ACTUATOR FOR OPENING AND CLOSING A DOOR OR A TAILGATE OF A CAR

Abstract

An actuator for opening and closing a door or a tailgate of a car contains a helical compression spring and a motor. The helical compression spring is provided for opening a door or the tailgate of a car when compressive forces of the helical compression spring are released. The motor is provided for compressing the helical compression spring in order to close the door or the tailgate of the car. The helical compression spring contains a helically coiled coated steel wire. The helically coiled coated steel wire contains a steel core and a metallic coating layer. The steel core contains a steel alloy. The steel alloy contains 0.8 to 0.95 wt % carbon, 0.2 to 0.9 wt % manganese; 0.1 to 1.4 wt % silicon; optionally one or more micro-alloying element. The microstructure of the steel core is drawn lamellar pearlite. The metallic coating layer contains at least 84% by mass of zinc.

Claims

1. An actuator for opening and closing a door or a tailgate of a car, comprising a helical compression spring, for opening a door or the tailgate of a car when compressive forces of the helical compression spring are released; and a motor, for compressing the helical compression spring in order to close the door or the tailgate of the car; wherein the helical compression spring comprises a helically coiled coated steel wire; wherein the helically coiled coated steel wire comprises a steel core and a metallic coating layer; wherein the steel core comprises a steel alloy; wherein the steel alloy comprises and preferably consists out of between 0.8 and 0.95 wt % carbon; between 0.2 and 0.9 wt % manganese; between 0.1 and 1.4 wt % silicon; optionally one or more than one of the micro-alloying elements chromium, vanadium, tungsten, molybdenum, niobium or boron; optionally aluminum; unavoidable impurities; and iron; wherein the microstructure of the steel core is drawn lamellar pearlite; wherein the metallic coating layer comprises at least 84% by mass of zinc; and preferably aluminum.

2. The actuator as in claim 1, wherein the metallic coating layer provides the surface of the helical compression spring.

3. The actuator as in claim 1, wherein the metallic coating comprises—and preferably consists out of—zinc, at least 4% by weight of aluminium, optionally between 0.2 and 2 wt % magnesium, optionally up to 0.6 wt % silicon, optionally up to 0.1 wt % rare earth elements; and unavoidable impurities.

4. The actuator as in claim 1, wherein the metallic coating layer consists out of zinc, between 3 and 8 wt % aluminum; between 0.2-2 wt magnesium; and unavoidable impurities.

5. The actuator as in claim 1, wherein the metallic coating layer comprises—and preferably consists out of—between 86 and 92 wt % Zn and between 14 and 8 wt % Al; and unavoidable impurities.

6. The actuator as in claim 1, wherein the metallic coating layer consists out of zinc, between 3 and 8 wt % aluminum; optionally up to 0.1 wt % rare earth elements; and unavoidable impurities.

7. The actuator as in claim 1, wherein the mass of the metallic coating layer is between 20 and 80 g/m.sup.2.

8. The actuator as in claim 1; wherein the metallic coating layer comprises aluminum and a globularized aluminum rich phase.

9. The actuator as in claim 1, wherein the metallic layer comprises aluminium and wherein the coated steel wire comprises an intermetallic coating layer provided between the steel core and the metallic coating layer, wherein the intermetallic coating layer comprises an Fe.sub.xAl.sub.y phase; preferably wherein the intermetallic coating layer provides between 30 and 65% of the combined thickness of the intermetallic coating layer and the metallic coating layer.

10. The actuator as in claim 1, wherein the metallic layer comprises aluminium and wherein the coated steel wire comprises an inhibition layer, wherein the inhibition layer is provided between the steel core and the metallic coating layer, wherein the inhibition layer is provided by an Fe.sub.xAl.sub.y phase; and preferably wherein the inhibition layer is less than 1 μm thick.

11. The actuator as in claim 1; wherein the coating layer consists out of zinc and unavoidable impurities, preferably wherein the mass of the metallic coating layer is more than 80 g/m.sup.2, more preferably more than 100 g/m.sup.2.

12. The actuator as in claim 1, wherein the steel alloy has a carbon equivalent higher than 1; wherein the carbon equivalent is defined as: C wt %+(Mn wt %/6)+(Si wt %/5)+(Cr wt %/5)+(V wt %/5)+(W wt %/5)+(Mo wt %/5)+(Nb wt %/5).

13. The actuator as in claim 1, wherein the steel alloy comprises at least one or more than one of the micro-alloying elements, vanadium, tungsten, molybdenum, niobium in individual quantities between 0.04 and 0.2 wt %; and/or comprises chromium in quantities between 0.15 and 0.4 wt % and/or comprises between 0.0005 and 0.008 wt % boron.

14. The actuator as in claim 1, wherein the microstructure of the steel wire in the helical compression spring comprises more than 97% by volume of drawn pearlite.

15. The actuator as in claim 1, wherein the steel alloy comprises between 0.02 and 0.06 wt % Al.

16. The actuator as in claim 2, wherein the metallic coating layer consists out of zinc, between 3 and 8 wt % aluminum; between 0.2-2 wt magnesium; and unavoidable impurities.

17. The actuator as in claim 2, wherein the metallic coating layer comprises—and preferably consists out of—between 86 and 92 wt % Zn and between 14 and 8 wt % Al; and unavoidable impurities.

18. The actuator as in claim 2, wherein the metallic coating layer consists out of zinc, between 3 and 8 wt % aluminum; optionally up to 0.1 wt % rare earth elements; and unavoidable impurities.

Description

BRIEF DESCRIPTION OF FIGURES IN THE DRAWINGS

[0061] FIG. 1 shows an SUV comprising an actuator for opening and closing its tailgate.

[0062] FIG. 2 shows an actuator for opening and closing a tailgate of a car.

[0063] FIG. 3 shows a helical compression spring as in the invention.

MODE(S) FOR CARRYING OUT THE INVENTION

[0064] FIG. 1 shows an SUV 12 comprising a tailgate 14 and an actuator 16 for opening and closing the tailgate. The actuator (FIG. 2 shows the actuator 16 for opening and closing the tailgate of a car) comprises a helical compression spring 18 and a motor 20. The actuator comprises two connectors 22, 23, one for connecting the actuator to the door or to the tailgate; and the other one for connecting the system to the body of the car. The helical compression spring is provided for opening the tailgate when compressive forces of the helical compression spring are released. The motor is provided for compressing the helical compression spring in order to close the tailgate. An example of a helical compression spring that can be used is shown in FIG. 3, such spring has a length L and a pitch p.

[0065] The helical compression spring comprises a helically coiled coated steel wire. The diameter d (in mm) of the helically coiled coated steel wire is preferably between 2 and 5 mm. The helically coiled coated steel wire comprises a steel core and a metallic coating layer.

[0066] The steel core comprises a steel alloy; comprising and preferably consisting out of between 0.8 and 0.95 wt % carbon, between 0.2 and 0.9 wt % manganese; between 0.1 and 1.4 wt % silicon; optionally at least one or more than one of the micro-alloying elements chromium, vanadium, tungsten, molybdenum, niobium or boron; optionally aluminum; unavoidable impurities; and iron.

[0067] Table I provides specific examples of steel alloys (with minimum and maximum wt % of the elements in the steel alloy) that can be used in the invention for the steel core.

[0068] The microstructure of the steel core in the helically coiled coated steel wire is drawn lamellar pearlite.

TABLE-US-00001 TABLE I Examples of steel alloys that can be used in the invention. C (wt %) Mn (wt %) Si (wt %) Cr (wt %) V (wt %) Al (wt %) Alloy min max min max min max min max min max min max A 0.84 0.88 0.60 0.70 0.15 0.35 0.20 0.30 0.04 0.09 0.02 0.06 B 0.84 0.88 0.60 0.70 0.60 0.80 0.20 0.30 0.04 0.09 0.02 0.06 C 0.80 0.84 0.70 0.85 0.15 0.35 0.20 0.30 0.05 0.08 0.02 0.06 D 0.90 0.95 0.25 0.45 0.15 0.30 0.15 0.30 0.01 E 0.90 0.95 0.25 0.45 1.10 1.30 0.15 0.30 0.01 F 0.80 0.85 0.60 0.90 0.80 1.00 G 0.85 0.90 0.60 0.90 0.80 1.00 H 0.90 0.95 0.30 0.60 1.10 1.30 0.20 0.40 I 0.90 0.95 0.30 0.60 1.10 1.30 0.20 0.40 0.04 K 0.84 0.88 0.65 0.85 0.80 1.00 L 0.88 0.94 0.35 0.55 1.10 1.30 0.20 0.30 M 0.90 0.94 0.35 0.55 1.20 1.40 0.20 0.40 N 0.85 0.90 0.60 0.70 0.15 0.35 0.20 0.30 0.04 0.08 0.02 0.06

[0069] A specific example of such helical compression spring has been coiled with a coated steel wire the steel core of which having a drawn pearlitic microstructure and 3.4 mm diameter. The helical compression spring has a length L 0.8 m in unloaded condition. The spring index of the exemplary helical spring is 6.5. The pitch p of the spring is 15.2 mm. The outer diameter of the helical compression spring is 26.8 mm.

[0070] In order to manufacture the coated steel wire used for coiling the helical compression spring, a steel wire rod of 10 mm diameter was used.

[0071] The steel wire rod was out of a steel alloy consisting out of 0.86 wt % C, 0.63 wt % Mn, 0.2 wt % Si, 0.22 wt % Cr, 0.06 wt % V; 0.04 wt % Al; unavoidable impurities and the balance being iron. This is an alloy of composition “A” of table I. The carbon equivalent is: 0.86+(0.63/6)+(0.2/5)+(0.22/5)+(0.06/5)=1.169.

[0072] The 10 mm diameter steel wire rod has been patented to provide it with a pearlitic microstructure; and has then been provided with a metallic coating via hot dip. The hot dip process used was a double dip process in which the steel wire was first dipped in a bath of molten zinc; followed by dipping the steel wire in a bath comprising 10% by weight of aluminum, and the remainder being zinc. The metallic coating layer of the hot dipped steel wire consisted of 10 wt % aluminum and the balance being zinc.

[0073] The patented—and hot dipped—wire rod of 10 mm diameter has been drawn to a steel wire of 3.4 mm diameter; this means that a drawing reduction of 88.4% has been applied. The resulting steel wire has a drawn pearlitic microstructure. The tensile strength Rm of the coated steel wire is 2354 MPa; the Rp0.2 value is 1990 MPa, which is 84.5% of the Rm value. The percentage reduction of area Z at break in tensile testing of the steel wire is 44.1%.

[0074] The metallic coating on the drawn wire of 3.4 mm was 45 g/m.sup.2.

[0075] After coiling this coated steel wire into a helical compression spring a thermal stress relieving operation was performed, by keeping the helical compression spring in unloaded condition at 250° C. during 30 minutes.

[0076] The coated steel wire of the helical compression spring comprised an intermetallic coating layer between the steel core and the metallic coating layer. The intermetallic coating layer provided 45% of the combined thickness of the intermetallic coating layer and the metallic coating layer. The intermetallic coating layer comprised a Fe.sub.xAl.sub.y phase. It has been observed that the metallic coating layer comprised a globularized aluminum rich phase.

[0077] Samples of the coated steel wire used for making the helical spring have been subject to a thermal treatment in an oven during 30 minutes at an oven temperature of 250° C. After this thermal treatment, tensile testing has been performed on the coated steel wire sample: the tensile strength Rm is 2426 MPa; the Rp0.2 value is 2366 MPa, which is 97.5% of the tensile strength Rm; and the percentage reduction of area Z at break was 42%.

[0078] Analysis of the steel core of the helical compression spring has shown that the steel core has a drawn pearlite microstructure, with more than 97% by volume of drawn pearlite and about 1% by volume of bainite.

[0079] The helical compression spring was used in an actuator for opening and closing a tailgate of a car. The metallic coating of the coated steel wire provided the surface of the helical compression spring.