CN111874087A

CN111874087A - Steering gear for vehicle

Info

Publication number: CN111874087A
Application number: CN202010618484.1A
Authority: CN
Inventors: 黄志富; 狄杰; 杨焕凤
Original assignee: Schaeffler Technologies AG and Co KG
Current assignee: Schaeffler Technologies AG and Co KG
Priority date: 2020-07-01
Filing date: 2020-07-01
Publication date: 2020-11-03

Abstract

The invention relates to a steering gear for a vehicle, comprising an electric motor (1), a steering gear output member (3) and a transmission, wherein the transmission transmits a rotary motion output by the electric motor (1) to the steering gear output member (3) in a conversion manner, wherein the transmission comprises: a planetary roller screw transmission assembly (21) capable of converting a rotary motion from the electric motor (1) received by a screw (211) of the planetary roller screw transmission assembly (21) into a linear motion output by a nut (213) of the planetary roller screw transmission assembly (21); and a motion conversion assembly (22) capable of converting linear motion of the nut (213) into rotational motion of the steering gear output member (3).

Description

Steering gear for vehicle

Technical Field

The invention relates to the technical field of vehicles. The invention relates in particular to a steering gear for a vehicle.

Background

A steering system of a vehicle is used to control the direction of travel of the vehicle. Hydraulic power steering systems or electro-hydraulic power steering systems have been widely used in existing steering systems.

However, power steering systems implemented hydraulically have complex hydraulic line systems with hydraulic valves, which results in a large space requirement for the steering system. Furthermore, the steering system is essential to the driving safety of the vehicle. Especially for heavy vehicles, the force applied by the driver through the mechanical drive train is far from sufficient to deflect the steered wheels to achieve steering in the event of a failure of the power steering. In such a case, when the hydraulic line system fails, the power it provides is limited or unavailable, possibly resulting in failure of the steering system.

There are also currently electric power steering systems. However, current electric power steering systems have not been able to meet the ever-increasing driving demands regarding safety, comfort and flexibility.

Furthermore, german patent document DE 102008008013B 3 and chinese patent application CN 106321761 a each describe a transmission for converting a rotary motion into a linear motion, i.e. a planetary roller screw transmission. The planetary roller screw transmission mechanism includes: a lead screw; a plurality of planetary rollers engaged with the lead screw; a planetary turntable rotatably supporting the planetary rollers about their axes, the planetary rollers being oriented parallel to the spindle axis; and a nut surrounding the planetary rollers, the nut being engaged with the planetary rollers and supported on the planetary turntable in at least one of the two axial directions.

Disclosure of Invention

The present invention is therefore based on the object of providing a steering gear, in particular for an electronic power steering system of a smart commercial vehicle, which has a particularly good load-bearing capacity and a compact design.

The above technical problem is solved by a steering gear for a vehicle. The steering gear includes an electric motor, a steering gear output member, and a transmission mechanism that transmits rotational motion output by the electric motor to the steering gear output member in a converted manner. Here, the transmission mechanism comprises a planetary roller screw transmission assembly capable of converting a rotary motion from an electric motor received by a screw of the planetary roller screw transmission assembly into a linear motion output by a nut of the planetary roller screw transmission assembly. In addition, the transmission mechanism includes a motion conversion assembly capable of converting linear motion of the nut into rotational motion of the steering gear output member.

The steering gear is designed as an electrically driven steering gear, in particular as a purely electrically driven steering gear. Steering gears are used in steering systems in vehicles, in particular in intelligent commercial vehicles, such as trucks and passenger cars. The transmission mechanism transmits the steering torque and the steering angle provided by the electric motor to the steering output member in a variable manner, so that the steering output member can rotate within a certain angle range. Preferably, the rotational axis of the steering gear output member is arranged perpendicular to the rotational axis of the rotor of the electric motor. Preferably, the steering gear output member is configured as a rotatable shaft. Preferably, the steering gear output member is directly or indirectly connected to the steering rod, so that the steering rod can be actuated to deflect the wheels.

The planetary roller spindle drive can be designed in a known manner. In particular, the planetary roller screw drive assembly comprises, in addition to the above-described screw serving as an assembly input and nut serving as an assembly output, a plurality of planetary rollers and planetary discs circumferentially distributed intermediate the nut and the screw. The spindle, the nut and the planetary wheel are arranged concentrically. The planet rollers are rotatably mounted in bores of the planet disk so as to be spaced apart from one another in the circumferential direction and so as to be rotatable relative to the planet disk. The planetary turntable is rotatably arranged relative to the nut. In this case, an external thread is formed on the outer circumference of the planetary roller, wherein at least a part of the external thread of the planetary roller can be screwed to the external thread of the spindle and at least a part of the external thread of the planetary roller can be screwed to the internal thread of the nut.

With the above-described design, in particular with a planetary roller spindle drive, such an electrically driven steering gear, in particular a purely electric motor-driven steering gear, on the one hand enables a high transmission ratio and a high load-bearing capacity, and on the other hand enables a particularly compact design. In this way, particularly in intelligent commercial vehicles, such as large-sized vehicles like trucks and buses, sufficient steering force can be provided to the wheels instead of hydraulic and electrohydraulic steering gears, so that hydraulic lines, hydraulic pumps, and the like can be omitted, the design of the steering gears and a steering system including the steering gears, which are easy to arrange in the steering system and which are light in weight, can be greatly simplified. In addition, the electrically driven steering gear provided herein has good shock resistance and thus works reliably and has a long service life. In addition, the electrically-driven steering gear is also advantageous to implement a steer-by-wire system of a vehicle, so that steering of the vehicle can be flexibly and rapidly performed, providing excellent steering performance. Meanwhile, the steering gear provided herein functionally supports the driving assistance function and the automatic driving function. In addition, the steering gear output component interface reserved by the steering gear can also be connected to a non-vehicle steering execution system.

Here, the motion conversion assembly may be configured as any assembly capable of converting a linear motion of the nut into a rotational motion of the steering gear output member.

Preferably, the motion converting assembly includes a rack portion provided at the nut and a sector gear portion provided at the steering gear output member, wherein teeth of the rack portion and teeth of the sector gear portion are engaged with each other. Thus, a rack-and-pinion type transmission pair is formed by the rack portion and the sector gear portion. The steering gear output member is designed as a toothed shaft, for example.

In a preferred embodiment, the electric motor is arranged coaxially with the planetary roller screw drive assembly. In this case, the rotational axis of the rotor of the electric motor coincides with the rotational axis of the spindle of the planetary roller spindle drive. Here, the electric motor is preferably configured as an inner rotor type motor. Since the planetary roller screw drive can be implemented with smaller axial dimensions than other drive assemblies of the same type, for example ball screw drive assemblies, the steering gear can be of compact construction and easy to arrange, with the electric motor arranged coaxially with the planetary roller screw drive, with relatively small axial gearing and very small radial dimensions with respect to the above-mentioned coinciding axes of rotation.

In this case, it is particularly preferred if the spindle of the planetary roller spindle drive is connected in a rotationally fixed manner directly to the output shaft of the electric motor. The planetary roller screw drive assembly can carry a high input rotational speed, so that the rotational movement of the electric motor can be transmitted to the planetary roller screw drive assembly without a reduction in speed, so that no reduction mechanism, for example a belt drive or a planetary gear drive, has to be provided between the electric motor and the planetary roller screw drive assembly. The steering gear can thereby be realized in a more lightweight and compact structure.

In a preferred embodiment, the steering gear further comprises a motor control unit. Preferably, the motor control unit is integrated at the electric motor. The motor control unit can determine the steering torque and the steering angle required for steering and select the current and the direction of rotation of the electric motor for this purpose. In this case, the motor control unit can know the steering demand information of the vehicle and the vehicle speed and/or vehicle acceleration information, and can determine the steering torque and the steering angle required for steering in combination with the steering demand information and the vehicle speed and/or vehicle acceleration information. The steering demand information can be obtained from the driver, for example, by a torque sensor arranged at the steering wheel or a microphone arranged in the on-board intelligent system. Alternatively, the steering demand information may also be sent by an intelligent system on board and/or remotely.

In an advantageous embodiment, the steering gear further comprises a position sensor for determining the position of the nut of the planetary roller screw drive assembly. The output of the motor can be more accurately adjusted using the position information of the nut to more accurately implement steering of the vehicle.

In an advantageous embodiment, the steering gear further comprises a speed control mechanism, in which an input/output member is connected in a rotationally fixed manner to a spindle of the planetary roller spindle drive. The input/output components in the governor mechanism can be understood here as: the member for introducing torque into or outputting torque from the speed adjusting mechanism, i.e., the member at the end of the path on the torque transmission path in the speed adjusting mechanism, depends on the direction of transmission of torque in the speed adjusting mechanism. In this case, the spindle of the planetary roller spindle drive is preferably connected with one axial end thereof in a rotationally fixed manner to an input/output member of the speed adjustment mechanism and with the other axial end thereof is coupled directly or indirectly to the output shaft of the electric motor for receiving the torque generated by the electric motor. In this case, a component of the governor mechanism at the other path end on the torque transmission path can be directly or indirectly connected to the steering demand input component of the vehicle. For example, the member at the other path end is connected to the steering demand input member of the vehicle via a telescopic shaft and/or a steering column. A steering demand input member is understood here to be any member that can be acted upon by the driver or acted upon by a torque to input a steering demand to the steering system, for example a steering wheel. The torque output by the electric motor can thus be fed back to a steering demand input member, for example a steering wheel, in a regulated manner, so that the movement, in particular the rotational movement, of the steering demand input member is adapted to the rotation of the spindle or thus to the deflection of the steered wheels with respect to force, in particular torque, and speed, in particular rotational speed.

Preferably, the governor mechanism is constructed as a planetary gear assembly, so that the governor mechanism can be realized in a compact structure. Here, preferably, the electric motor, the planetary roller screw transmission assembly and the planetary gear assembly are arranged coaxially. In this case, the steering gear can be implemented in a very compact structure.

Preferably, the steering gear further comprises a sensor for measuring the angular position and/or torque of a member in the governor mechanism. In this case, the steering demand, for example in the form of torque, which the driver inputs to the steering system by means of, for example, the steering wheel, can be represented as angular position and/or torque information of a component in the governor gear. The angular position and/or torque information mentioned above can thus be detected by means of the angular position sensor and/or torque sensor and can be transmitted to the motor control unit as steering demand information.

In a preferred embodiment, the electric motor is designed as a polyphase electric motor. Here, the driving reliability of the motor can be improved by using the multi-phase redundancy structure of the multi-phase motor. For example, when one or several stator windings of a multiphase motor fail, only the load down operation is required without having to stop.

In a preferred embodiment, the steering gear further comprises a housing on which the spindle of the planetary roller spindle drive is mounted. In this case, the spindle is supported, in particular at both axial ends, on the housing by means of bearings. If necessary, a seal can also be provided at the bearing point.

Drawings

Preferred embodiments of the present invention are schematically illustrated in the following with reference to the accompanying drawings. The attached drawings are as follows:

figure 1 is a schematic view of a diverter according to a preferred embodiment,

fig. 2 is a schematic view of a steering system arranged with a steering gear according to fig. 1.

Detailed Description

Fig. 1 shows a schematic view of a diverter according to a preferred embodiment. In the present embodiment, the steering gear is designed as a purely electrically driven steering gear and can be used in particular for steering systems of smart commercial vehicles.

As shown in fig. 1, the steering gear includes an electric motor 1, a motor control unit 4, a transmission mechanism, and a shaft member 3 as an output member of the steering gear.

Here, the motor 1 is configured as an inner rotor type motor. The motor 1 is configured as a multi-phase motor, thereby realizing a multi-phase redundant structure of the motor 1 and improving the driving reliability of the motor 1. When one or several stator windings of the motor 1 fail, only the load down operation is required without a stop. In addition, the safety level of the steering function can be improved through other redundancy designs, such as dual power supplies, dual electric control and the like.

The motor control unit 4 is integrated in the electric motor 1. Here, the motor control unit 4 can know the steering demand information of the vehicle and the vehicle speed and/or vehicle acceleration information, and can determine the steering torque and the steering angle required for steering in combination with the steering demand information and the vehicle speed and/or vehicle acceleration information. The motor control unit 4 controls the electric motor 1 to operate with a corresponding current and a rotation direction according to a steering torque and a steering angle required for steering. The output shaft of the electric motor 1 thus performs a corresponding rotary motion.

In the present embodiment, the transmission mechanism transmits the rotational motion output by the electric motor 1 to the shaft 3 via a speed change and a torque change. The transmission mechanism includes a planetary roller screw drive assembly 21 and a rack and pinion assembly 22.

The planetary roller screw drive assembly is arranged coaxially with the motor 1. The planetary roller screw drive assembly 21 includes a screw 211, a plurality of planetary rollers 212, a planetary turntable, and a nut 213. Here, the spindle 211, the nut 213 and the planetary turntable are arranged concentrically. Here, the rotation axis of the rotor of the motor 1 coincides with the rotation axis of the lead screw 211. A plurality of planetary rollers 212 are oriented parallel to the axis of the spindle 211 and are screwed to one another. The planetary turntable rotatably supports the planetary roller 212 around the axis of the lead screw 211. The nut 213 surrounds the plurality of planetary rollers 212 and is screwed to each planetary roller 212 inside. The spindle 211 is connected in a rotationally fixed manner directly to the output shaft of the electric motor 1, so that the spindle 211 receives a rotational movement from the electric motor 1 as a component input. The spindle 211 is rotatably mounted on the housing 23 of the steering gear by means of bearings. By means of the transmission mechanism of the planetary roller screw transmission assembly, the rotary motion of the motor 1 is converted into a linear motion of the nut 213 as an output member of the assembly.

The rack and pinion arrangement 22 comprises a rack, for example, which is integrally formed on the nut 213, and a toothed segment 221, for example, which is mounted in a rotationally fixed manner on the shaft 3. Here, the teeth of the rack portion and the teeth of the sector gear portion 221 are engaged with each other, so that the sector gear portion 221 can rotate the shaft member 3 within a certain angular range when the nut 213 is linearly moved by the driving of the motor 1.

Fig. 2 shows a schematic view of a steering system in which a steering gear according to the present embodiment is arranged. As shown in fig. 2, the rotational movement of the shaft element 3 over a certain angular range can be transmitted to a steering wheel (not shown), for example via a drop arm 6 and a steering rod 7, so that a deflection of the steering wheel is achieved.

Further, fig. 2 shows an example of acquiring the steering demand information of the vehicle. As shown in fig. 2, when the driver of the vehicle inputs a steering demand to the steering system by turning the steering wheel, the applied torque applied by the driver is transmitted to the governor mechanism 5 of the steering gear through the steering column 11, the telescopic rod 10, the angle driver 9, and the telescopic rod 8 in this order.

As can be seen from fig. 1 and 2 in conjunction, the governor mechanism 5 according to the present embodiment is configured as a planetary gear assembly. Here, the electric motor 1, the planetary roller screw drive assembly 21 and the planetary gear assembly 5 are arranged coaxially. The planet carrier of the planetary gear assembly 5 here introduces torque from the steering wheel into the planetary gear assembly 5. The respective components in the planetary gear assembly 5 thereby perform a rotational movement. The rotational movement of the component can be measured by an angular position sensor and/or a torque sensor arranged in the steering gear. The measurement signal thus obtained can be used as steering demand information for the control of the motor control unit 4.

The sun gear (corresponding to the input/output element described above) of the planetary gear arrangement 5 is connected in a rotationally fixed manner to one axial end of the spindle 211, which is opposite the other axial end of the spindle 211 that is connected in a rotationally fixed manner to the output shaft of the electric motor 1. So that the torque output by the electric motor 1 can be suitably fed back to the steering wheel of the vehicle.

In an alternative or in addition to the above-described embodiments with respect to obtaining steering demand information of the vehicle, the steering demand information may come from the driver, which is obtained, for example, by means of a torque sensor arranged at the steering wheel or a microphone arranged in the on-board intelligent system. Furthermore, alternatively, the steering demand information can also be emitted by the onboard intelligence system.

Although possible embodiments have been described by way of example in the above description, it should be understood that numerous embodiment variations exist, still by way of combination of all technical features and embodiments that are known and that are obvious to a person skilled in the art. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. From the foregoing description, one of ordinary skill in the art will more particularly provide a technical guide to convert at least one exemplary embodiment, wherein various changes may be made, particularly in matters of function and structure of the components described, without departing from the scope of the following claims.

List of reference numerals

1 electric motor

2 steering mechanism

21 planetary roller screw assembly

211 leading screw

212 planetary roller

213 nut

22 motion conversion assembly

221 sector gear

23 casing

3 a diverter output member; shaft member

4 Motor control Unit

5 speed regulating mechanism/planetary gear assembly

6 plumbing arm

7 drag link

8 telescopic rod

9-angle driver

10 telescopic rod

11 steering column

Claims

1. Steering gear for a vehicle, comprising an electric motor (1), a steering gear output member (3) and a transmission, wherein the transmission transmits the rotary motion output by the electric motor (1) to the steering gear output member (3) in a conversion manner,

characterized in that, drive mechanism includes:

a planetary roller screw transmission assembly (21) capable of converting the rotary motion received by the screw (211) of the planetary roller screw transmission assembly (21) from the electric motor (1) into a linear motion output by the nut (213) of the planetary roller screw transmission assembly (21); and

a motion conversion assembly (22) capable of converting linear motion of the nut (213) into rotational motion of the diverter output member (3).

2. The steering gear according to claim 1, wherein the motion conversion assembly (22) includes a rack portion provided at the nut (213) and a sector gear portion (221) provided at the steering gear output member (3), wherein teeth of the rack portion and teeth of the sector gear portion (221) are engaged with each other.

3. Steering gear according to claim 1, wherein the electric motor (1) is arranged coaxially with the planetary roller screw transmission assembly (21).

4. Steering gear according to claim 3, wherein the lead screw (211) is connected in a rotationally fixed manner directly to the output shaft of the electric motor (1).

5. The diverter according to claim 1, wherein the diverter further comprises a motor control unit (4).

6. The diverter according to claim 1, wherein the diverter further comprises a position sensor for determining the position of the nut (213).

7. The steering gear according to claim 1, wherein the steering gear further comprises a governor mechanism (5), an input/output member in the governor mechanism (5) being connected in a rotationally fixed manner with the lead screw (211).

8. The steering gear according to claim 7, wherein the steering gear further comprises a sensor for measuring the angular position and/or the torque of a member in the governor mechanism (5).

9. Steering gear according to claim 1, wherein the electric motor (1) is configured as a multi-phase electric motor.

10. The steering gear according to claim 1, wherein the steering gear further comprises a housing (23), the lead screw (211) being supported on the housing (23).