Patent Application
20100229821
The present invention relates to the field of oil sumps for internal combustion engines, typically placed at the bottom of the engine. The invention thus relates to a plastic oil pan/sump that is said to be structural, that is, that it supports dynamic bending and twisting forces (caused by the reactions of the engine mountings and of the gearbox of a vehicle). The invention also relates to the method of manufacturing this sump, and a use of a bottom part in an oil sump.
A combustion engine sump often has a structural role for the engine, when it is not made of thin steel plate. In a known manner, the sump comprises a pan or tank delimiting a volume for receiving oil on the one hand, and a top opening on the other hand. This top opening is edged by a flange joined to the pan, for mounting on a complementary member of a combustion engine. The engine sump thus adds rigidity in the cases where it forms a pan at the bottom of the engine or of the engine block because it has to withstand dynamic bending and twisting forces, caused by the reactions of the engine mountings and of the gearbox (to which it is also attached).
To address this issue of rigidity, it is known from the prior art, for the manufacture of oil sumps, to use molded metallic materials, such as cast iron or light alloys, ribbed in their design, supported by calculations and endurance tests. One drawback of these metallic materials used to obtain structural sumps is their weight. Furthermore, implementing them takes more energy. Their use gives an ecological budget that is therefore mediocre.
Known from document WO 03/102387 A1 is an oil pan for combustion engines, in which metal components are replaced by molded plastic components offering a rigidity comparable to that of the metal components. The pan comprises a molded plastic container on a metal or plastic support structure. An anti-turbulence or anti-emulsion plate can be inserted inside the pan and rest on appropriate mountings. Passages for the flow of oil are left around this plate.
This type of pan provides a way of addressing the two-fold issue of weight and rigidity. However, the overmolding manufacturing method is relatively complex to implement. The products obtained according to the teaching of document WO 03/102387 A1 are more costly to manufacture than a single-material sump, in particular made of injection molded plastic. A sump made up of a number of materials is also more difficult to recycle at the end of its life, because the components of different materials must be separated from one another, which components are moreover firmly linked to serve as reinforcements, particularly when these reinforcements have been overmolded.
It is also necessary to stress here the fact that, hitherto, the use of injected plastic to manufacture a sump has been limited to a very small number of applications, when the stresses exerted on the bottom of the engine are relatively weak. For more severe applications, the forces (bending, twisting, stresses exerted on the plastic walls) are too great and the sump must be designed using metal material. There is therefore a need for sumps mainly or completely produced using plastic material and offering good structural characteristics.
The aim of the present invention is therefore to eliminate one or more of the drawbacks of the prior art by defining a sump of light weight and of simplified design, and therefore less costly, which offers good structural resistance characteristics.
To this end, there is proposed according to the invention a structural oil sump for a combustion engine, provided with a top opening and comprising:
a single-piece top part made of plastic material comprising a number of lateral walls peripherally delimiting an internal volume, and at least one transversal part extending inside said internal volume and joining at least two of the lateral walls, the top part extending between a top end defining said top opening and a bottom end defining a bottom opening;
a bottom part comprising a bottom and fixed in a sealed manner to the bottom end of the top part;
the sump being provided with internal ribs formed integrally with the top part and positioned opposite the bottom.
Thus, the sump is obtained by the joining of two parts, at least the top part being able to be light (this top part also being simple to mould). The bridge formed by the transversal part which is firmly linked to the lateral walls makes it possible, with the internal ribs, to increase the rigidity and consolidate the structure of the sump. The priority function of this plastic bridge is a structural function, unlike the anti-emulsion plates whose main function is to allow for a circulation of the oil.
In various embodiments of the structural oil sump according to the invention, one or more of the following arrangements may, if necessary, be used:
the bottom part is made of plastic material;
the transversal part is further away from said bottom than from the top end of the top part;
the transversal part is further away from the bottom end than from the top end of the top part;
the internal ribs comprise ribs integrally linked both to one of the lateral walls and to said transversal part;
the transversal part forms a bridge provided with orifices distant from the lateral walls to allow a circulation of oil.
the top part has an inverted U shape, respectively according to two mutually orthogonal vertical cross-sectional planes;
the bottom part offers an internal volume of which a portion has a section, perpendicularly to the heightwise direction of extension of the top part, greater than the section of the internal volume of the top part (the heightwise direction of extension of the top part is typically also the direction of demolding of this part);
the bottom part is essentially made of plastic material and is secured by welding to the bottom end of the top part;
the welding extends continuously all around the bottom opening;
the sump also comprises a securing device for securing the bottom part to the top part;
the bottom part comprises, on at least one external face, one or more projecting fixing members formed with the bottom part;
the bottom part comprises a cavity for incorporating an oil treatment module in a housing situated inside the bulk volume delimited by the sump.
Moreover, another subject of the invention is a manufacturing method that is relatively simple and easy to industrialize that makes it possible to obtain a sump that is both lightweight and highly structural.
To this end, there is proposed a method of manufacturing a structural oil sump for a combustion engine, comprising a step for assembling two complementary parts, of which one is a bottom part comprising a bottom and the other a top part comprising a top end delimiting a first opening of the top part, characterized in that:
a molding is produced by injecting plastic material to provide, all in a single block, said top part with an integrated transversal part which extends inside an internal volume of the top part;
during the injection molding, there is formed, integrally with the transversal part, ribs projecting towards a second opening of the top part; and
during the assembly step, the bottom part is fixed to the bottom end of the top part, at a distance from the transversal part, to block off said second opening in a sealed manner.
Thanks to the present invention, it is possible to minimize the impact, on the cost of the manufacturing method, of changes made to an oil sump mainly made of plastic. It is thus possible to use a bottom part to form a part of a structural oil sump according to the invention, this bottom part being used in a method of closing said sump from the bottom. It is thus advantageously possible to easily and inexpensively have the shape of the sump changed, by modifying only the bottom part. Modifications do not relate to the top part which comprises the reinforcing ribs. Thanks to the flexibility of the design of the injected plastic shapes, it is possible to produce undercuts, pipe overmoldings, plastic welds, sometimes even an adhesive bonding.
Other features and benefits of the present invention will become more clearly apparent from reading the description herein below, given with reference to the appended drawings in which:
In the various figures, the same references designate identical or similar elements.
The oil sump for a combustion engine will now be described in association with
The structural oil sump 100 is formed by an assembly of two complementary parts of which one, the bottom part, comprises a bottom 10 of the sump 100 and the other, the top part, is a superimposed part provided with reinforcing ribs 24, 25. The two complementary parts are preferably made of plastic. Alternatively, the bottom part can be made of lightweight material other than plastic.
In a preferred embodiment, the plastic material used is, for example, a thermoplastic withstanding temperatures of the order of 100° C. and above. In a non-limiting manner, at least the top part of the sump 100 is based on polyamide. Plastic PA6.6GF35 can be used for the design of the parts of the sump 100. The temperatures accepted continually by such plastic materials such as PA6.6GF35 have reached those of alloys (as an indication, the mechanical properties of aluminum alloys drop away towards 150° C.).
The top part 30 consists of a multiple-walled single-piece part comprising lateral walls 31, 32, 33, 34 (typically at least four lateral walls), and at least one transversal part 20 linking at least two of the lateral walls 31, 32, 33, 34 to form a bridge. The lateral walls for example form a peripheral part 31, 32, 33, 34 which surrounds the transversal part 20. This transversal part 20 can consist of a plate. It can also form a wall extending inside the internal volume substantially transversally to the heightwise direction of extension of the top part 30. The distance separating the transversal part 20 from the top end of the top part is less (for example at least four times less) than the distance separating the transversal part 20 from the bottom end of the top part 30.
A seal-tight link 40 is produced between the bottom part 50 comprising the bottom 10 and the top part 30. The resulting assembly forms a sump 100 which is provided with internal ribs 26, 27 that are raised and opposite the bottom 10.
The sump 100 comprises at its top end a flange 36 which can be formed by a collar, continuous or otherwise, of the single-piece part 30. The flange 36 can extend laterally towards the outside relative to the top edge of the lateral walls 31, 32, 33, 34 of the single-piece part 30. This flange 36 delimits a top opening of the sump 100. The flange 36 constitutes a member by which the sump 100 can be attached, for example to an engine cylinder block 120. Holes 35 with vertical component are, for example, distributed over the flange 36 to provide the link to the bottom of the block 120. It will be understood in light of
Referring to
The bottom part 50 can also delimit cavities. Referring to
In the example of
One or more fixing members 67 for a pipe T can also be provided. A draining system 66, for example in the form of an interface for connecting to a drainpipe, can also be formed on the bottom part 50. Forms facilitating the flow of the oil to the draining plug can also be provided on the bottom part 50. Alternatively, the drain hole can be made in a bottom portion of the top part 30. A sensor 62 and/or an oil level gauge can be fixed to the bottom part 50. In the example of
As an example, the sump height can be minimized and a volume surplus 69 can be added at the bottom of the sump 100, as illustrated in
Two external lateral widenings or expansions 500 can be provided, as illustrated in
In the non-limiting example of
The multiple-wall top part 30 is therefore designed without a bottom. The result of this is ease of demolding: it is therefore easy to produce, on each side of the plastic transversal portion 20, ribs 24, 26, 27 joining lateral walls of the sump 100. In other words, the ribs 24, 26, 27 that are produced are integrally linked both to one of the lateral walls of the top part 30 and to said transversal part 20. Certain ribs 26, 27 formed on the underside of the transversal part 20 can extend downwards over a height representing at least half of the height of the volume delimited at the bottom of the sump by the transversal part 20.
As illustrated in
Referring to
An anti-emulsion plate (windage tray or baffle plate) can sometimes be included underneath the crankshaft 140, in a position, for example, higher than that of the transversal part 20. This type of plate does not adequately reinforce the inertia of the sump because it is not strongly linked to the lateral walls 31, 32, 33, 34 and is in contact with the latter only over an area that is reduced in height. To be truly structural, a sump 100 in accordance with the invention has at least one transversal part (plate, wall or similar element) integrally formed with the peripheral part of the top part 30. Naturally, an anti-emulsion plate can, if necessary, be directly attached to the top part 30.
In the example of
As illustrated in
With the transversal portion 20 formed integrally with the lateral walls 31, 32, 33, 34, such deformations are prevented. The transversal portion 20 is also provided with ribs 24, 26, 27 integral both to the transversal part 20 and to one of the lateral walls 31, 32, 33, 34 of the single-piece part 30. These ribs 24, 26, 27 provide reinforcement, and it is possible to retain a small thickness and so lighten the sump 100. The structural effectiveness obtained in this way is far greater than the use of a simple fitted-on adjoining plate. Moreover, the provision of the internal ribs 26, 27 does not cause any bulk problem for the sump 100. There is no need to provide ribs that project too much around the sump 100.
The benefit of providing a reinforcement in the form of a transversal part 20 and the associated ribs 24, 26, 27 is to improve the mechanical behavior of the sump 100, without requiring too great a wall thickness. The manufacturing of sumps with walls 5 mm or more thick is thus avoided. The top part 30 made of injected plastic, unlike parts with too great a thickness, can then easily be manufactured in series. A considerable time saving is obtained for the manufacturing cycles. Furthermore, the architecture of the top part 30 allows for demolding without difficulty, and notably without risk of deformation on removal from the mould.
The sump 100 represented in
In one embodiment of the invention, the transversal part 20 is positioned approximately at mid-height or a little higher, and, by itself, increases the rigidity of the link between the gearbox 150 and the cylinder block 120. In the example of
The multiple-walled single-piece part 30 can be made by a controlled injection of plastic material into a mould, through one or more injection points, so as to obtain one and the same thickness for the transversal part 20 and for the lateral walls 30, 31, 32, 33. In the example of
In one embodiment of the invention, the multiple-walled single-piece part 30 can be in the form of a U, inverted, in respectively two mutually orthogonal vertical cross-sectional planes. The multiple-walled top part 30 can also be in the form of an H in respectively two mutually orthogonal vertical cross-sectional planes.
In the example of
Referring to
The seal-tight link 40 can therefore be obtained by a continuous weld. In the example of
Referring to
It is then possible to position the bottom part 50 so as to cover the seal-tight ring and produce the joining of the two constituent parts 30, 50 of the sump 100. The sump 100 can be assembled with the multiple-walled single-piece top part 30 turned over relative to the position illustrated in
The two complementary parts 30, 50 are preferably made of the same plastic, which makes it possible to produce a plastic weld and obtain a single-material sump. To allow for laser welding, one and/or the other of the two parts 30, 50 is made of a material transparent to laser emissions. In the example of
Clipping the bottom part 50 makes it possible to hold this part 50 against the lateral walls 31, 32, 33, 34 of the top part 30. The holding action is obtained when the clips 113 are engaged with a complementary part. To take a by no means limiting exemplary embodiment in which the clips 113 are molded with the multiple-walled single-piece part 30 (case of
The method of manufacturing the oil sump 100 can include two steps of injection into a mould to obtain respectively the top part 30 and the bottom part 50, then a step of assembly of these two parts 30, 50. The injection steps are easy to implement. The multiple-walled top part 30 illustrated in
One of the benefits of the sump based on plastic material, in particular thermoplastic(s), is the natural ability for this sump 100 to absorb acoustic waves. Now, for environmental reasons, efforts are being made to reduce the vehicle passing noise, largely generated by the reflection of the acoustic waves originating from the engine on the road. Under-engine screens are no longer adequate to attenuate this energy, which is propagated towards the bottom of the engine, through the sump. The sump 100, consisting, for example, entirely of thermoplastic, can itself attenuate emitted noise of several dBA, in the audible frequency. Consequently, it makes it possible, in this large measure, to avoid having to use an additional absorption part which is costly, weighty, bulky and a hindrance to maintenance.
One of the benefits of the method is to give the possibility of ribbing the sump from a high position corresponding to the position of the transversal plate 20 towards the outside, in particular towards the bottom, with a rib height that is advantageous, because it is essential to minimize the height of the structural sump 100 to preserve the ground clearance of the vehicle and not reduce the necessary oil capacity. The ribs can be of great thickness and genuinely serve to increase the structural rigidity of the bottom portion of the sump 100, and not only limit the acoustic effects.
Another benefit of the method lies in the ease with which a plastic sump, of optimized form and rendered highly structural, can be manufactured. It is in fact easy to obtain the two parts to be assembled. Furthermore, it is possible to modify just one of the two parts 30, 50 to produce a new form of sump. The form of the bottom 10 can thus be modified locally, for example, without requiring a complete replacement of the manufacturing installation. This method can be easily industrialized and is more particularly ideal for meeting the requirements of mass-production manufacture, unlike methods of molding complex and therefore costly parts. Furthermore, the use of a plastic material of small thickness and therefore of little weight offers a benefit in both economic and environmental terms.
It should be clear to those skilled in the art that the present invention allows for embodiments in numerous other specific forms without departing from the scope of the invention as claimed. In particular, although the description relates to an oil sump, it will be understood that any equivalent liquid, any lubricating substance, a liquid medium with evaporation point higher than water (therefore less volatile) and preferably not miscible with water, can also fill the bottom 10 of the sump 100.
