Gas pressure spring comprising an expanding wax, actuation system comprising the gas pressure spring.

Abstract

GAS PRESSURE SPRING COMPRISING AN EXPANSION WAX, DRIVE SYSTEM COMPRISING THE GAS PRESSURE SPRING. The invention relates to a gas pressure spring comprising an expansion wax as a means of compensating for reducing a temperature dependence of a gas pressure spring force in an operating temperature range of the gas pressure spring spanning a minimum temperature of -40°C to +10°C up to a maximum temperature of +40°C to +100°C. The expansion wax comprises at least one liquid phase and at least one solid phase within the entire operating temperature range, the expansion wax comprising a number of primary alcohols. The invention further relates to a drive system for a flap comprising a gas pressure spring according to the invention, to support the flap, and an electromechanical drive unit to actuate the flap.

Description

Gas pressure spring comprising an expanding wax, actuation system comprising the gas pressure spring. Technical Field

[001] The invention relates to a gas pressure spring comprising an expanding wax as a means of compensation for reducing a temperature dependence of a gas pressure spring force in an operating temperature range of the gas pressure spring spanning a minimum temperature up to a maximum temperature.

[002] The invention also relates to a drive system for a flap comprising a gas pressure spring to support the flap and an electromechanical unit to actuate the flap. Previous Technique

[003] Because the operating gas pressure increases with temperature (in the case of an ideal operating gas linearly), a gas spring characteristic involving a temperature-dependent spring force is obtained in gas pressure springs. However, in several applications, for example, in actuation systems for flaps, particularly vehicle flaps, a temperature-independent spring force is desired. Thus, gas pressure springs, designed to compensate for the temperature-dependent characteristic of the gas spring with the aid of a compensation means, are known from the prior art.

[004] For this purpose, the gas pressure spring comprises, for example, a working cylinder defining a working chamber filled with a working medium together with a compensating piston assembly, and a working rod, projecting slidably into the working chamber through an opening in the working cylinder as described in EP. Petition 870220106746, dated 11 / 18 / 2022, pp. 82 / 101 2 / 17 795 777 A2. Here, the compensating piston assembly is actuated by the pressure of the working medium and the pressure of the compensating medium supplied in a compensating chamber and expands with an increase in temperature, so that the volume of the working chamber is increased. To allow the compensating piston to reversibly return to its initial position when the temperature decreases, it can additionally be actuated by a return medium supplied in a return chamber, so that the volume of the working chamber is reduced.

[005] With regard to substances that can be used as the compensation medium, DE 31 41 295 A1 generally refers to a special liquid. In contrast, hydraulic oil is expressly mentioned as a compensation medium in document DE 25 11 289 A1, originating from the same subject area. According to US 4,613,115, finally, two-phase systems of specific substances, more precisely, systems where the liquid and gaseous phases of the observed substance coexist under the respective pressure and temperature conditions, are used as the compensation medium.

[006] However, none of these means of compensation have proven satisfactory in practice. In particular, conventionally used mineral oil exhibits insufficient usable volume expansion in the commonly observed range of gas pressure spring operating states. In two-phase systems, the high volume expansion resulting mainly from the gas phase comes to nothing due to the high compressibility of the gas phase.

[007] According to EP 1 795 777 A2, the compensation medium is preferably a liquid slightly below its boiling point or in a hypercritical state, since such a liquid, on the one hand, exhibits a relatively high volume expansion but, on the other hand, due to its property of still being a liquid, is substantially incompressible. As Petition 870220106746, dated 11 / 18 / 2022, pp. 83 / 101 3 / 17 Examples of preferred compensating media include carbon dioxide (CO2), ethane (C2H6), propane (C3H8), hydrogen sulfide (H2S), ammonia (NH3), methylene chloride (CH3Cl), sulfur dioxide (SO2), and sulfur hexafluoride (SF6). However, it is disadvantageous for these compensating media that they can only be introduced into a gas pressure spring and permanently held there with great effort, particularly since they are highly volatile and partly corrosive and / or toxic. Furthermore, many of these compensating media are easily flammable, which, for reasons related to safety and transport legislation, is problematic, particularly for use in vehicles. Technical Object

[008] The technical object of the invention is to provide a gas pressure spring that is particularly simple to produce and durable, and a drive system for a flap comprising the spring, the temperature-dependent characteristic of the gas spring being reliably compensated. Technical Solution

[009] The material of the present invention provides a gas pressure spring according to claim 1 solving the technical object. Similarly, the object is solved by a drive system according to claim 10. Advantageous embodiments will become apparent from the dependent claims. Description of the Modalities

[010] The invention relates to a gas pressure spring comprising an expanding wax as a means of compensation for reducing a temperature dependence of a gas pressure spring force. Petition 870220106746, dated 11 / 18 / 2022, pp. 84 / 101 4 / 17 in an operating temperature range of the gas pressure spring covering a minimum temperature, particularly from -40°C to +10°C, up to a maximum temperature, particularly from +40°C to +100°C.

[011] For example, the gas pressure spring may be substantially designed as the gas pressure springs described in DE 31 41 295 A1 or in EP 1 795 777 A2. The gas pressure spring preferably comprises a working cylinder defining a working chamber filled with a particularly gaseous working medium together with a compensating piston assembly, and a working rod projecting, in a sliding manner, into the working chamber through an opening in the working cylinder. Herein, the compensating piston assembly is actuated by the pressure of the working medium and the pressure of the compensating medium supplied in a compensating chamber and expanding with an increase in temperature, so that the volume of the working chamber is increased.

[012] For the compensating piston to reversibly return to its initial position when the temperature drops, it can, in addition, be actuated by means of a return provided in a return chamber, so that the volume of the working chamber is reduced.

[013] In the event of an increase in temperature within the operating temperature range, the expanding wax undergoes at least one transition phase, in particular, from a wax-like solid to a liquid phase, involving a significant relative increase in volume, for example, from 5% to 20%, particularly from 10% to 15%. In this way, the increase in volume of the expanding wax can be used to enlarge the working chamber of the gas pressure spring to prevent an increase in the pressure of the working medium from an associated increase in the spring force of the gas pressure spring resulting from the increase in temperature. Petition 870220106746, dated 11 / 18 / 2022, pp. 85 / 101 5 / 17

[014] The relative increase in volume ÕV is defined as the quotient of the absolute increase in volume Δν divided by the volume VTm / n at the minimum temperature. The absolute increase in volume ΔV is the difference between the volume VTmax at the maximum temperature Tmax of the operating temperature range and the volume VTm / n at the minimum temperature Tm / n of the operating temperature range: ÕV = ΔV / VTm / n = (VTmax - VTm / n) / VTm / n

[015] For an operating temperature range from a minimum temperature of Tm / n = -30°C to a maximum temperature of Tmax = +80°C, advantageously, a relative increase in volume ÕV of 14% to 18% is obtained.

[016] In the present application, temperature-related effects are generally described based on the example of an increase in temperature. It is generally assumed that temperature-dependent effects are reversible, i.e., that they are substantially reversed in the event of a decrease in temperature compared to an increase in temperature.

[017] Compared with other working media, an expanding wax is advantageous because it can be easily introduced into the gas pressure spring due to its wax-like consistency and low chemical reactivity. Furthermore, since it is solid or liquid and has low chemical reactivity within the operating temperature range, it can be permanently confined within the gas pressure spring in a simple way, ensuring reliable long-term operation.

[018] The expanding wax preferably comprises at least one liquid phase and at least one solid phase throughout the entire operating temperature range. Due to the coexistence of at least one solid phase and at least one liquid phase, an at least approximately linear increase in the volume of the expanding wax will take place in the event of a temperature increase, whereby the increase Petition 870220106746, dated 11 / 18 / 2022, pp. 86 / 101 6 / 17 approximately linear equally general pressure of the working medium can be almost completely compensated over the entire operating temperature range.

[019] Due to the fact that there is at least one liquid phase and at least one solid phase throughout the entire operating temperature range, the expanding wax differs from the expanding waxes commonly used in thermostat valves in that a liquid phase and a solid phase should only coexist within the narrowest possible temperature range to achieve a well-defined alternating temperature of the thermostat valve.

[020] At least one liquid phase and at least one solid phase are preferably combined or form a gel to achieve a temperature-dependent homogeneous change in the volume of the compensation medium and to avoid potential interfacial effects that may affect the linearity of the volume change. However, at least one liquid phase and at least one solid phase may also be spatially separated from each other by at least one phase boundary.

[021] The properties of substances and mixtures of substances indicated in this application relate to standard pressure (100 kPa) unless otherwise specified.

[022] The expanding wax preferably comprises a number of primary alcohols. Primary alcohols as a means of compensation offer a variety of advantages, particularly, they cannot be mixed with water and thus constitute a protection against corrosion for the gas pressure spring. In addition to this fact, primary alcohols react neutrally and do not present any health risks. Furthermore, primary alcohols having a defined chain length, and therefore a defined melting temperature, are readily available. Petition 870220106746, dated 11 / 18 / 2022, pp. 87 / 101 7 / 17

[023] The minimum temperature is preferably from -30°C to 0°C, particularly -20°C to -10°C. The maximum temperature is preferably from +50°C to +80°C, particularly +60°C to +70°C. With the minimum and maximum temperatures mentioned above, an operating temperature range covering a vast number of typical applications of gas pressure springs, particularly in vehicle construction, is obtained, so that undesirable effects of a temperature dependence of the gas pressure spring force in typical applications are avoided.

[024] The expanding wax preferably comprises a number of alkanes, preferably a plurality of alkanes having chain lengths that differ from each other, the alkanes preferably having a minimum chain length in the range of 5 to 20, particularly preferably 10 to 15, and a maximum chain length in the range of 20 to 35, particularly preferably 25 to 30.

[025] The expansion wax may, for example, comprise from 10 to 25, particularly 15 to 20 alkanes having chain lengths that differ from one another.

[026] As a means of compensation, alkanes offer a variety of advantages; in particular, they have low reactivity, due to stable carbon chains without functional groups, are hardly flammable from a certain chain length, and are only divisible in the presence of catalysts. Furthermore, alkanes can be mixed, do not pose health risks, are available at low cost, and constitute corrosion protection for the gas pressure spring, due to their hydrophobic property from a chain length of around 16.

[027] Furthermore, the melting temperatures of alkanes with similar chain lengths are close to each other. With another carbon atom in the chain, the melting temperature typically Petition 870220106746, dated 11 / 18 / 2022, pp. 88 / 101 8 / 17 increases by approximately 3 K. The narrow gradation of melting temperatures allows for a particularly uniform expansion of the expanding material throughout the entire operating temperature range.

[028] Alkanes possessing the chain lengths mentioned above have melting temperatures distributed throughout the operating temperature range of the gas pressure spring, and thus ensure that at least one liquid phase and at least one solid phase coexist in the compensation medium throughout the entire operating temperature range. Experiments have shown that the melting temperatures of alkanes in the compensation medium do not deviate substantially from the associated melting temperatures of alkanes as pure substances.

[029] The disadvantage with alkanes is that elaborate separation methods are needed to obtain alkanes having a precisely defined chain length or a precisely defined mixture of chain lengths.

[030] The expanding wax preferably comprises or consists of a plurality of primary alcohols having chain lengths that differ from each other, the primary alcohols preferably having a minimum chain length in the range of 3 to 15, particularly preferably 5 to 10, and a maximum chain length in the range of 10 to 25, particularly preferably 15 to 20.

[031] The expanding wax may, for example, comprise from 2 to 15, particularly from 5 to 10, primary alcohols having chain lengths that differ from each other.

[032] Primary alcohols having the chain lengths mentioned above have melting temperatures distributed throughout the operating temperature range of the gas pressure spring and therefore ensure that at least one liquid phase and at least one solid phase coexist in the medium. Petition 870220106746, dated 11 / 18 / 2022, pp. 89 / 101 9 / 17 compensation throughout the entire operating temperature range. Experiments have shown that the melting temperatures of primary alcohols in the compensation medium do not deviate substantially from the associated melting temperatures of primary alcohols in pure form.

[033] The expanding wax preferably comprises or consists of a number of alkanes and a number of primary alcohols having chain lengths that differ from each other. Primary alcohols are generally miscible with alkanes, so that, advantageously, a homogeneous expanding wax can be produced from primary alcohols and alkanes.

[034] At extremely short chain lengths, for example, eight to ten carbon atoms, primary alcohols are characterized by a low melting point of -16°C to 7°C at a relatively high simultaneous flash point compared to alkanes having the same melting temperature. Thus, a low minimum temperature can be achieved with primary alcohols without producing high flammability of the expanding wax in this way.

[035] Furthermore, primary alcohols have a high melting point of 49°C to 59°C even at relatively short chain lengths of, for example, 16 to 18 carbon atoms. The melting point of an alkane having 18 carbon atoms, on the other hand, is only 28°C. Thus, a high maximum temperature can be achieved with relatively short-chain primary alcohols. For the same maximum temperature, alkanes with a considerably longer chain length, which would be chemically less stable and more expansive than shorter-chain primary alcohols, would be needed.

[036] Mixtures of primary alcohols are generally more expensive than mixtures of alkanes. In addition, the melting temperatures of primary alcohols with similar chain lengths are further apart than those of primary alcohols with similar chain lengths. Petition 870220106746, dated 11 / 18 / 2022, pp. 90 / 101 10 / 17 alkanes. Thus, it is more difficult to achieve uniform expansion of the expanding wax across the entire operating temperature range with primary alcohols than with alkanes.

[037] To provide an expanding wax that is as cost-effective and safe as possible and that exhibits uniform expansion over the entire operating temperature range, it is therefore particularly advantageous for the expanding wax to comprise a number of primary alcohols and a number of alkanes.

[038] The chain lengths of the primary alcohols and / or alkanes are preferably within the ranges mentioned above. The expanding wax may, for example, comprise or consist of primary alcohols having chain lengths of 8 to 18 carbon atoms and alkanes having chain lengths of 14 to 25 carbon atoms.

[039] The primary alcohols contained in the expanding wax preferably comprise a number of primary alcohols having a lower melting point than all the alkanes contained in the expanding wax, and / or a number of primary alcohols having a higher melting point than all the alkanes contained in the expanding wax.

[040] At the upper and / or lower edge of the operating temperature range, therefore, primary alcohols are used instead of alkanes, to ensure uniform expansion of the expanding wax without increasing the flammability and costs of the expanding wax or reducing the chemical stability of the expanding wax. At a mid-range of the operating temperature range, on the other hand, alkanes are used to ensure low costs and uniform expansion of the expanding wax due to the closely spaced melting temperatures of alkanes. With this combination of primary alcohols and alkanes, therefore, the respective advantages of both groups of substances are ideally utilized. Petition 870220106746, dated 11 / 18 / 2022, pp. 91 / 101 11 / 17

[041] Primary alcohols preferably constitute a percentage of the amount of substances from 1% to 30%, preferably 10% to 25%, of the expanding wax. With such a percentage of the amount of substances, the melting behavior of the expanding wax according to the present invention and a high application safety of the gas pressure spring can be achieved at low cost. A melting behavior according to the present invention is achieved, for example, by means of an expanding wax composed of 25% octanol and 75% of the commercially available alkane expanding wax RubiTherm RT35.

[042] The expanding wax preferably comprises at least one antioxidant to prevent potential degradation of the expanding wax, particularly primary alcohols, by reactions with oxygen. The antioxidant comprises, for example, ascorbyl palmitate. It is oil-soluble, readily available and safe. The antioxidant constitutes, for example, a percentage of the amount of substances in the expanding wax of 0.1% to 10%, particularly 0.5% to 5%.

[043] The expanding wax preferably comprises at least one oil, preferably a standard system oil for gas pressure springs, for example, the oil sold by Fuchs Schmierstoffe GmbH under the trade name Titan SAF 1720. A system oil is advantageous because it can be used both as a constituent of the expanding wax and to improve the tribological properties of the gas pressure spring. The oil constitutes, for example, a percentage of the amount of substances in the expanding wax of 0.1% to 10%, particularly 0.5% to 5%. The oil is advantageous because it exists as a liquid phase even at low temperatures, for example, below -10°C, and thus ensures the function of the expanding wax at low temperatures. In addition, the oil can also function as a lubricant and / or damping agent for the gas pressure spring and thus extend its service life. Petition 870220106746, dated 11 / 18 / 2022, pp. 92 / 101 12 / 17

[044] The invention relates to a drive system for a flap comprising a gas pressure spring according to the invention, to support the flap, and an electromechanical unit, for example, a linear drive, particularly a screw drive, to actuate the flap. For example, the flap could be a flap of a vehicle, particularly a hood, a trunk lid, a trunk lid, or a gull-wing door.

[045] Actuating systems for a flap comprising a gas pressure spring to support the flap and an electromechanical unit to actuate the flap are known from the prior art. Except for the use of a gas pressure spring according to the invention instead of a generic one, the actuating system according to the present invention can be designed as a corresponding actuating system according to the prior art, for example, according to DE 103 13 440 A1 or DE 10 2008 045 903 A1.

[046] The gas pressure spring of the drive system serves to support the flap in any position against gravity while the electromechanical unit serves to open and close the flap. In addition, a manual flap operation can be contemplated as in DE 103 13 440 A1 and DE 10 2008 045 903 A1.

[047] The gas pressure spring needs to have a spring force that is so high that it can support the flap even at low ambient temperatures. Since the spring force increases with rising temperatures in common gas pressure springs, this results in a very strong force needing to be applied by the electromechanical unit or an operator to close the flap at elevated temperatures. Therefore, the drive system needs to comprise a very powerful electromechanical unit that is expensive, occupies a lot of installation space, and consumes a lot of energy in operation. In addition, there will be a high level of wear on the electromechanical unit and other components mechanically connected to the flap, for example hinges. Petition 870220106746, dated 11 / 18 / 2022, pp. 93 / 101 13 / 17

[048] In the prior art, these problems are avoided by using a suspension mount instead of a gas spring (e.g., DE10 2008 045 903 A1, parag.

[0021] ). Although a suspension mount has a spring force that is almost independent of temperature, it is larger, heavier, and more expensive than a gas spring with a comparable spring force.

[049] By using a temperature-compensated gas pressure spring according to the present invention instead of a conventional gas pressure spring, a particularly cost-effective, easy-to-produce, durable, compact, energy-saving and easy-to-handle drive system for a flap is therefore provided. Brief Description of the Drawings

[050] Additional advantages, objectives, and properties of the invention will be explained with the aid of the following description and the accompanying drawings in which materials according to the invention are illustrated by way of example. Features at least substantially identical with respect to their function in the Figures may be designated by the same reference numbers herein. These features, not necessarily being provided with reference numbers, are explained in all the Figures.

[051] Figure 1 shows the relative change in volume of an expanding wax of a gas pressure spring according to the present invention, depending on the temperature.

[052] Figure 2 shows the relative change in volume of another expanding wax of a gas pressure spring according to the present invention, depending on the temperature. Fig. 1 Petition 870220106746, dated 11 / 18 / 2022, pp. 94 / 101 14 / 17

[053] Figure 1 shows the relative change in volume ÕV in % of an expanding wax of a gas pressure spring according to the present invention, depending on the temperature Tem °C.

[054] The expanding wax examined for Figure 1 was produced by mixing commercially available RubiTherm RT35, Mahle-Beer, and Paramelt Dilavest 0-30 waxes in equal proportions, and contains the alkanes listed in Table 1 below. The proportions of substance amount were determined by gas chromatography. Table 1: Company Name Chain Melting point / °C Percentage of substance / % n-dodecane 12 -10 0.0 n-tridecane 13 -5 0.1 n-tetradecane 14 6 9.5 n-pentadecane 15 9 6.2 n-hexadecane 16 18 3.9 n-heptadecane 17 21 6.5 n-octadecane 18 28 15.8 n-nonadecane 19 32 9.1 n-eicosane 20 37 10.4 n-eicosane 21 40 11.2 n-docosane 22 44 9.1 n-tricosane 23 48 6.1 n-tetracosane 24 50 4.4 n-pentacosane 25 54 3.1 n-hexacosane 26 56 1.8 n-heptacosane 27 59 0.8 n-octacosane 28 61 0.3 n-nonacosane 29 64 0.3 n-triacontane 30 65 0.0 Total 98.5 Petition 870220106746, dated 11 / 18 / 2022, pp. 95 / 101 15 / 17

[055] To measure the temperature dependence of the expanding wax volume, an initial volume of 3198.4 mm3 of expanding wax was filled into a cylindrical measuring cartridge (6 mm internal diameter, 114 mm internal length) using a cylindrical plunger (3.98 mm diameter, 12.4 mm2 cross-section) at an initial temperature of -10°C.

[056] The measuring cartridge was subjected to a temperature ramp in a temperature-controlled oven. At each temperature examined, the path in which the plunger was directed out of the cartridge compared to the initial temperature through the expansion of the expanding wax against a counterforce of 3 N was detected using a displacement detector after a waiting time of around 20 min.

[057] The relative change in volume of the expanding wax was calculated as the product of the detected path and the piston cross-section divided by the initial volume. Figure 1 shows the values ​​obtained in this way for the temperature rise (circles) and temperature reduction (squares) of the expanding wax.

[058] The essential components (percentage of the amount of substance > 5%) of the expanding wax examined for Figure 1 have melting temperatures within the range of 6°C to 48°C (Table 1). Consequently, the expanding wax comprises at least one solid phase and one liquid phase within an entire operating temperature range of about 10°C to about 50°C.

[059] As can be seen in Figure 1, this results in an approximately linear relative increase in volume with a rising temperature within the operating temperature range. A linear regression (dashed line) of the measurement data in this range shows a correlation coefficient of R2 = 0.96. Petition 870220106746, dated 11 / 18 / 2022, pp. 96 / 101 16 / 17

[060] In total, a relative volume increase of 15% is achieved over the examined temperature range of -10°C to +60°C, which is sufficient to compensate for the temperature dependence of the gas spring. With a relative volume increase of approximately 15%, it is possible to perceive a compensation stroke that is sufficient to fully compensate for, or even compensate beyond what is necessary, the temperature dependence of the gas spring in appropriate translation relationships in the construction.

[061] An overcompensation beyond what is necessary offers the possibility of working very flexibly and of approximately precisely adjusting the desired expansion for each type of gas pressure spring when mixing corresponding oils exhibiting a lower increase in volume. Fig. 2

[062] Figure 2 shows the relative change in volume ÓV and % of another expanding wax of a gas pressure spring according to the present invention, depending on the temperature Tem °C.

[063] The expanding wax examined for Figure 2 was produced by mixing three commercially available waxes from the Orbesen company having melting points of 6°C to 12°C, 15°C to 40°C, and 56°C to 62°C in equal proportions, and contains the primary alcohols listed in Table 2 below. The proportions of amount of substance were determined by gas chromatography. Table 2: Name Chain Length Melting Point / °C Percentage of Substance / % n-octanol 8 -16 0.0 n-decanol 10 7 43.8 n-dodecanol 12 24 0.0 n-tetradecanol 14 38 24.0 Petition 870220106746, dated 11 / 18 / 2022, pp. 97 / 101 17 / 17 n-hexadecanol 16 49 31.4 n-octadecanol 18 59 0.0 Total 99.3

[064] The relative change in volume of the expanding wax was determined as described in connection with Figure 1. In contrast to Figure 1, an initial temperature of -20°C was selected.

[065] The essential components (percentage of the amount of substance > 5%) of the expanding wax examined for Figure 1 have melting temperatures within the range of 7°C to 59°C (Table 2). Consequently, the expanding wax exhibits at least one solid phase and one liquid phase within an entire operating temperature range of about 10°C to about 50°C.

[066] As can be seen in Figure 2, this results in an approximately linear relative increase in volume with rising temperatures in the operating temperature range. A linear regression (dashed line) of the measurement data in this range shows a correlation coefficient of R2 = 0.98.

[067] In total, a relative increase in volume of 12% is achieved over the examined temperature range of -20°C to +75°C which is sufficient to compensate for, or even more than compensate for, the temperature dependence of the gas pressure spring. Petition 870220106746, dated 11 / 18 / 2022, pp. 98 / 101 1 / 17 Gas pressure spring comprising an expanding wax, actuation system comprising the gas pressure spring. Technical Field

[001] The invention relates to a gas pressure spring comprising an expanding wax as a means of compensation for reducing a temperature dependence of a gas pressure spring force in an operating temperature range of the gas pressure spring spanning a minimum temperature up to a maximum temperature.

[002] The invention also relates to a drive system for a flap comprising a gas pressure spring to support the flap and an electromechanical unit to actuate the flap. Previous Technique

[003] Because the operating gas pressure increases with temperature (in the case of an ideal operating gas linearly), a gas spring characteristic involving a temperature-dependent spring force is obtained in gas pressure springs. However, in several applications, for example, in actuation systems for flaps, particularly vehicle flaps, a temperature-independent spring force is desired. Thus, gas pressure springs, designed to compensate for the temperature-dependent characteristic of the gas spring with the aid of a compensation means, are known from the prior art.

[004] For this purpose, the gas pressure spring comprises, for example, a working cylinder defining a working chamber filled with a working medium together with a compensating piston assembly, and a working rod, projecting slidably into the working chamber through an opening in the working cylinder as described in EP. Petition 870220106746, dated 11 / 18 / 2022, pp. 82 / 101 2 / 17 795 777 A2. Here, the compensating piston assembly is actuated by the pressure of the working medium and the pressure of the compensating medium supplied in a compensating chamber and expands with an increase in temperature, so that the volume of the working chamber is increased. To allow the compensating piston to reversibly return to its initial position when the temperature decreases, it can additionally be actuated by a return medium supplied in a return chamber, so that the volume of the working chamber is reduced.

[005] With regard to substances that can be used as the compensation medium, DE 31 41 295 A1 generally refers to a special liquid. In contrast, hydraulic oil is expressly mentioned as a compensation medium in document DE 25 11 289 A1, originating from the same subject area. According to US 4,613,115, finally, two-phase systems of specific substances, more precisely, systems where the liquid and gaseous phases of the observed substance coexist under the respective pressure and temperature conditions, are used as the compensation medium.

[006] However, none of these means of compensation have proven satisfactory in practice. In particular, conventionally used mineral oil exhibits insufficient usable volume expansion in the commonly observed range of gas pressure spring operating states. In two-phase systems, the high volume expansion resulting mainly from the gas phase comes to nothing due to the high compressibility of the gas phase.

[007] According to EP 1 795 777 A2, the compensation medium is preferably a liquid slightly below its boiling point or in a hypercritical state, since such a liquid, on the one hand, exhibits a relatively high volume expansion but, on the other hand, due to its property of still being a liquid, is substantially incompressible. As Petition 870220106746, dated 11 / 18 / 2022, pp. 83 / 101 3 / 17 Examples of preferred compensating media include carbon dioxide (CO2), ethane (C2H6), propane (C3H8), hydrogen sulfide (H2S), ammonia (NH3), methylene chloride (CH3Cl), sulfur dioxide (SO2), and sulfur hexafluoride (SF6). However, it is disadvantageous for these compensating media that they can only be introduced into a gas pressure spring and permanently held there with great effort, particularly since they are highly volatile and partly corrosive and / or toxic. Furthermore, many of these compensating media are easily flammable, which, for reasons related to safety and transport legislation, is problematic, particularly for use in vehicles. Technical Object

[008] The technical object of the invention is to provide a gas pressure spring that is particularly simple to produce and durable, and a drive system for a flap comprising the spring, the temperature-dependent characteristic of the gas spring being reliably compensated. Technical Solution

[009] The material of the present invention provides a gas pressure spring according to claim 1 solving the technical object. Similarly, the object is solved by a drive system according to claim 10. Advantageous embodiments will become apparent from the dependent claims. Description of the Modalities

[010] The invention relates to a gas pressure spring comprising an expanding wax as a means of compensation for reducing a temperature dependence of a gas pressure spring force. Petition 870220106746, dated 11 / 18 / 2022, pp. 84 / 101 4 / 17 in an operating temperature range of the gas pressure spring covering a minimum temperature, particularly from -40°C to +10°C, up to a maximum temperature, particularly from +40°C to +100°C.

[011] For example, the gas pressure spring may be substantially designed as the gas pressure springs described in DE 31 41 295 A1 or in EP 1 795 777 A2. The gas pressure spring preferably comprises a working cylinder defining a working chamber filled with a particularly gaseous working medium together with a compensating piston assembly, and a working rod projecting, in a sliding manner, into the working chamber through an opening in the working cylinder. Herein, the compensating piston assembly is actuated by the pressure of the working medium and the pressure of the compensating medium supplied in a compensating chamber and expanding with an increase in temperature, so that the volume of the working chamber is increased.

[012] For the compensating piston to reversibly return to its initial position when the temperature drops, it can, in addition, be actuated by means of a return provided in a return chamber, so that the volume of the working chamber is reduced.

[013] In the event of an increase in temperature within the operating temperature range, the expanding wax undergoes at least one transition phase, in particular, from a wax-like solid to a liquid phase, involving a significant relative increase in volume, for example, from 5% to 20%, particularly from 10% to 15%. In this way, the increase in volume of the expanding wax can be used to enlarge the working chamber of the gas pressure spring to prevent an increase in the pressure of the working medium from an associated increase in the spring force of the gas pressure spring resulting from the increase in temperature. Petition 870220106746, dated 11 / 18 / 2022, pp. 85 / 101 5 / 17

[014] The relative increase in volume δν is defined as the quotient of the absolute increase in volume Δν divided by the volume VTmin at the minimum temperature. The absolute increase in volume ΔV is the difference between the volume VTmax at the maximum temperature Tmax of the operating temperature range minus the volume VTmin at the minimum temperature Tmin of the operating temperature range: δν = Δν / VTmin = (VTmax - VTmin) / VTmin

[015] For an operating temperature range from a minimum temperature of Tmin = -30°C to a maximum temperature of Tmax = +80°C, advantageously, a relative increase in volume δV of 14% to 18% is obtained.

[016] In the present application, temperature-related effects are generally described based on the example of an increase in temperature. It is generally assumed that temperature-dependent effects are reversible, i.e., that they are substantially reversed in the event of a decrease in temperature compared to an increase in temperature.

[017] Compared with other working media, an expanding wax is advantageous because it can be easily introduced into the gas pressure spring due to its wax-like consistency and low chemical reactivity. Furthermore, since it is solid or liquid and has low chemical reactivity within the operating temperature range, it can be permanently confined within the gas pressure spring in a simple way, ensuring reliable long-term operation.

[018] The expanding wax preferably comprises at least one liquid phase and at least one solid phase throughout the entire operating temperature range. Due to the coexistence of at least one solid phase and at least one liquid phase, an at least approximately linear increase in the volume of the expanding wax will take place in the event of a temperature increase, whereby the increase Petition 870220106746, dated 11 / 18 / 2022, pp. 86 / 101 6 / 17 approximately linear equally general pressure of the working medium can be almost completely compensated over the entire operating temperature range.

[019] Due to the fact that there is at least one liquid phase and at least one solid phase throughout the entire operating temperature range, the expanding wax differs from the expanding waxes commonly used in thermostat valves in that a liquid phase and a solid phase should only coexist within the narrowest possible temperature range to achieve a well-defined alternating temperature of the thermostat valve.

[020] At least one liquid phase and at least one solid phase are preferably combined or form a gel to achieve a temperature-dependent homogeneous change in the volume of the compensation medium and to avoid potential interfacial effects that may affect the linearity of the volume change. However, at least one liquid phase and at least one solid phase may also be spatially separated from each other by at least one phase boundary.

[021] The properties of substances and mixtures of substances indicated in this application relate to standard pressure (100 kPa) unless otherwise specified.

[022] The expanding wax preferably comprises a number of primary alcohols. Primary alcohols as a means of compensation offer a variety of advantages, particularly, they cannot be mixed with water and thus constitute a protection against corrosion for the gas pressure spring. In addition to this fact, primary alcohols react neutrally and do not present any health risks. Furthermore, primary alcohols having a defined chain length, and therefore a defined melting temperature, are readily available. Petition 870220106746, dated 11 / 18 / 2022, pp. 87 / 101 7 / 17

[023] The minimum temperature is preferably from -30°C to 0°C, particularly -20°C to -10°C. The maximum temperature is preferably from +50°C to +80°C, particularly +60°C to +70°C. With the minimum and maximum temperatures mentioned above, an operating temperature range covering a vast number of typical applications of gas pressure springs, particularly in vehicle construction, is obtained, so that undesirable effects of a temperature dependence of the gas pressure spring force in typical applications are avoided.

[024] The expanding wax preferably comprises a number of alkanes, preferably a plurality of alkanes having chain lengths that differ from each other, the alkanes preferably having a minimum chain length in the range of 5 to 20, particularly preferably 10 to 15, and a maximum chain length in the range of 20 to 35, particularly preferably 25 to 30.

[025] The expansion wax may, for example, comprise from 10 to 25, particularly 15 to 20 alkanes having chain lengths that differ from one another.

[026] As a means of compensation, alkanes offer a variety of advantages; in particular, they have low reactivity, due to stable carbon chains without functional groups, are hardly flammable from a certain chain length, and are only divisible in the presence of catalysts. Furthermore, alkanes can be mixed, do not pose health risks, are available at low cost, and constitute corrosion protection for the gas pressure spring, due to their hydrophobic property from a chain length of around 16.

[027] Furthermore, the melting temperatures of alkanes with similar chain lengths are close to each other. With another carbon atom in the chain, the melting temperature typically Petition 870220106746, dated 11 / 18 / 2022, pp. 88 / 101 8 / 17 increases by approximately 3 K. The narrow gradation of melting temperatures allows for a particularly uniform expansion of the expanding material throughout the entire operating temperature range.

[028] Alkanes possessing the chain lengths mentioned above have melting temperatures distributed throughout the operating temperature range of the gas pressure spring, and thus ensure that at least one liquid phase and at least one solid phase coexist in the compensation medium throughout the entire operating temperature range. Experiments have shown that the melting temperatures of alkanes in the compensation medium do not deviate substantially from the associated melting temperatures of alkanes as pure substances.

[029] The disadvantage with alkanes is that elaborate separation methods are needed to obtain alkanes having a precisely defined chain length or a precisely defined mixture of chain lengths.

[030] The expanding wax preferably comprises or consists of a plurality of primary alcohols having chain lengths that differ from each other, the primary alcohols preferably having a minimum chain length in the range of 3 to 15, particularly preferably 5 to 10, and a maximum chain length in the range of 10 to 25, particularly preferably 15 to 20.

[031] The expanding wax may, for example, comprise from 2 to 15, particularly from 5 to 10, primary alcohols having chain lengths that differ from each other.

[032] Primary alcohols having the chain lengths mentioned above have melting temperatures distributed throughout the operating temperature range of the gas pressure spring and therefore ensure that at least one liquid phase and at least one solid phase coexist in the medium. Petition 870220106746, dated 11 / 18 / 2022, pp. 89 / 101 9 / 17 compensation throughout the entire operating temperature range. Experiments have shown that the melting temperatures of primary alcohols in the compensation medium do not deviate substantially from the associated melting temperatures of primary alcohols in pure form.

[033] The expanding wax preferably comprises or consists of a number of alkanes and a number of primary alcohols having chain lengths that differ from each other. Primary alcohols are generally miscible with alkanes, so that, advantageously, a homogeneous expanding wax can be produced from primary alcohols and alkanes.

[034] At extremely short chain lengths, for example, eight to ten carbon atoms, primary alcohols are characterized by a low melting point of -16°C to 7°C at a relatively high simultaneous flash point compared to alkanes having the same melting temperature. Thus, a low minimum temperature can be achieved with primary alcohols without producing high flammability of the expanding wax in this way.

[035] Furthermore, primary alcohols have a high melting point of 49°C to 59°C even at relatively short chain lengths of, for example, 16 to 18 carbon atoms. The melting point of an alkane having 18 carbon atoms, on the other hand, is only 28°C. Thus, a high maximum temperature can be achieved with relatively short-chain primary alcohols. For the same maximum temperature, alkanes with a considerably longer chain length, which would be chemically less stable and more expansive than shorter-chain primary alcohols, would be needed.

[036] Mixtures of primary alcohols are generally more expensive than mixtures of alkanes. In addition, the melting temperatures of primary alcohols with similar chain lengths are further apart than those of primary alcohols with similar chain lengths. Petition 870220106746, dated 11 / 18 / 2022, pp. 90 / 101 10 / 17 alkanes. Thus, it is more difficult to achieve uniform expansion of the expanding wax across the entire operating temperature range with primary alcohols than with alkanes.

[037] To provide an expanding wax that is as cost-effective and safe as possible and that exhibits uniform expansion over the entire operating temperature range, it is therefore particularly advantageous for the expanding wax to comprise a number of primary alcohols and a number of alkanes.

[038] The chain lengths of the primary alcohols and / or alkanes are preferably within the ranges mentioned above. The expanding wax may, for example, comprise or consist of primary alcohols having chain lengths of 8 to 18 carbon atoms and alkanes having chain lengths of 14 to 25 carbon atoms.

[039] The primary alcohols contained in the expanding wax preferably comprise a number of primary alcohols having a lower melting point than all the alkanes contained in the expanding wax, and / or a number of primary alcohols having a higher melting point than all the alkanes contained in the expanding wax.

[040] At the upper and / or lower edge of the operating temperature range, therefore, primary alcohols are used instead of alkanes, to ensure uniform expansion of the expanding wax without increasing the flammability and costs of the expanding wax or reducing the chemical stability of the expanding wax. At a mid-range of the operating temperature range, on the other hand, alkanes are used to ensure low costs and uniform expansion of the expanding wax due to the closely spaced melting temperatures of alkanes. With this combination of primary alcohols and alkanes, therefore, the respective advantages of both groups of substances are ideally utilized. Petition 870220106746, dated 11 / 18 / 2022, pp. 91 / 101 11 / 17

[041] Primary alcohols preferably constitute a percentage of the amount of substances from 1% to 30%, preferably 10% to 25%, of the expanding wax. With such a percentage of the amount of substances, the melting behavior of the expanding wax according to the present invention and a high application safety of the gas pressure spring can be achieved at low cost. A melting behavior according to the present invention is achieved, for example, by means of an expanding wax composed of 25% octanol and 75% of the commercially available alkane expanding wax RubiTherm RT35.

[042] The expanding wax preferably comprises at least one antioxidant to prevent potential degradation of the expanding wax, particularly primary alcohols, by reactions with oxygen. The antioxidant comprises, for example, ascorbyl palmitate. It is oil-soluble, readily available and safe. The antioxidant constitutes, for example, a percentage of the amount of substances in the expanding wax of 0.1% to 10%, particularly 0.5% to 5%.

[043] The expanding wax preferably comprises at least one oil, preferably a standard system oil for gas pressure springs, for example, the oil sold by Fuchs Schmierstoffe GmbH under the trade name Titan SAF 1720. A system oil is advantageous because it can be used both as a constituent of the expanding wax and to improve the tribological properties of the gas pressure spring. The oil constitutes, for example, a percentage of the amount of substances in the expanding wax of 0.1% to 10%, particularly 0.5% to 5%. The oil is advantageous because it exists as a liquid phase even at low temperatures, for example, below -10°C, and thus ensures the function of the expanding wax at low temperatures. In addition, the oil can also function as a lubricant and / or damping agent for the gas pressure spring and thus extend its service life. Petition 870220106746, dated 11 / 18 / 2022, pp. 92 / 101 12 / 17

[044] The invention relates to a drive system for a flap comprising a gas pressure spring according to the invention, to support the flap, and an electromechanical unit, for example, a linear drive, particularly a screw drive, to actuate the flap. For example, the flap could be a flap of a vehicle, particularly a hood, a trunk lid, a trunk lid, or a gull-wing door.

[045] Actuating systems for a flap comprising a gas pressure spring to support the flap and an electromechanical unit to actuate the flap are known from the prior art. Except for the use of a gas pressure spring according to the invention instead of a generic one, the actuating system according to the present invention can be designed as a corresponding actuating system according to the prior art, for example, according to DE 103 13 440 A1 or DE 10 2008 045 903 A1.

[046] The gas pressure spring of the drive system serves to support the flap in any position against gravity while the electromechanical unit serves to open and close the flap. In addition, a manual flap operation can be contemplated as in DE 103 13 440 A1 and DE 10 2008 045 903 A1.

[047] The gas pressure spring needs to have a spring force that is so high that it can support the flap even at low ambient temperatures. Since the spring force increases with rising temperatures in common gas pressure springs, this results in a very strong force needing to be applied by the electromechanical unit or an operator to close the flap at elevated temperatures. Therefore, the drive system needs to comprise a very powerful electromechanical unit that is expensive, occupies a lot of installation space, and consumes a lot of energy in operation. In addition, there will be a high level of wear on the electromechanical unit and other components mechanically connected to the flap, for example hinges. Petition 870220106746, dated 11 / 18 / 2022, pp. 93 / 101 13 / 17

[048] In the prior art, these problems are avoided by using a suspension mount instead of a gas spring (e.g., DE10 2008 045 903 A1, parag.

[0021] ). Although a suspension mount has a spring force that is almost independent of temperature, it is larger, heavier, and more expensive than a gas spring with a comparable spring force.

[049] By using a temperature-compensated gas pressure spring according to the present invention instead of a conventional gas pressure spring, a particularly cost-effective, easy-to-produce, durable, compact, energy-saving and easy-to-handle drive system for a flap is therefore provided. Brief Description of the Drawings

[050] Additional advantages, objectives, and properties of the invention will be explained with the aid of the following description and the accompanying drawings in which materials according to the invention are illustrated by way of example. Features at least substantially identical with respect to their function in the Figures may be designated by the same reference numbers herein. These features, not necessarily being provided with reference numbers, are explained in all the Figures.

[051] Figure 1 shows the relative change in volume of an expanding wax of a gas pressure spring according to the present invention, depending on the temperature.

[052] Figure 2 shows the relative change in volume of another expanding wax of a gas pressure spring according to the present invention, depending on the temperature. Fig. 1 Petition 870220106746, dated 11 / 18 / 2022, pp. 94 / 101 14 / 17

[053] Figure 1 shows the relative change in volume ÕV in % of an expanding wax of a gas pressure spring according to the present invention, depending on the temperature Tem °C.

[054] The expanding wax examined for Figure 1 was produced by mixing commercially available RubiTherm RT35, Mahle-Beer, and Paramelt Dilavest 0-30 waxes in equal proportions, and contains the alkanes listed in Table 1 below. The proportions of substance amount were determined by gas chromatography. Table 1: Company Name Chain Melting point / °C Percentage of substance / % n-dodecane 12 -10 0.0 n-tridecane 13 -5 0.1 n-tetradecane 14 6 9.5 n-pentadecane 15 9 6.2 n-hexadecane 16 18 3.9 n-heptadecane 17 21 6.5 n-octadecane 18 28 15.8 n-nonadecane 19 32 9.1 n-eicosane 20 37 10.4 n-eicosane 21 40 11.2 n-docosane 22 44 9.1 n-tricosane 23 48 6.1 n-tetracosane 24 50 4.4 n-pentacosane 25 54 3.1 n-hexacosane 26 56 1.8 n-heptacosane 27 59 0.8 n-octacosane 28 61 0.3 n-nonacosane 29 64 0.3 n-triacontane 30 65 0.0 Total 98.5 Petition 870220106746, dated 11 / 18 / 2022, pp. 95 / 101 15 / 17

[055] To measure the temperature dependence of the expanding wax volume, an initial volume of 3198.4 mm3 of expanding wax was filled into a cylindrical measuring cartridge (6 mm internal diameter, 114 mm internal length) using a cylindrical plunger (3.98 mm diameter, 12.4 mm2 cross-section) at an initial temperature of -10°C.

[056] The measuring cartridge was subjected to a temperature ramp in a temperature-controlled oven. At each temperature examined, the path in which the plunger was directed out of the cartridge compared to the initial temperature through the expansion of the expanding wax against a counterforce of 3 N was detected using a displacement detector after a waiting time of around 20 min.

[057] The relative change in volume of the expanding wax was calculated as the product of the detected path and the piston cross-section divided by the initial volume. Figure 1 shows the values ​​obtained in this way for the temperature rise (circles) and temperature reduction (squares) of the expanding wax.

[058] The essential components (percentage of the amount of substance > 5%) of the expanding wax examined for Figure 1 have melting temperatures within the range of 6°C to 48°C (Table 1). Consequently, the expanding wax comprises at least one solid phase and one liquid phase within an entire operating temperature range of about 10°C to about 50°C.

[059] As can be seen in Figure 1, this results in an approximately linear relative increase in volume with a rising temperature within the operating temperature range. A linear regression (dashed line) of the measurement data in this range shows a correlation coefficient of R2 = 0.96. Petition 870220106746, dated 11 / 18 / 2022, pp. 96 / 101 16 / 17

[060] In total, a relative volume increase of 15% is achieved over the examined temperature range of -10°C to +60°C, which is sufficient to compensate for the temperature dependence of the gas spring. With a relative volume increase of approximately 15%, it is possible to perceive a compensation stroke that is sufficient to fully compensate for, or even compensate beyond what is necessary, the temperature dependence of the gas spring in appropriate translation relationships in the construction.

[061] An overcompensation beyond what is necessary offers the possibility of working very flexibly and of approximately precisely adjusting the desired expansion for each type of gas pressure spring when mixing corresponding oils exhibiting a lower increase in volume. Fig. 2

[062] Figure 2 shows the relative change in volume 5V and % of another expanding wax of a gas pressure spring according to the present invention, depending on the temperature Tem °C.

[063] The expanding wax examined for Figure 2 was produced by mixing three commercially available waxes from the Orbesen company having melting points of 6°C to 12°C, 15°C to 40°C, and 56°C to 62°C in equal proportions, and contains the primary alcohols listed in Table 2 below. The proportions of amount of substance were determined by gas chromatography. Table 2: Name Chain Length Melting Point / °C Percentage of Substance / % n-octanol 8 -16 0.0 n-decanol 10 7 43.8 n-dodecanol 12 24 0.0 n-tetradecanol 14 38 24.0 Petition 870220106746, dated 11 / 18 / 2022, pp. 97 / 101 17 / 17 n-hexadecanol 16 49 31.4 n-octadecanol 18 59 0.0 Total 99.3

[064] The relative change in volume of the expanding wax was determined as described in connection with Figure 1. In contrast to Figure 1, an initial temperature of -20°C was selected.

[065] The essential components (percentage of the amount of substance > 5%) of the expanding wax examined for Figure 1 have melting temperatures within the range of 7°C to 59°C (Table 2). Consequently, the expanding wax exhibits at least one solid phase and one liquid phase within an entire operating temperature range of about 10°C to about 50°C.

[066] As can be seen in Figure 2, this results in an approximately linear relative increase in volume with rising temperatures in the operating temperature range. A linear regression (dashed line) of the measurement data in this range shows a correlation coefficient of R2 = 0.98.

[067] In total, a relative increase in volume of 12% is achieved over the examined temperature range of -20°C to +75°C which is sufficient to compensate for, or even more than compensate for, the temperature dependence of the gas pressure spring.

Claims

CLAIMS 1. Gas pressure spring comprising an expanding wax as a means of compensation for reducing the temperature dependence of a gas pressure spring force within an operating temperature range of the gas pressure spring spanning a minimum temperature of -40°C to +10°C up to a maximum temperature of +50°C to +100°C, characterized in that a. the expanding wax comprises at least one liquid phase and at least one solid phase within the entire operating temperature range, b. wherein the expanding wax is composed of a number of alkanes and a number of primary alcohols having chain lengths that differ from each other, c. wherein the primary alcohols constitute a percentage of the amount of substances of 10% to 30% of the expanding wax, and d. wherein the primary alcohols contained in the expanding wax i.They comprise a number of primary alcohols having a lower melting point than all the alkanes contained in the expanding wax, and / or ii. they comprise a number of primary alcohols having a higher melting point than all the alkanes contained in the expanding wax.

2. Gas pressure spring, according to claim 1, characterized in that the minimum temperature is -30°C to 0°C.

3. Gas pressure spring, according to claim 1, characterized in that the maximum temperature is +50°C to +80°C. Petition 870240005968, dated 23 / 01 / 2024, page 7 / 8 2 / 2 4. Gas pressure spring, according to claim 1, characterized in that the expanding wax comprises a plurality of alkanes having chain lengths that differ from each other.

5. Gas pressure spring, according to claim 1, characterized in that the alkanes have a minimum chain length in the range of 5 to 20, and a maximum chain length in the range of 20 to 35.

6. Gas pressure spring, according to claim 1, characterized in that primary alcohols constitute a percentage of the amount of substances from 10% to 25% of the expanding wax.

7. Gas pressure spring, according to claim 1, characterized in that the expanding wax comprises a plurality of primary alcohols having chain lengths that differ from each other.

8. Gas pressure spring, according to claim 1, characterized in that the primary alcohols have a minimum chain length in the range of 3 to 15 and a maximum chain length in the range of 10 to 25.

9. Actuating system for a flap, characterized in that it comprises a. a gas pressure spring according to any one of claims 1 to 8 to support the flap, and b. an electromechanical unit for actuating the flap.