Spring-assisted linear actuator with flocked helical compression spring

Abstract

The invention relates to a 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, comprising at least a first drive component (110) for coupling to the body or the closure element, a second drive component (120) that 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) that is clamped between the two drive components and that supports the relative movement of the drive components (110, 120) relative to one another. The spring element (130) has an elastic outer layer in the form of flocking. According to the invention, at least one guide sleeve (111) made of a thermoplastic material is provided for guiding the spring element (13), and a lubricating emulsion and optionally a synthetic grease are applied to the flocking.

Description

[0001] The present application relates generally to a spring-assisted linear actuator with a flocked helical compression spring for reducing stick-slip noise and, in particular, to the technical features and methods for implementing this reduction.

[0002] In modern vehicles, spring-assisted linear actuators are used to open and close locking elements such as doors and tailgates. Spring-assisted linear actuators include, for example, spring struts, which consist of a piston-cylinder unit or a gas spring and a spring element that amplifies the extension force of the gas spring. In such struts, the extension force consists of the sum of the preloaded spring element and the force component of the gas spring in the extension direction, which dampens the extension movement of the linear actuator in a known manner.

[0003] Likewise, for example, DE 10 2007 047 625 A1 discloses an electric drive that features a helical compression spring for force support. This force support allows the electric drive to be designed for lower forces. Spindle drives have proven advantageous as electric drives. Such a drive is also considered a linear drive within the scope of the invention.

[0004] Linear actuators with flocked springs repeatedly experience stick-slip noises, both in normal field use and during endurance testing. End customers complain about these noises, which can result in high warranty costs. This noise is caused by a failure of the spring guide's sliding system. The noiseless sliding movement of the spring toward the guides changes into an intermittent stick-slip movement, accompanied by audible noise.

[0005] In order to avoid the noise of the stick-slip effects described, it is known, for example, from DE 10 2005 007 741 A1 to provide the helical compression spring of a piston-cylinder unit with a flocking coating, whereby greasing of the piston-cylinder unit to reduce friction and / or noise can be omitted.

[0006] In contrast, DE 10 2021 125 588 A1 describes a spring part for a drive device, the base material of which is provided with a flocking as a protective layer and a silicone-based lubricant for noise reduction.

[0007] From DE 10 2020 132 508 A1 it is also known to apply a dry lubricant to the flocking of the spring of the drive device in order to reduce friction.

[0008] The invention is therefore based on the object of offering a further improved reduction in friction and noise for spring-assisted linear drives.

[0009] This object is achieved according to the invention by a spring-assisted linear drive according to claim 1. Furthermore, the object is achieved by a method for reducing stick-slip noise in a linear drive according to claim 7.

[0010] A spring-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 a first drive component for coupling to the body or the closure element, a second drive component that is displaceable relative to the first drive component for coupling to the other element of the body or closure element, and a spring element that supports the relative movement of the drive components and is clamped between the two drive components. The spring element has an elastic outer layer in the form of flocking. Furthermore, a guide sleeve made of a thermoplastic material is provided for guiding the spring element.

[0011] According to the invention, a lubricating emulsion and a synthetic grease are applied to the flocking.

[0012] The invention is based on the knowledge that the noises caused by interrupted stick-slip movements, particularly over the service life of the linear drives, could not be avoided by the solutions known so far.

[0013] The inventive combination of a flocked spring element, to which a lubricating emulsion and a synthetic grease are applied, with a thermoplastic guide sleeve has proven in tests to be an effective and long-lasting measure for eliminating the stick-slip performance and the resulting noise through permanent lubrication.

[0014] The use of a guide sleeve made of thermoplastic material also contributes to precise guidance of the spring element and reliably prevents jamming.

[0015] The flocking preferably comprises polyamide and / or polyester fibers. These fibers enable good adhesion of lubricants and are applied in various lengths and thicknesses.

[0016] The use of polyamide and / or polyester fibers in the flocking provides high wear resistance and chemical resistance, which improves the performance of the spring element under various operating conditions. Furthermore, these fiber materials contribute to maintaining the elastic properties of the outer layer, resulting in good sliding and damping properties.

[0017] The flocking can be applied to the spring element using an electrostatic or electrostatic-pneumatic process. Applying the flocking using an electrostatic or electrostatic-pneumatic process enables even and precise distribution and a dense coating of the spring element, resulting in improved friction reduction and an increased service life of the flocked surface. Furthermore, the process ensures strong adhesion of the fibers to the spring. The flock fibers are applied to an adhesive bed previously applied to the spring element. The adhesive is a multi-component, solvent- or water-based adhesive.

[0018] The lubricating emulsion is preferably water-based and PTFE and silicone-free.

[0019] The use of a water-based, PTFE- and silicone-free lubricating emulsion ensures environmentally friendly application without any harmful components.

[0020] The thermoplastic material of the guide sleeve is made of POM, polyamide, polypropylene or polyethylene and is optionally glass fiber reinforced.

[0021] In principle, the use of all thermoplastics is possible; these can be used in pure form, with glass fibers, talc or other additives.

[0022] The option of reinforcing the thermoplastic material of the guide sleeves with glass fibers increases the stiffness and dimensional stability of the sleeves, which leads to improved guidance of the spring element and an increased service life of the entire drive.

[0023] The synthetic grease may contain PTFE or other additives.

[0024] The use of polytetrafluoroethylene (PTFE) or other additives in synthetic grease results in improved lubricating performance, significantly reducing friction between moving parts. The inclusion of additives can also increase the thermal and chemical stability of the synthetic grease, allowing it to be used over a wider temperature range and under more aggressive operating conditions.

[0025] 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.

[0026] Furthermore, the invention is achieved by a method for reducing stick-slip noise in a linear drive, which comprises at least the steps: Providing a spring element for a linear drive, applying the lubricating emulsion and the synthetic grease to the flocking of the spring element, mounting the spring element into the linear drive with a guide sleeve.

[0027] The stick-slip noise reduction process contributes to improving acoustic comfort by minimizing noise in the linear actuator, which is particularly important in noise-sensitive applications such as the automotive industry or office equipment.

[0028] By applying a lubricating emulsion to the flocking of the spring element, uniform lubrication is ensured, which improves friction consistency.

[0029] Preferably, the lubricating emulsion can be applied in liquid form to the flocked spring element by spraying or dipping.

[0030] Applying the lubricating emulsion by spraying or dipping allows for quick and even distribution of the emulsion and efficient application. Using these application methods, the lubricating emulsion can penetrate deep into the flock structure, ensuring long-lasting lubrication and noise reduction.

[0031] The spraying or dipping process is particularly suitable for mass production as it ensures high reproducibility and consistency of the coating, leading to improved product quality.

[0032] The lubricating emulsion can preferably be dried. Drying is preferably carried out in an oven at a temperature of 60–120°C, so that the lubricating emulsion particles can adhere permanently to the fibers.

[0033] The optimized adhesion properties of the lubricating emulsion prevent the lubricant from being worn away or washed away. The strong bond between the lubricating emulsion and the fiber also increases the effectiveness of noise dampening, as lubrication is maintained even under high loads, thus minimizing noise generation.

[0034] For good adhesion, the synthetic grease can be applied to the flocked spring element after the lubricating emulsion has been applied and dried.

[0035] The combination of lubricating emulsion and synthetic grease can create synergistic effects that result in superior lubrication performance and thus increase the operating efficiency of the linear actuator.

[0036] The sequential application of lubricating emulsion and synthetic grease enables targeted adaptation of the lubricating properties to specific requirements, providing a tailor-made solution for different applications and operating conditions.

[0037] The present invention is described below using an exemplary embodiment. It shows: Fig. 1 a schematic longitudinal section of a spring-assisted linear drive according to the invention.

[0038] Fig. 1 shows a schematic longitudinal section along the longitudinal axis L of a spring-assisted linear drive 100.

[0039] The linear drive 100 is designed to move a closure element of a motor vehicle relative to a body of the motor vehicle. A closure element is understood to be, for example, a door, in particular a side door, or a flap, in particular a tailgate.

[0040] The Fig. The linear drive shown in Figure 1 is embodied, by way of example, as an electric drive, which has a helical compression spring 130 as a spring element for force support. The force support allows the electric drive to be designed for lower forces. Depending on the design, the force support can be configured in the insertion or extension direction.

[0041] Spindle drives have proven advantageous as electric drives. The linear drive 100 in the illustrated embodiment comprises an outer tube 110 with a longitudinal axis L for coupling to the body (not shown). The outer tube 110 represents a first drive component. 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.

[0042] The outer tube 110 and the inner element 120 are each essentially hollow-cylindrical in shape, for example. The outer tube 110 and the inner element 120 are arranged, for example, coaxially to the longitudinal axis L.

[0043] The drive device 100 comprises a helical compression spring 130 arranged radially to the longitudinal axis L between the inner element 120 and the outer tube 110 as a spring element for force support and an inner guide element 122 arranged radially to the longitudinal axis L between the inner element 120 and the helical compression spring 130 and axially fixed to the inner element 120, which is designed for the internal guidance of an inner guide end section 132 of the helical compression spring 130.

[0044] The inner element 120 can be telescopically extended from the outer tube 110 along the longitudinal axis L, so that the closure element coupled to the inner element 120 is movable relative to the body coupled to the outer tube 110.

[0045] 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.

[0046] 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 the motor. The drive unit 140 can, for example, be attached to the outer tube 110 at the end of the outer tube 110 opposite the inner connection element 128 and coupled to the body via an outer connection element 118, for example, a further ball socket.

[0047] 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 external guidance of the helical compression spring 130, wherein the guidance is limited to an external guide end portion 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 such 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 from the outer tube 110.

[0048] The embodiment of the linear drive 100 shown is a spindle drive according to the paradoxical design, ie the spindle drive is tensile loaded.

[0049] 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.

[0050] 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.

[0051] The outer guide end portion 131 of the helical compression spring 130 is guided only by the guide sleeve 111 in at least one movement state of the inner element 120 relative to the outer tube 110, and the inner guide end portion 132 of the helical compression spring 130 is guided only by the inner guide element 122 in the movement state.

[0052] To avoid stick-slip-related noise problems during operation of the linear actuator 100, an optimized combination of a flocked helical compression spring 130 with a guide sleeve 111 made of a thermoplastic material is provided to guide the helical compression spring 130. The flocking of the helical compression spring 130 represents an elastic outer layer to which a lubricating emulsion is applied. Depending on the application, minimal lubrication with a synthetic grease is optionally provided.

[0053] The guide sleeve 111 is designed for use in a thermoplastic material such as POM, polyamide, polypropylene, or polyethylene, and is optionally glass fiber reinforced. In principle, all thermoplastics can be used, including pure thermoplastics or those with glass fibers, talc, or other additives.

[0054] The flocking consists of polyamide and / or polyester fibers of various lengths and thicknesses and is applied to the helical compression spring 130 using an electrostatic / electrostatic-pneumatic process. The flock fibers are applied to an adhesive bed previously applied to the helical compression spring 130, the adhesive being a multi-component, solvent- or water-based adhesive.

[0055] The water-based, PTFE- and silicone-free lubricating emulsion is applied in liquid form to the flocked helical compression spring 130 by spraying or dipping and dried in an oven at a temperature between 60 and 120°C, so that the lubricating emulsion particles permanently adhere to the fibers. Depending on the application method, the lubricating emulsion can be diluted with water prior to application to improve distribution on the helical compression spring 130 and penetration into the flock.

[0056] The synthetic grease used, for example based on lithium soap, which is optionally applied to the flocked helical compression spring 130 after the lubricating emulsion has dried, may contain PTFE or other additives to improve lubrication.

[0057] It should be expressly mentioned that the application of the invention is not limited to the described embodiment of a linear drive 100.

[0058] The invention is particularly advantageous, for example, in known piston-cylinder units or gas springs which have a spring element that reinforces the extension force.

[0059] The inventive combination of a flocked spring element guided in a thermoplastic guide sleeve with applied lubricating emulsion and optionally with synthetic grease can, for example, also be used in non-paradoxical spindle drives with a force-supporting spring element.

[0060] In the context of the invention, a 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 electrical, pneumatic, hydraulic, or purely mechanical.

[0061] Likewise, the use is not limited to the described, external guide sleeve. This means that the guide sleeve according to the invention can be provided as an inner and / or outer sleeve, whereby the guide sleeve can extend over a partial area or over the entire length of the cylinder.

Claims

[1] 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 respective other element of the body or closure element, and a spring element (130) which is clamped between the two drive components and which supports the relative movement of the drive components (110, 120) relative to one another and has an elastic outer layer in the form of flocking, wherein at least one guide sleeve (111) made of a thermoplastic material is provided for guiding the spring element (13), characterized bythat a lubricating emulsion and a synthetic grease are applied to the flocking. [2] Linear drive (100) according to claim 1, characterized by that the flocking contains polyamide and / or polyester fibers. [3] Linear drive (100) according to claim 1 or 2, characterized by that the flocking is applied to the spring element (130) in an electrostatic or electrostatic-pneumatic process. [4] Linear drive (100) according to one of claims 1 to 3, characterized by that the lubricating emulsion is water-based, PTFE and silicone-free. [5] Linear drive (100) according to one of claims 1 to 4, characterized by that the thermoplastic material of the guide sleeve (111) is made of POM, polyamide, polypropylene or polyethylene and is optionally glass fiber reinforced. [6] Linear drive (100) according to one of claims 1 to 5, characterized by that the synthetic grease contains PTFE or other additives. [7] Method for reducing stick-slip noise in a linear drive (100), comprising at least the steps: Providing a spring element (130) for a linear drive (1) according to one of claims 1 to 6, Applying the lubricating emulsion and a synthetic grease to the flocking of the spring element (130). [8] Method according to claim 7, characterized by that the lubricating emulsion is applied in liquid form to the flocked spring element (130) by spraying or dipping. [9] Method according to claim 8, characterized by that the lubricating emulsion is dried. [10] Method according to one of claims 7 to 9, characterized by that the optional synthetic grease is applied to the flocked spring element (130) after the lubricating emulsion has been applied and dried.

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