Push rod for a linear actuator and linear actuator with a push rod

Abstract

A push rod assembly (7) for a linear actuator (1) of an axle steering system of a vehicle, comprising at least a first rod (9.1) and a spindle (8) for translating a rotary movement of a drive device (3) into a linear movement of the push rod assembly (7), wherein the spindle (8) has a spindle shoulder (8.1) and, at a first axial end, a first connecting shoulder (8.2) for connection to the first rod (9.1), characterized in that the spindle (8) has, between the spindle shoulder (8.1) and the first connecting shoulder (8.2), a receiving shoulder (8.4) with a securing element (10) received thereon in a rotationally fixed manner for securing the push rod assembly (7) against rotation, wherein the securing element (10) is held in the axial direction between the spindle shoulder (8.1) and the first rod (9.1) and axially bears against the spindle shoulder (8.1) and the first rod (9.1).

Description

[0001] The invention relates to a push rod assembly for a linear actuator of an axle steering system of a vehicle, comprising at least a first rod and a spindle for translating a rotary movement of a drive device into a linear movement of the push rod assembly, wherein the spindle has a spindle shoulder and, at a first axial end, a first connecting shoulder for connection to the first rod.

[0002] Such push rods are known from the prior art for linear actuators. Such linear actuators are used, for example, in rear-axle steering systems on motor vehicles. It is common for a rod to have a shoulder with a non-circular geometry or radial projections as an anti-rotation device, which interacts with a corresponding geometry on a housing of the linear actuator to prevent rotation of the rod.

[0003] From EP 1 911 660 A1, for example, a linear actuator with a push rod is known, which comprises a spindle and a rod connected thereto, wherein an anti-twist device is formed on the rod, which holds the push rod in the circumferential direction relative to a housing.

[0004] DE 10 2016 206 576 B3 discloses a spindle drive for a steering actuator comprising a spindle and a spindle nut. Rotation of the spindle relative to a housing of the steering actuator is prevented by an anti-rotation device. The spindle has an eccentric bearing section guided in a plain bearing. The anti-rotation device is activated by the eccentricity of the plain bearing.

[0005] DE 10 2016 200 101 A1 discloses a spindle drive of a steering actuator with a spindle nut and a spindle engaging therewith, wherein rotation of the spindle relative to a housing of the steering actuator is ensured by a rotation lock fixed to the housing, in which a screw-on pin is guided and which is prevented from rotating due to a non-round profile.

[0006] DE 10 2016 200 102 B4 discloses a spindle drive similar to DE 10 2016 200 101 A1, wherein the anti-rotation device is arranged on both sides of the spindle section.

[0007] DE 10 2016 210 221 A1 and DE 10 2016 210 227 A1 both disclose a spindle drive of a steering actuator with a spindle nut and a spindle engaged therewith. Rotation of the spindle relative to a housing of the steering actuator is prevented by a hub ring designed as an anti-rotation device. The hub ring has a hub profile that engages a splined shaft profile at the end of a spindle section.

[0008] The disadvantage of such anti-rotation devices is that they are complex to manufacture, especially since the anti-rotation device must be firmly connected to the rod in the axial direction, for example, by means of a material connection. Accordingly, such anti-rotation devices are expensive.

[0009] In view of the aforementioned prior art, the object of the present invention is to propose a push rod assembly that is simple and cost-effective. This object is achieved by the subject matter of patent claim 1. Furthermore, the object is achieved by the subject matter of patent claim 9. Preferred embodiments can be found in the dependent claims.

[0010] A push rod assembly according to the invention is characterized in that the spindle has a receiving shoulder between the spindle shoulder and the first connecting shoulder with a securing element received thereon in a rotationally fixed manner to prevent the push rod assembly from rotating, the securing element being held in the axial direction between the spindle shoulder and the first rod.

[0011] For the purposes of the invention, the axial direction is understood to mean the longitudinal direction of the push rod. In a motor vehicle in which a linear actuator with the push rod is used for axle steering of the rear wheels, the longitudinal direction of the push rod is a transverse direction of the motor vehicle.

[0012] The invention now includes the teaching that a locking element that is independent of the first rod, i.e. manufactured as a single part, is used to prevent rotation. This locking element is pushed onto a shoulder of the spindle and held axially between the spindle and the first rod. Since the spindle is usually made of a different material than the first rod and a two-part design of spindle and first rod is therefore essential, the connection can be cleverly used by the invention to achieve axial securing of the locking element. Forming an anti-twist device on the first rod is therefore no longer necessary. The locking element is also a single part independent of the first rod and can therefore be manufactured in a simple manner. When assembling the push rod, the locking element can also be easily pushed onto the spindle over the first connecting shoulder.

[0013] In particular, the securing element is held axially between the spindle and the first rod in that the spindle shoulder and the first rod each have a larger outer radius than the receiving shoulder and thus radially project beyond the securing element. To the extent that the spindle, receiving shoulder, and / or first rod do not have a round geometry at the joints between them, radial projection is to be understood as the spindle and first rod radially projecting beyond the securing element at least over part of the circumference, particularly in sections.

[0014] The push rod assembly may further comprise a second rod connected to the spindle via a second connecting shoulder of the spindle. The second connecting shoulder is then located at a second axial end of the spindle, which is opposite the first end.

[0015] In one embodiment, the receiving shoulder has a non-circular outer geometry for the rotationally fixed connection of the receiving shoulder to the securing element, and the securing element has a corresponding inner geometry. For example, the outer geometry is a polygon or a knurled surface. In this way, the securing element is held to the receiving shoulder in a rotationally secure manner and, at the same time, can be easily mounted by axial sliding.

[0016] In a further embodiment, the securing element has a non-circular outer geometry. A corresponding countergeometry can then be provided on a housing of the linear actuator, in which the securing element is secured against rotation by its non-circular geometry. Such a countergeometry can also serve as an axial guide surface for the securing element during adjustment of the push rod. For this purpose, the securing element is particularly preferably formed from a material with good sliding properties or coated with such a material on contact surfaces intended for contact with such a guide surface.

[0017] In one embodiment, the securing element is made up of several parts, comprising a radially inner holding element and a radially outer sliding element that is connected to the holding element in a rotationally fixed manner. The holding element is then intended to hold the securing element on the receiving shoulder and to transmit a force between the securing element and the receiving shoulder when preventing rotation. In particular, the holding element is made of a suitably strong material, for example metal. The sliding element is intended to slide along a guide surface of a housing with the lowest possible friction. In particular, when a torsional load is applied to the push rod, there is pressure between the securing element and the guide surface, which, if the friction is too high, could prevent axial movement of the securing element. The push rod would then block.

[0018] In such an embodiment, the retaining element preferably has a non-circular outer geometry for the rotationally fixed connection of the retaining element to the sliding element, and the sliding element has a corresponding inner geometry. In particular, this involves knurling. The sliding element is then securely held to the retaining element.

[0019] Furthermore, in such an embodiment, the holding element is preferably held in the axial direction between the spindle shoulder and the first rod, and the sliding element is held axially relative to the holding element. A very large radial projection of the spindle shoulder and the first rod above the securing element is then not necessary. Particularly preferably, for axially holding the sliding element on the holding element, the holding element has a projection extending in the radial direction and the sliding element a corresponding recess, or the sliding element has a projection extending in the radial direction and the holding element a corresponding recess. Such projections and recesses can, for example, interrupt a knurling.

[0020] Alternatively, the securing element can be made in one piece from a material that simultaneously exhibits good strength properties and favorable friction properties. Furthermore, it is also possible for the securing element to be formed from a solid material with a sliding coating on the contact surfaces.

[0021] In one embodiment, the spindle has a thread on the first connection shoulder, wherein the first rod has a mating thread, and wherein the spindle is connected to the first rod by means of a screw connection of the thread to the mating thread. The securing element can then have an axial overhang over the receiving shoulder, so that by means of the screw connection, the first rod presses the securing element with an end face against a flank of the spindle shoulder. In particular, the threads are designed so that the screw connection is self-locking. The screw connection can also be additionally glued. The securing element is then held axially particularly securely. Alternatively, other fastening means can also be provided between the spindle and the first rod, such as clamping means, an adhesive bond, or a press fit in which the parts are thermally joined.

[0022] The invention further relates to a linear actuator for an axle steering system of a vehicle, comprising an axially movably mounted push rod assembly as described above, a drive device for axially adjusting the push rod assembly, and a gear for translating a rotary movement of the drive device into a linear movement of the push rod assembly by means of the spindle and a spindle nut acting thereon. The linear actuator utilizes the aforementioned advantages of the push rod assembly as well as the push rod assembly, or also has them.

[0023] Preferably, the linear actuator has a stationary housing and the housing has a guide geometry for axially guiding the securing element, wherein the securing element is held in a rotationally fixed manner on the guide geometry.

[0024] A stationary arrangement of an element means that this element is positioned and held independently of the movement of the push rod, i.e., when the push rod is adjusted, it does not move with the push rod, nor is its position influenced by its movement. For example, such an element can be fixed to a housing of the linear actuator or to the underbody of a motor vehicle to which the linear actuator is attached.

[0025] The guide geometry is made of a sliding material with a low coefficient of friction or coated with such a material. POM or PTFE, for example, can be used as sliding materials for this application, as well as for all other previously described applications where a material should have favorable friction properties.

[0026] Further measures improving the invention are described in more detail below together with the description of preferred embodiments of the invention with reference to the figures. Fig. 1 a simplified representation of a linear actuator, Fig. 2 a push rod according to the invention, Fig. 3 a push rod according to Fig. 2 in exploded view, and Fig. 4 a spindle with a securing element arranged thereon.

[0027] Fig. 1 shows a linear actuator 1 with a housing 2 in which a push rod 7 (not shown here) is guided. A drive device 3 acts on the push rod 7, which is arranged parallel to the push rod 7 and whose drive power is transmitted to the push rod 7 via a belt drive 4 in a belt housing. Forks 5.1, 5.2 are arranged at the ends of the push rod 7, by means of which a linear movement of the push rod 7 can be transmitted to the wheels of a vehicle. A sensor housing 6 is also arranged on the linear actuator 1.

[0028] Fig. 2 shows a push rod assembly 7 with a centrally arranged spindle 8 and rods 9.1, 9.2 arranged at the ends of the spindle 8. A securing element 10 is arranged between the spindle 8 and a first rod 9.1 and is pushed onto a receiving shoulder of the spindle 8. The securing element 10 has a non-circular outer geometry 10.1, which is designed here as a square geometry with truncated corners. With the non-circular geometry 10.1, the securing element 10 is axially guided and held against rotation on a counter geometry (not shown) in the housing 2.

[0029] Fig. 3 shows the push rod 7 from Fig. 2 in an exploded view. The spindle 8 has a spindle shoulder 8.1, a first connecting shoulder 8.2, and a second connecting shoulder 8.3, wherein the connecting shoulders 8.2, 8.3 each have external threads for connecting the spindle 8 to the rods 9.1, 9.2. Between the spindle shoulder 8.1 and the first connecting shoulder 8.2, a receiving shoulder 8.4 is provided, onto which the securing element 10 is pushed. The receiving shoulder 8.4 has a non-circular geometry that interacts with a knurling 10.2 of the securing element 10, so that the securing element 10 is held against rotation on the receiving shoulder 8.4. The securing element 10 rests axially on the spindle shoulder 8.1, with the first rod 9.1 also resting axially on the securing element 10 when the rod assembly 7 is assembled, so that the securing element 10 is held axially between the spindle 8 and the first rod 9.1. The spindle 8 further has a tool shoulder 8.5, which serves as a tool attachment point during assembly of the rod assembly 7 and has a corresponding tool geometry. The rods 9.1, 9.2 have shoulders with non-circular geometries at the ends facing away from the spindle 8 for the rotationally fixed connection of the rods 9.1, 9.2 to the forks 5.1, 5.2.

[0030] Fig. Figure 4 shows the spindle 8 with a securing element 10 arranged thereon in detail, whereby the spindle 8 is shown here without a tool shoulder 8.5. The securing element 10 is formed from a radially inner holding element 10.3 and a radially outer sliding element 10.4. The holding element 10.3 is made of a material with high strength, so that a secure connection exists between the securing element 10 and the spindle 8. The sliding element 10.4 is made of a material with favorable sliding properties, so that there is a low coefficient of friction between the securing element 10 and an axial guide in the housing 2. The holding element 10.3 and the sliding element 10.4 are connected to one another in a rotationally fixed manner via knurling. Also not shown is the knurling between the holding element 10.3 and the sliding element 10.4 is interrupted in the axial direction by at least one radially extending tongue and groove connection, which extends in particular around the entire circumference of the lateral surfaces of the holding element 10.3 and the sliding element 10.4. The tongue and groove connection holds the holding element 10.3 and the sliding element 10.4 together in the axial direction. The spindle shoulder 8.1 and the first rod 9.1 then only hold the holding element 10.3 in the axial direction. The securing element 10 is different here from . Fig. 3 is designed on its inner surface with a hexagonal geometry 10.5 instead of a knurling 10.2, by means of which it is held torsionally secure on the receiving shoulder 8.4. List of reference symbols 1 linear actuator 2 housings 3 Drive device 4 Belt drive 5.1 Fork 5.2 Fork 6 Sensor housing 7 push rods 8 spindle 8.1 Spindle shoulder 8.2 first paragraph 8.3 second paragraph 8.4 Recording paragraph 8.5 Tool sales 9.1 first bar 9.2 second bar 10 securing element 10.1 Non-circular geometry of the securing element 10.2 Knurling of the locking element 10.3 Holding element of the securing element 10.4 Sliding element of the securing element 10.5 hexagonal geometry

Claims

[1] Push rod (7) for a linear actuator (1) of an axle steering of a vehicle, comprising at least a first rod (9.1) and a spindle (8) for translating a rotary movement of a drive device (3) into a linear movement of the push rod (7), wherein the spindle (8) has a spindle shoulder (8.1) and, at a first axial end, a first connecting shoulder (8.2) for connection to the first rod (9.1), characterized by that the spindle (8) has a receiving shoulder (8.4) between the spindle shoulder (8.1) and the first connecting shoulder (8.2) with a securing element (10) received thereon in a rotationally fixed manner for securing the push rod (7) against rotation, wherein the securing element (10) is held in the axial direction between the spindle shoulder (8.1) and the first rod (9.1) and lies axially against the spindle shoulder (8.1) and the first rod (9.1) [2] Push rod (7) according to claim 1, characterized bythat for the rotationally fixed connection of the receiving shoulder (8.4) to the securing element (10), the receiving shoulder (8.4) has a non-circular outer geometry and the securing element (10) has a corresponding inner geometry. [3] Push rod (7) according to claim 1 or 2, characterized by that the securing element (10) has a non-circular outer geometry (10.1). [4] Push rod (7) according to one of the preceding claims, characterized by that the securing element (10) is formed in several parts from a radially inner holding element (10.3) and a radially outer sliding element (10.4) which is connected to the holding element (10.3) in a rotationally fixed manner. [5] Push rod (7) according to claim 4, characterized by that for the rotationally fixed connection of the holding element (10.3) to the sliding element (10.4), the holding element (10.3) has a non-circular outer geometry and the sliding element (10.4) has a corresponding inner geometry. [6] Push rod (7) according to claim 4 or 5, characterized by that the holding element (10.3) is held in the axial direction between the spindle shoulder (8.1) and the first rod (9.1) and the sliding element (10.4) is held axially relative to the holding element (10.3). [7] Push rod (7) according to claim 6, characterized by that for axially holding the sliding element (10.4) on the holding element (10.3), the holding element (10.3) has a projection extending in the radial direction and the sliding element (10.4) has a corresponding recess or the sliding element (10.4) has a projection extending in the radial direction and the holding element (10.3) has a corresponding recess. [8] Push rod (7) according to one of the preceding claims, characterized bythat the spindle (8) has a thread on the first connecting shoulder (8.1), wherein the first rod (9.1) has a counter thread, and wherein the spindle (8) is connected to the first rod (9.1) by means of a screw connection of the thread to the counter thread. [9] Linear actuator (1) for an axle steering of a vehicle with an axially movably mounted push rod (7) according to one of the preceding claims, a drive device (3) for axially adjusting the push rod (7) and with a gear for translating a rotary movement of the drive device (3) into a linear movement of the push rod (7) by means of the spindle (8) and a spindle nut acting thereon. [10] Linear actuator (1) according to claim 9, characterized bythat the linear actuator (1) has a stationary housing (2) and the housing (2) has a guide geometry for axially guiding the securing element (10), wherein the securing element (10) is held in a rotationally fixed manner on the guide geometry.

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