part, that the axial measuring device thereafter is moved axially so that it passes the position where the shoulder sur¬ face contains said point (P), and that this position is recorded for determining the axial measurement number for the shoulder surface , after which the procedure is carried out in an analogous manner for the remaining shoulder surfaces on the machine part (A ). 7. Process according to claim 6, characterized in that two light beams are sent out (at 59, 60) and received in such direc¬ tions that two intersection points (P_., P_) are obtained that are displaced, respectively, toward the one and the other end of the rotational axis .£) from the position where the light beam is sent out, so that the axial measurement numbers relating to shoulder surfaces (a.., a ? ) facing in opposite directions can be determined. 8. Process according to claim 1 and 6, characterized in that for every machine part (A) , while the entire measuring sequence is being carried out, the radial measuring device (30) and the axial measuring device (44) move from one end of the measuring axis (15) to the other in a constrained movement scheme that comprises axial and radial displacement of the axial measuring device on the radial measuring device. 9. Process according to any of the preceding claims, ofr gauging of shafts and similar machine parts that are produced with a keyway (k) in one end and with dowel holes 00 in both ends that are concentric to the rotational axis (£), characterized in that, for introduction into the measuring zone (16), the machine part (A ) is first supported on a transporter (61) that displaces the machine part into the measuring zone from under¬ neath, during which the keyway (k) has a predetermined rotational position and is near the carrier (26), that when the rotational axis 0O comes near to or coincides with the measuring axis (15) a dowel (14) moving parallel to the latter axis is engaged from each direction against the machine part (A ) so that the dowels engage into the dowel holes 00 at the same time that a key be¬ longing to the carrier is led into the keyway so that the tur¬ ning moment needed for rotation of the machine part can be transferred by way of the key and the keyway. 10. Process according to claim 9, characterized in that at the beginning of rotation the end of the machine part that is oppo¬ site its keyway end is nonrotatably coupled with a mechanism (27) that imparts rotational movement to an angle gauge (28) for producing a signal indicating the momentary position of rotation of the machine part (A ) in the frame, related to the keyway (10. 11. Process according to claim 9, characterized in that upon insertion of the key (26) into the keyway (k) there is intro¬ duced therein a measuring gauge (20) for checking the width of the keyway. 12. Apparatus for contactless and accurate gauging of series mass produced machine parts that have in their design a defined rotational axis 00 along which there are finely finished sur¬ faces (r, a) that are located separately from one another, com¬ prising means for irradiating the surfaces with light, light sensitive detector means for generating electrical signals upon irradiation, and means for determining from the signals measurement numbers for the surfaces, characterized by a measuring frame (1) that forms a three-dimensional measuring zone (16) through which there extends a well defined measuring axis (15), the length of which exceeds the length of the rotational axis 00 of the machine parts that are to be gauged, a carrier (26) rotatable relative to the frame and which, when a machine part is so introduced into the measuring zone (16) that its rotational axis coincides with the measuring axis, can be connected with the machine part in an unambiguous angular position relative to it, so that by means of the carrier the machine part can be caused to rotate around the measuring axis, a radial measuring device (30) that is movably arranged in the frame (1) and is arranged to be able to move through the measuring zone (16) in a direction 00 parallel to the measuring axis and has a laser scanner that operates in a plane (33) at right angles to the measuring axis and is arranged to scan, by means of a laser beam (32) which the scanner rapidly displaces parallel to itself in said plane, a radially directed surface (r) which is intersected 24 by the plane, and a detector that receives the laser light that passes the surface during scanning to produce a measurement value corresponding to the radial extent of the surface from the measurement in the direction of displacement (y_) of the laser beam in which the detector is prevented by the surface from receiving laser light, a measuring instrumentality (13) cooperating with the radial measuring device (30) arranged to emit a signal indicating the position in the direction 00 of the measuring axis of said plane (33), an angle gauge arranged to emit a signal idicating existing rotational position of the machine part (A) during scanning of a surface (_r), and means for processing said signals and calculate therefrom measurement num¬ bers for the radial extension and axial position of the surface. 13. Apparatus according to claim 12, characterized in that the laser scanner is arranged to produce three parallel laser beams (32) that are mutually displaced in the direction (x) of the measuring axis (15), and that the detector has separate channels for detecting laser light, one for each laser beam, so that three measurement numbers can be obtained for the radial extent of a surface. 14. Apparatus according to claim 12 or 13, characterized in that the measuring device (30) has a sharp-edged screen (41) so positioned in the outer part of the scanning plane (33) that it blacks out the laser beam (32) after it has scanned a surface, so that there is thereby optaiήed a reference for accurate deter¬ mination of diameter measurement and roundness of the surface. 15. Apparatus according to claim 12 for gauging of a machine part (A ) that has bearings eith shoulder surfaces (a) facing in the direction of the rotational axis, characterized by an axial measuring device (44) that is movable partly axially, partly radially relative to the measuring axis (15) and which at oppo¬ site sides of the latter has a transmitter (56, 57) and a re- 25 ceiver (55, 58) for light which are directed at an oblique angle relative to the measuring axis towards a point (P_) at it, so that when the axial measuring device (44) is adjusted to a radial position in which the design of the machine part allows light from the transmitter (56, 57) to be reflected by a shoul¬ der surface 00 on the machine part, and with that position is moved axially, a location of the axial measuring device is passed where the shoulder surface ( a) contains said point (P_), from which location the axial measurement number for the shoul- der surface can be determined. 16. Apparatus according to claim 15, characterized in that the axial measuring device (44) has two arrayed transmitters and receivers with which for the one array said point (P_.) is lo¬ cated closer to the one end of the measuring axis (15) than the transmitter (57) and the receiver (55), while for the other array the point (P 2 ) is located nearer the other end of the measuring axis, so that with the axial measuring device the axial measure¬ ment number can be determined both for the shoulder surface (a,.) facing toward said one end and for the shoulder surface (a ? ) facing toward the other end. 17. Apparatus according to claims 12 and 15, characterized in that the frame (1) supports a first measuring table (31) that can be accurately positioned in an arbitrary axial position along the whole measurement zone (16) and beside which the radial measuring device (30) is fixed, a second measuring table (46) that supports the axial measuring device (46) is supported beside the first measuring table (31) so that it follows along therewith in its positioning and is arranged to position the axial measuring device (44) axially within a defined portion of the length of the measuring zone through axial displacement relative to the first measuring table, and a third measuring table (49), which supports the transmitter and receiver (55- 58) of the axial measuring device, is supported beside the second measuring table (46), so that it follows it during its positioning and is arranged to adjust the said transmitter and receiver to the radial position provided for axial measuring by right angle displacement toward or from the measuring axis (15) relative to the second measuring table (46). 18. Apparatus according to any of the preceding claims for gauging shafts and similar machine parts (A ) with a keyway 0<) in one end and a dowel hole (d) in each end that is con¬ centric with the rotational axis 00, characterized in that the measuring axis (15) is defined by means of two oppositely directed dowels (14) which are movable relative to the frame (1), which define the measuring zone (16) in the axial direction and which, with the machine part (A ) so inserted that its rotational axis in the main coincides with the measuring axis (15) and the keyway (J ) is near the carrier (26) and having a predetermined rotational position, can be forced axially inwardly until each dowel (14) engages in the dowel hole (d), and that the carrier has a key (26) arranged to be guided into the keyway (k) and to transfer from the carrier to the machine part the turning moment needed for its rotation. 19. Apparatus according to claim 18, characterized in that in the end of the measuring axis (15) opposite the carrier and the key (26) there is a mechanism (27) to which the angle gauge is coupled, which mechanism is arranged to be nonrotatably coupled with the adjacent end of the machine part (A ) after it is fixed by means of the dowels (14) and connected with the carrier. 20. Apparatus according to claim 18, characterized in that the key (26) is combined with a gauge (20) that can be introduced into the keyway (k) for gauging its width.

Inventors: MARKLUND CHRISTER, STENBERG LARS, MARKLUND, CHRISTER, STENBERG, LARS
Applicants: ELOPTRICON AB
Application year: 1987
Main classification: G01B11
IPC codes: G01B5, G01B11