System and method for locking a vehicle steering

A system and method for locking a motor vehicle steering column to prevent accidental locking of the steering column is provided. The system electro-mechanically locks the steering column in rotation using a bolt driven by an electronic control circuit that receives commands from an electronic calculator via a multiplexed bus. A blocking device mechanically blocks displacement of the bolt.

FIELD OF THE INVENTION

The invention relates to motor vehicle steering devices, and, more particularly, to locking a motor vehicle steering column.

BACKGROUND OF THE INVENTION

A locking device for locking the steering column of a vehicle is a standard feature on virtually all modern automobiles. For safety reasons, it is important that a vehicle's steering column locking device operate so that in the event of a simple failure, be it software or material, the device under no circumstances will cause an accidental locking of the steering column while the vehicle is in motion. Systems are therefore designed as a safety feature to prevent the unintended locking of the steering column.

Conventional systems for preventing unwanted locking of a steering column use two electronic microcontrollers operating in tandem. The microcontrollers monitor each other so as to prevent electrical, software, mechanical or other failures from causing an accidental locking of the steering column. Such a solution is described in European Patent No. 496,509 A1 filed in the name of Lucas Industries Public Limited Company in connection with an electronic calculator for an ABS wheel anti-locking system.

The main drawback of such a system, however, is its high cost. Not only must the microcontroller be duplicated, but also its clock and reset circuit. Accordingly, there is the need for a system that can effectively prevent the unwanted locking of a steering column, but that is more efficient than conventional systems.

SUMMARY OF THE INVENTION

An object of the invention is to overcome this drawback by proposing a steering lock whose operation is made secure by a blocking device and blocking means as such when the steering column must be in the unlocked position, notably during motion.

To this end, the invention provides a system for locking a vehicle steering column, comprising a locking device or means for locking electromechanically in rotation the steering column using a bolt, and which is driven by an electronic control circuit receiving commands from an electronic calculator via a multiplexed bus. The system further comprises blocking means or a blocking device for blocking the displacement of the bolt when the steering is in the unlocked position. The blocking device may be driven by the electronic calculator by a drive transistor. The system may also include a sensor for the position of the blocking means, a double sensor for the position of the bolt, and an electronic control circuit for controlling the means for locking the steering column. The electronic control circuit may comprise a microcontroller which receives on the one hand information on the position of the blocking means and on the other hand information on the vehicle speed, on the state of the engine, and/or on the detection of an impact via the multiplexed bus.

According to another aspect of the invention, the means for mechanically blocking the bolt for locking the steering may include a soft iron core arranged to be displaceable perpendicular to the direction of displacement of the bolt, and under the effect of the magnetic field created inside a solenoid passed through by a variable current.

Another object of the invention is a method of operating the above system for locking a vehicle steering. The method may comprise the following steps for unlocking and locking the steering. For unlocking the steering, the method may include after identifying the driver, sending a steering unlocking command on the multiplexed bus by the electronic calculator, reading this command by the microcontroller for the locking means with immediate execution, and monitoring changes of state on the information delivered by the sensors for the position of the bolt and the blocking means in view of an eventual start of the vehicle engine. For locking the steering, the method may include sending a locking command on the multiplexed bus by the electronic calculator, reading the command by the microcontroller for the locking means, after a time delay, sending by the drive transistor of the electronic calculator a command to unlock the bolt by the blocking means, checking safety conditions by the microcontroller for the locking means, and commanding, by the microcontroller for the locking means, the blocking of the steering by the bolt.

The elements identified by like references in the different figures have the same functions in view of the same results.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The vehicle steering column locking system in accordance with the invention comprises electromechanical means for preventing steering rotation while the vehicle is stationary, with the engine stopped under normal conditions. These locking means are essentially formed by a movable part provided with a bolt that enters into engagement with a toothed wheel of the steering column to prevent it from turning. However, this movement of the bolt to its steering column locking position should never occur outside well-defined and strict conditions. To this end, the invention includes means for mechanically blocking the bolt when the latter must imperatively leave the steering free in rotation to make the system secure.

According to the functional diagram ofFIG. 1, the steering column1must be able to turn freely around its axis of rotation δ, perpendicular to the plane of the drawing, in the unlocked position. Locking means2comprise notably a mechanical part3equipped with a bolt30and movable in a direction which is orthogonal to the steering column's axis of rotation δ in response to a rotational movement of an eccentric member31. A spring32is provided to push the part3so that the bolt30prevents this rotation when the means2receive the order to do so. To this end, the locking means2are driven by a control circuit4having an electronic microcontroller5which receives commands from an electronic calculator6of the vehicle, via a CAN-type multiplexed bus7.

This calculator6can be a central unit for controlling the passenger compartment, ensuring electrical power supply distribution by three relays. A first relay60is for controlling the motor electrical power circuit, referred to as the after-contact relay “+APC”, supplying among others the engine control unit61, the air bag62, and the dashboard. A second, service relay63“+SERV” is for the power supply notably to the radio64, the window openers65, the passenger compartment motor ventilator unit GMV, etc. (It additionally supplies the electrical anti-theft device formed by the steering lock system). A third, starter relay66“+DEM” is for supplying the starter motor67of the engine68. (The motor control unit61communicates to the passenger compartment control unit information concerning the state of the engine, which is stopped or running).

To make the steering lock system secure, the invention adds to the locking means for mechanically blocking its displacement when it must allow the column to rotate freely. These means are formed by a magnetic core9placed at the center of a solenoid8, the core being movable under the effect of a magnetic field created by a current circulating in the coil and biased to its stable equilibrium position by a spring10, whose end11opposite the core9is fixed. The current in the coil8is driven by the passenger compartment central unit6via a drive transistor12located within the central unit itself.

In the rest state, without any current in the coil8, the magnetic core9is only subjected to the spring10which places it such that it projects considerably from the coil. To block the bolt30, the blocking means must be positioned such that the core is placed just in front of the mechanical part3, along its face33perpendicular to the displacement direction of the bolt30. When the central unit6commands the current in the coil8, the magnetic core9is displaced such that it is retracted into the solenoid to leave the bolt free for displacement to the steering column1. Then the current is cut off and the core9is retained by the face34of the mechanical part3parallel to the displacement direction of the bolt.

The locking system according to the invention also comprises a sensor13for the position of the blocking means, for delivering information concerning the stable position of the magnetic core9, and hence projecting from the coil8, to render secure the unlocked position of the steering. The system also comprises a dual sensor14for the position of the bolt, for delivering firstly information on the activated, or readied, position of the bolt3which blocks the steering column1and secondly information on the retracted position which leaves the steering column free to rotate.

The control circuit4for the locking means2comprises an electronic microcontroller5which receives both position information concerning the bolt3and concerning the core9from their respective sensors14and13, and information vital for defining the safety conditions, from the different microcontrollers via the multiplexed bus7. The latter information are the vehicle speed, the engine's operating state and the detection of an impact.

Indeed, in accordance with the invention, the control circuit4for the locking means2of the steering column, before authorizing a locking requested by the passenger compartment central unit6, checks the following information reaching it via the multiplexed bus, and independently of the information which the central processing unit itself sends. The information includes that the vehicle speed exists and is of zero value, which is information delivered by the microcontroller for the wheel anti-lock braking system ABS69, or by a wheel speed sensor located in the transmission; that the engine is not turning, which is information delivered by the engine control calculator61; and that no accident, impact or fault has occurred to trigger the protection means, which is information sent by the airbag microcontroller62.

If all the required safety conditions are fulfilled, the microcontroller5for the steering locking means4waits for the locking means to cease blocking the bolt30, hence for the magnetic core9to be retracted in the coil8, to authorize the command of the bolt (FIG. 2). The bolt30is then pushed by the spring32by a rotational movement of an eccentric member31which frees the bolt to the locked position of the steering column1(FIG. 3).

Accordingly, if the passenger compartment central unit6were to send by error an order to lock the steering column to the bolt locking means, this order would not be executed, except if the above-mentioned safety conditions were fulfilled for the driver, i.e. zero speed for the vehicle, engine stopped, no air bag incident and no accident. By virtue of the architecture of the system according to the invention, a code-error type of software failure can never lead to the steering column being blocked during motion. Likewise, a simple electrical failure cannot cause the steering to block either. Accordingly, if there were to occur e.g. a short-circuit within the circuit controlling the eccentric, and this short-circuit were such as to command to lock, then the readying could not take place as the core9prevents translation of part3. Likewise, if there were to occur a short circuit in the cabling, and this short circuit were such as to command the solenoid8unintentionally, then, there would be no displacement of the bolt30because the command of the eccentric is independent and internal to the locking system.

A second object of the invention is to provide a method of locking the steering column implementing the above-described system, which comprises different steps during the phase of unlocking the steering on the one hand (FIG. 4), and the phase of locking on the other (FIG. 5). In the unlocking phase, e.g. when the driver enters his/her vehicle to start it, he/she enters a personalized code serving to identify him/her. After the identification, at the instant to, the passenger compartment central unit6sends a command to unlock the steering on the multiplexed bus7, at instant t1.

This command is then read at instant t2by the microcontroller5for the locking means4and immediately executed if the identification code is recognized. The eccentric31rotates by half a turn and displaces the bolt30which unlocks the steering column. The bolt thus passes from the steering column locking position, holding the core9in the coil8, to the unlocked position, freeing the core outside the coil, which is kept away by the spring. It secures the unlocked position of the bolt, which is blocked in the retracted position and can no longer be readied at the instant t4.

The respective positions of the bolt30and of the core9are then sent by the respective sensors14and13to the microcontroller5sending them on the multiplexed bus7to the passenger compartment central unit6, which monitors changes of state in this information concerning the retracted bolt and the blocking means engaged in view of an eventual starting of the engine. This follows from the fact that there must be a transition in these two types of information attesting that the steering is indeed released for the central unit to authorize starting.

FIG. 4is a timing chart showing the states of the different elements of the locking system according to the invention. In the unlocking phase, the first line L1on top of the chart represents the driver identification information, which passes from the 0 to the 1 state when the latter is correctly recognized at instant t0. The second line L2represents the commands sent by the passenger compartment central unit6to the steering locking means microcontroller, i.e. the order to unlock at instant t1. The third line L3represents the information the locking means microcontroller sends via the bus to the passenger compartment central unit, i.e. the execution of the unlocking command at instant t2, the change of state of the core's position being detected by sensor13at instant t3and the blocking of the bolt retracted at instant t4. The arrows in dotted lines represent periodic messages sent on the multiplexing bus.

The fourth L4and sixth L6lines represent the change of state of the bolt, detected by the position double sensor, which passes, for the “readied” position, from state 1 to state 0 at instant t2and which passes, for the “retracted” position from state 0 to 1 at instant t4. The fifth line L5represents the change of state of the magnetic core for blocking the bolt, which passes to the 0 state, corresponding to its position retracted in the coil passed through by a current, to state 1 corresponding to its projected position mechanically blocking the bolt, at instant t3. At instant t5, relay “+APC” for the electrical ignition switch of the vehicle is activated (seventh line L7) and at instant t6the passenger compartment central unit authorizes the starting of the engine (eighth line L8).

In the steering column locking phase, when the driver wishes, for example, to leave to his/her vehicle, the passenger compartment central unit6sends a locking command at instant t10to the locking means, via the bus. The first line l1of the timing chart5represents the frames sent by the central unit6to the locking means. The second line l2represents the information that the microcontroller for the locking means sends by the bus to the passenger compartment central unit. The arrows in dotted lines correspond to periodic messages sent on the bus.

When the steering column is still unlocked, the bolt30is retracted. The position sensor hence shows an information at state 1 on the sixth line l6and an information at state 0 on the seventh line l7corresponding to a “readied” state, and the magnetic core9is projected to block it. Hence the coil8is not passed through by a current and its command by the passenger compartment central unit6is at the 0 state (fourth line l4).

From the instant t10, the microcontroller for the steering locking means reads this command and waits for the core to be retracted, freeing the bolt at the instant t11upon a command from the passenger compartment central unit, after a time delay on the order of 100 ms, for example, after the locking command. During this time delay, the microcontroller for the locking means carries out safety checks, i.e. it reads the frames sent by the calculator of the ABS system (eighth line l8), by the engine control calculator (ninth line l9) and the one for the airbag (tenth line l10). If the required safety conditions are effectively fulfilled, and the change of state on the position of the core blocking the bolt is detected, at the instant t12according to the information from the position sensor (fifth line l5), the microcontroller commands the readying of the latch at the instant t13and sends a frame via the bus.

As from that instant t13of locking the steering column, the command for the eccentric to project the bolt passes from the 0 state to the 1 state (third line l3), the command for the core is at state 1, its “projected” position is at state0, the bolt goes from the “retracted” position up till t14to the “readied” position at instant t15under the command of the eccentric. At that instant, the eccentric no longer needs to be commanded since the bolt blocks the steering column, therefore the state of its command returns to 0. Likewise, the core being raised, the passenger compartment central unit no longer needs to command a current in the coil which returns to state0(fourth line l4) since the core is mechanically blocked by the surface34of mechanical part3.

The bolt blocking means, formed of the solenoid whose core comes to block the bolt when the latter is retracted, in a locking phase of the steering, are managed by the passenger compartment central unit. To authorize the readying of the steering lock, the central unit electrically excites the coil to unlock the steering. The core is not electrically driven but simply submitted to the action of the spring which maintains it away from the coil, in order to ensure the safety of the unlocked position of the bolt.

By virtue of the locking system according to the invention, the movement of the bolt to lock the steering column is only authorized when locking means receive the order from the passenger compartment central unit. By contrast, when the steering column is to be unlocked, in particular when the engine is turning and the vehicle is in motion, the bolt cannot physically leave its retracted position since the blocking means physically stop it from being readied, without themselves having to be electrically controlled. This system thus ensures excellent safety.

Moreover, this approach has the advantage of using calculators or microcontrollers existing in the vehicle, as well as the multiplexed bus, which reduces the costs of the drive circuits for the locking means, while ensuring a very high level of safety.