EP2160574A1

EP2160574A1 - Oil level dipstick guide assembly

Info

Publication number: EP2160574A1
Application number: EP07805668A
Authority: EP
Inventors: Mario Zasa; Roberto Defilippi
Original assignee: Dytech Dynamic Fluid Technologies SpA
Current assignee: SumiRiko Italy SpA
Priority date: 2007-06-26
Filing date: 2007-06-26
Publication date: 2010-03-10
Also published as: WO2009001380A1

Abstract

A guide assembly (1) for an oil level dipstick comprising a tube (2) and fastening means (3) for coupling with the crankcase of an engine, wherein the tube (2) comprises a copolymer obtained from dicarboxylic units and amine unites, wherein the dicarboxylic units are 60-100% terephthalic acid and 60- 100% is diamine units which are selected from 1,9- nonanediamine and 2 -methyl -1, 8-octanediamine.

Description

OIL LEVEL DIPSTICK GUIDE ASSEMBLY

TECHNICAL FIELD

The present invention relates to an oil level dipstick guide assembly, and specifically an oil level dipstick guide assembly of a motor vehicle engine. More specifically, the present invention relates to the use of a polymeric material structure having excellent heat and chemical resistance properties for making the guide assembly tube. BACKGROUND ART

It is known that level dipsticks which are inserted in the engine oil tank are used to check the lubrication oil level. The level dipstick passes through a pipe, also called "guide assembly". According to the engine dimensions and geometry, this pipe must have a predetermined shape which allows to be appropriately inserted in the engine compartment.

The guide assemblies generally used in motor vehicles are formed by metal to resist the high temperatures which are developed in the engine crankcase during the entire lifespan of the vehicle.

It is also however known from GB2317931 a guide assembly for an oil level dipstick for an internal combustion engine formed by polymeric material. Specifically, such guide assembly comprises a tube segment of predetermined length formed by resilient plastic material, and first coupling means engaged on an end of the tube, so as to obtain the fastening with second coupling means inserted in an opening obtained in the housing of an engine for allowing access to the corresponding oil tank, wherein the first and the second coupling means snappingly and reciprocally interact.

Preferably, the guide tube is formed by polyamide material .

The guide pipe of an oil level dipstick formed by thermoplastic or elastomeric material may be comprised between two connectors, one fitted on directly on the engine crankcase and the other in a fastening part of the dipstick, respectively.

Alternatively, the guide assembly is secured to the crankcase by means of a nut-biconical ring coupling. The connectors are usually formed by injection molding in glass-filled polymeric material.

However, the guide assemblies of an oil level dipstick formed by polymeric material present some major problems. Superficially, they may only be used in applications in which the temperature of the engine compartment is not particularly high, such as on trucks. The need is instead currently felt on the automotive market, specifically for diesel applications, but potentially also for gasoline applications, for oil level dipstick guide assemblies capable of resisting much higher temperatures, with fluid peak temperatures of up to 160⁰C and working temperatures of approximately

145°C. Further problems . found in the use of guide assemblies formed by polymeric material are the poor chemical stability towards the chlorides which may occasionally be present in aqueous solution inside the engine compartment and a poor resistance to engine oil. Such problems result in a rapid dissolution of the materials forming the guide assembly with corresponding frequent breakages . DISCLOSURE OF THE INVENTION It is therefore the object of the present invention to make a plastic material oil level dipstick guide assembly adapted to solve the above-described problems and which presents good rigidity, heat and chemical stability properties, in addition to good compatibility with the co-molding process of accessory elements needed to secure the guide assembly inside the engine compartment.

According to the present invention, an oil level dipstick according to claim 1 is thus made. A further object of the present invention is the use of a copolymer obtained from dicarboxylic units and diamine units for manufacturing an oil level dipstick guide assembly according to claim 21.

According to another aspect of the present invention, a manufacturing method for an oil level dipstick guide assembly of a motor vehicle engine is provided according to claim 22. The method comprises the step of extruding a tube comprising a copolymer obtained from tricarboxylic units and diamine units. BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, it will now be further described with reference to the accompanying figures, in which:

- Figure 1 shows a perspective view of an oil level dipstick guide assembly according to the present invention;

- Figure 2 shows a cross section view of the two- layer tube of the guide assembly of the oil level dipstick in figure 1.

BEST MODE FOR CARRYING OUT THE INVENTION

In Figure 1, numeral 1 indicates an oil level dipstick guide assembly as a whole. Guide assembly 1 according to the present invention comprises a tube 2, securing means 3 for stably connecting and positioning the guide assembly itself with respect to the engine crankcase of a motor vehicle (not shown) . Guide assembly 1 may further comprise an abutting or stop element 4, designed to ensure an optimal and precise positioning of the guide assembly with respect to the oil tank in the engine compartment of a motor vehicle and thus ensure the correct reading of the oil level. Fastening means 3 and abutting element 4 are preferably formed on tube 2 by co-molding.

Fastening means 3 may consist of a bracket 5, also formed by plastic material, comprising a ring element 6 directly fixed to tube 2 and a protruding portion 7 defining an essentially flat plate, within which there is obtained at least one through hole 8 adapted to accommodate fastening means, e.g. a screw, for connecting guide assembly 1 to the engine crankcase. Through hole 8 may be further provided a metallic reinforcement insert 9. Furthermore, guide assembly 1 may be provided with a stiffening sheath 12 in the upper portion, i.e. the one most directly stressed at each insertion of the level dipstick.

According to the present invention, tube 2 comprises at least one layer comprising a copolymer obtained from dicarboxylic units and diamine units .

Alternatively, tube 2 is entirely formed by a single layer comprising a copolymer obtained from dicarboxylic units and diamine units.

Alternatively, as shown in Figure 2, tube 2 is formed by a first layer 10 comprising a copolymer obtained from dicarboxylic units and diamine units and a second layer 11 comprising a polyamide resin, preferably a polyamide 12.

Alternatively, tube 2 is formed by three or more layers in which at least one comprises a copolymer obtained from dicarboxylic units and diamine units and a second layer 11 comprising a polyamide resin, preferably a polyamide 12.

Preferably, the layer formed by a copolymer obtained from dicarboxylic units and diamine units comprises more than 60% of the copolymer. More preferably, the first layer comprises more than 90% of the copolymer. Even more preferably, the first layer is entirely formed by the copolymer. In the copolymer, the dicarboxylic units are preferably terephthalic acid for more than 60%. More preferably, the dicarboxylic units are preferably terephthalic acid for more than 90%. Even more preferably terephthalic acid constitutes 100% of the dicarboxylic units .

Preferably, the diamine units are 1,9- nonanediamine or 2-methyl-1, 8-octanediamine for more than 60%. Preferably, the diamine units are 1,9- nonanediamine or 2-methyl-l, 8-octandiamine for more than 90%. Even more preferably, the diamine units are 1,9- nonanediamine or 2-methyl-l, 8-octanediamine for more than 100%.

Examples of dicarboxylic units other than terephthalic acid comprise dicarboxylic aliphatic acids come malonic acid, dimethylmalonic acid, succinic acid, glutaric acid, adipic acid, 2-methyl adipic acid, trimethyl adipic acid, pimelic acid, 2,2- dimethylglutaric acid, 3 , 3-diethylsuccinic acid, azelaic acid, sebacic acid and suberic acid; alicyclic dicarboxylic acid as 1, 3-cyclopentandicarboxylic and 1, 4-cyclohexandicarboxylic acid; aromatic dicarboxylic acids such as isophthalic acid, 2,6- naphthalenedicarboxylic acid, 2,7- naphthalenedicarboxylic acid, 1, 3-phenylene- dioxyάiacetic acid, diphenic acid, 4, 4 ' -dioxybenzoic acid, diphenylmethane-4, 4 ' -dicarboxylic acid, diphenyl sulphone-4 , 4 ' -dicarboxylic acid and 4,4' -diphenyl dicarboxylic acid; or a mixture thereof.

Among these, the aromatic dicarboxylic acid are preferred.

Examples of diamine units other than above- mentioned 1 , 9-nonanediamine and 2-metil-l, 8- octanediamine comprise aliphatic diamines such as ethylenediamine, propylenediamine, 1, 4-butanediamine, 1, β-hexanediamine, 1, 8-octanediamine, 1,10- decanediamine, 3-metil-l, 5-pentanediamine; alicyclic diamines such as cyclohexanediamine, methyl cyclohexanediamine and isophoronediamine; aromatic diamines such as p-phenylenediamine, m-phenylenediamine, p-xylenediamine, m-xylenediamine, 4,4'- diaminodiphenylmethane, 4,4' -diaminodiphenylsulfone, 4 , 4 ' -diaminodiphenyl ether; and an arbitrary mixture thereof .

Polyamide resin is preferably of the type described in patent US6989198 and thus named PA9T or P9T.

More preferably, the polyamide resin is a Genestar® resin by Kuraray. Even more preferably it is a Genestar® resin by Kuraray of the series.

The mechanical features of a P9T are appropriately modified by means of the use of additives and fillers of various type.

P9T not filled with elastomers or with a low elastomer filler content have proven to be particularly suitable for the production of guide assemblies according to the present invention.

Examples of usable P9T are Genestar series NlOOO, NlOOl and N1006 by Kuraray, e.g. N1001D-U83 and N1006C- H31, and N1000D-H31 is particularly preferred.

Tubes formed by P9T having elastic modulus from 1.5 to 3 GPa, and more preferably from 2 to 2.8 Gpa, are preferred.

If tube 2 is formed by two layers, the first layer is preferably entirely formed by P9T.

A P9T filled with copper, with optimal heat resistance, has proven to be particularly suitable' for the production of guide assemblies according to the present invention, whose melting point temperature is even higher than that of a non-additivated P9T. For example, a Genestar® NlOOOD H31, which presents a melting point of approximately 270⁰C, and a elastic modulus of about 2.4 GPa.

Second layer 11 preferably comprises a polyamide 12 (PA12), more preferably a modified PA 12 for resisting cold impacts . Preferably, polyamide 12 allows for flexibility, adhesion and heat resistance and co-molding of fastening elements with a broadest choice of materials.

Preferably, polyamide 12 is selected so as to have a melting point from 170 to 176°C, a tensile stress from 25 to 35 MPa, a flexural strength from 20 to 30 MPa, a flexural modulus from 400 to 600 MPa, an impact resistance from 100 to 120 kJ/m² at 23⁰C and from 10 to 20 kJ/m² at -40⁰C.

The structure comprising a P9T layer and a layer of material having a considerably lower elastic modulus, for example a polyamide, preferably a PA12, presents an intermediate elastic modulus between the corresponding values of the two materials .

If the tube also comprises a third layer, this layer is also preferably 'formed by P9T. Specifically, the tube preferably comprises a first internal layer formed by P9T, an intermediate layer formed by PA12 and an external layer formed by P9T.

In this manner, the guide assembly tube according to the invention maintains the high chemical resistance properties (particularly important for the innermost layer directly in contact with the oil) and heat resistance properties (particularly important for the outermost layer most exposed to high temperatures in the engine compartment) which are proper of P9T, and at the same time the use of a less costly material, such as PA12 for the intermediate layer of the tube allows to reduce the total cost of the guide assembly, the global thickness of the tube being equal.

Advantageously, it is possible to make the layers adhere without the presence of an adhesive. Particularly, use of the triple layer is preferred for ambient temperatures in the engine compartment higher than 135⁰C.

Specifically, the use of the polyamide resin layer promotes the thermoforming process with the use of lower temperatures and an easer machining.

Fastening means 3 are preferably co-molded and formed by a polyamide resin appropriately modified or additivated to resist high temperatures. Preferably, the polyamide resin of fastening means 3 has a Brookfield viscosity (at 232⁰C) from 2.5 to 4 Pa-s, and softening point from 180 to 220⁰C, elongation at break (at 23°C) from 550 to 650% and tensile stress from 12 to 16 MPa. For example, THERMELT 195 by BOSTIK TRL may be used as particularly preferred polyamide resin.

Alternatively, other types of Thermelt, such as for example Thermelt 181, 817, 857, 861, 865, 866 may be used. An oil level dipstick guide assembly 1 made according to the present invention solves the presented problems of the guide tubes made according to the known art.

Specifically, the assembly made according to the present invention is directly usable inside the engine compartment for running temperatures from -60⁰C to

160⁰C, without requiring the use of a further protective external layer . Furthermore, the guide assembly according to the present invention presents a high thermal stability

(approximately 1% of maximum deformation) , important to maintain the level measurement unchanged and to ensure the sealed coupling between the guide assembly tube and the oil level dipstick itself.

Furthermore, a guide assembly for an oil level dipstick made according to the present invention passes all the standard chemical and mechanical property verification tests. Specifically, it passes the aging tests in ZnCl₂ aqueous solution, in CaCl₂ aqueous solution, in air and in an engine oil bath and the heat cycle resistance tests and the resistance test for occasional contact with fluids which may be present inside the engine compartment.

Advantageously, a guide assembly made according to the present invention presents optimal values in the tensile stress and elongation at break tests, dimensional stability tests, cold impact strength tests, bursting tests (new and after aging in oil vapours, in ZnCl₂, in CaCl₂, in air, etc.), oil level dipstick insertion/extraction load cycle tests, tightness and vibration resistance tests, chemical stability to chlorides, to solutes occasionally present in solution inside the engine compartment, and in general to the salts of the PAl2 used_..

Advantageously, the tube was checked to present a high resistance to engine oil. Advantageously, the guide assembly according to the present invention was further checked to be rigid and not to present problems, also after long times of use and numerous extractions of the oil dipstick. It is apparent that changes may be made to the two-layer tube belonging to the oil dipstick guide assembly herein described and illustrated, specifically to the thickness of the layers or the materials, without, because of this, departing from the scope of protection of the present invention. The invention will now be described through examples but is not limited to this. EXAMPLE 1

An oil level dipstick guide assembly made according to the present invention was subjected to a series of bursting, cold impact resistance and layer adhesion tests.

Structure and composition of a guide assembly according to the present invention are shown in table 1. The layers are numbered from the inside outwards .

Table 1

The bursting tests was performed on a guide assembly having the structure and composition shown in table 1, according to SAE J2260 standard procedures.

Operatively, approximately 200 mm long tube segments, or alternatively the whole component, are capped on one end while pressurized fluid (test fluid: water and Paraflu® 50%) is introduced into the other end, at gradually increasing pressure with an increase of 5⁺² bars per minute, until bursting occurs.

Such tests were repeated, in addition to new components at different temperatures, on tubes subjected to different aging treatments in different applicable fluids, and more specifically in the following fluids:

- CM 15, a test fuel consisting of 85% vol. of Haltermann CEC-RF-08-A-85 (unleaded alcohol-free gasoline, with a maximum content of oxygenates equal to 1,5% vol.), and for the remaining 15% vol. by methanol;

- CE 10, a standard Haltermann reference fuel containing 10% vol. of ethanol;

- an self-oxidized gasoline. The bursting test results are shown in table 2.

Table 2

Method MPa unit at 23⁰C 7.9 at 115°C 3.7

After knotting 8.0

After aging in 5000 h at 60⁰C 9.8 CElO

After aging in 1000 h at 6O⁰C 7.9 CE15

EXAMPLE 2

Cold impact resistance tests were performed in the conditions specified in the SAE J 2260 standard. The specimens were positioned, along with the test jig, in an environmental chamber at a temperature of -40 ± 2⁰C and left there for 4 h. Afterwards, an impactor was dropped onto each of the specimens . The cold impact resistance test results are shown in table 3.

Also in this case, the impact resistance tests were repeated following the same aging treatments, similarly as described above for the bursting tests, and after aging in a zinc and chloride solution.

Table 3

COLD IMPACT TEST AGING EVALUATION RESULTS

-40⁰C on new No cracks Passed tube 10/10

After aging in 5000 h at 60⁰C No cracks Passed CElO 10/10

After aging in 1000 h at 6O⁰C No cracks Passed CMl5 10/10

After aging in 1000 h at 40⁰C No cracks Passed self-oxidizing 90 PN 10/10 gasoline

After aging in a 200 h at 23°C No cracks Passed 50% solution by dry + 24 h at 10/10 weight of ZnC12 23⁰C in solution The guide assembly made according to the present invention passed all the tests in all conditions .

Furthermore, layer adhesion tests between the forming layers were performed on the same guide assembly, also in this case repeating the tests following aging treatments . The results are shown in table 4.

Table 4

ADHESION TEST AGING EVALUATION

After aging in 5000 h at 60⁰C No chipping CElO

After aging in 1000 h at 60⁰C No chipping CE15

After aging in 1000 h at 40⁰C No chipping self-oxidizing 90 PN gasoline

No chipping was found between the layers in the guide assembly according to the invention in any of the treatment conditions taken into consideration. EXAMPLE 3

Finally, ^' a guide tube according to the present invention formed by an external layer in PA12 3030JI26L 0.75 mm and an internal layer in P9T N1001D-U03 0.25 mm was compared with a tube formed entirely by polyamide 12 and the results were shown in table 5. It was proven that only the tube made according to the present invention was capable of resisting the required tests at the high operating temperatures of modern diesel engines . Table 5

Claims

1. An oil level dipstick guide assembly (1) comprising a tube (2), characterized in that said tube (2) comprises a copolymer obtained from dicarboxylic units and from diamine units.

2. A guide assembly (1) according to claim 1, characterized in that said copolymer presents an elastic modulus comprised between 1.5 and 3 GPa.

3. A guide assembly (1) according to claim 1, characterized in that said tube is entirely made of a first layer (10) comprising a copolymer obtained from dicarboxylic units and diamine units.

4. A guide assembly (1) according to claim 3, characterized in that said copolymer presents an elastic modulus comprised between 1.5 and 3 GPa.

5. A guide assembly (1) according to claim 1, characterized in that said tube comprises a first layer (10) comprising said copolymer obtained from dicarboxylic units and diamine units and a second layer (11) .

6. A guide assembly (1) according to claim 5, characterized in that said second layer (11) comprises a polyamide resin.

7. A guide assembly (1) according to claim 6, characterized in that said polyamide resin is polyamide

12.

8. A guide assembly (1) according to claims 6 or 7, characterized in that said second layer (11) comprises more than 60% of said polyamide resin.

9. A guide assembly (1) according to claim 8, characterized in that said second layer (11) is entirely formed by said polyamide resin.

10. A guide assembly (1) according any of the claims from 1 to 9, characterized in that said dicarboxylic units are terephthalic acid for more than 60%.

11. A guide assembly (1) according to any of the claims from 1 to 10, characterized in that said diamine units are 1, 9-nonanediamine or 2-methyl-I₇8- octanediamine for more than 60%.

12. A guide assembly (1) according to any of the claims from 7 to 12, characterized in that said copolymer is filled with elastomers in a percentage by weight comprised between 10 and 40%.

13. A guide assembly (1) according to claim 7, characterized in that said polyamide 12 is modified for cold impacts .

14. A guide assembly (1) according to claim 10, characterized in that said polyamide 12 has a melting point from 170 to 176°C, a tensile stress from 25 to 35 MPa, a flexural strength from 20 to 30 MPa, a flexural modulus from 400 to 600 MPa, a shock resistance from 100 to 120 kJ/m² at 23⁰C and from 10 to 20 kj/m² at -4O⁰C.

15. A guide assembly (1) according to any of the claims from 5 to 15, characterized in that said first layer (1) has a thickness from 0.20 mm and 0.60 mm.

16. A guide assembly (1) according to any of the claims from 5 to 15, characterized in that said second layer (11) has a thickness from 0.9 mm and 1.50 mm.

17. A guide assembly (1) according to any of the preceding claims, characterized in that it comprises first securing means (3) for connecting and positioning the guide assembly itself with respect to the crankcase of an engine .

18. A guide assembly (1) according to claim 18, characterized in that said securing means (3) are preferably formed on said tube (2) by co-molding.

19. A guide assembly (1) according to one of the claims 18 or 19, characterized in that said securing means (3) are co-molded in a polyamide resin modified for resisting to high temperatures.

20. A guide assembly (1) according to any of the claims from 5 to 20, characterized in that said tube (2) comprises a third layer comprising a copolymer obtained from dicarboxylic units and diamine units .

21, Use of a copolymer obtained from dicarboxylic units and from diamine units for manufacturing an oil level dipstick guide assembly.

22. A method for manufacturing an oil level dipstick guide assembly, characterized in that it comprises the step of extruding a tube comprising a copolymer obtained from dicarboxylic units and from diamine units.