A METHOD AND AN APPARATUS FOR JOINING CRANK SHAFTS

Abstract: Method and apparatus for joining within accurate geometrical tolerances two crank shaft halves (D, M) via a crank pin (6) into a complete crank shaft (1). Each crank shaft half has a shaft (2, 3) which over a flange (12) continues into a crank disk (4, 5) in at least one of which there is at an accurate distance from the shaft made a through bore (7 and 8, respectively) for the crank pin. The crank pin may be separate or integral with one crank shaft half. The crank shaft halves are joined in that the crank pin is pressed into said bore(s) by the application of a press force (P) to the outer sides of the crank disks. During the pressing-in of the crank pin (6) into the bores (7, 8) of the crank disks the shafts (2, 3) of the crank shaft halves are carefully aligned in dependence of the accurate tolerances and are retained relative each other within said tolerances, while the crank pin in turn is allowed to be lined up by the bores of the crank disks, taking advantage of the possibilities of inclination of the crank pin relative to the crank disks and within the deformation zone of said press fit joint.

Description: A method and an apparatus for oining crank shafts Technical field The present invention relates to a method and an apparatus for joining, within accurate geometrical tolerances two crank shaft 5 halves via a crank pin into a complete crank shaft, said crank pin being separate or part of one crank shaft half, each of which crank shaft halves comprises a shaft which by an intermediate flange con¬ tinues into a crank disk, at least one of which having, at an accurate distance from the crank shaft, a through bore for receiving the 10 crank pin. The crank shaft is completed in a pressing operation by a press fit joint between the crank pin and the respective crank disk bore. Background art In prior art methods and apparatus of the above mentioned kind it has 15 appeared that ' the tolerances which in the manufacturing unavoidably must exist for the crank shaft halves, particularly for the centre distance of the crank pin bore to the shaft centre of the crank shaft half as well as the angle deviation of the crank pin bore from paral- lεllism to the shaft of the crank shaft half, during the pressing-in 20 procedure of the crank pin result in that the shafts of the complete crank shaft do not become parallel and do not either meet the tole¬ rances of shaft - concentricity. Therefore, after the joining pro¬ cedure a straightening operation has to be performed which is undesi- . __. r_able_since_ " .i causes.de ormations which give rise to lasting stresses 25 in the components of he press fit joint, said stresses then being superposed on to the normal stresses which appear during the rotation αf the crank shaft-in an internal combustion engine. Such, undesirable " stress superpositions can cause breakage of the crank shaft, resulting in a shorter life duration than it should have normally. 30 Disclosure of the invention The object of the present invention is to remedy said drawbacks by ..providing a method and an apparatus of the kind mentioned by way of " introduction for joining crank shaft halves, said Imethod and apparatus producing a complete crank shaft the shafts of which, in the joining ' procedure, become parallel and concentic within stipulated tolerance In this way the expensive and from a technical point of view undesi¬ rable straightening operation is dispensed with and the crank shaft 5 retains its full strength. This object is achieved by a method wherein the crank disks are plac in opposing relation, the crank pin being aligned with the borε(s) o the crank disk(s), and the shafts of the crank shaft halves are accur tely aligned and retained within accurate tolerances during the press 10 ing-iπ of the crank pin into said bore(s), while permitting the crank pin to be lined up by said bore(s) and thereby permitting inclination of the crank pin from perpendicularity to the crank disk(s) within th possibilities of the deformation zone of the press fit joint. The apparatus for performing the method of the- invention for joining 15 said two shaft halves includes a press tool having two sections which are movable to and from each other in a pressing direction, means for positioning the crank disks in opposition and the crank pin ' aligned with the bore(s) of the crank disks there between, a shaft fixing sto in each of said sections for aligning said shafts in the pressing dir 20 tion and a movable jaw cooperating in with the respective stop in a transversal plane to the shaft for retaining the shaft within the stipulated tolerances, said stops and jaws having in at least one of the press tool sections small axial extension lengths for permitting tilting of the shaft retained, pull means for seizing the shaft ends 25 and holding the crank disks against supporting means, at least that press tool section which permits tilting having universally pivotable crank disk supporting means, as well as measuring means for acting on said tiltably retained shaft for measuring in two perpendicular planes, one of which includes the axes of the shafts and the cran 30 pin, the angular deviations of the shaft in relation to predetermined master angular values, and tilting means acting on the shaft in said planes for tilting the shaft. Brief decription of the drawings A preferred embodiment of the apparatus of the invention and its operation for joining two crank shaft halves via a separate crank pin will be described below in detail with reference to the enclosed drawings. Fig. 1 illustrates in a perspective view the components of the press fit joint of the crank shaft, said components being shown after a first short portion of the pressing-in procedure, as well as the geometry of the crank shaft and the forces which during the joining procedure act upon the crank shaft halves. Fig. 2 in a view of the complete joined crank shaft shows the accurate geometrical tolerances which by way of example are to be met by the crank shaft. Fig. 3 shows at a larger scale a section through the press fit joint of " ; the joined crank shaft and illustrates as a principle the inclination ' .. ' .of the crank pin within the deformation zone. Figs. 4 and 5 in partly sectional side elevational views, illustrate a joining apparatus according to the invention far the crank shaft halves and the crank pin of the crank shaft, said press fit joint being shown in different stages of the joining procedure. . Fig.6 is a sectional view taken along a line VI-VI in fig. 5 and shows ■ as a principle sensors for measuring the actual angular positions of the shafts of the crank shaft halves in the joining apparatus. . Fig. 7, in a side elevational view of said joining apparatus, shows sensors for the determination, and adjustable stop means for limiting the length of the pressing-together movement of the press fit joint. Fig. 8 is a sectional view taken along a line VIII-VIII in fig. 7 and shows in more detail the sensors and the stop.s shown in fig. 7. Fig. 9 is a side elevational view taken along a line IX-IX in fig. 8 and further illustrates the relation of a sensor to the flange of a crank shaft half. Fig.- 10 shows a side elevational view of said joining apparatus when the joining procedure is at an end. Fig. 11 illustrates a master shaft manufactured within extremely accurate tolerances and by means of which master shaft the joining apparatus of the invention is calibrated. Fig. 12 shows a complete crank shaft with a mounted connecting rod. This figure in greater detail explains those dimensions which are measured by the sensors shown in fig.s 7, 8 and 9. Mode for carrying out the invention and industrial applicability In a preferred embodiment of the invention described in detail be¬ low it is presupposed that the crank pin is initially separate from both crank shaft halves to be joined. Thus, the crank pin is press fitted to both said crank shaft halves. In some cases it is preferred to have the crank pin initially inte¬ gral with one crank shaft half. As mentioned at the end of descrip¬ tion the invention also covers such cases. First a typical crank shaft is described, said crank shaft parts being press fit joined. In the drawings Fig. 2 shows a completely joined crank shaft 1 with accurate geometrical tolerances which by way of example are stipu¬ lated for the same. The complete crank shaft is joined from two crank shaft halves D and M which both include a shaft 2 and 3, respectively, and a crank disk 4 and 5, respectively, integrally manufactured there¬ with. The complete crank shaft is obtained by means of a press fit formed between a crank pin 6 and crank pin bores 7 and 8 made in the respective crank, disks. In joining the press fit also a bearing 9, shown as a needle bearing^ and a connecting rod 10 are mounted on the crank pin between the crank shaft halves, such that a unit 11 of mo¬ tion transformance is provided, including the complete crank shaft with the connecting rod. Shafts 2 and 3 of the complete, joined crank shaft have four bearing portions A, B, C, and F which shall, be mu¬ tually concentric within a permissible interval of 0,025 mm, as is shown in Fig. 2. At the continuation of the shaft into the respec¬ tive crank disk there is formed each a flange 12. For the joined crank shaft a dimension L encompassing these flanges shall be with¬ in a tolerance of - 0,1 mm. Shafts 2 and 3 of the crank shafts termi¬ nate in threaded portions 13 and 14, respectively. Fig. 3 shows a principal view of crank pin 6 press fitted into the two crank disks 4 and 5 of the joined crank shaft. As a result of i manu acturing tolerances the two crank disk pin bprεs 7, 8 are mutually displaced in lateral respect, and the lower bore 8 in the figure also inclines relative to a normal N to crank disks 4 and 5. In the manufacturing, the tolerance of the location of the bore is based on the dimension E between the centre of bores 7, 8 and the centre axis of shafts 2 and 3, respectively, and is - 0,01 mm. A hatched, in reallity annular region 15 in both crank disks desig¬ nates a deformation zone of the press fit joint, i.e. that portion closest to the bore wall of the crank disk which is geometrically determined by the pin and bore tolerances of the actual press fit joint and which is radially compressed when the crank pin is pressed into the crank disks. As shown * in Fig. 3 the crank pin 6 (axis N ) held within the deformation zone in the crank disk is inclined in relation to the normal N of said disks 4 and 5. This is most clearly seen by the fact the distal faces of the pin are not parallel to outer sides 16 and 17 of .the crank disks. Due to the accurate anu- facturing tolerances for the location of the pin bores in the crank disks, this inclination of the pin, which for sake of clarity is exaggerated in the figure, in reallity is of such a small magnitude that it does not detrimentally influence the operation of the bearin of the connecting rod. However, the possible inclination of the cran pin within the deformation zone is fully sufficient in order to fa¬ cilitate, at the pressing of the pin into the two crank shaft halves D and M, a mutual alignment thereof with their shafts 2 and 3 in positions within the accurate tolerances which are shown in Fig. 2 and to be ratained thereafter in this carefully adjusted position during the pressing-in operation. Fig. 1 in more details and principally illustrates the method of the invention for said alignment and rεtainment of the crank shaft halve during the joining operation. In the figure the crank shaft halves are provided with the crank pin therebetween and concentrically lined up with the crank pin bores. Bearing 9 and connecting rod 10 are passed on to the crank pin. According to the invention shafts 2, 3 of the two crank shaft halves, during the continued pressing of the crank pin into the crank disks, are retained in positions with their centre axis -coinciding with an intersectional line- between two rnu- tually perpendicular planes X and Y. This is obtained in that shafts 2, 3 close by the flanges 12 are concentrically lined up with their bearing portions A and 8 placed in shaft fixing stops 18 and 19, respectively, being accurately adjusted relative each other in trans¬ versal planes to the shafts, said stops having a ' short extension length along the respective shaft for permitting tilting of the re¬ spective shaft. The shafts are retained in the stops by means of a force P u acting on the respective shaft against the stop.. Moreover, shafts 2, 3 are tilted in the shaft fixing stops 18, 18 over angles ^X and β> in the planes X and Y, respectively, into tolerance true angular positions,' through the application of forces P and P , x y respectively, acting in said planes at the shaft ends, and then are fixed in these positions. The crank shaft halves D, M thus aligned and retained are then brought together carefully parallelly controlled relative each other in axial direction, maintaining the correct space alignments, and by means of a press force P applied on the crank disks at the crank pin, in order to complete the press fit joint between the crank pin and the crank disks. The bringing together of the crank disks pro- • gresses until the dimension L including the stipulated tolerances is obtained over the flanges 12. A preferred embodiment of the joining apparatus is discribed below with reference to Fig.s 4 - 10. In the depicted apparatus the two imagined planes X and Y (see Fig. 11) are orientated with the Y-plane in the plane of the drawings and the X-plane in the normal thereto. As shown in Fig.s 4 and 5 the apparatus is built on a two-sectioned pillar stand press tool 20 which can be placed in a press and which comprises two press tool sections, an upper section 21 and a lower section 22. The two tool sections are movable to and from each other by means of the press and are during movement carefully and paral- lelly controlled relative each other by two guide columns 23, 24. The aligning and fixing means of the joining apparatus for controlling the crank shaft halves and the crank pin are next to be described. In order to line up and fix the two crank shaft halves D, M and the crank pin 6 with bearing 9 and connecting rod 10 passed thereori the upper and.lower sections have the following structure. The two press tool sections have two main members, one base plate 2 and 26, respectively, and an aligning member 27 and 28, respectivel for each crank shaft half. Two adjacent bores in the Y-plane, one guide pin bore 29 and one shaft bore 30, are made in the direction of motion of the press through the base plate and the aligning mem¬ ber of the two press tool sections. The guide pin bores 29 are accurately concentric and have in the aligning member such a dia¬ meter to guide as carefully and displaceably therein a guide pin 31 accurately fitting into the crank pin bores of the crank ' disks. The shaft bores 30 extend all through the tool sections in opposed positions and have such a diameter that there is ample clearance to shafts 2, 3 of the crank shaft halves which are insertable into sai bores. A spherical recess 32 is made in the aligning members concentric with the guide pin bores 29, said recess having its centre of cur¬ vature on an imagined extension of the axis of the guide pin bores outside the aligning members. In this recess there is a complemen¬ tary spherical segment plate 33 which has a centre hole 34 allowing ample clearance for the guide pin 31 to be displaced through the plate. The spherical face 35 of the plate resting in recess 32 is accurately fitted to the recess, the other face 36 of the plate is plane and constitutes a stop face for the outer sides 16, 17 of the crank disks. The face of the plate facing shafts 2, 3 has a groove to allow clearance between the plates and the flanges 12 of the shafts 2, 3 of the cranks shaft halves. The shaft fixing stops 18, 19 are formed in the aligning members at a level with spherical segment plates 33 and are shaped as blocks grasping the shafts 2, 3 at portions A and B, respectively. As al- ready mentioned the shaft fixing stops have a small axial extension length and have their respective stop face against the shaft accu¬ rately adjusted in relation to each other in transversal planes, suc that the shafts of the crank shaft halves at the stops have their axes located in the intersectioπal line of the X- and Y-plaπes. Directly opposite each shaft fixing stop there is ' provided a jack operated jaw-37 movable to and from the shaft and having a dog portion 38 facing the shaft, said dog portion having the same small axial extension as the shaft fixing stops. The jack is excluded from the drawings and only its direction of action is illustrated by means of a force arrow P u . At the end of each shaft 2, 3 there is a pull means 39A for holding crank disks 4, 5 of the crank shaft halves in contact to the plane face 36 of spherical segment plate 33. To this end said pull means has a pull bushing 39 thrεadable on to the threaded ends 13, 14 of shafts 2, 3, and a jack (not shown) connected to the pull bushing. In a similar way as mentioned above this jack is represented in the figure by force arrows P_. and P.,, respectively. Guide pin 31 has such a length that it, maintaining guidance in the guide pin bore 29, can be pushed into crank disk 4, 5 in order to be guided into the same into its correct position for the pressing-in of the crank pin into crank pin bore 7, 8. The insertion of the guide pin into the crank disk is achieved by means of a pressure spring 40 which is placed between the guide pin and the respective base plate 25, 26. The guide pin has a push rod 41 passing through the pressure spring and extending into the base plate through a bore 42 where there is a stop screw 43 limiting the motion of the guide pin in the direction from the crank disk. The movement of the guide pin in the base plate is limited by the stop screw such that the guide pin, when its push rod 41 is. pushed in to about the stop screw, stands some tenths millimeters beyond the plane face 36 of the spherical, segment plate 33. Before the start of the pressing-in procedure and during a first stage thereof the crank pin is held by a principally shown crank pin fixing means 44 in a predetermined position between crank disks 4, 5 of crank shaft halves D, M in which position the pin is practically concentric to the guide pins 31 and consequently to the crank pin bores 7, 8 of the crank disks. Crank pin fixing means is pivotable between this fixing position and a parking position to the side of the crank shaft parts placed in the press tool. Connecting rod 10 passed on the pin via its bearing 9 rests with its piston pin bearing end 45 on the bottom of a guide groove 46 which extending paral- lei to the Y-plane is formed in the lower aligning member 28. Means of the joining apparatus for measuring and position aligning of the shafts of the crank shaft halves relative to each other are next to be described. Due to the fact that each of the crank shaft halves is supported by a tiltable spherical segment plate 33, and their shafts 2, 3 in their transversal planes are fixed by shaft fixing stops 18, 19 having a small axial extension length, each cran shaft half can be tilted over limited angular arcs , β , e.g. from an incorrect angle position i<..,β ., to a correct one. Fig.s 5 and 6 in principal illustrate those means 47A and 55A in the two sections 21, 22 of the press tool, by means of which the angular positions JX 1 ,p 1 of shafts 2, 3 of the crank shaft halves D, M are measured and from these angular positions are positioned in relation to each other by tilting the shafts over angles Xand S into angular positions complying with the tolerances in the X- and Y-planes. As best shown in Fig. 6 measuring means 47A for the angular positions of the shafts comprises for each shaft two gauge arms 47, 48 which, orientated perpendicular to the X- and Y-plane, respectively, are pivotable in a transversal plane to the shafts in that they are jourπalled in base plate 25 and 26, respectively. Said gauge arms have one respective end 49, .50 spring biased against the shaft end of shaft 2, 3 the other end 51 , 52 of the gauge arms contacting a sensor 53 provided to measure the angular position of - the shaft in relation to a master shaft 54 of correct * dimension and shape, said master shaft having been placed previously in the joining apparatus in a calibrating procedure. The master shaft is shown in Fig. 11 and is subsequently described. Tilting means 55A is only shown in Fig.5 as two movement transferring arms 55, 56 grasping the pull bushing 39, said arms 55, 56 being orientated in the X- and Y- planes and being connected to not shown jacks, the actions of which are shown in said planes by means of force arrows P and P . Both 3 x y sensor 53 and jacks P and P are connected to a not shown process ϋ x y v computer, which is provided to control the entire operation as sub¬ sequently described. Means of the joining apparatus for determining a correct pressing-in length of the crank pin is next to be described. In Fig.s 7 - means 58A, 63A in the press tool sections 21, 22 of the joining apparatus is principally illustrated, said means facilitating deter¬ mination of the length of the pressing-in movement of crank pin 6 for obtaining the dimension L shown in Fig.s 2 ' and 10 for the joined crank shaft over its flanges 12. Said means comprises measuring means 58A which measures deviations in the actual flange width di¬ mensions k_, k,, for each individual crank shaft, of which Fig. 12 illustrates an example 57, in relation to the flanges of the master shaft 54 having a correct shape and dimensions. Said measuring means 58A has a gauge arm 58 which is orientated in an X-plane and which is pivotable in this plane journalled at its center in the aligning member 27, 28. The gauge arm has one end 59 spring biased against the distal surface 60 of flanges 12, and has its other end 61 con¬ tacting a sensor 62 which is provided to measure the axial position of the distal surface 60 of the flange in relation to a reference position for the same surface calibrated by means o f the master shaft. The sensor is connected to calculating means in the above mentioned process computer. The process computer controls a means 63A which in dependence of the widths of the measured flanges' 12 limits the press movement by means of a mechanical stop means. Said means 63A includes two fixed stops 63 orientated in the pressing direction and mounted in the upper a- ligning member .27 and spaced in the X-direction. Said stops are pro¬ vided above a stop 64 which is adjustable in the pressing direction. To this end stop 64 has two plane wedges 65, one opposite-each fixed stop. Said wedges are inclined in the Y-plane relative to a plane - transversal to the pressing direction. In order to facilitate adjust¬ ment in the pressing direction the adjustable stop 64 has a U-coπ- figuration in a plane perpendicular to said direction and includes two parallell legs 66, 67 which extend in the Y-direction and are provided with guides journalled in the lower aligning member. Stop 64 is displaceable in the Y-direction by means of a not shown jack, the action of which is shown by a double-headed arrow P. on the drawing; Plane wedges 65 which are provided at the leg ends, are with- drawn from or advanced to the fixed stops 63 at said displacement in the Y-direction of the adjustable stop. For actuating the different, .above described means of aligning, fixing, measuring, positioning and limiting of the pressing-in length of the joining apparatus, as well as an industrial manipulat or robot which may be provided to "charge" the crank shaft halves, the crank pin, the needle bearing and the connecting rod into the joining apparatus, and to remove from the same the completed crank shaft, said means are controlled from a not shown control console by means of any suitable and not shown automatics. Said automatics then also includes the above mentioned process computer which in a manner known per sε handles measured dimensions and on the basis thεrεof dεlivεrs command signals to thε jacks for the positioning and fixing of the crank shaft halves and controls the above mention differεnt means in a correct sequence for the entire joining opera¬ tion. The astεrshaft for thε calibration of thε joining apparatus is nεx to bε described. The master shaft 54 shown in Fig. 11 have for thos portions and those dimensions which correspond to the portions and dimensions designatεd in Fig. 2,- thε samε rεfεrεnces as in Fig. 2, only with the addition of an index _m_. The master shaft is manufac- tured in one ' p r iece, the two shafts 2m, 3m being made with p r articula accuracy as to shape and dimensions and being accurately concentric with each other well within the tolerancε shown in a symbol 69. That master shaft portion which corresponds to the crank disks and the space thεrεbεtwεen is shaped as a solid centre portion 68. As to shape and dimensions said centrε portion is accuratεly correct only as regards its face 16 , 17 facing the shafts 2 , 3 and the flanqe m m 3 m m * •■ 12 as well as a bore 7 /8 through said portion and located at a m distance E to the centre axis of the shafts. The master shaft serve m as a reference which is correct as to shape and dimensions for cali- brating the joining apparatus. The above described measuring means 47A, 58A of the joining apparatus are set to zero by means of the master shaft which is lined up an fixed in the joining apparatus. Deviations, if any, as to shape and dimensions from the refεrence fixεd by thε mastεr shaft can thεn bε mεasurεd at thε actual crank shaft halves which are placed in the joining apparatus to be joined in press fit as subsequently described. OM An individual crank shaft is now to described. An εxamplε of a comp- lεtεly joined individual crank shaft is shown in Fig.12. The flanges 12 of the crank shaft halves D, M have differεnt widths, which for sakε of clarity is exaggerated in the figure. The respective actual flange widths are designated by the dimension k_ and k.. The operation of the joining apparatus in assembling a crank shaft according to the method of the invention is explained below with re¬ ference to the different stages of the joining operation. First the .lining up an fixing of the crank shaft halves and the crank pin in the press tool is described. The two crank shaft halves D, M and crank pin 6 to be joined, connecting rod 10 and its bearing 9 are placed in press tool 20 by means of an industrial robot such that the initial position shown in Fig. for the joining operation is obtained. The crank shaft half D is inserted into the upper press tool section 21, the shaft 2 bεing inserted into the shaft bore 30 and the crank disk 4 with its crank pin bore 7 being passed on thε guidε pin 31. By mεans of pull mεans 39A, pull bushing 39 of which is screwed on to the threaded por¬ tion 13 of the crank shaft half, the crank disk is pulled by means αf force P. into contact to the plane face 36 of the spherical segment plate 32. In a similar way the other crank shaft half M is placed into the lower press tool sεction 22 and thεre is pulled into contact. Connecting rod 10 with mounted bearing 9 is passed on crank pin 6 and is placed on the lower aligning me bεr 28 with piston journal επd 45 in guidε groovε 46 and the crank pin at the crank pin bores 7, 8. The two crank shaft halves are fixed with their shafts 2, 3 against the shaft fixing stops 18, 19 by means of the jaws 37 which with their rε- spεctivε dog portion 38 press against the respective shaft with a rela¬ tively small tightening force P... Then the crank pin is fixed in a correct position concentrically to and between the two crank pin bores 7, 8 by being seized and retained by crank pin fixing means 44. The measuring and the aligning of the shafts of the crank shaft halves in relation to each other and the press tool is now to be dεscribed. First the press in a slow motion brings the press tool sections together until approximately 3 mms remain before the crank pin enters the crank pin bores. During this slow motion of th'e press tool thε following mεasurεs arε takεn: By mεans of measuring means 47A shown in Fig.s 6 and 7 the actual angular positions of shafts 2, 3 of the crank shaft halves are εasurεd in relation to thε angular rεference position calibrated by means of the master shaft. An angu- lar deviation, if any, of shafts 2, 3 in the X-plane relative of the rεference position is measurεd by gaugε arm 47 and sensor 53 as an error angle (X j . An angular deviation of the shafts in the Y-plane from the refεrεnce position is measured by gauge arm 48 and the sensor 53 as an error angle & . . The two error angle values tx., and i are . supplied by the sensors 53 to the process computer which in response to these values delivεrs command signals to the jacks P , P of tilting mεans 55A. By means of the motion transferring arms 55, 56 said jacks tilt in dirεctions oppositε to said measured de¬ viations the shafts into a correct angular reference position both in the X-plane and thε Y-plane. The determination of a correct pressing-in length for the crank pin is now to be described. In the course of the above mentioned mea¬ suring also the deviations of the actual flange widths k_. and k,, of flangεs 12 arε mεasurεd rεlativε to thε flangε widths k of thε maste shaft and by means of measuring means 58A, shown in Fig.s 7 - 9. The gauge arm 56 and the sensor 62 which have been put to zero by means of the master shaft, supply the two deviation values,,, Z n and ^ dZ,,, respεctivεly, from the master flange width k for the rεspεctive crank shaft half D, M and delivεr thε dεviation values on to the process computer. The computer first adds said dεviation valuεs to thε two master flange widths k.for obtaining the combined width of the actual flange widths k_, and k„, and thεn subtracts this width 3 D M from thε master dimension L for obtaining a calculated dimension L Λ m 1 which later is to be obtained ovεr thε outεr faces 16, 17 of the cra disks after a terminated pressing-in of crank pin 6 into the crank disks, in order for the complete crank shaft to obtain over its flangεs 12 thε dimεπsion L which is correct as to tolerances. In dependence of this calculated dimension L,. the process computer de¬ livεrs a command signal to thε jack P. of * movablε stop 64 which jack movεs thε stop in thε Y-dirεction up to that position at which thε* distancε in the pressing direction between the fixed stop 63 and O thε movable stop 64, 65 limits the pressing-in . motion to said men¬ tioned actual dimension L for the complete crank shaft. The continued joining operation is now described.- After said measure¬ ments and the ' alignment of the shafts 2, 3, the crank pin is pressed by mεans of forcε P, about 3 mms into εach crank disk, this position - being shown in Fig. 5. Now a further measurεment is made by means of measuring means 47A in order to check if the pressing-in of the crank pin has changed the angular positions of the shafts from the aligned angular reference position. The computer records the amount of change of thε angular positions of the shafts. The angular deviation now recorded is caused by the effect of the crank pin tilted in the crank pin bores on the crank disks upon the pressing-in of said pin therεin. In αrdεr to compensate- for this continued effect in the pressing-in of thε crank pin up to a complεtε press fit joint is reached, the computer is provided to deliver to tilting means 55A pulsed command signals for tilting shafts 2, 3 in directions opposite to the angular deviation directions and over cer¬ tain excess angles κ< ύj β e beyond shaft parallellism. The mangitudes of thεsε excess angles are calculated by the computer and are dependent of the remaining pressing-in length. Of course said excess angles can be set to zero if dεsired. Since said excess anglεs arε gradually re¬ duced in the continued pressing-in of the crank pin, the complεtεly joinεd crank shaft will have its shafts at angular positions within stipulated tolerances. After this the process computer commands a tightening of jaws 37 of the shaft fixing stops 18, 19 for obtaining a position fixing of the crank shaft halves, as well as a disengagement of the grip of the crank pin fixing means 44 about the crank pin and a withdrawal of said fixing means to its parking position. Then the final pressing-in of thε crank pin into the crank disks of the position fixed crank shaft halves takes place by means of force P with a fast motion of the press. The compression pressure used in this connection is monitored by the computer which is also provided to sense immediately that increase of the compression pressure which occurs when the mechanical stops " 63,65 of prεss motion limiting means 63A are εngagεd at a complete, joined prεss fit. Thε computεr is also provided to reduce at this moment the compressing pressure to zero such that the press motion is immediately interrupted and the stipulated correct dimension L i obtained for the complεte crank shaft. At the end of the press stro guide pins 31 have reached bottom and their push rods 41 engage stop screws 43, as shown in Fig. 10. Crank pin 6 has a shorter length tha the smallεst actual di εnsion L.. which can exist and the guide pins have, when they reach their bottom position 3 adjusted the position of the crank pin in axial direction such that this is well within the outer sides of the crank disks. In thε rεmaining εnd stages of the joining operation jaws 37 are removed from shafts 2, 3 and the actual angular positions of the shafts obtained in the joining pro- cεdurε as well as the actual dimension L over flaπgεs 12, are measurεd by measuring means 47A and 56A in relation to the refεrεπce of the master shaft. It is convenient to have the computer record the result of said measuring. Then the completely joined motion transforming unit 11, now also checked as to dimensions is picked out from the joining apparatus by the industrial robot. The method of joining and the joining apparatus according to the in¬ vention as describεd above have provεd to considerably reducε thε rεjection of completε crank shafts. In thε method and apparatus dεscribεd the crank shaft is joined froir. two similar crank shaft halves and a separatε crank pin, requiring said particular means 44 for positioning and fixing the crank pin. However, the invention is also applicable in cases where the cirank pin is initially integral with one of said crank shaft halves, in which case fixing and positioning means 44 can be dispεnsεd with. The above describεd apparatus can still bε usεd in this modifiεd mεthod for joining the crank shaft halves, one of which includes the crank pin, .presupposing only that the crank disk of the crank shaft half including thε crank pin has a guidε borε madε in its outεr side concentrically to the crank pin for recεiving thε guidε pin 31. For the rest the apparatus operates in the same way as described above. C O In performing the modified method said apparatus may have an addi¬ tional measuring means for measuring in the X- and Y-planes the angular position of the free end of thε crank pin in order to secure the correct initial aligning with the crank bore in the opposing crank disk. Measuring values obtained from said additional measuring means are suppliεd to thε process computer and are considered in the tilting of the crank shaft halves. It is recognized that in some cases one crank shaft half can be rigidly fixed in one press tool section with its shaft parallel to the pressing direction, only the other crank shaft half being til- tably supported in the other press tool section. In these cases said one press tool section supporting the rigidly fixed crank shaft half will requirε positioning mεans securing a correct position of the crank disk in a plane transversal to thε pressing direction, and fixing mεans for rigidly retaining the crank shaft half in the pressing dirεction. No measuring means or tilting means will bε requried in this one press tool section. Said other press tool section permitting tilting of thε crank shaft half is provided with the above mentioned means for measuring and aligning of the crank shaft half. The method and apparatus according to the invention include all modi¬ fications within the frame of all three cases as discussed only limited by the scope of the claims.

Claims: Claims 1. A εthod for joining within accuratε geometrical tolerances two crank shaft halves (D, M) via a crank pin (6) into a complete crank shaft, said crank pin being separatε or part of one crank shaft half, εach "of said crank shaft halves (D, M) including a shaft (2, 3) which by intermediary of a flange (12) continues into a crank disk (4, 5), at least one of said crank disks havin at an accurate distance from the shaft (2, 3) a through bore (7, 8) for receiving the crank pin (6), wherεin thε crank shaft halves (D, M) and the crank pin (6) are joined into a complete crank shaft by pressing the crank pin into said bore(s) for ob¬ taining a press fit joint therebetweεn, c h a r a c t ε r i z ε d in that thε crank shaft halves (D, M) are placed with their crank disks (4, 5) in opposed relation and the crank pin (6) aligned with said bore(s) (7, 8) thεrεbetweεn and that during thε prεssin - in of the crank pin (6) into the borε(s) (7, 8) of thε crank disk(s) (4, 5) thε shafts of thε crank shaft halvεs (D, M) arε accurately aligned and retained relative each other within the accurate tolerances, while the crank pin (6) is permitted to be lined up by said bore(s), thεrεby pεrmitting, within the possi- bilities of the deformation zone (15) of the press fit joint, inclination of the crank pin (6) from perpendicularity to the crank disk(s) (4, 5). 2. The method as claimed in claim 1, c h a r a c t e r i z ε d by retaining each shaft (2, 3) of thε crank shaft halvεs (D, M) against an individual stop (18, 19) for aligning the shafts con¬ centrically, at lεast one of said stops (18, 19) permitting til¬ ting of the respεctivε shaft, mεasuring aftεr a first portion of the pressing - in operation the angular positions ( b . , β ) of the tiltable shaft(s) (2, 3) of the crank shaft halves in rela- tion to predetermined master angles for determining deviations, if any, relative to said master angles and in two pεrpεndicular planεs (X, Y), one of which includes the axes of said shafts and the crank pin, tilting in said two planes the tiltable shaft(s) (2, 3) until compliance with the accurate tolerances, and sub- sequεntly prεssing thε crank pin (6) into the crank disk bore(s) for forming the complete press fit joint. 3. The method as claimed in claim 2, c h a r a c t e r i z ε d in that after the measuring of the angular positions (&- | , Φ..) of said shaft(s), said tilting of the shaft(s) in said two perpendicular planes (X, Y) takes place opposite to the deviation directions of said anglεs. ( !X,, β ) measured in said planes and to parallεl- lism or to excess angles ( Cx , β ) beyond shaft parallellism, said excess angles automatically being reduced to within tolerancεs in the final pressing-in operation in that the crank pin (6), when passing through thε deformation zone (15) of the crank pin bore(s), tilts back said shaft(s). 4. The method as claimed in any one of claims 1 to 3, c h a r a c t e - rizεd in that εach crank shaft half (D, M) is placεd in εach a sεc- tion (21 , 22) of a prεss tool, thε two sεctions of which, for obtai- ning said press fit joint, are brought together in a controlled parallel relation, that said stop(s) (18, 19) permitting tilting engages the shaft (2, 3) close by said flange (12) along a short length of the shaft to permit said tilting thereof, and said two stops (18, 19) having an accurate relativε location in thε press tool sections for aligning the shafts in the pressing dirεction, that each crank shaft half (D, M) is supported for receiving the press force (P) axially against the side (16, 17) of the crank disk facing away from the crank pin (6) and at least thε crank disk of thε tiltablε crank shaft half being supported for universal tilting rela- tivε to the respective press tool section (21, 22), that at least the crank disk (45) of the tiltablε crank shaft half is positioned in that its crank pin bore (7, 8) for rεcεiving the crank pin is lined up by a guide pin (31) inserting into the crank pin bore (7, 8) and to bε pushed out therefrom by the crank pin against a spring back pressure when the crank pin is pressed into the crank disk(s). 5. The method as claimed in any one of the preceding claims, c h a r a c terized in that for εach crank shaft half (D, M) the actual diffe¬ rential dimensions ( ~ - - p . and -- -, ., respectively) between the outer side of the crank disk and a master position for jsaid outer side is measured, that the actual differential dimensions and the two master ORE, O PI flange widths ( k ) are added for obtaining the actual flange widths ( j< ' , k M ), and the sum of the actual flange widths are subtracted from a flange encompassing master dimension (L ), therεby obtaining a calculated dimension (L 1 ) over thε outεr sides * of the crank disks, 5 and that pressing of thε crank pin into thε crank disks is performe up to said last mentioned dimension (L..). 6. An apparatus far press fit joining within accurate geometrical toler ces two crank shaft halves (D, M) via a crank pin (6) into a complet crank shaft, said crank pin being separatε or part of onε crank 0 shaft half, each of said crank shaft halvεs including a shaft (2, 3) which by intermediary of a flange (12) continues into a crank disk (4, 5) in at least one of which there is at an accurate distance fro thε shaft (2, 3) madε a through borε (7, 8) for receiving the crank pin, said apparatus including a press tool (20) having two spaced 5 sections (21, 22) to bε movεd towards εach othεr in a prεssing dirεc tion and in the opposite direction, c h a r a c t e r i z e d by including means for positioning the crank disks (4, 5) in opposed relation and the crank pin (6) aligned with said bore(s). there¬ between-in each of said sections (21, 22) a shaft fixing stop (18, 1 Q being accurately provided relative to each othεr for aligning thε shafts of the crank shaft halvεs concentrically in the pressing direction, and a movable jaw (37) cooperating with the respective st in a transversal plane to the shaft for retaining the shaft within the tolerances, said stops and jaws having in at least one of said 5 sections (21 , 22) small axial extension lengths for permitting tilting of the shaft retained, and that thε prεss tool section (21, including a stop and jaw that permit tilting of the shaft, has uni¬ versally pivotable crank disk supporting means (33) for supporting said crank disk, and measuring means (47A) acting on the shaft for 0 measuring in two perpεndicular planes (X, Y), one of which includes thε axes of the shafts (2, 3) and the crank pin (6), the angular de¬ viations of the shaft in rεlation to predetεrmined master angular va and tilting means (55A) acting on the shafts in said planes (X, Y) for tilting the shafts relative to the shaft fixing stop (18, 19). 7. The apparatus as claimed in claim 6, c h a r a c t e r i z ε d in that said supporting means is a spherical segmεnt plate (33) having a plane face for contacting the outer side of thε crank disk and an opposing sphεrical bearing surface (35) having its center of cur- vature located at the axes of said bore(s) (7, 8), and that said segment plate (33) is at a level with said shaft fixing stop (18, 19). 8. The apparatus as claimed in claim 7, c h a r a c t e r i z e d in that at least the press tool section (21, 22) including a stop and a jaw that permit tilting of the shaft has pull means (39A) to seize ' the shaft end (13, 19) of the crank shaft- half and hold thε crank disk (4, 5) against said supporting mεans (33). 9. Thε apparatus as claimed in any one of claims 6 to 8, c h a r a c ¬ t e r i z e d in that each press tool section (21, 22) includes measuring means (55A) for measuring in axial direction the actual differential dimensions (ΔZ-^, Δ Z,,) of thε widths (k_., k.,) of thε flanges in relation to predetermined master flange dimensions (k), that calculating means are connected to the press tool for adding said differential dimensions and the two master flange di εnsions (k) for obtaining the actual flange widths (k~, k,,) as well as subtract the sum of the actual flange widths from a flange encompassing master dimension (L ) for obtaining a calculated dimension (L„), over the m 1 outer sides (16, 17) of the crank disks, that thε prεss tool includes stop means (63A) having a fixing stop membεr (63) in one press tool section (21) and a movable stop mεmber (64, 65) in the other press tool sεction for varying the final distance betwεεn said sections and limiting the pressing-in of the crank pin (6) into the crank disk bore(s) (7, 8), said movable stop member (65) being adjustable in the pressing direction relative to the fixed stop member (63) and in dependence of the magnitude of the dimension (L 1 ) over the outer sides of said crank disks calculated in said calculating mεans. 10. The apparatus as claimed in any one of claims 6 to 9, c h a r a c ¬ t e r i z e d in that said positioning means include concentrically to the axes of said bore(s) a longitudinally displaceablε guide pin (38) biased from an end position against the crank disk and displaceable through a bore (34) in said support means (33) and fitting into the crank disk borε (7, 8) for lining up thε borε of the crank disk into a position for recεiving thε crank pin (6). '

Inventors: HOLMBERG C
Applicants: HOLMBERG C, SAAB SCANIA AB
Application year: 1981
Main classification: B23P19
IPC codes: B23P19, F16C3