Method for chassis actuator and transmission assembly for operating chassis actuator

Abstract

The invention relates to a chassis actuator (1), in particular for a rear-axle steering system, comprising a rotary linear transmission (5) which is arranged for coupling to a chassis element on the output side, wherein a rotatable input-side element (9) of the transmission (5) is mounted in a housing (13) by means of at least one axial bearing (16, 17). The transmission (5) is set in a self-locking manner by means of an adjustable preload device (21) which loads the axial bearings (16, 17) with an axial force.

Description

Technical Field

[0001] The invention relates to a chassis actuator, in particular a chassis actuator suitable for use in a rear-axle steering system of a motor vehicle according to the preamble of claim 1. The invention also relates to a method for operating a transmission assembly of such a chassis actuator. Background Art

[0002] A universal chassis actuator is known, for example, from WO 2018 / 149441 A1. The chassis actuator is known to be part of a device for adjusting the level of a motor vehicle and comprises a spindle nut rotatably mounted by means of an axial bearing. To limit the spindle nut, a locking unit is provided, which comprises a locking profile that rotates when the spindle nut rotates and a deflectable locking lever.

[0003] For example, DE 2013 211 230 A1 describes a device for steering the rear axle of a motor vehicle. The device comprises an actuator, with which a steering movement can be carried out between a fixed point on the vehicle and a pivot point of a steering linkage. In order to produce the displacement movement, the actuator has an axle element, which is rotatably mounted relative to a housing element. As a means of temporarily preventing a rotational movement between the axle element and the housing element, the device according to DE 10 2013 211 230 A1 has two pins, which are arranged in the housing element or in the axle element and can engage in a recess of the other element.

[0004] DE 10 2008 024 910 A1 discloses an actuator with a load torque lock, which can be used in the chassis of a motor vehicle. In this case, the load torque lock comprises a coil spring. Summary of the invention

[0005] Compared to the cited prior art, it is an object of the present invention to further develop the chassis actuator, in particular with regard to its use in rear-axle steering systems.

[0006] According to the invention, this object is achieved by a chassis actuator having the features of claim 1. The object is also achieved by a method for operating a two-stage transmission assembly of a chassis actuator, which comprises a continuously variable transmission and a rotary linear transmission, according to claim 9. The configurations and advantages of the invention explained below in conjunction with the operating method also apply to the device, i.e. the chassis actuator, and vice versa.

[0007] In the known basic concept, a chassis actuator comprises a rotary-linear transmission which is provided for coupling to at least one chassis element on the output side, wherein a rotatable input-side element of the rotary-linear transmission is mounted in a housing by means of an axial bearing.

[0008] According to the invention, an adjustable preload device is provided, which loads the axial bearing with an axial force, wherein the rotary-linear transmission can be set in a self-locking manner by the axial force, possibly in combination with a further upstream transmission.

[0009] If the transmission assembly of the chassis actuator is designed as a two-stage, i.e. continuously variable transmission and a rotary linear transmission connected downstream, the input-side element of the rotary linear transmission, in particular the rotatable nut, is loaded with an axial force acting on the axial bearing of the rotary linear transmission by means of a fine fine-tuning element, usually in the form of a preloaded nut, so that the overall efficiency of the two-stage transmission assembly remains below 50%.

[0010] Regardless of the number of gear stages, the preload is preferably set in such a way that, on the one hand, a reliable self-locking operation, i.e. operation of the transmission assembly, is provided with an overall efficiency of less than 50%, and, on the other hand, no unnecessarily high friction losses occur in one of the gear stages. The overall efficiency is preferably set to a value of at least 35% to a maximum of 45%. The efficiency is always set by the axial force loading the input-side element of the rotary linear transmission.

[0011] In order to adjust the preload of the axial bearing and thus the efficiency of the rotary linear transmission, a preload nut is preferably provided which is screwed into the internal thread of the housing. Optionally, the setting of the preload nut, which can be used as a fine tuning element, can be fixed by means of a locking nut.

[0012] The preload nut either rests directly on the bearing element of the axial bearing or exerts an axial force on the bearing element indirectly. In both cases, the bearing element is preferably a bearing ring or a bearing washer of a rolling bearing. In addition to the axial bearing function, in a preferred embodiment, the rolling bearing also fulfills the radial bearing function. This can be achieved by means of separate rolling element groups, wherein a first group of rolling elements is exclusively used for the axial bearing and a second group of rolling elements is exclusively used for the radial bearing. Here, both groups of rolling elements can roll on the same bearing element.

[0013] Alternatively, the rolling bearing can be designed as an oblique rolling bearing, in which rolling elements, such as balls, cylindrical rollers or needle rollers, are arranged in the bearing with a contact angle greater than 0° and less than 90°, in particular at least 20° and at most 70°, and can therefore be used to transmit both radial forces and axial forces.

[0014] A rotary linear transmission, which converts the rotation of an input-side gear element mounted by means of a preloaded axial bearing into the feed of an output-side gear element, is designed, for example, as a planetary rolling gear system. With regard to the design of the planetary rolling gear system, reference is made, for example, to the documents WO 2015 / 081951 A1 and DE 10 2015 212 333 A1. In the case of a chassis actuator, the input-side gear element can be the spindle nut of the planetary rolling gear system or can be a part which is connected to the spindle nut in a rotationally fixed manner. Alternatively, a planetary gear carrier can be provided as a drive element of the planetary rolling gear system. In this case, the planetary rolling gear system is designed as a quasi-pitch rotary linear transmission and, from this point of view, can be likened to a simple transmission thread. With regard to the basic design of the quasi-pitch planetary rolling gear system, reference is made, for example, to DE 195 40 634 C1.

[0015] In an advantageous embodiment, a further transmission, in particular a continuously variable transmission, is connected upstream of the rotary linear transmission, in particular a planetary rolling gear system. The continuously variable transmission can be a belt drive or a chain drive. Alternatively, the input-side element of the rotary linear transmission can also be driven via a gear-based transmission. In all cases, the transmission connected upstream of the rotary linear transmission is preferably electrically driven, so that the chassis actuator as a whole is designed as an electromechanical actuator. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In the following, several exemplary embodiments of the present invention are described in more detail with the aid of the accompanying drawings. In the drawings:

[0017] Figure 1 A schematic overview of the electromechanical chassis actuator of a rear-axle steering system is shown.

[0018] Figure 2 A cross-sectional view of a chassis actuator for a rear axle steering system of a motor vehicle is shown.

[0019] Figure 3 With Figure 2 A similar representation shows an alternative embodiment of a chassis actuator for a rear-axle steering system.

[0020] Unless otherwise specified, the following description relates to all exemplary embodiments. In all drawings, parts that correspond to each other or have substantially the same function are denoted by the same reference numerals. DETAILED DESCRIPTION

[0021] A chassis actuator, indicated as a whole by reference numeral 1, is provided for use in a rear-axle steering system of a two-axle vehicle, i.e. a passenger car. The chassis actuator 1 thus represents a steering actuator of a rear-axle steering system. The chassis actuator 1 is assigned an electric motor 2 and a transmission assembly 3 actuated by the electric motor 2. The motor controller of the electric motor 2 is marked with reference numeral 27. The transmission assembly 3 comprises a continuously variable transmission 4, i.e. a belt drive, and a rotary linear transmission 5 in the form of a planetary rolling gear system, which is connected downstream of the continuously variable transmission 4. The belt of the belt drive 4 is marked with reference numeral 6. A drive pulley 7, which is firmly connected to the motor shaft of the electric motor 2, is coupled to an output pulley 8 via a belt 6. The output pulley 8 is in turn firmly connected to a spindle nut 9, which represents a rotatable input-side element of the rotary linear transmission 5. The corresponding threaded shaft of the rotary linear transmission 5, which is marked with reference numeral 10, represents an output element of the rotary linear transmission.

[0022] The threaded shaft 10 is displaceably guided in a housing 13 of the chassis actuator 1 by means of linear guides 11, 12. At the ends of the threaded shaft 10 there are located connecting elements 14, 15 which enable coupling to the wheels of the vehicle to be steered via chassis elements not shown.

[0023] Two axial bearings 16, 17 are provided for mounting the spindle nut 9 in the housing 13. Each axial bearing 16, 17 comprises a housing washer 18 as a bearing washer and a shaft washer 19. The ball 20 serves as a rolling element that rolls between the bearing washer 18, 19 and can be guided in a cage that is not shown.

[0024] The chassis actuator 1 further comprises a preloading device 21 which loads the housing washer 18 of the axial bearing 17 with an axial force. The efficiency of the rotary linear transmission 5 designed as a planetary rolling gear system does not depend heavily on this axial force, but rather depends to a large extent on it. The axial force is set by means of the preloading device 21 in such a way that the efficiency of the chassis actuator 1, more precisely the efficiency of the transmission assembly 3, is at least 35%, at most 45%, and is therefore reliably in the self-locking range, i.e. below 50%. The efficiency of the entire transmission assembly 3 mentioned above is obtained by multiplying the efficiency of the continuously variable transmission 4 by the efficiency of the rotary linear transmission 5.

[0025] Applicable according to Figure 1 Various possible configurations of the preloading device 21 are arranged in Figure 2 and Figure 3 In the diagram, the diagram is shown in a somewhat greatly simplified form.

[0026] In accordance with Figure 2In the exemplary embodiment of FIG. 1 , in addition to the axial bearings 16 , 17 , two radial bearings 22 , 23 can also be seen. Figure 2 In the design shown, the radial bearings 22, 23 include balls 24 as rolling elements. The rolling elements 24 of the radial bearings 22, 23 are not necessarily sized to match the rolling elements 20 of the axial bearings 16, 17. In any case, the row of rolling elements 20 that performs the function of the axial bearing rolls on the housing washer 18, and the rolling elements 24 that perform the function of the radial bearing also roll on the same housing washer 18.

[0027] according to Figure 3 Exemplary embodiments and according to Figure 2 The exemplary embodiment of the invention differs in that exactly one row of rolling elements 20 is assigned to the rolling bearings 16, 17, wherein, as can also be seen in Figure 1 As can be seen in , the angular ball bearing is designed as an axial-radial bearing. Since the main loading direction is aligned in the axial direction of the chassis actuator 1, ie in the longitudinal direction of the threaded shaft 10, the rolling bearings 16, 17 are also referred to as axial bearings in this case.

[0028] In all exemplary embodiments, the preload device 21 comprises a preload nut 25 which is screwed into the housing 13 and is also generally referred to as a fine tuning element. Screwing the preload nut 25 into the housing 13 is accompanied by an increase in the preload force and a decrease in the efficiency of the rotary linear transmission 5 .

[0029] exist Figure 2 and Figure 3 6 and the output pulley 8 can also be seen to a limited extent. The output pulley 8 is connected to the spindle nut 9 in a rotationally fixed manner via a sleeve 26 and therefore represents a transmission element of the rotary-linear transmission 5.

[0030] Description of Reference Numerals

[0031] 1 Chassis actuator 2 Electric motor 3 Transmission assembly 4 Continuously variable transmission, belt drive 5 Rotary linear transmission, planetary rolling gear system 6 Belt 7 Drive pulley 8 Output pulley 9 Spindle nut 10 Threaded shaft 11 Linear guide 12 Linear guide 13 Housing 14 Connecting element 15 Connecting element 16 Axial bearing 17 Axial bearing 18 Housing washer 19 Shaft washer 20 Rolling element, ball 21 Preload device 22 Radial bearing 23 Radial bearing 24 Rolling element, ball 25 Preload nut, fine tuning element 26 Sleeve 27 Motor controller.

Claims

1. A chassis actuator (1) having a rotary linear transmission (5) which is arranged for coupling to at least one chassis element on the output side, wherein: The rotatable input-side element (9) of the transmission (5) is mounted in a housing (13) by means of at least one axial bearing (16, 17), characterized in that the chassis actuator also includes an adjustable preload device (21) for loading the axial bearing (16, 17) with an axial force, wherein the transmission (5) is set and the efficiency is reduced by the axial force to be in a self-locking range.

2. The chassis actuator (1) according to claim 1, characterized in that The preloading device (21) comprises a preloading nut (25) screwed into the internal thread of the housing (13), and the preloading nut serves as a fine tuning element.

3. The chassis actuator (1) according to claim 2, characterized in that The preload nut (25) is in contact with a bearing element (18) of the axial bearing (16, 17).

4. The chassis actuator (1) according to claim 3, characterized in that The axial bearings (16, 17) are designed as rolling bearings.

5. The chassis actuator (1) according to claim 4, characterized in that The axial bearing (16, 17) comprises, in addition to rolling elements (20) performing the function of the axial bearing, rolling elements (24) for radial bearings, wherein all rolling elements (20, 24) are in contact with the same bearing element (18).

6. The chassis actuator (1) according to claim 4, characterized in that The axial bearing (16, 17) comprises rolling elements (20) which perform both the axial bearing function and the radial bearing function.

7. Chassis actuator (1) according to any one of claims 1 to 6, characterized in that A planetary rolling gear system is provided as the rotary linear transmission (5).

8. The chassis actuator (1) according to claim 7, characterized in that A continuously variable transmission (4) is connected upstream of the planetary rolling gear system (5).

9. A method for operating a two-stage transmission assembly (3) of a chassis actuator (1) as claimed in any one of claims 2 to 8, the transmission assembly comprising a continuously variable transmission (4) and a rotary linear transmission (5) connected downstream, wherein the input-side element (9) of the rotary linear transmission (5) is loaded with an axial force acting on the axial bearings (16, 17) of the rotary linear transmission (5) by means of a fine adjustment element (25), so that the overall efficiency of the transmission assembly (3) is kept below 50% in order to be in the self-locking range.

10. The method according to claim 9, characterized in that By means of the axial forces acting in the rotary linear transmission (5), the efficiency of the entire transmission assembly (3) is set to a value of at least 35% to a maximum of 45%.

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