FR2779191A1 - Rotary guide and support for crankshaft whilst being machined - Google Patents

Abstract

The guide for a crankshaft (100) whose one end is (110) fixed in the jaws of a drive chuck (M) has its free end (120) guided by a bearing (D). This bearing is fed by a fluid under pressure which interposes a film (F) between the inner surface of the bearing (D) and the outer surface of the part of the crankshaft (100) which it guides. The fluid can be air or oil.

Description

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  DEVICE FOR GUIDING THE ROTATION OF WORKPIECES

  REVOLUTION, ESPECIALLY CRANKSHAFT, DURING THEIR

MACHINING

  The present invention relates to the field of machining of parts of revolution, in particular of crankshafts and relates more particularly to the adaptations making it possible to ensure for certain specific applications a machining of the bearings, crankpins and ends of such

  parts in the best conditions.

  The original concept of the invention was detected by

  the plaintiff by conducting research on a machine-

  prior art tool described in its French patent

  n 94 14826. This patent describes and represents a machine-

  tool for the machining of crankshafts, the working process and the machining chain of such a machine tool having the aim of reducing the idle times due to the so-called auxiliary operations such as those of unclamping, clamping, loading, unloading and indexing of the part on the machine tool. The machine tool, assigned in particular to the machining by turning-shaving of crankshafts for four-cylinder in-line engines, comprises, arranged on a frame along the transfer axis of a chain of machining of said crankshafts and in the same horizontal plane: a machining station equipped with at least one tool-carrying disc ensuring the turning-leveling operations of the crankshafts, - and two workstations which, ensuring the rotational drive of two crankshafts, are arranged parallel upstream and downstream of the machining station, so that the tool-disc of the latter mounted mobile along the transfer axis can move in a reciprocating movement of a station work to the other and ensure the machining of a crankshaft during the auxiliary operations necessary for the installation of a new crankshaft on the other -2-

workstation, and vice versa.

  Although perfectly meeting the needs of users of a fully automated crankshaft production line, the Applicant has noticed that this type of machine tool may have a constraint for certain applications by offering only limited accessibility to the various workstations. , especially during manual installation of workpieces. Indeed, the arrangement of a machining station between two workstations reduces the possibilities of access, which obliges the designers to provide a gantry provided with gripping arms ensuring the passage of the parts or crankshafts to be machined from a first workstation to another, or to change the

machining station tools.

  In addition, another constraint of the machine tool as previously designed lies in the fact that the gripping of the crankshaft forming the part of revolution to be machined is carried out by the mandrels which, located at each end of the crankshaft, close their jaws on these to drive and guide the crankshaft in rotation during the machining operation. This arrangement prevents machining of the ends of the crankshafts on these workstations. Also, the complete machining of a part of revolution is not possible from

of such an installation.

  A solution to these constraints, developed by

  plaintiff, resides in the realization of a machine-

  tool adopting workstations comprising a single spindle and therefore a single mandrel for producing

  the rotational drive of the part of revolution.

  This solution has in particular the following advantages, namely: - to facilitate access to the machining station as well as to the two workstations, - to authorize a manipulator to ensure the installation and -3- removal of the parts to machine in workstations, - and allow the machining of the ends of the parts of revolution as soon as a single mandrel is used to hold the part. However, this solution is difficult to apply for the machining of certain parts of revolution, including parts of long revolutions, such as crankshafts. Indeed, during the rotation of the part of revolution, its free end can be subjected to a radial clearance which can prove to be a drawback for the machining operation in good conditions and in particular during the machining of the 'end

of the piece of revolution.

  On the basis of this fact, the applicant has carried out research aimed at guaranteeing effective guidance of a long part of revolution when it is rotated at one of its ends by an actuator while allowing optimum accessibility with complete machining. . This research led to the design of a device for guiding a part of revolution, particularly

  advantageous by being able to apply as well to the machine-

  tool described in the prior art than others

  applications involving auxiliary guidance.

  According to the invention, the device for guiding a part of revolution, such as a crankshaft, is of the type of which one of the ends of the part of revolution is inserted in a conventional rotation drive device, such as the jaws of '' a mandrel, for the purpose of machining said part according to any method, the free end of said part of revolution being guided at a substantially cylindrical surface of the part of revolution and theoretically coaxial with that inserted in the jaw of the above drive mandrel by

  at least one guide bearing in rotation.

  According to the main characteristic of the invention, said guide bearing is supplied with fluid and interposes a film of said fluid between said outer cylindrical surface of the above-mentioned part of revolution at

  guide and the inner surface of the bearing.

  This characteristic is particularly advantageous in that it allows the machining of internal or external cylindrical surfaces concentric to functional surfaces already produced, by guiding the piece of revolution at these

litters.

  On the other hand, this judicious technological choice makes it possible not to deteriorate the state of the guide surfaces during the rotation. The interposition of a fluid has the effect of self-centering the end of the part of revolution with respect to the end engaged in the jaws of the mandrel. Another advantage of the interposition of a film of fluid for guiding allows the guiding device to reproduce the context of real use of the part, in particular when the part of revolution is a crankshaft. Another advantage in the use of a fluid lies in the fact that said fluid ensures an optimal balance during the rotation of the part of revolution. Indeed, a fluid makes it possible to correct shape defects

  of the cylindrical surface that the bearing guides.

  According to a preferred embodiment, said fluid

is of the liquid type.

  According to another embodiment, the fluid constituting the guide film of said bearing is of the air type. The use of air as the fluid of a guide bearing is particularly advantageous in that it avoids the problems of pollution and recycling of the liquid. This air may be of the dry type or, of course,

  possibly added any lubricant.

  According to a particularly advantageous characteristic of the invention, said guide bearing opens to allow the insertion of said coaxial cylindrical surface of the free end of said part of revolution on said bearing and closes precisely to guiding it in rotation during the setting in motion in rotation produced by the drive mandrel. This characteristic is remarkable in that it allows guiding at the end left free of long parts such as a crankshaft not only at the end itself but also on one of the guide bearings present along a crankshaft . In fact, such a device has the advantage of allowing the guiding of a pre-machined cylindrical surface whatever its position relative to the end of said part. Of course, the optimal position is when it is possible to bring the guide area closer together.

  as close as possible to the chip removal area.

  The fundamental concepts of the invention having just been exposed above in their most basic form, other details and characteristics will emerge more clearly on reading the

  description which follows, giving by way of example no

  limiting and with reference to the accompanying drawings, an embodiment of a guide device in accordance with

  the invention. This description refers to the drawings

  annexed in which: FIG. 1 is a schematic overview of an embodiment of a guide device according to the invention, FIG. 2 is a side view of the device

guide of figure 1.

  As illustrated in the drawing of Figure 1, the guide device referenced as a whole D is integral with a frame referenced B of a machine tool having the function of machining a long part of revolution

, here a crankshaft.

  One of the ends 110 is inserted into the jaws of a mandrel referenced M of said machine tool, for the purpose of machining said crankshaft 100 by a tool O, the end 120 left free of said crankshaft 100 is, as to it, guided at a substantially cylindrical surface of the crankshaft and theoretically coaxial with that inserted in the jaws of the drive mandrel M by a guide bearing in rotation constituting said guide device and referenced D. According to the invention and as illustrated in the drawing in FIG. 2, said guide bearing D interposes a film F of liquid between said outer cylindrical surface of the crankshaft 100 to be guided and the inner surface of the bearing D. This guide device D not only has the advantage of '' guiding a long piece driven at one end only but also correcting the cylindrical defects of the surface it guides due to the very nature of the liqu ide which, during the rotation of the crankshaft, self-centers the latter with respect to a

fictitious axis of rotation.

  Another advantage of a device with fluid interposition is that, unlike a roller device, it prevents premature heating of the guided area during machining by circulation

some cash.

  On the other hand, as soon as the guide element itself, namely the liquid, is wear-free, a guide bearing using such technology offers a duration of

very long life.

  According to the illustrated embodiment, the guide bearing 200 is constituted at its guide surface by a succession of chambers C each receiving the guide liquid so that when said bearing 200 receives the workpiece 100, the substantially cylindrical guided surface of the latter forms an additional wall to said chambers C, the clearance left between the internal surface of the bearing and said cylindrical surface authorizing the creation of a film of

guide fluid.

  This liquid, according to a preferred but non-limiting embodiment, is of the cutting liquid type. Also, the use of a bearing with liquid interposition between the surface of the bearing 200 and the surface to be guided allows

  the use of a liquid already used on the machine-

  tool on which said guide device D is installed.

  Thus, depending on the liquid used on said machine-

  tool, the cutting fluid used to supply the bearing can be of the whole oil liquid type or else

of the aqueous type.

  According to a first preferred embodiment, said guide bearing 200 is of the hydrostatic type. The liquid is then sent under pressure to the chambers C

from level 200.

  According to another preferred embodiment, said guide bearing 200 is of the hydrodynamic type. In this application, it is the movement of the part to be machined that creates pressure in the film of liquid. According to the invention, the rotary guide bearing comprises two parts 210 and 220, which together, form the inner walls of a cylinder, namely: - a first fixed lower part 210 fixed to the frame B to which the fixed part is linked of said drive device M, and - a second mobile upper part 220 separating from the lower part 210 in order to allow the insertion of the part of revolution, here the crankshaft, in the bearing 200 before returning to its initial position by compared to the above lower part 210

  in order to guide said crankshaft 100.

  According to a preferred embodiment, the translation allowing the guide bearing 200 to pass from an open position authorizing the insertion of the part to be guided to a closed position authorizing the guiding of said part to be guided is ensured by a cylinder device. The operation of a machine tool comprising a

  such guide device D is simple and the following.

  The crankshaft 100 is placed with its end 110 in the jaws of the mandrel M of a drive spindle and one of the bearings machined in a previous machining phase in the cradle formed by the lower part 210 of the guide bearing 200 , the part

upper being retracted.

  The upper part 220 of the bearing is replaced by covering the lower part 210 and the reconstituted bearing is then supplied with liquid to create the guide film F with the guide end 110 enclosed in the jaws of the mandrel M, The crankshaft is then rotated by the mandrel M and the tool O is approached in a conventional manner to carry out the desired machining. The tool can be either fixed or rotating, single or multiple, or even of the grinding wheel type. The schematic drawing of another tool

  turning point O 'illustrates one of the above possibilities.

  It is understood that the device for guiding in rotation which has just been described and shown above, was for the purpose of disclosure rather than limitation. Of course, various arrangements, modifications and

  improvements could be made to the example below

  above, without departing from the scope of the invention

  taken in its broadest aspects and spirit.

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Claims (10)

  1. Device for guiding a part of revolution (100), such as a crankshaft, one of its ends (110) of which is inserted into a conventional rotary drive device, such as the jaws of a mandrel (M), for the purpose of machining said part (100) according to any method, the left free end (120) of said part of revolution (100) being guided at a substantially cylindrical surface of the part of revolution (100) and theoretically coaxial with that inserted in the jaws of the aforesaid driving mandrel (M) by at least one guide bearing in rotation (D), CHARACTERIZED BY THE FACT THAT said guide bearing (D) is supplied with fluid and interposes a film (F) of said fluid between said outer cylindrical surface of the said part of revolution   (100) to guide and the inner surface of the bearing (D).   2. Guidance device according to claim 1, CHARACTERIZED BY THE FACT THAT said fluid is of the liquid type. 3. Guide device according to claim 1,   CHARACTERIZED BY THE FACT THAT said fluid is of the air type.   4. Guide device according to claim 1, CHARACTERIZED BY THE FACT THAT said guide bearing (D) is of the hydrostatic type.   5. Guide device according to claim 1, CHARACTERIZED BY THE FACT THAT said guide bearing (D) is of the hydrodynamic type.   6. Guide device according to claim 1, CHARACTERIZED BY THE FACT THAT said liquid interposed between the substantially cylindrical surface to be guided of the part of revolution (100) and the guide bearing (D) is of the cutting liquid type.   7. Guidance device according to claim 6, CHARACTERIZED BY THE FACT THAT said cutting liquid is of liquid type with whole oil.   8. Guide device according to claim 6, - 10- CHARACTERIZED IN THE FACT THAT said cutting liquid is aqueous type.   9. Guide device according to all of the claims from 1 to 8 taken together, CHARACTERIZED BY THE   FACT THAT said guide bearing (D) opens to allow insertion of said coaxial cylindrical surface of the free end (120) of said part of revolution (100)   on said bearing and closes precisely, to ensure the guiding in rotation when setting in motion10 in rotation produced by the drive mandrel (M).   10. Guidance device according to claim 9, CHARACTERIZED BY THE FACT THAT said rotating guide bearing (D) comprises two parts (210 and 220), which together, form the inner walls of a cylinder, namely: - a first fixed lower part (210) integral with a frame (B) to which the fixed part of said drive device is linked, and - a second mobile upper part (220) separating from the lower part (210) in order to allow inserting the part of revolution (100) in said bearing (D) before returning to its initial position relative to the above-mentioned lower part (210) in order to ensure   guiding said part of revolution (100).