CN105667573B - Rear-axle steering system for motor vehicles - Google Patents

Abstract

The invention relates to a rear axle steering system for a motor vehicle with a central actuator for moving a steering rod connected to the two wheels of the rear axle and changing the steering angle of these wheels, wherein the steering rod Engages with the steering pinion and can be blocked for blocking the movement of the steering rod by means of a blocking device, which is designed as a clutch. In order to enable the driver to safely and controllably implement the reverse mode without energy supply, according to the invention, the clutch (23) has a plurality of discs (5), and the lowermost disc rests on the pressure plate (8), which is tensioned against the leaf spring set (12) by means of a motor-driven ball ramp (9), so that the steering pinion (3) can pass through the leaf spring set (12) when the power supply is stopped. ) spring tension and the clutch (23) is closed.

Description

Rear axle steering system for motor vehicles

technical field

The invention relates to a rear axle steering system for a motor vehicle with a central actuator for moving a steering rod connected to the two wheels of the rear axle and changing the steering angle of these wheels, wherein the The steering rod engages with a steering pinion, and the steering pinion can be blocked in order to prevent the movement of the steering rod by means of a blocking device, which is designed as a clutch.

Background technique

Rear axle steering systems are generally known from the prior art, which either provide an individual actuator for each wheel of the rear axle, or provide a central actuator to jointly steer the two rear axles of the motor vehicle. wheel. For rear-axle steering with a central actuator, it is in principle conceivable to modify the front-axle steering in such a way that it can also be used for steering the rear axle.

A rear wheel steering system for a motor vehicle is known from DE 40 25 950 A1, in which an essentially standard front wheel steering system is used as the rear wheel steering system.

DE 10 2009 033 912 A1 discloses a steering transmission with a hollow shaft motor, which can be used both in a front-axle steering system and in a rear-axle steering system. It is proposed therein that when used as a rear axle steering system, the rotating shaft is designed to be self-locking.

When the power supply is switched off, the steering rod can be moved in such a rear-axle steering system due to dynamic or static loads and adjust the steering angle for the rear wheels. Small steering angles are not problematic for the driving behavior of the motor vehicle here, but the driver has to constantly countersteer via the front-axle steering or to fix the changing linear motion of the motor vehicle. For the deenergized reverse mode (stromlose Rückfallebene), the rear axle steering must therefore be blocked.

Contents of the invention

In view of this, the object of the present invention is to improve a rear axle steering system of the type mentioned at the outset in such a way that the reverse mode is safe and controllable for the driver.

This object is achieved with a rear axle steering system having the features of the invention. An advantageous development of the invention can be derived from the extended protection concept.

It is proposed here that the clutch has a plurality of discs and that the lowermost disc bears against a pressure plate which is tensioned via a motor-driven ball ramp against the leaf spring, so that in the When the power supply is stopped, the steering pinion can be blocked by the spring tension of the leaf spring pack and the clutch can be closed.

Description of drawings

The invention will be explained in detail below by means of exemplary embodiments with reference to the drawings. The figure shows:

Figure 1 shows a schematic diagram of using the front axle steering system as the rear axle steering system;

Figure 2 shows a schematic diagram of a rear axle steering system according to the present invention;

Figures 3a, b show a schematic view of a locking device with a clutch.

Figures 4a, b show an embodiment of a locking device as a clutch.

Detailed ways

FIG. 1 shows a substantially standard electromagnetic front-axle steering system, which has been modified for use as a rear-axle steering system, as will be explained in more detail below. The rear-axle steering system of FIG. 1 is distinguished in that a central actuator 1 actuates a steering rod 2 , which in turn is connected to the rear wheels HL, HR, not shown. This central actuator 1 consists of an electric motor 27 and a ball screw drive 29 which converts the rotational movement of the electric motor 27 into a translational movement of the steering rod 2 . The electric motor 27 is controlled by an electric control unit 28 . When the rear axle steering is actuated, the steering rod 2 is moved to the right or to the left in the drawing depending on the direction of rotation of the electric motor 27 . Correspondingly, a consistent steering angle is set jointly on the rear wheels HR, HL. As can also be seen from FIG. 1 , the rear axle steering has a steering pinion 3 . When the steering system shown is used as a front-axle steering system, a steering wheel can be connected to this steering pinion 3 . Thrust block 30 engages steering rod 2 and steering pinion 3 .

Since the ball screw drive 29 is not designed to be self-locking, the steering rod 2 can drift and adjust the steering angle for the rear wheels HL, HR when the power supply is stopped, which is undesirable. For the current-free reverse mode, the rear axle steering must therefore be blocked. As shown in FIG. 2 , it is provided for this purpose that the steering pinion 3 is connected to a locking device 4 , wherein the locking device 4 is able to lock the steering pinion 3 . This measure prevents the movement of the steering rod 2 in the de-energized reverse mode.

In FIGS. 3 a, b, the locking device 4 is formed by a clutch 23 . The clutch 23 is formed by a first disc 24 and a second disc 25 . The first disc 24 is connected to the steering pinion 3 and the second disc 25 is engaged or disengaged from the first disc 24 by means of two electromagnets 26 . The second disk 25 is arranged stationary in the direction of rotation, so that the steering pinion 3 can be locked by engaging the clutch 23 . The electromagnets 26 are preferably designed in such a way that they bring about the clutch 23 being closed in the deenergized state.

The exemplary embodiment according to FIGS. 4 a , b shows an expansion of the locking device 4 , which is designed as a clutch 23 , and which comprises a plurality of alternating disks 5 arranged one above the other. The discs 5 are arranged here in each case such that between the upper discs 6 there is a connection to the first connecting element 13 of the ball ramp 9 and between the lower discs 7 there is a second connection to the steering pinion 3 Components 14 are connected, and the lowermost disk is placed flat on the pressure plate 8. In this case, these connecting elements 13 , 14 are respectively integral with the steering pinion 3 and the ball ramp 9 . The function of the ball ramp 9 formed by the balls 11 and the ramp 10 is to press the pressure plate 8 against the leaf spring pack in the direction of the steering pinion 3 during actuation by an electric motor, not shown, connected to the ball ramp 9 12 sports. The leaf spring pack 12 is located between the steering pinion 3 and the pressure plate 8 and releases pressure in the direction of the steering pinion 3 by positioning the pressure plate 8 . Thus, the locking unit visible in FIG. 4b is opened. In the event of failure of the electric motor and its associated current supply, the clutch 23 is closed (as shown in FIG. 4 a ) by the fact that the pressure plate 8 is retracted by the pressure of the leaf spring pack 12 and the discs 5 interact with each other. Engagement, which in turn achieves the locking of the steering pinion 3.

The idea of the invention is to modify the front axle steering of the electric motor in such a way that it can also be used as a central actuator for the rear axle steering. The difference between front-axle steering and rear-axle steering is essentially that it must be possible to block the rear-axle steering in the event of a lack of power supply or other faults, so that the rear-axle steering is not automatically adjusted for undesired steering of the rear wheels horn. Provision is made for this purpose that the steering pinion, on which the steering wheel may be fastened in the case of front-axle steering, is provided with a locking device. This measure makes it possible to block the steering pinion and prevent the movement of the steering rod. This measure makes it possible to use the front-axle steering as the rear-axle steering.

Claims (8)

1. A rear-axle steering system for a motor vehicle having a central actuator (1) for pushing a steering rod (2) connected to the two wheels of the rear axle (HL; HR) are connected and change the steering angle of the wheels (HL, HR), wherein the steering rod (2) is engaged with a steering pinion (3), wherein the steering pinion (3) can be (4) is locked, thereby being able to restrain the movement of the steering rod (2), and wherein the locking device (4) is constituted as a clutch (23), which is characterized in that the clutch (23) has a plurality of discs ( 5), and the lowermost disk rests against a pressure plate (8), which is tensioned against the force of a leaf spring set (12) by a ball ramp (9) driven by an electric motor Therefore, when the power supply stops, the steering pinion (3) can be blocked by the spring tension of the leaf spring set (12) and the clutch (23) can be closed. 2. The rear axle steering system according to claim 1, characterized in that, the clutch (23) has a plurality of discs (5) stacked on top of each other and arranged alternately, and these discs are connected to the ball ramps (9) respectively. ) or the steering pinion (3), wherein the upper discs (6) are connected to the ball ramp (9), and the lower discs (7) are connected to the steering pinion (3) . 3. The rear axle steering system according to claim 2, characterized in that, the ball ramp (9) and the pressure plate (8) are integrated through a connecting element (13), wherein the clutch (23) respectively The upper disc (6) is arranged on the connecting element (13), and the steering pinion (3) is in turn connected via a second connecting element (14) to the respective lower disc (7). 4. The rear axle steering system according to claim 1, characterized in that, the leaf spring set (12) is arranged between the steering pinion (3) and the pressure plate (8), and the pressure plate passes through the The ball ramp (9) is tensioned towards the steering pinion (3). 5. The rear axle steering system according to claim 4, characterized in that the leaf spring group (12) is tensioned by manipulating the ball ramp (9), wherein the ball ramp (9) can be controlled by the electric motor The motor operates and the ball ramp (9) positions the pressure plate (8) against the leaf spring pack (12) by movement in the direction of the steering pinion (3) in order to open the clutch (23) . 6. The rear axle steering system according to claim 5, characterized in that, when the electric motor fails, the ball ramp (9) closes the clutch (23) because the electric motor is not powered, wherein, The pressure plate (8) retreats toward the ball ramp (9) due to the spring tension of the leaf spring set (12). 7. Rear axle steering system according to claim 6, characterized in that the clutch (23) is closed by causing the circles arranged on the ball ramp (9) and the steering pinion (3) The discs (5) engage each other and effect the locking of the steering pinion (3). 8. The rear axle steering system according to claim 1, characterized in that the steering pinion (3) and the leaf spring pack (12) are surrounded by a common housing (15).