Wired power steering system for motor vehicles

Abstract

The invention relates to a wired power steering system for a motor vehicle, comprising: - a higher-level mechanism including a steering wheel and a motorized return device having a motor coupled to said steering wheel; - a lower-level mechanism (200) including a rack (210) and two motorized assistance devices (250, 260) each having a respective motor (251, 261) coupled to said rack by means of a corresponding coupling shaft (253, 263) carrying an actuating pinion (254, 264) meshing with said rack; - a control module connected by wired electrical linkage means (F2, F3) to said motorized return and assistance devices, and capable of controlling the motors of these devices by transmission of electrical signals;said rack having a single toothed track (211) on which are meshed the actuating pinions of the two said motorized assistance devices. Figure to be published with the abbreviation: Fig. 2;

Description

Title of the invention: Power steering system with wire connection for a motor vehicle Technical field

[0001] The present invention relates, in general, to the field of power steering systems for motor vehicles. It relates in particular to such a wired power steering system. Prior art

[0002] The steering systems comprise on the one hand an upper level mechanism comprising a steering wheel and on the other hand a lower level mechanism which comprises a rack driven via an actuating pinion and which mechanically acts on the steered wheels of the vehicle to modify the yaw orientation (i.e. the steering angle) of said wheels.

[0003] Conventionally, the upper and lower level mechanisms are connected by mechanical means comprising a steering column generally fixed to the dashboard crossmember and divided into two parts connected by a universal joint, namely an upper column on which the steering wheel is fixed and a lower column fixed to the rack.

[0004] Such steering systems are generally provided with electric driver assistance (known by the acronym DAE) making it possible to reduce the driver's effort on the steering wheel to steer the wheels, particularly when the vehicle is stationary during parking maneuvers or when the vehicle is moving during emergency situations.

[0005] Recent years have seen the emergence of power steering systems with wired and non-mechanical connections, commonly referred to by the Anglo-Saxon term “Steer By Wire”, and in which traditional mechanical means of connection are replaced by wired electrical means of connection.

[0006] In such a “Steel By Wire” system, the upper level mechanism comprises a motorized restitution device whose motor is coupled to the steering wheel and which provides force feedback to the driver of the vehicle.

[0007] The lower level mechanism comprises at least one motorized assistance device whose motor is coupled to the rack via a coupling shaft, commonly referred to as a “valve stem” and carrying an actuating pinion meshing with said rack.

[0008] A control module, connected by wired electrical connection means to the motorized restitution and assistance devices, ensures control by transmission of electrical signals from the motors of these devices so as to correlate the position of the steering wheel with the actual position of the steering wheels as well as the force feedback returned to the driver via the steering wheel.

[0009] Such “Steer By Wire” systems thus make it possible to simplify vehicle design, improve safety and refine the control laws of functional components. They also make it possible to significantly improve driving assistance by ensuring variable gear ratios for the steering wheel, generally depending on the speed.

[0010] For safety reasons, the implementation of a power steering system with a wired and non-mechanical connection requires the provision of two redundant motorized assistance devices so that one can replace the other in the event of failure.

[0011] Such redundancy of the motorized assistance devices, however, leads to a significant increase in the mass and cost of the power steering system. It also poses space problems which complicate its integration into the vehicle as well as the coupling of the motors of its devices to the rack. Statement of the invention

[0012] The present invention aims to improve the situation.

[0013] To this end, it proposes a power steering system with wired connection for a motor vehicle, comprising: - a higher level mechanism comprising a steering wheel and a motorized restitution device provided with a motor coupled to said steering wheel; - a lower level mechanism comprising a rack and two motorized assistance devices each provided with a respective motor coupled to said rack by means of a corresponding coupling shaft carrying an actuating pinion engaged with said rack; - a control module, connected by wired electrical connection means to said motorized restitution and assistance devices, said control module being capable of ensuring control by transmission of electrical signals of the motors of these devices; characterized in that said rack carries a single toothed track on which the actuating pinions of the two said motorized assistance devices are engaged.

[0014] Such a conformation of the rack with a single toothed track thus makes it possible to limit the design and manufacturing costs of this rack.

[0015] It also makes it possible to simplify the operating kinematics of this rack and to facilitate the installation of the power steering system in a motor vehicle.

[0016] According to preferred characteristics of said power steering system according to the invention: - said coupling shafts extend parallel to each other, forming the same angle with the longitudinal axis of said rack; - said motorized assistance devices are arranged in an aligned manner in a direction parallel to the longitudinal axis of said rack; - each said motorized assistance device comprises an electronic control card managing the operation of the motor of this device, said electronic control cards being arranged at the two opposite ends of said motors; - the connection between said control module and the two said motorized assistance devices is provided by two separate, non-intertwined electrical harnesses; - said control module is configured so that the two said motorized assistance devices are activated alternately; - said control module is configured so that the two said motorized assistance devices are activated simultaneously so as to operate synchronously; - the motors of the two said motorized assistance devices are sized so that they can each develop sufficient torque to drive the translational movement of said rack alone; and / or - said control module is configured, in the event of failure of one of said motorized assistance devices, to only request the other motorized assistance device.

[0017] The invention also relates, in a second aspect, to a motor vehicle comprising such a power steering system. Brief description of the drawings

[0018] The description of the invention will now be continued by the detailed description of an exemplary embodiment, given below for illustrative but non-limiting purposes, with reference to the appended drawings, in which: - [Fig.l] represents a schematic diagram of the power steering system with wire connection according to the invention; - [Fig.2] is an enlargement seen from above of the lower level mechanism of the power steering system of [Fig.l]; and - [Fig.3] represents an enlargement seen in elevation of the lower level mechanism of the power steering system of [Fig.l]. Description of the embodiments

[0019] With reference to [Fig.l], the wire-link power steering system (or “Steer By Wire”) according to the invention 1 conventionally comprises a first mechanism called “upper level mechanism” 100, comprising a steering wheel 110 allowing the driver to modulate the steering angle of a set of steering wheels of the vehicle.

[0020] The upper level mechanism 100 also comprises a motorized restitution device 120 provided with a restitution motor 121 whose operation is managed by an electronic control card 122, this motor 121 being coupled to the steering wheel 110 via a gear reduction device 123.

[0021] The main function of this motorized restitution device 120 is to provide force feedback to the driver so that the driver's driving experience is similar to that provided by conventional power steering systems with mechanical connection equipped with a steering column transmitting the forces to the wheels up to the steering wheel.

[0022] The wire-connected power steering system 1 also comprises a second mechanism called the “lower level mechanism” 200, comprising a rack 210 mounted to move in translation along its longitudinal axis in a steering casing 220 fixed to the body structure of the vehicle.

[0023] Each end of this rack 210 is connected to a corresponding steering wheel 230 of a train of the vehicle by means of two steering rods 240.

[0024] More precisely, each steering rod 240 connects one end of the rack 210 to a steering knuckle, not shown, which can be yaw-oriented, and which itself carries a corresponding steering wheel 230.

[0025] The lower level mechanism 200 also comprises a first motorized assistance device 250 provided with a motor 251 whose operation is managed by an electronic control card 252.

[0026] As is better seen in [Fig. 2], this motor 251 is coupled to the rack 210 via a coupling shaft 253, commonly referred to as a “valve stem”, a first end of this coupling shaft 253 carrying an actuating pinion 254 engaged with this rack 210 while its second end is coupled to the rotation axis of this motor 251 via a gear reduction device 255.

[0027] The lower level mechanism 200 further comprises a second motorized assistance device 260, similar to the first motorized assistance device 250, and provided with a motor 261 whose operation is managed by an electronic control card 262.

[0028] This motor 261 is coupled to the rack 210 via a coupling shaft or “valve stem” 263, a first end of this coupling shaft 263 carrying an actuating pinion 264 in engagement with this rack 210 while its second end is coupled to the rotation axis of this motor 261 via a gear reduction device 265.

[0029] Referring again to [Fig.l], the power steering system 1 further comprises a control module 300, connected by wired electrical connection means FB F2, F3, on the one hand to the electronic control card 122 of the motor 121 of the restitution device 120, and on the other hand to the electronic control cards 252, 262 of the motors 251, 261 of the assistance devices 250, 260.

[0030] This control module 300 is also connected to various vehicle modules (not shown) transmitting to it in real time the value of certain internal driving parameters such as the angle of the steering wheel, the speed of rotation of this steering wheel, the acceleration of this steering wheel, the torque exerted on this steering wheel, the speed of the vehicle, etc.

[0031] Comprising a computer 310 provided with one or more interconnected microprocessors as well as a memory module 320 comprising non-volatile and non-volatile memory, this control module 300 is capable of controlling by transmission of electrical signals, as a function of the information received, the operation of the motors 121, 251, 261 of the motorized restitution 120 and assistance 250, 260 devices, so as to correlate the position of the steering wheel 110 to the actual position of the steered wheels 230 as well as the force feedback returned to the driver via this steering wheel 110 to the forces exerted on these steered wheels 230.

[0032] According to a first preferred operating mode, the control module 300 is configured so that the two motorized assistance devices 250, 260 are activated alternately, each being activated for example over a half-period for each predetermined driving period.

[0033] Such an operating mode thus makes it possible to obtain uniform wear of the two assistance motors 251, 261 over time, so as to optimize their longevity.

[0034] According to a second preferred operating mode, the control module 300 is configured so that the two motorized assistance devices 250, 260 are activated simultaneously so as to operate synchronously.

[0035] Such an operating mode thus makes it possible to reduce the stresses exerted on these two motors 251, 261 and therefore to limit the torque that they each have to develop to cause the translational movement of the rack 210.

[0036] The control module 300 is also configured, in the event of failure of one of these two motorized assistance devices 250, 260, to only request the other motorized assistance device.

[0037] Thus, in the context where the second operating mode is retained, the two motors 251, 261 of the motorized assistance devices 250, 260 must be sized so that they can each develop sufficient torque to drive the translational movement of the rack 210 alone.

[0038] As illustrated in Figures 2 and 3, the rack 210 of the lower level mechanism 200 carries a single toothed track 211 on which the pinion is engaged actuating pinion 254 of the motorized assistance device 250 as well as the actuating pinion 264 of the motorized assistance device 260.

[0039] With reference to [Fig.2], the two coupling shafts 253, 263 extend parallel to each other, forming the same angle 0 with the longitudinal axis of this rack 210.

[0040] Such a conformation of the rack 210 with a single toothed track thus makes it possible to limit the design and manufacturing costs of this rack 210.

[0041] Still with reference to figures 2 and 3 and in order in particular to facilitate the installation and to limit the overall size of the power steering system 1 in the vehicle, the two motorized assistance devices 250, 260 are advantageously arranged in an aligned manner in a direction parallel to the longitudinal axis of the rack 210.

[0042] Furthermore, the electronic control cards 252, 262 are preferably arranged at the two opposite ends of the two assistance motors 251, 261, so as to avoid electrical interference between these two motors 251, 261.

[0043] Still with the aim of avoiding electrical interference between the two motors 251, 261, the connection between the control module 300 and the motorized assistance devices 250, 260 is ensured by two separate electrical harnesses F2, F3 which are not intermixed.

[0044] Numerous variants are conceivable and it is recalled in this regard that the present invention is not limited to the embodiments described and shown, but also encompasses all the variants of execution within the reach of those skilled in the art.

Claims

Claims

1. A wire-link power steering system (1) for a motor vehicle, comprising: - an upper level mechanism (100) comprising a steering wheel (110) and a motorized restitution device (120) provided with a motor (121) coupled to said steering wheel (110); - a lower level mechanism (200) comprising a rack (210) as well as two motorized assistance devices (250, 260) each provided with a respective motor (251, 261) coupled to said rack (210) via a corresponding coupling shaft (253, 263) carrying an actuating pinion (254, 264) engaged with said rack (210); - a control module (300), connected by wired electrical connection means (Fb F2, F3) to said motorized restitution (120) and assistance (250, 260) devices, said control module (300) being capable of ensuring control by transmission of electrical signals of the motors (121, 251, 261) of these devices (120, 250, 260);characterized in that said rack (210) carries a single toothed track (211) on which the actuating pinions (254, 264) of the two said motorized assistance devices (250, 260) are engaged.;

2. Power steering system (1) according to claim 1, characterized in that said coupling shafts (253, 263) extend parallel to each other forming the same angle (0) with the longitudinal axis of said rack (210).

3. Power steering system (1) according to one of claims 1 or 2, characterized in that said motorized assistance devices (250, 260) are arranged in an aligned manner in a direction parallel to the longitudinal axis of said rack (210).

4. Power steering system (1) according to claim 3, characterized in that each said motorized assistance device (250, 260) comprises an electronic control card (252, 262) managing the operation of the motor (251, 261) of this device (250, 260), said electronic control cards (252, 262) being arranged at the two opposite ends of said motors (251, 261).

5. Power steering system (1) according to one of claims 1 to 4, characterized in that the connection between said control module (300) and the two said motorized assistance devices (250, 260) is ensured by two separate, non-intermingled electrical beams (Fb F2).

6. Power steering system (1) according to one of claims 1 to 5, characterized in that said control module (300) is configured so that the two said motorized assistance devices (250, 260) are activated alternately.

7. Power steering system (1) according to one of claims 1 to 5, characterized in that said control module (300) is configured so that the two said motorized assistance devices (250, 260) are activated simultaneously so as to operate synchronously.

8. Power steering system (1) according to claim 7, characterized in that the motors (251, 261) of the two said motorized assistance devices (250, 260) are sized so that they can each develop sufficient torque to drive the translational movement of said rack (210) alone.

9. Power steering system (1) according to one of claims 1 to 8, characterized said control module (300) is configured, in the event of failure of one of said motorized assistance devices (250, 260), to request only the other motorized assistance device.

10. Motor vehicle comprising a power steering system (1) according to one of claims 1 to 9.

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