The embodiments described herein relate to vehicle steering systems and, more particularly, to a lock mechanism for a steering assist system.
Steering systems commonly include a steering assist system that reduces the effort required by a driver to manually steer the wheels of a vehicle. Such systems may include a lock that is installed in the upper column assembly. Some designs may require that the lock mechanism is located within an assist mechanism housing.
An example of the aforementioned lock mechanism includes an inner hub, a lock sleeve ring, grease and an outer shaft lock sleeve. The lock sleeve ring is captured in compression between the inner hub and the outer shaft lock sleeve. A solenoid activated shaft drops into engagement with the lugs on the outer diameter of the outer shaft lock sleeve during the “locked” condition. As torque is applied through the main shaft that is in engagement with the inner hub, the lock sleeve is designed to resist this torque and prevent movement. Within a predetermined torque range, the lock sleeve ring reaches a “breakaway” torque and is allowed to slip. The assembly must be able to experience several overloads of torque and recover to resist a torque up to the lower torque of the predetermined torque range. This assembly example has three precision components, assembly grease, requires assembly, requires axial space on the output shaft, requires a press operation for the lock assembly and another press operation to install the lock assembly to the shaft assembly and has significant mass. Improving the packaging space and mass of the lock mechanism would be well received by those in the art.
According to one aspect of the disclosure, a steering assist system of a steering column assembly is provided. The system includes a worm rotatably driven by an actuator. The system also includes a worm gear having a first set of teeth and a second set of teeth, the first set of teeth in meshed engagement with the worm, the worm gear operatively coupled to a steering shaft. The system further includes a lock feature moveable into and out of engagement with the second set of teeth of the worm gear to define a locked condition and an unlocked condition of the worm gear.
According to another aspect of the disclosure, a lock mechanism of a steering assist system is provided. The lock mechanism includes a slide assembly located within a housing of the steering assist system. The lock mechanism also includes a wedge shaped lock feature moveable into and out of engagement with a set of teeth of a worm gear to define a locked condition and an unlocked condition of the worm gear.
The subject matter that is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
Referring now to the Figures, where the invention will be described with reference to specific embodiments, without limiting same,
The steering column assembly 10 includes a steering assist system 20 that includes an actuator (not shown), such as an electric motor, that is coupled to a worm 22. The worm 22 is in meshed engagement with a first set of teeth 23 of a worm gear 24, as shown in
Referring now to
A lock feature 36 is operatively coupled to the slide assembly 34 for translation between an unlocked condition (
As shown in
In the embodiments of
In
Referring now to
The embodiments described herein provide a lock feature that can be an “as molded” part (i.e., no additional machining) that operates in the slide assembly of the housing with an accompanying spring 42 to serve as the force component of the lock mechanism 30. The disclosed lock mechanism 30 is less complex and results in a reduced cost, when compared to typical lock mechanisms for similar applications. Hand assembly of the lock mechanism 30 is possible, thereby avoiding assembly machines and their associated costs. The lock mechanism 30 also reduces the axial packaging requirements when compared to typical lock mechanisms and reduces weight.
In addition to the advantages described above, the lock mechanism 30 provides benefits associated with what are referred to herein as ingress/egress events or loads. In particular, many drivers use a steering wheel attached to the steering column assembly 10 as a handle during ingress or egress of the vehicle. Prior steer-by-wire systems use an EPS motor to resist such a load and this is the highest torque requirement for steer-by-wire systems. However, the mechanical lock mechanism 30 described herein resists the ingress/egress events, thereby allowing for a smaller motor and/or a smaller overall system. A significant reduction in motor size on steer-by-wire systems may be achieved, while still having adequate resistance for ingress/egress loads. The lock mechanism may be adjusted or tuned to the proper slip-torque to avoid damage to any of the EPS components while still maintaining the proper resistive loading for driver ingress/egress.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description.
Number | Name | Date | Kind |
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20020116962 | Zillmann | Aug 2002 | A1 |
20090133452 | Hirche | May 2009 | A1 |
20200291681 | Markanday | Sep 2020 | A1 |
20200391784 | Saito | Dec 2020 | A1 |
Number | Date | Country |
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1671588 | Sep 2005 | CN |
202102950 | Jan 2012 | CN |
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2004216959 | Aug 2004 | JP |
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Entry |
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English translation of First Office Action regarding corresponding CN App. No. 2020110396797; issued Jul. 7, 2022. |
Number | Date | Country | |
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20210094507 A1 | Apr 2021 | US |