GB2521518A

GB2521518A - Steering column assembly

Info

Publication number: GB2521518A
Application number: GB1418886.6A
Authority: GB
Inventors: Harsh Shah; Slawomir Kwasny; Tomasz Karp; Raghavendra Dasadi
Original assignee: TRW Ltd; TRW Steering Systems Poland Sp zoo
Current assignee: TRW Ltd; TRW Steering Systems Poland Sp zoo
Priority date: 2013-10-24
Filing date: 2014-10-23
Publication date: 2015-06-24
Anticipated expiration: 2034-10-23
Also published as: GB201318833D0; GB201418886D0; GB2521518B

Abstract

A steering column assembly has a clamp securing a shroud 2 to a bracket 4 fixed to a vehicle. The clamp comprises a locking lever 8 and a clamp pin 5 having a cam mechanism. The cam mechanism comprises first and second cam portions relatively moveable by operating lever 8, varying the length of the cam mechanism and applying a variable clamping force to shroud 2. The clamp mechanism also includes a friction brake acting on pin 5, preferably a coiled spring (20, Figure 2) mounted on pin 5, applying an increasing amount of braking force opposing movement of lever 8 during unlocking; suitably, this may prevent rapid movement of lever 8 during movement over centre. The spring may have legs 21, 22 fixed respectively to lever 8 and to shroud 2, bracket 4 or pin 5; typically, legs 21, 22 move angularly relative to each other during clamping and unclamping.

Description

STEERING COLIJMN ASSEMBLY

This invention relates to improvements in steering assemblies.

It is known to provide a steering cohtmn assemb'y, The assembly can be adjusted for reach allowing the steering wheel to move towards and away from a driver, or for rake allowing the steering wheel to be moved upwards and downwards relative to the driver.

This allows for a comfortable driving position to be achieved and, where provided, for the optimum positioning of a driver airbag attached to the steering wheel relative to the torso of the driver. A steering column that adjusts for reach or rake is known as a single adjust assembly, and one that adjusts for both is known as a double adjust assembly.

It is important that the assembly is easy to adjust when required and yet fixed rigidly in position when the vehicle is being driven. This is achieved by providing a steering column shroiLd which surrounds a steering column shaft that supports the steering wheel.

The shroud is fixed in position by a releasable clamp assembly. When the clamp assembly is in a damped condition the shroud, and the svhee. are fixed relative to a part of the vehicle, typically the bulkhead, When it is in an unclamped position the shroud is free to move relative to the bulkhead so that the position of the wheel can be adjusted.

Sever& damp assembhes are known, but a most common type includes a clamp mechanism which can be released or locked by rotation of a handle attached to a clamp pin or bolt. The handle is fixed to a first part of a cam mechanism which rotates with the handle about the axis of the clamp pin or bolt. A second part of the cam mechanism is prevented from rotating and co-operates with the first part. Rotating the handle moves the two cam parts relative to each other along the axis of the clamp pin, which increases or decreases the overall length of the cam mechanism depending on which way the handle is rotated. This change in length of the cam mechanism provides the locking function of the clamp assembly.

A problem with such an arrangement is that, on release of the lever the clamp force will start to be reduced allowing the shroud to move. At the same time, the clamp force is rdeased due to the shortening of the cam mechanism, aHowing the bracket arms to expand to release the clamp force, This movement can cause the lever to move more easily during the final stages of opening than in the early stages. If a user is not expecting this change the lever can be moved too rapidly to its final fully unlocked state once the cam mechanism moves over centre which can surprise a user. This also leads to an inconsistent feel to the lever.

According to a first aspect the invention provides a steering column assembly comprising a shroud and a clamp mechanism that sccurcs thc shroud to a brackct that is secured to a fixed part of the vehicle, the clamp mechanism comprising a clamp pin that extends through an opening in the shroud, a cam mcchanism that is located on thc clamp pin, and a locking lever that can be turned to cause a moving part of the cam mechanism to rotate Mound the clamp pin, in which the cam mechanism comprises first and second cam portions which can be moved relative to each other by operation of the locking handle to vary the overall length of the cam mechanism in turn applying a variable clamping force to the shroud, and in which the clamp mechanism includes a friction brake which acts upon the clamp pin that is arranged so that it applies an increasing amount of braking force that opposes movement of the lever as the lever moves from the locked to the unlocked condition.

The brake may comprise a spring comprising a wound portion that is wrapped around the clamp pin and two legs which extend away from opposing ends of the wound portion of the spring, one leg being arranged to move relative to the other leg as the lever is rotated to tighten at least part of the coil, and further in which the assembly includes means for causing a part of the spring to move along the clamp pin as the lever rotates, thereby creating a friction force that opposes the movement of the lever.

The assembly may be arranged so that movement of the lever causes the wound portion of the spring to be forced to move axially along the clamp pin as the lever rotates, thereby creating friction between the spring and the clamp pin which damps the movement of the lever.

Additionally or alternatively, the assembly may be arranged so that movement of the lever causes a portion of one or more of the legs to move through an angle and be swept across the clamp pin, thereby creating friction between the spring and the clamp pin which damps the movement of the lever.

The spring may be arranged so that at the lever moves a portion of the leg moves axially along the damp pin at the same time as being wrapped around the clamp pin, The cofled part of the spring may generally not rotate around the clamp pin, the braking force being provided by the axial movement of the coil along the clamp pin.

The spring may have three coils, bitt could have more or less. Each coil may be spaced from the adjacent coil.

The clamp pin may be arranged to rotate as the lever rotates or may be arranged so that it does not rotate with the levcr rotating around the pin. Because the friction is produced by axial movement of the coil along the pin it will function well in either arrangement.

Forcing the spring axially along the clamp pin creates the friction which controls the movement of the lever and provides the desired braking.

The spring may be arranged so that the kgs are moved together as the clamp mechanism is moved to the unclamped condition and moved apart as it is clamped.

One leg may be fixed angularly in position relative to the lever and the other may be fixed angularly in position relative to the shroud or to the clamp pin or to the bracket or any other fixed part of the assembly.

The spring may be arranged so that the internal diameter of the coiled part reduces as the legs move relative to each other on movement of the lever to tighten around the clamp pin, this in turn increasing the friction as the lever approaches the unlocked position.

The lever may be connected to a moving cam that rotates with the movement of the lever rdative to a fixed cam, the moving cam also moving axially along the damp pin as the lever rotates, the axia' movement of the moving cam along the damp pin causing an axia' movement of the spring along the clamp pin. The spring may therefore be restrained to follow the axial movement along the clamp pin of the cam mechanism.

One end of the spring may be secured to the moving cam, or to the lever or to any other part that rotates with the lever, The end of the spring that moves with the lever relative to the other end may therefore be connected to the lever directly or may contact another part that is in turn fixed to the lever or otherwise moves with the lever. For instance, it may be secured to a part of the moving cam.

The other leg of the spring may be connected to a fixed cam of the cam mechanism.

The assembly may include a plurality of locating parts which one of the legs of the spring may be secured to, each part holding the end of the spring in a different position rclativc to thc othcr parts and so allowing thc spring to bc prcloadcd at diffcrcnt tensions.

The brake, for example the coiled part of a spring, may contact the clamp pin directly so that the frictional force is between the spring and the clamp pin.

Alternatively the brake may contact a sleeve that is provided around the clamp pin, the friction being between the sleeve and the spring as the spring moves axially along the clamp pin.

Thc coilcd part of thc spring may bc located on thc clamp pin by a locating block that moves axially along the clamp pin as the lever rotates. For example, where the clamp mechanism comprises a fixed cam and a moving cam, thc locating block may be secured to the moving cam. One end of the pin may be located within an opening in the block which prevents relative movement of that end as the lever rotates.

The locating block may, for instance, be secured to or form a part of the moving cam portion by a thrust washer.

The clamp pin may be prevented from rotating as the clamp mechanism is locked and unlocked and the locating block may in turn be prevented from rotating relative to the clamp pin. The block in such an arrangement acts as the fixed datum for the one end of thc spring. To prevent rotation the block may include a non-circular bore that is fitted onto a complimentary non-circular portion of the clamp pin.

The second cam portion may be a moving cam portion which rotates with the clamp pin as the handk is operated and the first cam portion may comprise a fixed cam portion which is restrained so that it cannot rotate.

One of the cam portions may include a cam and the other of the cam portions a cam follower which moves over the cam as the handle rotates to change the length of the cam mechanism.

There wifl now be described, by way of example only, one embodiment of the present invention as illustrated in the accompanying drawings of which: Figure 1 is a perspective view of a complete embodiment of a steering column assembly in accordance with the present invention, Figure 2 is perspcctivc vicw of the basic components of a brake which may be included in the clamp mechanism of the embodiment of Figure Ithe fixed cam portion of the assembly of figure I prior to instaflation, Figure 3(a) is a perspective view of several parts of the assembly of Figure 1 that form part of the clamp mechanism when unclamped; Figure 3(b) is a perspective view equivalent to Figure 3(a) with the clamp mechanism moved to an unclaniped condition; Figure 4 is a view of the locating block and coil spring on the clamp pin in the embodiment of Figure 1; Figure 5 (a) shows a partial perspective view of an alternative assembly which falls within the scope of the present invention, the assemMy shown in the ocked position; and Figure 5 (b) shows a partial perspective view of the alternative assembly of Figure 5(a), the assembly instead being shown in the locked position and As shown iii Figure 1 a steering column assembly 100 comprises an adj ustable shroud which as shown comprises a fixed shroud part I and a moving shroud part 2, each in the form of a tube. The moving shroud part 2 fits telescopically around the fixed shroud part to aHow the ength of the steering column to be adjusted. The shroud surrounds a steering shaft 3 (one end of which can be seen in Figure 1) and this in turn supports a steering whccl (not shown) of the vehicle, The end of the steering shaft that is not connectcd to the steering wheel is connected through a steering mechanism (also not shown) to road whccls of thc vchiclc. This mechanism may comprise an clcctric powcr assistance motor.

A clamp mechanism connects the fixed shroud part 1 to the moving shroud part 2 and also fixes thc shroud in position relative to a bracket 4 secured to thc body of thc vehicle, The clamp mechanism comprises a clamp pin S which passes through spaced apart openings in a rail 6 secured to the moving part 2 of the shroud. The clamp pin also passes through slots in downwardly extending arms 4a, 4b of the bracket. A nut or head 7 is provided on one end of the pin 5 and a locking handle or lever 8 on the other. The lever is retained by an adjustable nut 9 that is threaded to the end of the damp pin 5. The lever 8 includes a grip sized so that it can be comfortably griped by a driver of the vehicle, A cam mechanism 10. 11 is located on the pin between the locking handle 8 and the adjacent bracket arm 4a which is sized so that it cannot pass through the opening in the bracket arm 4a.

As will become apparent the lever 8 can be rotated to clamp and unclamp the clamp mechanism and doing so changes the overall length of the cam mechanism 10, 11. At its greatest ength the damp mechanism is in a clamped condition and the moving and fixed shroud parts are squeezed together so they cannot move, At its shortest length the shroud parts are unsqueezed and free to move, constrained by the dimensions of the opening in the moving shroiLd part. As shown the opening is elongate along the axis of the steering shaft so that the overall length of the steering column assembly can be adjusted for reach.

The cam mechanism comprises a fixed cam portion 10 of sintered metal that is restrained against rotation by engagement with the arm 4a of the clamp bracket, The clamp pin S passes through a hole in the centre of the fixed cam portion. The cam mechanism also includes a moving cam portion 11, also of sintered metal, and which is also fitted to the clamp pin 5 and which is fixed to the lever 8. This is fixed so that it rotates with the lever by allowing it to rotate, with the lever, around the clamp pin, The fixed cam part 10 has a cam surface which faces and engages a cam follower formed on the moving cam part. As the moving part rotates relative to the fixed cam part 10 the cam follower moves along the cam surface, and this causes the overall width of the cam mechanism to vary (as measured in a direction paraflel to the axis of the clamp pin). As shown there are in fact four equispaced cam snrfaces on the fixed part and four equispaced cam followers on the second cam portion. The moving cam portion can move axially along the clamp pin and is arranged so that it does move as the mechanism is locked and unlocked.

In nse the driver can operate the lever to clamp and unclamp the steering column assembly. To move the clamp assembly from the unclamped to the clamped position, the lever is rotated by the driver. This causes the moving cam portion to rotate and move along the clamp pin. The fixed cam portion does not rotate, preventing rotation of the clamp pin to which it is fixed, and so the overall width of the cam mechanism increases as the cam faces ride over one another, The effect of this is to pull the clamp pin in the direction of the lever end of the clamp pin, squeezing together the arms of the bracket.

The moving cam potion and lever slide along the clamp pin. As the lever reaches the fully clamped position of the clamp mechanism it will become progressively harder to turn as the cam mechanism, clamp bracket arms and moving and fixed shroud portions arc squeezed together, On the other hand, as the lever S is turned to i'nove the assembly from the clamped to the unclamped condition it will get easier to turn. The overall width of the cam mechanism reduces and the moving cam portion and lever slide back along the clamp pin. In prior art arrangements this often leads to the lever 8 being moved to the fully nnclamped position at great speed if the user misjudges the resistance to movement.

To help control the movement of the lever when unlocking the steering clamp mechanism, a friction brake is provided. The essential components of the brake are shown in Figure 2 of the drawings. To provide the braking force a coil spring 20 of one or more turns is wrapped around the clamp pin 5 at the end that carries the cam mechanism and lever 8, The free ends or legs 21, 22 of the spring extend away from the clamp pin. One leg 21 is fixed in position relative to the shroud, as shown by the block X in Figure I. The other leg 22 is fixed relative to the lever, which is represented by the block Y, As the lever is turned, the block X and spring are located so that the ends move towards each other, which has the effect of tightening the spring coil around the clamp

S

pin or otherwise deforming it. This motion increases the grip of the coil on the pin.

Simultaneous to the rotation of the lever, a further dement located on the damp pin and represented by block Z applies a force to the coil along the axial direction of the clamp pin. This element Z pushes the coil along the pin, which is resisted by friction between the coU and the pin. As the lever is moved further towards the unlocked condition, the coil becomes tighter and thc friction increases. As the friction increases the greater the force that resists movement of the coil along the pin. This braking force helps control the movcmcnt of thc lcvcr during unlocking.

Also, the end of the spring that moves may move along a path with a component along the axis of the clamp pin, causing it to sweep across the pin. This generates some friction that will damp the movement of the lever.

A first practical implementation of the brake of Figure 2 is shown in Figures 3(a) and 3(b) of the accompanying drawings. As can be seen, a locating block 30 is slid onto the clamp pin at the end of the clamp pin. This block 30 is fixed against rotation around the clamp pin by providing a non-round bore in the block which dosely corresponds to a non-round profile on the end portion of the clamp pin, it is free to slide along the clamp pin together with the moving cam portion to which it is fixed through a thrust washer, one side of which rotates and is fixed to the moving cam and the other side of which stays stifl and is fixed to the Hock, Figure 4 shows the block 30 in more detail. The block is fixed to the moving part of the cam, and so as the moving cam rotates around the clamp pin it moves axiafly along the clamp pin drawing the block along the pin at the same time, Figure 3(a) shows the mechanism locked with little clamp pin protruding from the block, and Figure 3(b) shows it unlocked with a portion of the clamp pin protruding from the block.

One leg 21 of the coil spring 20 is secured in a hole in the block so that it is held in a fixed angular rdationship relative to the damp pin. Because the clam pin does not rotate this provides a set datum angle for that leg of the spring (the datum X of figure 2). As shown prior to installation the legs arc splayed at an angle of about 90 degrees in this

example.

The other leg 22 of the spring is secured to the lever so that with the assembly locked the two kgs are pushed shghtlv towards each other compared with the angle they adopt prior to being assembled. For instance, if they are splayed apart by 90 degrees when under no load, they win be pushed together so they are splayed by an angle alpha which is less than 90 degrees. This provides some preload to the spring.

The spring is therefore shaped so that with the lever in the locked position shown iii Figure 3(a) there is a light pressure on tile ends of the spring, and as the lever moves to the ufflocked position the pressure increases and the ends move closer together as shown in Figure 3(b). When fully unlocked the angle has reduced from alpha to a smaller angle beta as shown, Note also that as the angle changes the spring leg moves with a component that lies along the axis of the clamp pin.

The coil spring 20 is threaded onto the clamp pin S so that the coiled part is within the block 30. The movement of the block 30 along the clamp pin therefore causes the coil 20 to slide along the damp pin 5. As the kver is moved, the ends of the spring move rdative to one another by a small amount as the coil get tighter on the clamp pin, The braking force provided by the friction of the coil as it moves over the clamp pin will therefore increase, The precise manner in which it increases will depend on the relative movement of the ends of the spring, the material used, the spring dimensions and the spring shape, such as the number of turns of the spring around the clamp pin.

Additionally, the movement of the lever causes an angular movement of the leg which causes it to be swept across the clamp pin with a component along the axis of the pin.

This sweeping movement generates friction which also helps damp the movement of the lever. In some cases, this may be the dominant or even sole source of friction, in others, it may provide little or no friction with the bulk being provided by the general shortening of the spring as the coils are wound tight.

In an alternative arrangement shown in Figures 5(a) and 5(b) the spring is located on the clamp pin between the moving cam part and the fixed cam part, One leg 21 is located in a hole in the moving cam, and the other in a hole in the fixed cam. To allow the spring to be shown the fixed cam is omitted from the figures. The cam mechanism acts between a thrust nut on the end of the clamp pin and the bracket arm adjacent the cam mechanism, pushing the arm away from the thrust nut along the clamp pin. This movement causes the bracket arms to be pinched together.

In this second embodiment, as the lever rotates it svill cause the moving cam to rotate r&ative to the fixed cam, causing the egs of the spring to move relative to each other.

This causcs the spring to tightcn onto the clamp pin. As the clamp pin is drawn through the moving cam, an axial movement of the coil of the spring along the clamp pin is produccd which provides thc rcquired braking forcc. At thc samc time. onc of thc lcgs foHows a path in which it starts to wrap around the pin whilst also moving axially a'ong it, in a sweeping motion, which generates friction. As with the first embodiment this may be dominant braking force, or may be negligible, depending on the shape and configuration of the spring relative to the pin and the amount of movement of the ends of the spring as the mechanism is ocked and un'ocked, Thc skillcd pcrson will apprcciatc that various modifications arc possible within thc scope of the invention, in particular to the configuration of the spring and the ocating block. ll

Claims

CLAIMS1. A steering column assembly comprising a shroud and a clamp mechanism that secures the shroud to a bracket that is secured to a fixed part of the vehicle, the clamp mechanism comprising a clamp pin that extends through an opening in the shroud, a cam mechanism that is located on the clamp pin, and a locking lever that can be turned to cause a moving part of the cam mechanism to rotate around the clamp pin, in which the cam mechanism comprises first and sccond cam portions which can be moved relative to each other by operation of the locking handle to vary the overall length of the cam mechanism in turn applying a variable clamping force to the shroud, and in which the clamp mechanism includes a friction brake which acts upon the clamp pin that is arranged so that it applies an increasing amount of braking force that opposes movement of the lever as the lever moves from the locked to the unlocked condition.
2. A steering column assembly according to claim 1 in which the brake comprises a spring comprising a wound portion that is wrapped around the clamp pin and two legs which extend away from opposing ends of the wound portion of the spring, one leg being arranged to move relative to the other leg as the lever is rotated to tighten at least part of the coil, and further in which thc assembly includes means for causing thc wound portion of the spring to be forced to move axially along the clamp pin as the lever rotates, thereby creating friction between the spring and the clamp pin which damps the movement of the lever.
3. A steering column assembly according to claim I or claim 2 in which the assembly is arranged so that movement of the lever causes a portion of one or more of the legs to be swept across the clamp pin, thereby creating friction between the spring and the clamp pin which damps the movement of the lever.
4. A steering column assembly according to claim 3 in which the spring is arranged so that as the lever moves a portion of the leg moves axially along the clamp pin at the same time as being wrapped around the clamp pin.
5. A steering column assembly according to claim 2, 3 or 4 in which the spring is arranged so that the legs are moved closer together as the clamp mechanism is moved to the unclamped condition and moved apart as it is clamped.

6, A steering column assemb'y according to claim 2, 3, 4 or claim 5 in which one leg is fixed angularly in position relative to the lever and the other is fixed angularly in position relative to the shroud or to the clamp pin or to the bracket or any other fixed part S of the assembly and in which the spring is arranged so that the internal diameter of the coiled part reduccs as the legs move relative to each other on movement of thc lever to tighten around the clamp pin, this in turn increasing the friction as the lever approaches the unlocked position.

7, A steering column assembly according to any one of claims 2 to 6 in which the lever is connected to a moving cam that rotates with the movement of thc lever relative to a fixed cam, the moving cam also moving axially along the clamp pin as the lever rotates, the axial movement of the moving cam along the clamp pin causing an axia' movement of the spring along the clamp pin.S. A steering column assembly according to any one of claims 2 to 7 in which the coiled part of the spring is located on the clamp pin by a ocating block that moves axially along the clamp pin as the lever rotates, 9. A steering column assembly substantially as described herein with reference to and as illustrated in the accompanying drawings.