FR2488178A1 - Cutting of microscopic spiral groove on shaft journal - uses axially reciprocating stone applied to rotating shaft during alternate strokes - Google Patents

Abstract

The process uses an abrasive stone (6) to cut a microscopic spiral groove on a cylindrical workpiece (7), to provide a micro-turbine oil seal at e.g. the location of a shaft journal in a housing aperture. The workpiece (7) and the stone (6) are subjected to relative reciprocal displacement parallel to the axis of the workpiece while it is rotated, being brought into contact and separated during succeeding inverse movements. The cutting machine may use an hydraulic device (28) to move a stone-holder (2) relative to the workpiece, and includes a mechanism (11,21,22,24) which automatically compensates for the wear of the stone.

Description

 The present invention relates to a superfinishing device intended for execution on journals of camshafts, crankshafts or any other parts comprising cylindrical bearings, the surface condition of which must be particularly careful, of microscopic grooves called "microturbines "intended to constitute a seal for oil which tends to pass between the seat and the seal during the rotation of the part.

 Superfinishing a staff is usually done by drawing parallel or crossed lines on the surface.

 An improvement in sealing is obtained by making microturbines which are formed of helical wings, inclined relative to the axis of rotation of the part.

 As already mentioned above, such an arrangement makes it possible to stop the liquid, for example the lubricating oil which tends to escape through the seal and its bearing surface and d '' thus improving the tightness of the assembly.

 The superfinishing devices for this embodiment used up to now are based on the cloth, they have the advantage of requiring frequent changes of the abrasive cloth which considerably slows down their operation and gives rise to multiple manipulations.

 The invention aims to create a device which allows the execution of microturbines by honing so as to increase the duration of use of the superfinishing device.

 It therefore relates to a method of making by grinding microscopic helical grooves called micrcturbznes on a cylindrical piece characterized in that the cylindrical piece is rotated about its axis and, the stone and the piece are subjected to a movement relative back-and-forth parallel to the axis of said piece, the stone is brought into contact with the piece during a stroke of said relative back-and-forth movement and the stone of the piece is charted during the other back and forth movement.

 The invention also relates to a device for superfinishing cylindrical parts by honing for the production of microscopic helical grooves called microturbines, comprising means for rotating the part and charac peris in that it further comprises means for subjecting the stone and the workpiece to a relative back-and-forth movement parallel to the weary of said workpiece and means for bringing the stone into contact with the workpiece during a stroke of said relative back-and-forth movement and putting the stone and the workpiece out of contact during the back-and-forth movement.

 The invention further relates to a device for superfinishing by honing cylindrical parts subjected to combined movements of rotation about their axis and back and forth along said axis, characterized in that it comprises a carrier unit stone intended to intermittently apply said stone to the workpiece and a hydraulic device for controlling the application by the stone holder unit of the stone on the workpiece during a stroke of said reciprocating movement of the workpiece and the removal of said stone during the other stroke of said back-and-forth movement.

 According to another characteristic of the invention, the superfinishing device further comprises an automatic device for compensating for the wear of the stone between two superfinishing operations.

Other characteristics of the invention will appear during the description which follows, given with reference to the appended drawings, given solely by way of example and in which
Fig. 1 is a schematic sectional view of the superfinishing device according to the invention in the starting position.

 Fig. 2 is a view similar to that of FIG. 1 showing the stone in contact with the part.

 Fig. 3 is a view similar to the previous ones, showing the withdrawal of the stone during the return movement of the part.

 Fig. 4 is a view in elevation and in section of the hydraulic distributor intended to control the device according to the invention.

 The superfinishing device shown in fig. 1 comprises a frame 1 of which only a part is shown and a hydraulic cylinder 2 integral with said frame.

 The jack 2 comprises a cylinder 2a in which is housed a piston 3 provided with two opposite rods 4 and 5.

 The rod 4 passes through the wall of the body of the jack 2 and carries at its free end an abrasive stone 6 intended to come into contact with a part 7 on which the superfinishing operation is to be carried out.

 The part 7 which has a circular section is connected to entraj # ne # ent nen means shown intended to impart to it a rotational movement combined with a reciprocating movement.

 The rod 4 is guided by means of a bracket constituted by a support 8 integral with the body of the cylinder 2 and in which is mounted a rod 9 which carries a guide 10 at its end.

 The rod 5 opposite the rod 4 has a smaller diameter than the latter so that the free surface S of the piston 3 delimited by this rod is greater than the free surface s delimited by the rod 4.

 The rod 5 is slidably mounted in a sheath ll disposed in a bore 12 of the bSti 1.

 In the end of the sleeve 11 opposite the piston rod5 is screwed an adjustable stop 13.

 The piston rod 5 has, near its end, a flange 14. Between this flange and the bottom of the sheath, the rod 5 is surrounded by a first spring 17 while a second spring 18 is disposed between said flange and a shoulder 19 provided on the adjustable stop 13.

 In the frame 1 is also mounted a device for blocking the sleeve 11 in translation in the bore 12.

 This device consists of a piston 20 mounted in a stepped bore 21 and urged towards the sheath 11 by elastic washers 22 mounted in a cover 23 fixed on the frame 1. The cylinder 21 is connected to a pressure source P by a conduit 24 connected to the source via a solenoid valve not shown.

 The cylinder 2 is connected to the pressure source P by lines 25 and 26 which terminate on either side of the piston 3.

 Line 25 is connected directly to the pressure source P while line 26 is connected to the pressure source by means of a solenoid valve 27, a rotary distributor 28 and a second solenoid valve 29.

 The solenoid valve 27 is connected to the distributor 28 by two pipes 30 and 31.

 The distributor 28 and the solenoid valve 29 are also connected to a cover 32.

 As can be seen in fig. 4, the distributor 28 comprises a rotating part 33 provided with a peripheral groove 34 and a groove 35 extending over a portion of its periphery. The grooves 34 and 35 are connected to each other by a channel 36. The rotating part 33 of the dispenser is linked by suitable means not shown to the reciprocating movements of the part 7 subjected to the superfinishing operation.

 The distributor also comprises a fixed part 37 in the form of a socket, in which two passages 38, 39 are arranged respectively opposite the grooves 34 and 33.

 The rotating part 33 carries at one of its ends a disc 40 provided with peripheral lights 41, in which are engaged screws 42 for fixing the disc to a drive pulley, not shown, in a position suitable for compensating for the offset of the action of the distributor with respect to the reciprocating movement of the part 7.

 The device described above therefore comprises - a stone holder unit constituted by the hydraulic cylinder 2 with double rod 4, 5; - A hydraulic control device constituted by the distributor 28 and the means, not shown, of connection of the rotating part thereof to the reciprocating movements of the part 7; a device for taking up the wear of the stone 6, constituted by the sheath it linked to the stone-carrying cylinder 2 by the two springs 17 and 18 and by the device 20 for locking in translation of the sheath 11.

 The operation of the super-finishing device according to the invention will go between described with reference to FIGS.

 16 4.

 Due to the length of the connections between the jack 2 and the distributor 28, there is a shift between the zone where the stone 6 is pressed against the part 7 and the start of the reciprocating stroke thereof. .

 In order to compensate for this offset, a slight advance is given to the disc 40 by loosening the screws 42 by moving the disc using lights 41 so as to give the rotating part an appropriate advance relative to the back and forth movement. - comes from the part and again tightening the screws 42.

At the start of a superfinishing cycle, the device is in the state shown in FIG. 1. The pressure
P is applied to the piston 3 on the side of the rod 4 which carries the stone 6 while the opposite side of this piston is connected to the ball so that the piston 3 is pushed back and the stone 6 is released from Exhibit 7.

 The pressure P is also applied to the blocking device of the sheath ll so that the latter is kept in equilibrium by the two springs 17 and 18. In this position the movable stop 13 is placed with a clearance j relative to the end of rod 5 of piston 3.

 This game corresponds to the withdrawal stroke that we want to execute on stone 6 during the operation of the device.

 This stroke can be adjusted by displacement of the stop 13 in the sleeve 11, to a minimum value of the order of a few tenths of a millimeter.

 In order to bring the stone 6 into contact with the part 7, the solenoid valve 29 is actuated so as to place the conduit 26 at the pressure P.

 Since the useful surface S of the corresponding face of the piston 3 and greater than the useful surface s of its opposite face the piston 3 is pushed towards the part 7 and the stone 6 comes into contact with the latter.

 The various organs of the device then occupy the positions shown in FIG. 2 on which we see that the sleeve 11, after its displacement in its bore 12 under the action of the piston 3 is immobilized in translation by the piston 20. In fact the pressure P is no longer applied thereto, the washers elastic 22 push it towards the outer surface of the sleeve 11, which ensures its immobilization.

 The part 7 is then rotated and driven back and forth so that the rotating part 33 of the distributor 28 is also set in motion in synchronism with the back and forth movements of the part.

 In order to perform heli-cotidal microturbines on the part, it is necessary that the stone 6 is in contact with the part 7 only during a single stroke of the reciprocating movement so as not to cross the grooves that she traces. This race can be either the outward race or the return race.

 For this purpose the distributor 28 is switched on and ensures the contact of the stone with the part during a half-turn of its rotating part 33 and the withdrawal of the stone during the other half-turn and so on.

 The distribution of the distributor 28 is ensured by the solenoid valve 27 which provides the connection between the jack 2 and the solenoid valve 29 via the distributor.

the first the first half of it, the pressure
P from the source applied to the passage 39 by means of the solenoid valves 27 and 2, is transmitted by the groove 35 and by the channel 36 to the passage 38 which is connected to the jack 2 by the conduit 26. It follows that the piston 3 is biased towards the part 7 and the stone 6 is applied against it.

 During the second half-turn of the distributor, the groove 35 is no longer in front of the passage 39 so that the pressure P is no longer applied to the duct 26. On the other hand, the chamber of the jack 2 located on the side of the rod 5 is placed in communication with the cover 32 by the path formed by the conduit 26, the solenoid valve 27, the passage 38 of the fixed part 37 of the distributor, the channel 36, the groove 35 which is then in communication with radial passages 43 arranged in the fixed part 37.

 Since the pressure P is permanently applied to the face of the piston 3 located on the side of the rod 4 the piston is then pushed towards a distance equal to the stroke j determined by the adjustment of the stop 13 in the sheath 11.

 The sheath ll remains blocked by the piston 20, so that at the end of the second half-turn of the dispenser the various organs of the device occupy relative positions shown in FIG. 3. The cycle just described is repeated until microturbines of appropriate depth and density are obtained.

 Then the distributor 28 is switched off and the pressure P is again applied to the sheath blocking device 11. The piston 20 of this device releases the sheath against the action of the plastic washers 22 and the piston 3 moves back under the effect of the pressure P applied to its face directed towards the rod 4.

 Part 7 is Prmnobilisae and the device is ready for a new cycle.

 It is noted that during the application of the stone against a new workpiece, the sheath 11 will be in an axial position slightly advanced relative to its position during the previous cycle, the difference between the two positions being equal to the value of the wear of the stone 6.

 Thus the device according to the invention makes it possible to carry out an automatic take-up of the luster of the stone.

 The device which has just been described makes it possible to produce microturbines of steps to the right or of steps to the left according to the combination of the directions of rotation of the part and the stroke during which the stone 6 is applied to the part 7. The combination of the value of the speed of rotation of the part 7 and the value of the speed of its back-and-forth movement determines the value of the pitch of the propellers obtained.

 Although in the embodiment which comes between describes the part on which we realize the miero-turbines is animated by a rotational movement around its axis and by a reciprocating movement while the stone is animated by an alternative movement of bringing into contact with the part and of withdrawal, it will be understood that it is possible to design devices which, while being of different construction, subject the part to be treated animated by a rotary movement and the stone, to a relative back-and-forth movement parallel to the axis of rotation of the stone, when the stone and the workpiece come into contact during a stroke of the relative back-and-forth movement and a spacing of the stone relative to the part during the other stroke of the relative back-and-forth movement.

 To this end, the stone can for example be subjected to a double oscillation movement along two axes perpendicular to each other.

Claims (9)

 RE1 # NDICATlONS  l - Method of reali3ation by honing microscopic helical grooves called microturbines on a cylindrical part, characterized in that the cylindrical part is rotated around its axis, the stone and the part are subjected to a relative movement of va- back and forth parallel to the axis of said piece, the stone is brought into contact with the piece during one stroke of said relative back-and-forth movement and the stone is moved away from the piece during the other stroke of the movement of back and forth.  2 - Device for superfinishing cylindrical parts by honing for the production of microscopic heli cotidal grooves called microturbines, comprising means for rotating the part and characterized in that it further comprises means for subjecting the stone ( 6) and to the part (7) a relative movement back and forth parallel to the axis of said part - (7) and means (2) for bringing the stone (6) into contact with the part (7) during a stroke of said relative movement back and forth and putting out of contact of the stone (6) and the workpiece (7) during the other stroke of the movement back and forth.  3 - Device according to claim 2 for superfinishing by honing cylindrical parts subjected to combined movements of rotation about their axis and back and forth along said axis, characterized in that it comprises a stone-holding unit (2 ) intended to intermittently apply the said stone (6) to the part (7) and a hydraulic device (28) for controlling the application by the stone holder unit (2) of the stone (6) to the part (7) during one stroke of said back-and-forth movement of the workpiece and the removal of said stone during the other stroke of said back-and-forth movement.  4 - Superfinishing device according to claim 3, characterized in that it further comprises a device (11, 20, 21, 22, 24) for automatic compensation of the wear of the stone (6) between two superfinishing operations .  5 - Superfinishing device according to one of claims 3 and 4, characterized in that the stone holder unit comprises a hydraulic cylinder (2) whose piston (3) is integral with a first rod (4) which carries said stone (6) at its free end, and of a  second rod (5) opposite the first and of a section  (8) smaller than the section (s) thereof, said second rod cooperating with a stop (13) for determining the stroke (j) for withdrawing the stone (6) said jack (2) being connected on the side from the first rod (4) directly to a pressure source (P) and from the side of the second rod (5) either to said pressure source  (P) or at atmospheric pressure, according to a sequence determined by the hydraulic control device (28).  6 - Superfinishing device according to one of claims 3 & S, characterized in that the control device comprises a rotary hydraulic distributor (28) whose rotating part (33) is rotated in synchronism with the movement of va- and comes from the part (7) to be treated, solenoid valves (27, 29) inserted in the conduit (26) for supplying the stone cylinder (2) on the side of said second rod (5) being intended for one ( 27) when the hydraulic distributor (28) is switched on and the other (29) when said conduit (26) is placed in communication with either the pressure source  (P) either with the atmosphere.  7 - Superfinishing device according to claim 6, characterized in that the rotating part (33) of the hydraulic distributor is integral with means (40, 41, 42) for adjusting the offset of the rotation of the dis  tributor on the back-and-forth movement of the part (7) to be treated dt to the length of the hydraulic lines between the stone cylinder (2) and the distributor (28).  8 - Superfinishing device according to one of claims 4 to 7, characterized in that the automatic device for taking up the wear of the stone (6) comprises a sheath (11) slidably mounted in the frame (1) of the device and in which is in turn sliding mounted said second rod (5) of the piston (3) of the stone cylinder (2), said sleeve (11) further carrying said stop (13) for determining the stroke (;;) stone removal (6), the end of said second rod (5) being held at said distance (j) from the stop by two springs (17, 18) one of which (17) surrounds said second rod ( 5) and is supported between a collar (14) thereof and the bottom of the sheath (11) and of which the other (18) is supported between this same collar (14) and the stop (13), as well as a jack hydraulic (20, 21, 22) locking in translation of said sheath (ll) in a position corresponding to the contacting of the stone (6) with said part (7).  9 - Superfinishing device according to claim 8, characterized in that the axial position of the stop (13) in the sleeve (11) is adjustable.