Spring-assisted linear actuator with flocked helical compression spring

Abstract

Spring-assisted linear drive (100) for moving a closure element, in particular a door or a tailgate of a motor vehicle relative to the body of the vehicle, with at least a first drive component (110) for coupling to the body or the closure element, a second drive component (120) which is displaceable relative to the first drive component (110) for coupling to the other element of the body or closure element, and a spring element (130) which supports the relative movement of the drive components (110, 120) to one another and is clamped between the two drive components and which has an elastic outer layer in the form of flocking, characterized in that at least one guide sleeve (111) made of a thermoplastic material is provided for guiding the spring element (13) and that a lubricating emulsion and a synthetic grease are applied to the flocking.

Description

The present application relates generally to a spring force assisted linear actuator with flocked compression coil spring for reducing stick-slip noise and more particularly to the technical features for implementing this reduction.In modern vehicles, linear drives are used for opening and closing closure elements such as doors and flaps with spring force assistance. Spring-force-assisted linear drives are understood to mean, for example, spring struts which have a piston-cylinder unit or a gas spring and a spring element which amplifies the extension force of the gas spring. In such spring struts, the extension force consists of the sum of the prestressed spring element and the force component of the gas spring present in the extension direction, which dampens the extension movement of the linear drive in a known manner.Likewise, for example, from DE102007047625A1 an electric drive is known, which has a helical compression spring for force support. By means of the force support, the electric drive can be designed for lower forces. Spindle drives have proven to be advantageous as electric drives. Such a drive is also to be understood within the scope of the invention as a linear drive.In linear drives with flocked spring, stick-slip noises occur repeatedly both in normal use in the field and in continuous-running testing, which noises are subscribed by the end customer, as a result of which high subscription costs can arise. The noise is due to failure of the sliding system of the spring guide. At this time, the noise free sliding movement of the spring with respect to the guides changes to an intermittent stick-slip movement accompanying audible noises.To avoid the noise of the stick-slip effects described, it is known, for example, from DE102005007741A to provide the helical compression spring of a piston-cylinder unit with flocking, whereby it is possible to dispense with fating of the piston-cylinder unit for friction reduction and / or noise reduction.In contrast, DE102021125588A1 describes a spring part for a drive device, the base material of which is provided with flocking as a protective layer and a silicone-based lubricant for noise reduction.The object of the invention is therefore to offer a further improved friction reduction and noise reduction for spring-force-assisted linear drives.This object is achieved according to the invention by a spring-force-assisted linear drive.A spring-force-assisted linear drive for moving a closure element, in particular a door or a tailgate, of a motor vehicle relative to the body of the vehicle is proposed. The linear drive has at least one first drive component for coupling to the body or the closure element, a second drive component, which is displaceable relative to the first drive component, for coupling to the respective other element from the body or closure element, and a spring element, which assists the relative movement of the drive components with respect to one another in a force-supporting manner and is clamped between the two drive components and has an elastic outer layer in the form of a flocking.According to the invention, a guide sleeve formed from a thermoplastic material is provided for guiding the spring element, and a sliding emulsion and optionally a synthetic grease are applied to the flocking. The invention is based on the knowledge that the noises arising due to interrupted stick-slip movements, in particular over the service life of the linear drives, could not be avoided by the solutions known hitherto.The combination according to the invention of a flocked spring element, to which a sliding emulsion is applied, with a thermoplastic guide sleeve has proven in tests to be an effective and long-lived measure for adjusting stick-slip performance and the resulting noises by means of permanent lubrication. Optionally, a synthetic fat can additionally be applied.The use of a guide sleeve made of thermoplastic material also contributes to precise guidance of the spring element and reliably prevents tilting.Preferably, the flocking comprises polyamide and / or polyester fibers. These fibers allow good adhesion of lubricants and are applied in different lengths and thicknesses.The use of polyamide and / or polyester fibers in flocking provides high wear resistance and chemical resistance, which improves the performance of the spring element under various operating conditions. Further, said fibrous materials contribute to the preservation of the elastic properties of the outer layer, leading to good sliding and cushioning properties.The flocking can be applied to the spring element in an electrostatic or electrostatic-pneumatic method. The application of flocking by means of an electrostatic or an electrostatic-pneumatic method enables uniform and precise distribution and a dense coating of the spring element, which leads to an improved friction reduction and an increased service life of the flocked surface. Furthermore, the method ensures strong adhesion of the fibers to the spring. The flock fibers are applied into an adhesive bed previously applied to the spring element, wherein the adhesive is a multi-component adhesive based on solvent or water.The slip emulsion is preferably water-based, PTFE-free and silicone-free.The use of a water-based, PTFE- and silicone-free sliding emulsion ensures an environmentally friendly application without components which are harmful to health.The thermoplastic material of the guide sleeve is made of POM, polyamide, polypropylene or polyethylene and optionally glass fiber-reinforced.In principle, the use of all thermoplastics is possible; these can be used in pure form, with glass fibers, talc or other additives. The option of reinforcing the thermoplastic material of the guide sleeves with glass fibers increases the rigidity and dimensional stability of the sleeves, which leads to improved guidance of the spring element and an increased service life of the entire drive.The synthetic grease may contain PTFE or other additives.The use of polytetrafluoroethylene (PTFE) or other additives in the synthetic grease results in improved lubricating performance, which significantly reduces friction between moving parts. The incorporation of additives may also increase the thermal and chemical stability of the synthetic grease, thereby allowing it to be used in a broader temperature range and under more aggressive operating conditions.In addition, the corrosion resistance of the lubricant can be improved, which increases the protection of the drive against environmental influences and thus the reliability of the overall system.The application of a sliding emulsion to flocking the spring element ensures uniform lubrication, which improves the friction consistency.Preferably, the slide emulsion can be applied in liquid form to the flocked spring element by the spraying or dipping method.Application of the lubricating emulsion by the spraying or dipping method enables rapid and uniform distribution of the emulsion and efficient application.By using these application methods, the lubricating emulsion can penetrate deeply into the structure of the flock, ensuring permanent lubrication and noise reduction.The spraying or dipping method is particularly suitable for mass production, since it ensures high reproducibility and consistency of the coating, which leads to improved product quality.The slip emulsion may preferably be dried. The drying is preferably carried out in an oven at a temperature of 60-120° C., so that the particles of the slide emulsion can permanently adhere to the fibers.The optimized adhesion property of the lubricant emulsion prevents the removal or flushing away of the lubricant. The strong bond between the lubricant emulsion and the fiber also increases the effectiveness of the noise damping, since the lubrication is maintained even under high loads and thus the noise generation is minimized.For good adhesion, the synthetic grease may be applied to the flocked spring element after the slip emulsion has been applied and dried.The combination of the slide emulsion and synthetic grease can produce synergistic effects which result in superior lubricating performance and thus increase the operating efficiency of the linear actuator.The sequential application of lubricating emulsion and synthetic grease thereby enables a specific adaptation of the lubricating properties to specific requirements, which offers a customized solution for different applications and operating conditions.The present invention will be described below with reference to an exemplary embodiment. It represents: FIG. 1 shows a schematic longitudinal section of a spring-force-assisted linear drive according to the invention.FIG. 1 shows a schematic longitudinal section along the longitudinal axis L of a spring-force-supported linear drive 100.The linear drive 100 is designed for moving a closure element of a motor vehicle relative to a body of the motor vehicle. A closure element is to be understood, for example, as a door, in particular a side door, or a flap, in particular a tailgate.The linear drive shown in FIG. 1 is designed, for example, as an electric drive which has a helical compression spring 130 as a spring element for force support. By means of the force support, the electric drive can be designed for lower forces. Depending on the design, the force support can be designed in the insertion or extraction direction.Spindle drives have proven to be advantageous as electric drives. In the exemplary embodiment shown, the linear drive 100 comprises an outer tube 110 with a longitudinal axis L for coupling to the body, not shown. The outer tube 110 constitutes a first driving member. Furthermore, the linear drive 100 comprises an inner element 120 partially arranged in the outer tube 110 for coupling to the closure element, for example via an inner connection element 128, in particular a ball socket, fastened to one end of the inner element 120. The inner element 120 represents a second drive component that is displaceable relative to the first drive component.The outer tube 110 and the inner element 120 are each shaped, for example, substantially hollow cylindrically. The outer tube 110 and the inner member 120 are, for example, disposed coaxially with the longitudinal axis L.The drive device 100 comprises a helical compression spring 130, which is arranged radially to the longitudinal axis L between the inner element 120 and the outer tube 110, as a spring element for force assistance, and an inner guide element 122, which is arranged radially to the longitudinal axis L between the inner element 120 and the helical compression spring 130 and is axially fixed to the inner element 120 and is designed for the inner guidance of an inner guidance end section 132 of the helical compression spring 130.The inner element 120 is telescopically extendable from the outer tube 110 along the longitudinal axis L, such that the closure element coupled to the inner element 120 is movable relative to the body coupled to the outer tube 110.The inner guide element 122 comprises a support element 126, for example a projection radially away from the longitudinal axis L, for supporting the helical compression spring 130 along the longitudinal axis L.The linear drive 100 comprises, for example, an electromechanical drive unit 140 for displacing the inner element 120 relative to the outer tube 110 along the longitudinal axis. The drive unit 140 can in particular comprise an electric motor and a threaded spindle driven by it. The drive unit 140 can be fastened to the outer tube 110 at the end of the outer tube 110 opposite the inner connection element 128, for example, and can be coupled to the vehicle body via an outer connection element 118, for example a further ball socket.A guide sleeve 111 arranged radially to the longitudinal axis L between the outer tube 110 and the helical compression spring 130 and axially fixed to the outer tube 110 is provided for the outer guidance of the helical compression spring 130, wherein the guidance is limited to an outer guidance end section 131 of the helical compression spring 130. The helical compression spring 130 is clamped between the inner guide element 122 and the guide sleeve 111 in such a way that the helical compression spring 130 is compressed against a spring tension of the helical compression spring 130 during a withdrawal movement of the inner element 120 out of the outer tube 110.The embodiment of the linear drive 100 shown is a spindle drive according to the paradox design, i.e. the spindle drive is tension-loaded.The outer guide end section 131 of the helical compression spring 130 is supported along the longitudinal axis L on the guide sleeve 111, in particular on a centering element 117 of the guide sleeve 111.The inner guide end section 132 of the helical compression spring 130 is supported along the longitudinal axis L on the inner guide element 122, in particular on the support element 126 of the inner guide element 122.The outer guide end portion 131 of the compression coil spring 130 is guided only by the guide sleeve 111 in at least one state of movement of the inner member 120 relative to the outer tube 110, and the inner guide end portion 132 of the compression coil spring 130 is guided only by the inner guide member 122 in the state of movement.In order to avoid noise problems caused by stick-slip during operation of the linear drive 100, an optimized combination of a flocked helical compression spring 130 with a guide sleeve 111 formed from a thermoplastic material is provided for guiding the helical compression spring 130. Flocking of the helical compression spring 130 represents an elastic outer layer to which a sliding emulsion is applied. Optionally, depending on the application, a minimal fatliquoring with a synthetic fat is additionally provided.The guide sleeve 111 is formed from a thermoplastic material such as POM, polyamide, polypropylene or polyethylene and optionally is provided with glass fibre reinforcement. In principle, the use of all thermoplastics is possible; these can be used in pure form, with glass fibers, talc or other additives.The flocking consists of polyamide and / or polyester fibers of a wide variety of lengths and thicknesses and is applied to the helical compression spring 130 in an electrostatic / electrostatically pneumatic method. The flock fibers are applied into an adhesive bed previously applied to the helical compression spring 130, wherein the adhesive is a multi-component adhesive based on solvent or water.The water-based, PTFE- and silicone-free sliding emulsion is applied in liquid form by the spraying or dipping method to the flocked helical compression spring 130 and dried in an oven at a temperature between 60-120° C., so that the particles of the sliding emulsion permanently attach themselves to the fibers. Depending on the method of application, the sliding emulsion can be further diluted in water from the application in order to improve the distribution on the helical compression spring 130 and the penetration into the flock.The synthetic grease, for example, based on lithium soap, which is optionally applied to the flocked helical compression spring 130 after the drying of the sliding emulsion, can contain PTFE or other additives in order to improve the lubrication.It should be expressly mentioned that the application of the invention is not limited to the described exemplary embodiment of a linear drive 100.The invention is particularly advantageous, for example, in known piston-cylinder units or gas springs which have a spring element which amplifies the extension force.The inventive combination of a flocked spring element guided in a thermoplastic guide sleeve with applied sliding emulsion and optionally with synthetic grease can also be used, for example, in non-paradox spindle drives with a force-supporting spring element.Within the scope of the invention, linear drive is generally understood to mean a linearly operating drive for moving a closure element with a supporting spring element. The drive can be designed electrically, pneumatically, hydraulically or purely mechanically.Likewise, the use is not limited to the described outer guide sleeve. That is to say that the guide sleeve according to the invention can be provided as an inner and / or outer sleeve, wherein the guide sleeve can extend over a partial region or over the entire cylinder length.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 102007047625A1

[0003] DE 102005007741A

[0005] DE 102021125588A1

[0006]

Claims

Spring-force-assisted linear drive (100) for moving a closure element, in particular a door or a tailgate of a motor vehicle relative to the body of the vehicle, having at least one first drive component (110) for coupling to the body or the closure element, a second drive component (120), which is displaceable relative to the first drive component (110), for coupling to the respective other element of the body or closure element, and a spring element (130), which assists the relative movement of the drive components (110, 120) with respect to one another and is clamped between the two drive components and has an elastic outer layer in the form of a flocking, characterized in that at least one guide sleeve (111), which is formed from a thermoplastic material, is provided for guiding the spring element (13), and in that a sliding emulsion and a synthetic grease are applied to the flocking.Linear drive (100) according to Claim 1, characterized in that the flocking comprises polyamide and / or polyester fibres.Linear drive (100) according to claim 1 or 2, characterised in that the flocking is applied to the spring element (130) in an electrostatic or electrostatic-pneumatic method.Linear drive (100) according to one of the preceding claims 1 to 3, characterized in that the sliding emulsion is water-based, PTFE- and silicone-free.Linear drive (100) according to one of the preceding claims 1 to 4, characterized in that the thermoplastic material of the guide sleeve (111) is provided formed from POM, polyamide, polypropylene or polyethylene and is optionally glass fibre-reinforced.Linear drive (100) according to one of the preceding claims 1 to 5, characterized in that the sliding emulsion is provided applied to the flocked spring element (130) in liquid form by the spraying or dipping method.Linear drive (100) according to claim 6, characterised in that the sliding emulsion is provided in a dried manner.Linear drive (100) according to claim 7, characterised in that the synthetic grease is provided on the flocked spring element (130) after application and drying of the slide emulsion.Linear drive (100) according to claim 8, characterised in that the synthetic grease contains PTFE or other additives.

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