FR2654968A1 - BORE EXPANSION LAPPING MACHINE. - Google Patents

Abstract

Machine for lapping bores, comprising at least one lapping spindle (1) driven by a rotational movement about its axis and an oscillatory movement in axial translation, and carrying at its free end at least one expanding lapping rod the expansion of which is controlled by an expansion head (5) mounted on the spindle at a location remote from the lapping rod, this head comprising for each lapping rod an expansion control motor (9, 9 ') whose movement is transmitted lapping machine by a mechanical transmission, characterized in that a displacement sensor (23) is associated with the transmission, between the expansion motor (9, 9 ') and the lapping rod, to detect the position of an element of said transmission and transmit it to the expansion control.

Description

The present invention relates to an expansion lapping machine

  of part bores, comprising at least one lapping spindle with a rotational movement about its axis and a

  oscillatory movement in axial translation.

  On known expansion lapping machines of this type as they have been marketed by the Applicant among others for years, the lapping spindle carries, at its free end, at least one abrasive machining tool or lapping machine whose l expansion during machining is controlled by an expansion head mounted on the spindle at a location remote from the lapping point This head comprises, for each lapping point, an expansion control motor whose movement

  is transmitted to the lapping machine by a mechanical transmission.

  On the machines sold by the applicant, an expansion control motor mounted on the housing of the expansion head attacks a push rod known as a dagger by means of an irreversible reducer comprising an endless screw meshing with the teeth outer of a ring whose inner thread is engaged with a screw whose axial movement, in response to the rotation of the motor, causes a corresponding axial displacement of the dagger, which leads to an expansion of the lapping machine The presence of this chain kinematics between the expansion control motor and the lapping rod, which can also include a flexible transmission of the double gimbal type, leads to the formation of uncontrolled and uncompensated mechanical clearances, thus producing a significant drift between the range d practical machining and the theoretical machining range Under these conditions, a planned machining value can only be obtained after a series of tests taking into account any play and bending in the kinematic chain. The present invention relates to a lapping machine by expansion of bores on which the lapping of each spindle comprises an expansion control eliminating all of the clearances so as to allow very tight machining tolerances to be obtained by

compared to the theoretical value.

  The invention also relates to a lapping machine by expansion of bores on which the expansion control of the lapping is improved in precision by simple, inexpensive and reliable means. Finally, the subject of the invention is a lapping machine by expansion of bores on which each lap has two expansion laps whose expansion is controlled by two motors via two transmissions, these two expansion commands comprising means which not only improve the precision of the expansion of the two rods, therefore the machining precision of the two rods, but also eliminates any risk of interference between the

  expansion controls for the two laps.

  The lapping machine by expansion of bores according to the invention comprises at least one lapping spindle driven in a rotational movement around its axis and in an oscillating movement in axial translation and carrying at its free end at least one expansion lapper whose expansion is controlled by an expansion head mounted on the spindle at a location remote from the lapping point This expansion head comprises, for each lapping point, an expansion control motor whose movement is transmitted to the lapping point by a mechanical transmission According to the invention, a displacement sensor is associated with the transmission, between the expansion control motor and the lap, to detect the position of an element of said transmission and transmit it to the engine control. expansion command to allow the latter to

  precisely control the expansion of the lapping machine.

  The provision of this displacement sensor, not directly on the engine, but on an element of the transmission closer to the lap, eliminates all the games likely to occur

between the engine and this element.

  The sensor may for example be a rotary displacement sensor, in which case it is provided for detecting the displacement of a rotary element of the transmission. However, according to a preferred embodiment, the sensor is a linear displacement sensor and detects the position of an element of the transmission

movable along the axis of the spindle.

  The sensor can in principle be mounted on the lapping itself, but since the lapping itself is rotated, such mounting leads to difficulties in transmitting information from the detector to the control. This is the reason for which, according to a preferred embodiment, the sensor is mounted on a part of the spindle not participating in the rotation of the latter, of

  preferably on the expansion head.

  In the case of a running-in spindle with two expansion rods controlled by a double expansion head with two motors via two transmissions, it is advantageous to associate a displacement sensor with each transmission so that each sensor detects the position of an element of one of the two transmissions between the two motors and the two laps These two sensors also prevent interference from the two expansion commands (possible collision of the two laps in the case where the train abrasive stones from one of the laps would wear out faster

  than the abrasive stone train on the other lap).

  According to a preferred embodiment, the two linear displacement sensors associated with the two transmissions controlling the two laps include two detectors each connected to one of said

  two elements and cooperating with a common rule.

  The or each displacement sensor used in the context of the invention can be an optoelectronic, capacitive sensor or, preferably, a magnetic sensor comprising a magnetic detector

  cooperating with a ruler fitted with magnetic marks.

  Referring to the accompanying drawings, there will be described below in more detail an illustrative and nonlimiting embodiment of a lapping spindle with two expansion lapping pins of a lapping machine for bores; in the drawings: FIG. 1 is a front view of an expansion lapping spindle with two laps of a machine according to the invention; Figure 2 is an axial section of the expansion head and part of the spindle of Figure 1, on a larger scale and along a section plane parallel to the drawing plane of Figure 1; Figure 3 is an enlarged rear view of the expansion head of Figure 1, showing the displacement sensors; Figure 4 is a side view, partially in section, along

  IV-IV of Figure 3, of the expansion head.

  The lapping spindle 1 according to FIG. 1 is part of a lapping machine by expansion of bores of parts such as automobile parts (connecting rods, pinions, differential shoemakers, etc.) hydraulic distributors and other mechanical elements requiring a very high geometrical precision, machine which part 2 serves to support spindle 1 in FIG. 2. Spindle 1 animated during the running-in of a rotational movement around its axis and an oscillatory movement in axial translation by means not shown has at its lower end a double expansion lapper 3 comprising two lappers 4, 4 'each consisting of a train of abrasive parts Such expansion lappers are well known and therefore there is no need to describe the structure in more detail as part of this

invention.

  The expansion movement of the two lappers 4, 4 ′ during the running-in is controlled by a double expansion head 5 which surrounds the pin 1 at the top and which is immobilized in rotation relative to the support 2 by a rod of guide 6 Spindle 1 receives its rotational and oscillatory translation movement by a drive end piece 7, this movement being transmitted to the two rods 3, 4 by a flexible transmission 8, for example a double cardan transmission, located between the double expansion head and the two rods 4, 4 '. The expansion head 5 comprises, for the expansion control of the two rods 3 and 4, two expansion control motors 9 and 9 ',

  for example electric stepper motors.

  In FIG. 2, it is recognized that each of the two expansion control motors (only the motor 9 'is visible) drives an endless screw 10, 10' which meshes with the external toothing of a ring 11, li 'which is mounted in rotation, but immobilized in axial translation in the casing 12 of the head 5 Each ring 11, It 'has an internal thread engaged with a screw 13, 13' movable in

axial translation.

  The body 14 of the spindle 1 is mounted for rotation inside the double head 5 The spindle body 14 provided with a connection cone 15 at its upper end passes through the head 5 in the form of a tubular section 16 provided, from top to bottom, with a first pair of opposite transverse transverse slots 17 and with a

  second pair of transverse opposite transverse slots 17 ′.

  Inside the tubular section 16 of the spindle body 14 are concentrically disposed a first hollow transmission element 18 and a second transmission element 18 'arranged inside the element 18 The two transmission elements 18, 18' which are mounted movable in axial translation, one in the spindle body 14

  and the other in the transmission element 18.

  The transmission element 18 has at its upper end a transverse head 20, the two ends of which pass through the slots 17 of the spindle body 14 and are mounted in the screw 13, by means of two stops 21 and a nut 22 , so as to make the element 18 integral in axial translation with the screw 13,

  but to allow it to rotate relative to the latter.

  Similarly, the inner transmission element 18 'has, at its upper end, a transverse head 20', the ends of which pass through both opposite transverse transverse slots 19 of the external transmission element 18 and the slots 17 ' of the spindle body 14 and are mounted in the screw 13 ', by means of two stops 21' and a nut 22 ', so as to make the element 18' integral in axial translation with the screw 13 ', but to allow it to rotate relative to the latter. Thanks to this arrangement, the two transmission elements 18, 18 ′ are integral in rotation with the spindle body 14, but movable in axial translation relative to the latter and relative to each other, their axial positions being controlled by the two expansion control motors 9, 9 ', via irreversible transmissions comprising the worms 10, 10', the

  rings 11, 11 'and screws 13, 13'.

  The expansion head 5 is equipped with a double displacement sensor illustrated by FIGS. 3 and 4 to determine and allow precise control of the axial position of the two transmission elements 18, 18 'and, consequently, the degree

  for expansion of the two rods 4, 4 '.

  The double displacement sensor 23 comprises a rectilinear rule 24 of a type known per se, fixed by its two ends by means of support 25, 26 to the casing 12 of the double expansion head, so as to extend parallel to the axis of the spindle 1 The casing 12 has two slots 27, 27 'each of which is traversed by a part 28, 28' serving as detector support and integral with the nut 22, 22 'and serving as support for a detector 29, 29 'cooperating with the rule 24 In the example shown, the rule 24 is a filiform rule and the two detectors 29, 29' surround the rule 24 Such sensors are sold commercially for example

  in the form of magnetic displacement and position sensors.

  It should also be noted that the detectors 30, 30 'are initialization detectors of the control, while the detectors 31, 31' and 32, 32 'are electrical stops, the detectors 31, 31' constituting high stops and the detectors 32, 32 'of the bottom stops All the detectors 30, 30', 31, 31 ', 32, 32' provided

  on the casing 12 cooperate with the sensor supports 28, 28 '.

  As already mentioned, the user of a double displacement sensor 23 on a double expansion control head for a lapping pin with double expansion lapping not only makes it possible to precisely control the expansion of each lapping, by compensating all the play likely to occur between the expansion-control motors and the laps, but also to prevent any interference between the two laps, for example a collision of the two laps. Such a collision could indeed occur in the event of faster wear of one of the two lappers than the other, at which

  in this case the expansion control of the other lap would become ineffective.

  Of course, the invention is not limited to detecting the position of double expansion lappers, but also applies to

simple expansion rods.

  Furthermore, it is possible to use, within the framework of the invention, displacement sensors other than that shown and described, for example opto-electronic sensors and / or rotary sensors instead of linear sensors. In the latter In this case, it is of course necessary to detect the movement of a rotary element of the transmission of the expansion command, for example the movement of

  rings 11, 11 'on the double expansion head shown.

  Finally, the displacement sensor (s) can be provided not only on the expansion head 5, but also on any other part of the transmission of the expansion movement to the rods 4, 4 ′,

  for example on the seal 8 or even on the laps 4, 4 'themselves.

  However, the sensors then participate in the rotation of the spindle,

  which is not the case when mounting on the expansion head.

Claims (4)

  1 lapping machine by expansion of bores, comprising at least one lapping spindle (1) driven in a rotational movement about its axis and in an oscillating movement in axial translation, and carrying at its free end at least one expansion lapping (4, 4 '), the expansion of which is controlled by an expansion head (5) mounted on the spindle at a location remote from the lapping point, this head comprising for each lapping an expansion control motor (9, 9 '), the movement of which is transmitted to the lap by a mechanical transmission, characterized in that a displacement sensor (23) is associated with the transmission, between the expansion motor (9, 9') and the lap ( 4, 4 '), to detect the position of an element of said transmission and transmit it to the command of the motor.   2 Machine according to claim 1, characterized in that the sensor is a linear displacement sensor and detects the position of an element of the transmission along the axis of the spindle. 3 machine according to claim 2, characterized in that   that the sensor is mounted on the expansion head (5) of the spindle.   4 Machine according to any one of claims   above, characterized in that it comprises at least one lapping spindle (1) with two expansion rods (4, 4 ') controlled by a double expansion head (5) with two motors (9, 9') by means of two transmissions, characterized in that a displacement sensor is associated with each transmission so as to each detect the position of an element of one of the two transmissions.   Machine according to claims 3 and 4, characterized by   the fact that the two sensors comprise two detectors (29, 29 ′) each connected to an element of each of the two transmissions and   cooperating with a common rule (24).   6 Machine according to any one of claims   previous, characterized in that the or each sensor   includes a magnetic detector cooperating with a magnetic ruler.