FR3116039A1 - Casing of a power steering system device provided with a cover - Google Patents

Abstract

Housing (3) of an assist device (1) comprising an orifice (4, 5) comprising an edge (18) projecting from the housing (3) and defining a hollow cylinder, a cover (22) intended to be placed on the edge so as to obstruct the hole (17), the lid comprising a cylindrical side portion (24), a clamping means, when the lid is placed on the projecting edge, the side portion surrounds the edge, making it possible to carry out a fitting of the lid on the edge, the clamping means exerting a mechanical clamping action in a uniform radial direction on the lateral portion so as to allow the lid to be held in position on the edge. Figure for abstract: Fig. 4

Description

Casing of a power steering system device provided with a cover

The invention relates to the field of casings of motor vehicle power steering systems, and more specifically, a cover intended to plug a hole in the casing as well as a method for fixing the cover to the casing.

Motor vehicles have a steering system provided with a steering wheel driving a steering column. The steering column is connected to a steering box comprising a rack extending along an axis transverse to an elongation axis of the vehicle. The rack makes it possible to pivot the steering wheels of the vehicle.

A power-assisted steering system also comprises an assistance device delivering on the rack an assistance force dependent on that given by the driver on the steering wheel. In this way, the force required of the driver to pivot the steering wheel is reduced.

As shown on the , a type of known electric assistance device 1, comprises an electric motor 2 connected to a casing 3, as shown in , comprising a reduction wheel (not visible in the figures) and an endless screw (not visible in the figures), which drive a toothed wheel fixed on a shaft linked to a pinion of the rack (not visible in the figures).

Such a casing 3 generally comprises one or more access orifices 4, 5 which pass through a wall 6 of the casing 3 to allow introduction and assembly of all or part of the elements arranged inside the casing 3. Once the assembly of the casing 3 made, the orifices 4, 5 are obstructed by means of a cover 7, generally made of thermoplastic material.

The elements arranged inside the casing 3 are lubricated, for example by oil bath or lubrication. Such a lubricant must be able to be kept inside the casing 3, both to avoid, for example, the fouling of other parts of the engine due to lubricant leakage, and to allow the proper functioning of the assistance device 1. In addition, in order to avoid any jamming of the assistance device 1, it is essential to prevent the entry of foreign bodies, for example dust. Also, it is necessary that the covers 7 obstructing the orifices 4, 5 can withstand such external attacks. In addition, the cowls 7 must be able to cope with the overpressures generated by the thermal variations prevailing within the casing, but also with occasional contact with the different types of fluid from other engine components (for example brake or cooling fluid , fuel). The connection between the covers 7 and the casing 3 must remain sealed.

It is known to ensure such sealing using an O-ring 8, arranged for example in a groove 9 made on the periphery of the cover 7. The cover 7 is held in position with a predetermined force, so as to guarantee sealing, i.e. both to prevent a lubricant leak and to prevent the intrusion of water, which generates corrosion, inside the casing 3.

As shown on the , it is known to provide the cover 7 with lugs 10 provided with holes 11, so as to receive fixing screws 12, which themselves extend into the casing 3. Such a principle applies for example to allow the obstruction of the first orifice 4 intended to receive a shaft fitted with a toothed wheel. Such holding in position is not satisfactory, since it requires a positioning operation followed by the screwing in of the screws 12 for fixing. Such screwing operations lead to a loss of assembly time, impacting the assembly time of the casing 3. In addition, such an assembly requires at least the use of three parts (two fixing screws 12 and an O-ring 8) to perform the sealing function. Finally, the lugs 10 and fixing screws 12 occupy a relatively large volume.

Alternatively, as shown in the , the cover 7 comprises a periphery 13 provided with one or more lugs 14 arranged circularly projecting and intended to cover a second orifice 5 intended to receive a shaft provided with splines. Often the splined shaft is supplemented with a clearance adjustment system and may be in two parts. Such a second orifice 5 comprises an outline 15 provided with a groove 16. When the cover 7 is inserted on the second orifice 5, the lug 14 comes into contact with the outline 15 of the second orifice 5, until it is lodged within of the groove 16. In this way, the cover 7 is held in position on the orifice 5 by snap-fastening. Moreover, in such an alternative, the shaft provided with the spline is completed by a clearance adjustment system, and the groove is formed by the insertion of a second part inserted into the cover 7. Although it allows 'improve the ease of assembly by reducing the number of parts, the positioning of the lug 14 within the groove 16 requires the performance of machining operations. Such operations are generally expensive, and result in a loss of productivity.

Finally, in the assembly methods described above, it is necessary to make a groove 9 on the cover 7, to allow the installation of an O-ring 8 to accomplish the sealing function. The use of the O-ring seal 8, and the making of the groove 9 (in the case of the cover 7 according to the alternative shown in ), generate costs and loss of productivity.

The invention proposes to respond to the aforementioned drawbacks.

A first objective is to provide a casing provided with a lid, the lid being capable of obstructing an orifice in a sealed manner.

A second objective is to provide a casing provided with such a cover that is easy to manufacture, allowing rapid assembly, and without requiring screwing.

A third objective is to provide a casing provided with such a cover having a reduced cost compared to known covers.

A fourth objective is to propose an electric assistance device comprising a casing as described above.

A fifth objective is to propose a method for mounting such a cover on the casing.

To this end, there is firstly proposed a casing of an assistance device comprising an orifice comprising an edge projecting from the casing and defining a hollow cylinder forming a hole, a cover intended to be placed on the edge so as to obstruct the hole, the cover comprising a cylindrical side portion, a clamping means, when the cover is placed on the projecting edge, the side portion surrounds the edge, making it possible to carry out a fitting of the cover on the edge, the clamping means exerting a mechanical clamping action in a uniform radial direction on the side portion so as to allow the lid to be held in position on the edge.

Such a cover making it possible to obstruct a hole in the casing in a liquid- and dust-tight manner, without requiring the addition of an O-ring. Such a lid is easy to obtain, and has a reduced cost of obtaining.

Various features can be provided alone or in combination:

• the cover comprises a core of circular contour, the lateral portion extending projecting from the core, at the periphery of the core, the cover having a U-shaped section along a radial plane,
• the cover is made of a thermoplastic material that is sufficiently deformable to be able to be positioned manually on the edge,
• the cover is made of elastomer,
• the clamping means comprises a clamp, the clamp surrounding the side portion when the cover is placed on the edge,
• the clamp includes an assembly capable of receiving a crimping tool

Secondly, an electric assistance device for a power-assisted steering system is proposed comprising a wheel and worm screw system, a casing as presented above, the orifice being intended for the housing of a toothed wheel, or for the housing of a clearance adjustment system or reduction housing.

Thirdly, a power steering system with the above assistance device is proposed.

Fourthly, a method for assembling the casing presented above is proposed, comprising the steps of positioning the cover on the edge by fitting, positioning the clamping means around the lateral portion and tightening the clamping means .

Other characteristics and advantages of the invention will appear more clearly and concretely on reading the following description of embodiments, which is made with reference to the appended drawings in which:

represents a schematic view in perspective of an electrical assistance device of a power steering system according to the prior art,

represents a schematic sectional view according to plan II-II of the a prior art housing orifice, the orifice being obstructed by a cover,

represents a schematic sectional view according to plan III-III of the a prior art housing orifice, the orifice being obstructed by a cover,

represents a schematic view in perspective of an electric assistance device of a power-assisted steering system provided with covering means,

represents a schematic perspective view of a covering means,

shows a schematic perspective view of an example of a clamping means,

shows a schematic sectional view of an orifice provided with a covering means.

We refer to the representing an electric assistance device 1 of a power steering system (not shown) of a motor vehicle (not shown).

The electric assistance device 1 comprises a casing 3 intended to receive a wheel and endless screw system (not shown).

In the embodiment shown, the casing 3 comprises a first orifice 4 and a second orifice 5, each of them comprising a hole 17 (visible on the ), intended to allow the integration respectively of a toothed wheel (not visible in the figure), and of a worm (not visible in the figures).

In embodiments not shown, other orifices are provided in the casing 3 to allow the integration of other parts within the casing 3.

As can be observed on the , the orifices 4, 5 are each obstructed, plugged, covered, in a leaktight manner by a covering means. In this way, no liquid, or dust likely to hinder the operation of the electrical assistance device 1 can penetrate within the casing 3. The production of a sealed cover also makes it possible to avoid any leakage of lubricant, or of avoid any penetration of water inside the casing 3.

We refer to the and 7 representing a first orifice 4 covered by a covering means. We limit ourselves to the description of a first orifice 4, but this description applies identically mutatis mutandis to a second orifice 5.

The first orifice 4 comprises an edge 18 projecting from the wall 6 of the casing 3. The edge 18 comprises an internal surface 19, and an external surface 20, connected by a stop surface 21. In this way, it may be possible to fit the cover means onto the outer surface 20, which facilitates the positioning of the cover means over the first orifice 4. The edge 18 has a sufficiently large height and thickness to make it possible to guarantee the stability and maintenance over time of the covering means on the first orifice 4.

Advantageously, the edge 18 is made in one piece from the wall 6 of the casing 3, and is for example obtained by molding. Thanks to such an arrangement, the first orifice 4 can be obtained without it being necessary to carry out any machining operation. In this way, the cost and the production time of the casing 3 are reduced.

As can be seen in Figures 4, 5 and 7, the covering means comprises a lid 22 as well as a clamping means.

When the first orifice 4, in particular the hole 17, is covered by the cover means, the cover 22 is fitted by fitting, or is fitted on the edge 18, the clamping means exerts a concentric, radial and uniform clamping force. . The force being distributed evenly over the entire edge 18 of the hole, the connection between the cover 22 and the edge 18 is sealed.

The cover 22, of generally cylindrical shape of revolution, advantageously comprises a core 23 and a lateral portion 24, having a U-shaped section along a radial plane. Such a shape gives it an easy grip, which allows easy handling. In addition, thanks to the side portion 24, the cover 22 can be held on the casing 3, freeing the hands of the user to add the clamping means.

In the embodiment shown, the core 23 is intended to be at least facing the hole 17. Such a core 23 is advantageously in the form of a circular contour plate, which allows it to occupy a reduced volume.

Preferably, when the cover 22 is placed on the hole 17, the stop surface 21 is in contact with the core 23. In this way, the stop surface 21 acts as a stop, allowing the user to be certain of the correct positioning of the cover 22.

As can be seen on the , the side portion 24 protrudes from the core 23 by defining for example a cylinder, of axis identical to the axis of revolution of the core 23. In this way, the side portion 24 has a flat side face 25 allowing the reception of a concentric clamping means.

Advantageously, in a radial plane, the angle A between the core 23 and the lateral portion 24 is identical to the angle B between the stop surface 21 and the outer surface 20 of the edge 18. In this way, the cover 22, and in particular the side portion 24, matches the edge 18. The first orifice 4 is obstructed in a sealed manner.

Preferably, the angle A between the core 23 and the lateral portion 24 is identical to the angle B between the stop surface 21 and the outer surface 20 of the edge 18. The angle A and B preferably have all the two a value slightly greater than 90°, for example 91-92°. In this way, forms of undercut are avoided, both at the level of the cover 22 and at the level of the edge 18. In this way, obtaining the casing 3, and the cover 22 is possible by molding process.

Advantageously, the side portion 24 extends around the periphery of the core 23, which makes it possible to limit the size of the cover 22. In such a configuration, as can be seen on the , the cover 22 has, along a plane passing through the axis of revolution of the cover, in other words a radial plane, a general U-shape.

The cover 22 is advantageously made of a thermoplastic material, which allows mass production at reduced cost. The chosen thermoplastic, for example a thermoplastic from the family of elastomers, has sufficient elasticity to facilitate assembly by fitting of the cover on the edge 18.

In the embodiments shown, the clamping means is a piece attached to the edge 18, in contact with the side face 25. The installation of such a clamping means on the cover 22 is thus facilitated, as explained above. later in this description.

In the embodiments shown, the clamping means is for example in the form of a collar 26 comprising a deformable strip 27 forming a circular loop 28 of variable size. Loop 28 thus evolves between a positioning configuration and a clamping configuration. In the positioning configuration, the loop 28 has a diameter greater than the diameter of the side portion 24, while in the tightening configuration, the loop 28 has a diameter less than the diameter of the side portion 24.

Such a collar 26 is intended to be placed around the lateral portion 24, then to exert a clamping force allowing the throttling of the lateral portion 24. In this way, it is possible to press the lateral edge 18 against the external surface 20 of the edge making it possible to eliminate any residual space between the external surface 20 and the lateral portion 24, which makes it possible to seal the connection between the casing 3 and the cover 22.

Such a throttling force also allows the cover 22 to be able to withstand the internal pressure prevailing within the casing 1, caused in particular by the thermal variations generated in particular by the engine.

Advantageously, the strip 27 has a width less than or equal to the dimension of the edge 18, in order to allow a homogeneous distribution of the forces all around the edge 18. In this way, the entirety of the strip exerts a strangulation force on the side face 26.

As seen on the , the connection means is formed of a notch 29 provided on the strip 27 and openings 30 formed on one end 31 of the strip. In this way, the size of the loop can be adjusted without difficulty. Such an adjustment also avoids the use of additional parts. Thus, the number of parts to make it possible to obstruct the casing 3 is reduced, limiting the cost of obtaining the cover 22.

The collar 26 is advantageously deformable, and comprises for example a clamping assembly 32 comprising for example two clamping section 33 connected to a connecting section 34. Such a clamping assembly 32 makes it possible, once the collar has been placed around the edge 18, to reduce the diameter of the loop 28 by means of a crimping tool, such as pliers, bringing the sections 33 closer to tightness between them. In this way, the collar 26 can be tightened to the edge 18 by means of a crimp, which facilitates the maintenance in position of the cover 22 on the edge 18.

As explained above, the embodiments have been described with reference to a first orifice 4, but also relate to a second orifice 5. Also, unlike the structures of the prior art, the same principle can be used independently of the type of orifices 4, 5 of the casing 3 to be blocked.

Such a collar 26 is easy to obtain, economical, resistant to pressure, easy and quick to put on the lid.

We now describe the installation of a cover 22 on an orifice 4, 5.

The cover 22 is approached and then positioned manually on the orifices 4, 5 by a simple pressure force, ensuring that the cover 22 is fully abutted against the stop surface 21, which guarantees correct positioning on the cover 22 .

Then, the user grasps the collar 26, and places the loop 28 around the edge 18, previously placed in the open configuration.

The loop 28 is then placed in a tightening configuration, for example by bringing the tightening sections 33 closer together, which has the effect of reducing the diameter of the loop 28.

The cover 22 is arranged for example on a hole 17 capable of receiving a hole intended for the housing of a toothed wheel, or for the housing of a clearance adjustment system or reduction housing.

The cover 22 provided with the clamping means offers many advantages, for example:

• reduced production cost,
• a possibility of mounting on hole 17 without prior learning being necessary,
• quick assembly,
• mechanical and thermal resistance adapted to the constraints of the vehicle engine.

Claims (9)

Casing (3) of an assistance device (1) comprising:
an orifice (4, 5) comprising an edge (18) projecting from the casing (3) and defining a hollow cylinder forming a hole (17),
a cover (22) intended to be placed on the edge (18) so as to obstruct the hole (17), the cover (22) comprising a cylindrical lateral portion (24),
a clamping means,
characterized in that when the cover (22) is placed on the projecting edge (18), the lateral portion (24) surrounds the edge (18), allowing the cover (22) to be fitted onto the edge (18) , the clamping means exerting a mechanical clamping action in a uniform radial direction on the lateral portion (24) so as to make it possible to hold the cover (22) in position on the edge (18). Casing (3) according to Claim 1, characterized in that the cover (22) comprises a core (23) of circular contour, the lateral portion (24) projecting from the core (23), at the periphery of the core, the cover (22) having a U-shaped section along a radial plane. Casing (3) according to Claim 1 or 2, characterized in that the cover (22) is made of a thermoplastic material which is sufficiently deformable to be able to be positioned manually on the edge (18). Housing (3) according to the preceding claim, characterized in that the cover (22) is made of elastomer. Housing (3) according to any one of the preceding claims , characterized in that the clamping means comprises a clamping collar (26), the clamping collar (26) surrounding the lateral portion (24) when the cover (22) is placed on the edge (18). Casing (3) according to the preceding claim, characterized in that the clamping collar (26) comprises an assembly (32) capable of receiving a crimping tool. Device (1) for electric assistance of a power-assisted steering system comprising a wheel and worm screw system, a casing (3) according to any one of the preceding claims, the orifice (4, 5) being intended for the housing of a toothed wheel, or for the housing of a clearance adjustment system or reduction housing. Power-assisted steering system provided with the assistance device (1) of the preceding claim. Method of mounting the casing according to claim 6, characterized in that it comprises the following steps:
- placing the cover (22) on the edge (18) by fitting,
- placing the clamping means around the side portion (24),
- tightening of the clamping means.