FR3115849A1 - GEARBOX DIFFERENTIAL WITH SATELLITE CARRIER SHAFT STOP RINGS - Google Patents

Abstract

Title: GEARBOX DIFFERENTIAL WITH SATELLITE CARRIER AXIS STOP RINGS This transmission differential for a motor vehicle comprising a housing (l), a cylindrical bar (5) extending along a transverse axis carrying two pinions satellites (20, 21) which mesh with two planet pinions (22,23) centered on the longitudinal axis of the differential, the cylindrical bar (5) comprising two peripheral grooves (4) located between the two planet gears (20,21) in each of which is housed a snap ring (6) elastically mounted between a retracted position in one of the two peripheral grooves (4) and a projecting position out of said peripheral groove (4). Figure for abstract: [Fig 1]

Description

GEARBOX DIFFERENTIAL WITH SATELLITE CARRIER SHAFT STOP RINGS

The present invention relates to transmission differentials for motor vehicles. A motor vehicle transmission differential makes it possible to unevenly distribute the outgoing movement of the gearbox towards the drive wheels, in particular when cornering, where the inside wheel travels a shorter path and therefore has a reduced speed. The differential also has the function of applying a reduction ratio to the output bar of the gearbox.

The present invention aims to constitute a transmission differential for a motor vehicle which minimizes the elements used for holding the planet bar in position.

Prior techniques

An output differential consists of a box integral with an axle ring driven in rotation by a lowering pinion, which is driven by the movement of the output shaft of the gearbox. The housing contains a transverse planet carrier shaft around which rotate two planet gears which mesh with two output planet gears centered on the longitudinal axis of the differential.

To block the planet carrier shaft in the housing, a known arrangement is proposed in document FR 3 018 328. This document presents a differential housing comprising a transverse shaft held in position by a stop ring. The stop ring extends between an inner groove of the differential case and a peripheral groove on a circumference of the planet carrier shaft. Nevertheless, keeping the ring in position requires the machining of a groove in the case, which weakens it, in addition to being particularly expensive for carrying out the machining of the groove inside the case, in an area that is difficult to access and subject to high bending stresses. To guarantee the resistance to fatigue of the casing, a calculation by finite elements is necessary and obliges the designer to maximize the radii of the bottom of the groove.

In other known systems, the rod is made of elastic material and particular care must be taken in the vibration study of the system and imposes a high calibration and the installation of hooks for securing the rod in the windows of the box.

Other solutions propose stopping the planet carrier shaft by an element crossing the shaft lengthwise (metal pin, plastic clips, pinning, stapling, etc.), which requires drilling the planet carrier shaft and weakens so her outfit. An increase in its diameter should be considered to compensate for the loss of section.

Furthermore, solutions that do not require specific machining (external strapping on the differential housing, spring washers, etc.) involve planning additional assembly operations.

Finally, the solution of knurling the satellite shaft causes a deformation of the bore of the differential housing and immobilizes the shaft in relation to the housing.

The object of the invention is to overcome at least some of the aforementioned drawbacks and to propose a transmission differential for a motor vehicle capable of combining the advantages of speed, simplicity and reliability for its implementation, and this, by reusing parts known from an existing system as well as very economical standard snap rings.

In view of the foregoing, the subject of the invention is a transmission differential for a motor vehicle comprising a housing, a cylindrical bar forming the planet carrier shaft and extending along a transverse axis carrying two planet pinions which mesh with two planetary gears centered on the longitudinal axis of the differential, the cylindrical bar having two peripheral grooves located between the two planetary gears in each of which is housed a snap ring mounted elastically between a retracted position in one of the two peripheral grooves and a projecting position out of said peripheral groove.

Preferably, each snap ring is in the form of an open ring, comprising two ends facing each other.

For example, each snap ring is made of steel.

Advantageously, the radial section of at least one snap ring is circular.

According to one embodiment, the two peripheral grooves are distributed symmetrically with respect to the longitudinal axis.

In one embodiment, the housing comprises a chamfered opening opposite a central opening passing through the planet gears, the chamfer of the chamfered opening being adapted to allow the positioning of the stop rings in the retracted position in the grooves devices when inserting the cylindrical bar through said chamfered opening.

Advantageously, the cylindrical bar is fully retracted into the housing.

Preferably, each of the rods is in abutment against one of the satellite pinions.

The transmission differential for a motor vehicle may further comprise a friction shell between the housing and the satellite and planetary pinions, said friction shell being traversed by the cylindrical bar.

The invention also relates to a method of manufacturing and assembling a transmission differential for a motor vehicle having a first step during which the chamfered opening is machined in the housing, then a second step during which the minus the two satellite pinions in the case and their spacing is measured, then a third step during which the bar forming the satellite axis and the two peripheral grooves are machined at a distance from each other less than the spacing between the two satellite pinions measured during the second step then the stop rings are placed in the peripheral grooves, and a fourth step during which the casing and the cylindrical bar are assembled by deforming the stop rings in a position retracted thanks to the chamfer of the chamfered opening until said stop rings are positioned between the two satellite pinions.

The invention will be better understood on detailed study of the embodiment taken by way of non-limiting example and illustrated by the appended drawings, in which:

shows a view of a motor vehicle transmission differential before the insertion of the snap ring bar.

represents a snap ring.

represents the cylindrical bar before inserting the snap rings.

To represent the steps of inserting the cylindrical bar into the case.

shows a method of manufacturing and assembling the transmission differential.

detailed description

There illustrates a transmission differential for a motor vehicle.

The differential is comprised of a housing 1 integral with a crown wheel 2 driven in rotation by a descent of a pinion, not shown, and driven by the movement of the output shaft of the gearbox.

A bore is made in the housing l, in which houses a planet carrier shaft 5 comprising a cylindrical bar 5 which extends along a transverse axis Z. The bar 5 can be made of treated steel.

Around bar 5 rotate two satellite pinions 20 and 21 which mesh with two output planetary pinions 22 and 23 centered on the longitudinal axis Y of the differential.

These planetary gears 22 25 and 23 respectively drive two output half-shafts 24 and 25 each connected to a driving wheel.

The output half-shafts 24 and 25 are also rotatably mounted in respective bores 26 and 27 provided in the housing 1.

The satellite pinions 20 and 21 thus transmit the torque from the crown wheel 2 to the planetary pinions 22 and 23 while distributing the movement between the two driving wheels, with respect to an average speed of the vehicle. In this way, an increase in the speed of one wheel is compensated by a corresponding decrease in the speed of the other wheel.

The differential may further comprise a friction shell 3 between the housing 1 and the planet gears 20, 21 and planetary gears 22,23, said friction shell 3 being crossed by the cylindrical bar 5.

The shell 3, made for example of a material comprising plastic, makes it possible to adjust the positioning of the satellite and planetary pinions 20,21,22,23.

The bar 5 has on its periphery two peripheral grooves 4 located between the two satellite pinions 20,21.

A stop ring 6 serving as a means of abutment in translation to replace the existing stop rings is housed in each of the peripheral grooves 4.

Each rods 6 is elastically mounted in one of the two grooves 4 between a retracted position in said groove 4 and a projecting position out of said peripheral groove 4.

The snap rings 6 have the function of holding the bar 2 in position in the bore of the housing 1 .

As illustrated by the which illustrates a snap ring 6 isolated from the bar 5, each snap ring 6 is in the form of an open ring, comprising two ends 6a, 6b facing each other, which makes it possible to achieve elastically mount the snap rings 6 in the grooves 4 despite their high mechanical strength.

It can be seen that the radial section of at least one stop ring is circular 6, which facilitates the mounting of the stop ring in a groove 4 for the operator, but other section shapes could be envisaged, for example example a square section or a rectangular section, without departing from the scope of the invention.

The generally circular shape of each rod 6 makes it possible to match the shape of the grooves 4, which here is made of circular section with diameters L3 and L4.

More specifically, the general shape of the rods 6 is that of an open circle, in other words an arc of a circle with an angle approximately equal to nine tenths of a turn.

Each rod 6 therefore has two circular end surfaces 6a and 6b facing each other.

The advantage of having rods of generally open shape is that it facilitates the action of arranging them around the bar 5 in the grooves 4, by making it easier to separate the ends 6a and 6b, and therefore by allowing temporarily increase the diameter of the snap ring 6 with less effort.

The force required to disengage the bar 5 from the casing 1 must be high enough to compress each rod 6 and overcome the adhesion force due to the pressure of the rods 6 against the bore of the casing 1.

Each stop ring 6 should preferably have a strong elasticity in order to reduce the effort necessary to set up the bar 5 provided with the ring 6 in the housing l. This elasticity also decreases the effort required to dislodge it.

The stop rings 6 are made of steel, the necessary elasticity being obtained by the open shape of the ring 6.

Unlike some of the known differentials, no specific machining is carried out in the housing 1 to house the rods 4, these being integrated into the differential by being arranged around the bar 5.

As illustrated by the , the two peripheral grooves 4 can be distributed symmetrically with respect to the longitudinal axis Y.

Thus, the balancing of the entire differential is improved and a bar 5 is obtained which can be mounted in any direction in the housing 1.

The housing 1 comprises a cylindrical inner chamber 10 delimited by the satellite and planetary pinions 20,21,22,23 and extending over a length L1.

As illustrated by the , the length L1 of the chamber 10 corresponds to the spacing between the two satellite pinions 20,21 in the housing 1.

The two grooves 4 are therefore spaced apart by a length L2 so that the length L5 corresponding to the sum of said length L2 and the lengths L3, L4 of the grooves 4 is less and substantially close to the length L1 of the chamber 10.

Thus, if the rods 6 are mounted substantially close to the satellite pinions 20, 21 or in abutment against them, the axial displacement of the bar 5 along the transverse axis Z is limited, since the rods 6 come into abutment against the shoulders 10 , 10b formed by the planet gears 20, 21 with respect to the bar 5.

Bar 5 is thus locked in translation relative to housing 1.

Figures 4 to 7 illustrate the steps for inserting bar 5 into housing 1.

The housing 1 comprises an opening 7 which can be provided with a peripheral chamfer, said opening 7 being opposite a central opening passing through the satellite pinions 20,21, the chamfer of the chamfered opening 7 being adapted to allow the placing the stop rings 6 in the retracted position in the peripheral grooves 4 during the insertion of the cylindrical bar 5 through said chamfered opening 7.

During the insertion of the bar 5 into the bore of the housing 1, so as to position the bar 5 correctly, a first snap ring 6 is gradually put under compression stress by the chamfer of the chamfered opening 7 until 'to reach a retracted position in its throat 4.

The retracted ring 6 remains in the retracted position under the effect of radial compressions towards the transverse axis Z exerted first by the housing 1 then by the friction shell 3 then by a satellite pinion 20,21, until said rod 6 reaches chamber 10 and is released by the effect of its elasticity at a shoulder 10a, 10b.

The absence of a chamfer at the level of the shoulders 10a, 10b of the satellites 20,21 prevents the rods 6 from closing again in the retracted position in their groove 4 without external action.

The position of the grooves is defined to minimize the residual travel of the shaft while guaranteeing the axial locking function.

In the same way, the other rod 6 undergoes a compressive stress through the chamfered opening 7, when it reaches it and until the bar 5 is correctly placed, that is to say that rods 6 are both in chamber 10.

At this time, the rods 6 extend in a protruding position, that is to say at least partially outside the grooves 4.

In this way, the rods 6 are positioned to exert a force in reaction to any external force tending to remove the bar 5 from its operating position.

By referring to the , it can be seen that the cylindrical bar 5 can be completely retracted into the housing 1 when the cylindrical bar 5 is positioned correctly, that is to say positioned in such a way that the transmission differential is in working order.

There describes the method of manufacturing and assembling the differential.

This process begins with a first step E1 during which the chamfered opening 7 of the housing 1, in particular, is machined.

It continues with a second step E2 during which at least the two satellite pinions 20,21 are mounted in the housing 1 and their spacing L1 is measured. The length L1 of the chamber 10 is thus measured. This length dimensions the diameter L3, L4 and the spacing of the L2 of the grooves 4.

The method continues with a third step E3 during which the bar 5 is machined and the two peripheral grooves 4 are machined so that their diameters L3, L4 added to their distance L2 with respect to each other are equal or equal. slightly less than the distance L1 between the two satellite pinions 20,21 measured during the second step E2; then the snap rings 6 are placed in the peripheral grooves 4.

The third step E3 continues with a fourth step E4 during which the casing 1 and the bar 5 are assembled by deforming the stop rings 6 in the retracted position thanks to the chamfer of the chamfered opening 7 until said snap rings 6 are positioned between the two satellite pinions 20,21.

The method continues with a fourth step E4 during which the housing 1 and the cylindrical bar 5 are assembled.

This is done by inserting the bar 5 as described in Figures 4 to 7, that is to say by deforming the rods 6 in the retracted position thanks to the chamfer of the chamfered opening 7 until that said rods 6 are positioned between the two satellite pinions 20,21, in chamber 10.

Step E4 can easily be carried out by hand by an operator, without tools. At the end of this step E4, there is an automotive differential comprising a transverse axis provided with a snap ring intended to hold it in position.

Thus, by means of a device and a method such as those described above, it is possible to manufacture, reuse and assemble the sets of known and standard components constituting a transmission differential, and this without requiring tools. and in fewer steps than the state of the art allows. This results in a reduction in manufacturing costs.

In addition, the low cost of the rods 6 allows inexpensive replacement. For this, the planet carrier shaft 5 can be removed by passing a tool through a window of the case 1 to replace the rods 6 in the retracted position in order to allow the sliding of the bar 5.

In addition, the use of stop rings 6 in the shape of a ring and of circular section with a diameter substantially equal to the diameter L3, L4 of the grooves 4, makes it possible to achieve savings in material compared to a conventional system comprising a ring stop, more voluminous.

Such a device also avoids making a groove within the housing 1 or openings for securing hooks 25 as in the known state of the art. This results in a part that is more resistant to high stress and fatigue.

Unlike a differential fitted with a stop ring, a differential of this type does not present the risk of failure of the system for holding the transverse pin in position due to the elasticity of the material constituting the rods 6.

Claims (10)

Transmission differential for a motor vehicle, comprising a housing (1), a cylindrical bar (5) extending along a transverse axis (Z) carrying two satellite pinions (20, 21) which mesh with two planetary pinions (22, 23) centered on the longitudinal axis (Y) of the differential, characterized in that the cylindrical bar (5) has two peripheral grooves (4) located between the two satellite pinions (20,21) in each of which is housed a snap ring (6) elastically mounted between a retracted position in one of the two peripheral grooves (4) and a projecting position out of said peripheral groove (4). Motor vehicle transmission differential (1) according to claim 1, in which each snap ring (6) is in the form of an open ring, comprising two ends (6a, 6b) facing each other. Motor vehicle transmission differential (1) according to any one of claims 1 and 2, in which each snap ring (6) is made of steel. Motor vehicle transmission differential (1) according to any one of the preceding claims, in which the radial section of at least one snap ring is circular (6). Motor vehicle transmission differential (1) according to any one of the preceding claims, in which the two peripheral grooves (4) are distributed symmetrically with respect to the longitudinal axis (Y). Transmission differential for a motor vehicle (1) according to any one of the preceding claims, in which the housing (1) comprises a chamfered opening (7) facing a central opening passing through the planet pinions (20,21), the chamfer of the chamfered opening (7) being adapted to allow the snap rings (6) to be placed in the retracted position in the peripheral grooves (4) during the insertion of the cylindrical bar (5) through said the chamfered opening (7). Motor vehicle transmission differential (1) according to any one of the preceding claims, in which the cylindrical bar (5) is fully retracted in the housing (1). Motor vehicle transmission differential (1) according to any one of the preceding claims, in which each of the rings (6) abuts against one of the planet pinions (20, 21). Motor vehicle transmission differential (1) according to any one of the preceding claims, comprising a friction shell (3) between the housing (1) and the satellite (20, 21) and planetary (22, 23) pinions, said friction shell (3) being traversed by the cylindrical bar (5). Method of manufacturing a transmission differential for a motor vehicle comprising a housing (1) having a chamfered opening (7) facing a central opening passing through two satellite pinions (20,21) which mesh with two planetary pinions (22 , 23), a cylindrical bar (5) in which are formed two peripheral grooves (4) and in each of which is housed a snap ring (6) elastically mounted between a retracted position in one of the two peripheral grooves (4) and a projecting position out of said peripheral groove (4),
the method being characterized in that it comprises a first step (E1) during which the chamfered opening (7) is machined in the casing (l), then a second step (E2) during which at least the two satellite pinions (20,21) in the housing (1) and their spacing is measured (L1), then a third step (E3) during which the bar (5) is machined and the two peripheral grooves (4 ) so that the diameters (L3, L4) of said peripheral grooves (4) added to their distance (L2) relative to each other is equal to or slightly less than the spacing (L1) between the two satellite pinions (20,21) measured during the second step (E2) then the snap rings (6) are placed in the peripheral grooves (4), and a fourth step (E4) during which the casing ( l) and the cylindrical bar (5) by deforming the stop rings (6) in their retracted positions thanks to the chamfer of the chamfered opening (7) until the said rings stopper (6) are positioned between the two satellite pinions (20,21).