GB2508947A

GB2508947A - Vehicle seat assembly

Info

Publication number: GB2508947A
Application number: GB1310541.6A
Authority: GB
Inventors: Mark Pagett; Troy Kenion; Peter Barron; Kah Ming Chan; Lee Humphries; David Smith
Original assignee: Nissan Motor Manufacturing UK Ltd
Current assignee: Nissan Motor Manufacturing UK Ltd
Priority date: 2012-12-13
Filing date: 2013-06-13
Publication date: 2014-06-18
Anticipated expiration: 2033-06-13
Also published as: EP2931554A1; WO2014091193A1; GB201310541D0; GB2508857A; GB2508857B; GB201222444D0; GB2508947B

Abstract

A seat adjustment mechanism for providing fore and aft adjustment of a vehicle seat comprises a runner 18, 20 for rigid fixing to the vehicle floor and a slider 22, 24 for rigid fixing to a frame of the seat. The slider is arranged for cooperating with the runner to provide fore and aft adjustment to a position of the vehicle seat, and the runner 18, 20 is inclined upwardly towards the rear of the vehicle. The adjustment mechanism can have screw threaded members 26, 28 and 30, 32 driven by a motor 36.

Description

VEHICLE SEAT ASSEMBLY

Field of the invention

The invention relates to a seat assembly for a vehicle and, in particular, but not exclusively, to a seat assembly for a land-based automotive vehicle. The invention finds particular application in the field of Light Goods Vehicles (LGVs) but also extends to a seat assembly for other types of vehicle, such as one that travels over sea.

Background to the invention

It is common in automotive vehicles for the driver of the vehicle, together with the passengers, to sit in a semi-recumbent position with his or her legs extended towards the front of the vehicle. The seat assembly for the driver typically has a seat base upon which the driver sits, and a seat back against which the driver rests his or her back for support. A frame of the seat assembly supports the seat base and the seat back.

It is common for the seat assembly to be adjustable so as to optimise the postural comfort of the driver and the capability of dynamic control of the vehicle via the vehicle controls including, for example, the foot-operated pedals and the steering wheel. Typically, for example, the seat assembly is adjustable in a front-to-rear or longitudinal direction, so as to adjust the position of the seat assembly relative to the vehicle controls. Longitudinal adjustment is commonly provided by movement of the seat frame along seat tracks that are fixed with respect to the vehicle floor. This ensures the vehicle can accommodate drivers of different height and leg length and with different comfort requirements. Some common seat assemblies have seat tracks that slope downwards from the front of the vehicle towards the rear of the vehicle to provide increased head room for taller drivers when the seat assembly is adjusted rearwardly. The seat base height and incline, and the incline of the seat back, may also be adjustable for a similar reason.

While existing mechanisms provide an extent of adjustment over a useful range, in certain vehicle categories the need for flexibility and adjustment is greater. In Light Commercial Vehicles (LCVs) the ability to adjust various positional features of the seat assembly is particularly useful because there are often multiple users of the same vehicle. Light Commercial Vehicles (LCVs), otherwise known as Light Goods Vehicles (LGVs), are commercial carrier vehicles with a light capacity, typically a Gross Vehicle Weight (GVW) of up to 3.5 tonnes. This category of vehicle includes commercially based goods or passenger vehicles such as vans, trucks, taxis and other delivery vehicles, where the driver of the vehicle is frequently entering and exiting the vehicle to unload cargo. Such vehicles are typically designed with inter-city use in mind and therefore require a compromise between being light and compact for ease of manoeuvrability, and having a large load capacity.

It is a problem with vehicles of the aforementioned type that the requirements to provide a useful range of adjustment for various seat parameters (such as height and position) are not compatible with the requirements for maximising cargo space and minimising vehicle weight.

It is with the aforementioned issue in mind that the present invention provides an improved seat assembly that is particularly useful when utilised in a Light Commercial Vehicle (LCV) or a Light Goods Vehicle (LGV).

Summary of the invention

According to a first aspect of the invention there is provided a seat adjustment mechanism for providing fore-aft adjustment of a vehicle seat. The adjustment mechanism comprises a runner rigidly fixed to the vehicle floor and a slider for rigid fixing to a frame of the seat. The slider is arranged for cooperating with the runner to provide fore-aft adjustment of a position of the vehicle seat with respect to the vehicle floor, with the runner being inclined towards the rear of the vehicle. As a result, the fore-aft adjustment can be used to adjust the seat rearwards and upwards. This arrangement enables the runner to be placed at a steeper than conventional angle of incline, for example an angle in the range 15° to 45° with respect to the horizontal, without compromising the driver's view of the road. As a result, a full range of adjustment can be provided for driver comfort and access to vehicle controls without requiring such a large distance in the longitudinal direction of the vehicle. This can be used to create a saving in cargo length which is particularly advantageous in commercial vehicles such as LGV5.

Preferably, the adjustment mechanism comprises a motor to drive the fore-aft adjustment of the seat. In this case, the seat adjustment mechanism may further comprise a first member for coupling to the seat, and a second member coupled to the runner. In this arrangement, the first and second members are movable relative to one another, and the motor is arranged to drive cooperation between the first and second members for propelling the first member. The first member may, for example, comprise a lead screw, and the second member may comprise a threaded nut. In this case, it is suitable for the motor to be arranged to drive rotation of the first member for propelling the first member with respect to the second member.

If the adjustment mechanism is motor-driven, it may further comprise a biasing means such as a gas strut for urging the slider along the runner in an upwards direction of the runner incline. This aids the motor in providing a sufficient force to drive the seat upwards along the steeper than conventional incline of the runner. This finds particular application in the provision of a weight-on adjustment in which the driver lemains seated whilst the fore-aft adjustment takes place.

According to a second aspect of the invention there is provided a seat adjustment mechanism for providing height adjustment of a vehicle seat. The adjustment mechanism includes a user-operable locking means comprising a recline mechanism assembly. The use of a recline mechanism assembly as a locking means in the height adjustment mechanism is advantageous because the recline mechanism assembly is an established carry-over component that is known to be capable of withstanding crash forces.

The recline mechanism assembly preferably comprises a first and second parts such as plates or disks which are arranged to move relative to one another, and a locking member.

Each of the plates has a formation for receiving the locking member such that when it is received by both formations, the locking means is placed into a locked configuration for locking a position of the seat. The relative motion between the first and second plates may suitably be a relative rotation. In that case, the first and second plates may take the form of disks and the formations may be holes formed in the disks.

Optionally, the height adjustment mechanism comprises a biasing means such as a gas strut for urging the seat upwards when the locking means is in an unlocked configuration. This arrangement can be used, for example, to provide a weight-off adjustment in which the driver has his weight lifted from the seat during an upward height adjustment.

For ease of operation, the height adjustment mechanism preferably comprises a handle and a cable for the driver to operate the locking mechanism remotely. For example, the handle can be positioned in proximity to a seat base of the seat. This is particularly useful when the seat is adjusted to a relatively high position, in which the driver is further away from the locking means and would theretore have to stretch to operate the locking means. The handle and cable thus provide a more convenient arrangement for operating the height adjustment mechanism.

The recline mechanism assembly may be adapted by replacing one of the disks with a plate or other planar element of a vehicle seat assembly. In this case, the planar element is adapted to provide a formation such as a hole for receiving the locking member such that the adapted recline mechanism assembly provides a locking function when the locking member engages corresponding formations, for example by passing through corresponding holes, in the disk and planar element. This arrangement reduces the total number of elements in the seat assembly and provides savings in space occupied by the seat assembly and vehicle weight.

The invention also resides in a composite seat adjustment mechanism comprising a seat adjustment mechanism for fore-aft adjustment according to the first aspect of the invention and a seat adjustment mechanism for height adjustment according to the second aspect of the invention.

The invention may also be expressed as a seat assembly comprising a seat base, a seat back, and a seat adjustment mechanism according to any of the above expressions of the invention. The seat back is preferably tilted back from the vertical at an angle in the range 5° to 15°. This helps to provide positional comfort and back support for the driver in a more upright seating position which is naturally associated with the invention.

The height of the seat back of the seat assembly is preferably in the range 650 to 750 mm to help provide back support to the driver in the more upright seating position. Preferably, the seat base increases in width in a direction towards the front of the vehicle for accommodating seating positions in which the seat occupant is seated with a wide gait. This helps to provide positional comfort because a seating position with a wider gait is more natural in a more upright seating position. The length of the seat base in a longitudinal direction of the vehicle is preferably in the range 300 mm to 400 mm. This is shorter than a conventional seat base and helps to provide positional comfort to the driver in the more elevated seating position associated with the invention. In particular, the shorter seat base enables the driver's knee angle to open up to facilitate ease and comfort of access to the foot-operated vehicle controls. The seat assembly should comprise a frame having dimensions corresponding to those of the seat base and the seat back.

It will be appreciated that preferred and/or optional features of the first aspect of the invention may be incorporated alone, or in appropriate combination, within the second aspect of the invention also.

Brief description of the drawings

Specific embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, of which: Figure 1 is a perspective view of a vehicle seat assembly according to an embodiment of the invention; Figure 2 is a perspective view of the seat assembly of Figure 1 with the seat base and seat back removed; Figure 3 is a perspective view of part of the seat assembly of Figure 1 having the seat pan removed to show a view of the seat adjustment mechanism of the seat assembly; Figure 4 is a right side view (corresponding to the seat occupant's right hand side) of a lower portion of the seat assembly of Figure 1; Figure 5 is a right side view of a lower portion of the seat assembly of Figure 1 having the right side panel removed to show the seat adjustment mechanism of the seat assembly; Figure 6 is a perspective view of a lower portion of the seat assembly of Figure 1 having the right side panel removed to show a perspective view of the seat adjustment mechanism of the seat assembly; Figure 7 is a perspective view of the underside of the seat assembly of Figure 1 showing an underside view of the seat adjustment mechanism of the seat assembly; Figure 8 is a bottom side view of the seat assembly of Figure 1 showing a bottom side view of the seat adjustment mechanism of the seat assembly; Figure 9 is a rear side view of the seat assembly of Figure 1 showing a rear side view of the seat adjustment mechanism of the seat assembly; Figure 10 is a schematic diagram of a seating position of a vehicle driver to illustrate the definitions of the Hip Point, the Heel Point and the Pedal Point, and to illustrate the PH Gap and the HH Gap; Figure 11 is a schematic diagram of a seating position of a vehicle driver to illustrate the definition of the Heel Step, and to further illustrate the definitions of the PH Gap and HH Gap; and Figure 12 is a graph showing the dynamic adjustment range of the seat assembly of Figures ito 9.

Throughout the figures, like reference numerals are used to denote like features

Detailed description of preferred embodiments

A seat assembly having a seat adjustment mechanism according to an embodiment of the invention is shown in Figure 1. The seat assembly includes a seat base 10 and a seat back 12, the lower end of which abuts or engages the rear side of the seat base 10. Each of the seat base 10 and seat back 12 are supported by a respective frame of the seat assembly.

The seat adjustment mechanism is housed below the seat base 10 between two side panels 14 and 16, and provides both fore-aft and height adjustment of the seat.

Fore-aft adjustment of the seat is provided for adjusting the horizontal position of the seat assembly in the longitudinal direction of the vehicle. The fore-aft adjustment is inclined such that when the seat position is adjusted away from the vehicle controls! i.e. towards the rear of the vehicle, the position of the seat increases in height. This is achieved by a runner-slider arrangement providing adjustable anchorage of the seat to the vehicle floor.

With reference to Figures 1 to 9, the seat adjustment mechanism comprises left and right runners 18 and 20 rigidly fixed with respect to the vehicle floor. The runners 18, 20 are positioned at an angle of 25° with respect to the vehicle floor. The runners 18, 20 are perhaps best shown in Figure 7 which is a perspective view of the underside of the seat assembly. Left and right sliders 22 and 24 cooperate with channels provided in each of the runners 18, 20, thereby providing a sliding mechanism for the fore-aft adjustment of the seat.

With particular reference to Figure 7, movement of the sliders 22 and 24 with respect to the respective runners 18 and 20 is effected by a first member provided as a lead-screw and a second member provided as a threaded nut. Left and right threaded nuts 26 and 28 are provided for cooperation with left and right lead-screws 30 and 32, respectively. The nuts 26, 28 are rigidly fixed with respect to the runners 18, 20 and with respect to an underside cross bar 34. This means that the nuts 26, 28 are fixed with respect to the vehicle floor, while the lead screws 30 and 32 can rotate through the nuts 26, 28 along a direction parallel to the runners 18, 20. Movement of the lead-screws 30, 32 is driven by a motor 36 which rotates the screws 30, 32 for example via a worm-gear such that the threads of the nuts 26, 28 and the threads of the screws 30, 32 cooperate to propel the lead screws 30, 32 along the direction of the runners 18, 20. The motor 36 is controlled by means of a user-operated control unit in the vehicle cabin. The lead-screws 30, 32 and the seat itself are coupled such that the longitudinal movement of the lead-screws 30, 32 provides the fore-aft adjustment of the seat.

The longitudinal seat adjustment mechanism is a weight-on adjustment mechanism. This means that a seat occupant can remain seated on the seat base 10 whilst the fore-aft adjustment takes place. As a result, one of the forces present during the fore-aft adjustment is the combined weight of the seat and the occupant. A gas strut 38 providing an expansive biasing force is provided to assist the motor 36 in driving the upward, rearward for-aft adjustment. The gas strut 38 is at one end anchored to the underside cross bar 34 which is fixed with respect to the vehicle floor, and at the other end coupled to an upper cross bar 40 which is itself coupled to the sliders 18, 20. As a result, the gas strut 38 provides a biasing force urging the sliders 18, 20 to move in an uphill and rearward direction with respect to the runners 22, 24, and therefore assists the motor 36 in providing an uphill rearward adjustment of the seat against the combined weight of the seat and the seat occupant. Other embodiments are envisaged in which the expansive biasing force is provided by an alternative biasing means such as a spring arrangement, a rubber dampener or any other dampening device.

After a rearward adjustment the seat can be returned to a previous position by a forward adjustment. This is achieved by the motor 36 driving a rotation of the lead screws 30, 32 in the opposite direction so that the sliders 18, 20 can be brought back along the runners 22, 24 in a direction towards the vehicle controls. Since the runners 22, 24 are inclined to the rear, the forward adjustment is downhill and the weight of the seat and occupant aids the forward adjustment.

The seat adjustment mechanism of the present embodiment enables the height of the seat assembly to be adjusted separately from the fore-aft adjustment. In this height adjustment the height of the seat is unlocked by user-operation of a locking mechanism in order to enable an upward or downward adjustment. The upward adjustment is driven by a biasing means which urges the seat upwards when the seat occupant lifts his or her weight from the seat. The upwards adjustment is therefore a weight-off adjustment. When the desired higher position is reached, the user re-engages the locking mechanism and may then sit back down on the seat with the seat assembly having adopted the new, higher position.

For a downward adjustment, the user unlocks the locking mechanism and the seat assembly moves downwards under the combined weight of the seat and the seat occupant. Once a desired lower height is reached, the user reengages the locking mechanism and the seat is locked at its new, lower position.

With particular reference to Figures 5, 6 and 7, the locking mechanism of the height adjustment assembly of the present embodiment is provided by a recline mechanism locking assembly 42. This carry-over component is a proven component with respect to its capability to withstand vehicle crash forces.

When utilised in its conventional recline function, the locking assembly 42 of a recline assembly provides a recline and locking functionality for allowing the seat back 12 of the assembly to tilt relative to the seat base 10, and to be locked securely in a selected recline position. This provides a range of seat back angles for a user's positional comfort. In the present invention, the locking assembly 42 is utilised in a different way, to provide a means for locking the seat assembly in a selected vertical position.

The assembly 42 comprises first and second facing plates or disks which are arranged to move relative to one another -in the present embodiment this relative motion is relative rotation. Each plate has formations provided as holes which can be aligned relative to holes in the other plate so that a locking member (not shown) can pass through the holes to place the mechanism in a locked configuration in which the plates cannot rotate relative to one another. When the locking member is removed from the holes the plates are free to move relative to one another to allow selection of a different vertical height for the seat assembly.

In the present embodiment, the locking member is operated remotely by a handle 44 provided to the user's right of the seat base 10. A cable 46 couples user-operation of the handle 44 to the locking member such that by operating the handle 44 the user can move the locking member in and out of the cooperating holes in the facing plates in order to switch between the locked and unlocked configurations, respectively.

This arrangement is particularly convenient when the seat has adopted a relatively high position and the seat base 10 and seat occupant are relatively remote from the locking assembly 42. In this circumstance, remote operation of the locking member using the handle 44 avoids the need for the user to stretch to reach the member for direct operation.

With particular reference to Figure 7, a weight-off upward adjustment is driven by gas struts 48 and 50. Each of the gas struts 48, 50 is fixedly anchored towards the rear of the seat assembly to the upper cross bar 40. Towards the front of the seat assembly, the gas struts 48, 50 are attached to a front cross bar 52 on which they exert a force for raising the seat.

The front cross bar 52 is fixedly coupled at each end to attachment points of respective left and right attachment plates 54 and 56 which are pivotally attached to a point rigidly fixed with respect to the vehicle floor. As the gas struts 48, 50 urge the front cross bar 52 upwards to raise the seat, the upward movement of the cross bar 52 causes the attachment plates 54 and 56 to pivot about the respective pivot points, resulting in a curved trajectory of the front cross bar 52 and of the seat.

On the user's right hand side, the pivot point of the attachment plate 56 coincides with the centre of the locking assembly 42. The attachment plate 56 is coupled to the locking assembly 42 by attachment to the inner of the two disks so that when the locking assembly 42 is in a locked configuration, the attachment plate 56 -and by consequence the front cross bar 52 and left attachment plate 54 -are also locked in position. When the locking assembly 42 is in an unlocked configuration, the attachment plate 56 -and by consequence the front cross bar 52 and left attachment plate 54 -are free to move upwards following the curved trajectory for raising the seat.

In a variation of this arrangement a similar locking functionality is achieved by a single disk in combination with the plate 56. A locking member locks the arrangement by passing through holes in the disk and the plate. In this way, the plate effectively takes the place of the inner disk.

Returning to the main embodiment, and with particular reference to Figures 5 and 6, the arrangement of the pivoted attachment plates 54, 56 and the front cross bar 52 at the front of the seat assembly for lifting the seat is reflected in a corresponding rear lifting arrangement towards the rear of the seat assembly. The rear lifting arrangement comprises pivoting attachment plates 58 and 60 which are coupled to the front attachment plates 54, 56 by left and right plate links 62 and 64, respectively, such that the rear lifting arrangement follows the motion of the front lifting arrangement. The front and rear lifting arrangements together enable the seat to be raised as a whole without altering the angle of the seat base 10 on which the seat occupant is seated. It is an important feature of the seat assembly that, for all positions within the adjustment range, the seat base 10 is maintained in a substantially horizontal position.

When the seat has adopted a high position it can be adjusted back down to a lower height in a weight-on height adjustment. To effect this adjustment, the user dis-engages the locking assembly 42 using the handle 44 and the combined weight of the seat and the seat occupant pushes the seat back downwards to follow a curved trajectory.

The adjustment mechanism of the present embodiment provides a full range of seat adjustment so as to accommodate an optimum position for comfort and for capability of access to vehicle controls across a full range of anthropometric body types.

In order to quantify or measure the seating position of different anthropometric body types, the automotive industry has adopted a convention which refers to several vehicle hard points' and the distances between them for defining a driver's seating position.

Referring to Figures 10 and 11, the Pedal Point is defined as the geometric centre point of the accelerator contact surface with the driver's foot. The Hip Point of the driver represents the idealised position of the driver's hip and, specifically, the pivot point between the torso and the thigh of the driver's body. Combining these two points, a distance called the Pedal-to-Hip (PH) gap is then defined as the distance in the longitudinal direction of the vehicle between the Pedal Point and the Hip Point.

Another hard point located on the driver's foot is called the Heel Point. This is defined as the point where the driver's heel makes contact with the vehicle floor when the ball of the driver's foot is placed on the vehicle accelerator pedal. A second distance is then defined as the Heel Step, which is the vertical distance between the driver's Hip Point and Heel Point.

The range of adjustment of a vehicle seat assembly can be defined in terms of the range of these two distances, the PH Gap and the Heel Step, that can be accommodated by an adjustable seat assembly. A useful way of representing the range of adjustment provided by a seat adjustment mechanism is to plot the range of values of Heel Step and PH Gap that the adjustment mechanism makes available.

Furthermore, specific combinations of values of PH Gap and Heel Step are associated with an optimum level of comfort and ease of vehicle control for specific anthropometric body sizes. As a result, the optimum seating position for a specific anthropometric body type can be represented by a point on the Heel Step-PH Gap plot. If the point representing that anthropometric body type falls within the range of values made available by the seat adjustment mechanism, then a person having that anthropometric body type can use the adjustment mechanism to place the seat in a position providing them with optimal comfort and ease of vehicle control.

A plot of Heel Step against PH Gap, each in units of millimetres (mm), is shown in Figure 12. The dynamic envelope, or seat adjustment range, of the seat adjustment mechanism of the present embodiment is represented by the region bound by the red line 66. The straight sides of this region represent the increase in Heel Step with PH Gap resulting from adjustment of the seat assembly along the runners 22, 24 which are inclined to the rear.

The angle of incline of the runners is 25° with respect to the vehicle floor. The runners 22, 24 are inclined more steeply than those of typical prior art seat adjustment mechanisms and as a result a much greater adjustment can be provided within a smaller distance in the longitudinal direction of the vehicle. This creates a saving in cabin length of the vehicle. For an application in LGVs, for example, this provides the advantage that a greater load space can be provided rearward of the vehicle cabin for the same overall length of vehicle.

Alternatively, the overall length of the vehicle can be reduced for the same cargo volume, and the overall mass of the vehicle can therefore be reduced.

The curved sides of the envelope represent the curved trajectory of the seat during the height adjustment involving the pivoted attachment plates 54, 56, 58, 60. The points of intersection between the straight sides and the right-hand curved side create pointed corners of the dynamic envelope.

Regions of comfort for specific anthropometric body types are also shown in Figure 12.

These are represented by rectangles each having a centre point which represents an optimal seating position for that body type. For example, the top right rectangle 68 represents a region of comfort for AM99, where AM99 represents a 9901 percentile American male! representing larger people in the population. At the other end of the scale, at the bottom left of the figure, is shown a rectangle 70 representing a region of comfort for JFO5, where JFO5 represents a 5th percentile Japanese female, representing smaller people in the population. Other body types are also shown in the figure for illustration.

Three curves 72, 74 and 76 intersecting the centre points and boundaries, respectively, of the regions of positional comfort of the different anthropometric body types are also shown.

Each curve has an upwardly curving tail towards the top right of the figure in the region representing the larger people of the population. It can be seen that the tail of the middle curve 74 fits conveniently inside the upper pointed corner of the dynamic envelope, indicating that the larger people of the population are well accommodated by being able to adjust the seat to an optimum seating position for their anthropometric body type.

A seating assembly having a seat adjustment mechanism according to the present embodiment provides a driver with a seating position moved upwardly and forwards compared to a conventional seating position because the seating position is elevated and the fore-aft adjustment takes place within a shorter longitudinal distance of the vehicle. The seating position provided by the present embodiment is particularly elevated compared with a conventional seating position when the seat assembly is adjusted to its uppermost height position, and when the seat is adjusted rearwardly along the rear inclined runners 22, 24.

In a conventional seating position, the hip point is typically at 372 mm above the vehicle floor, compared to a Hip Point of, for example, 660 mm in the present embodiment. In a conventional seating position the horizontal distance between the Hip Point and the Heel Point -the Hip-to-Heel (HH) Gap -is typically 703 mm, compared with, for example, 483mm in the present embodiment. This seating position, which is elevated and much closer to the front of the cabin than in a conventional arrangement, places the driver position forwards in the vehicle by, for example, around 220 mm. A maximum saving in the horizontal direction is around 250 mm which, as indicated above, can be used advantageously as a saving in cabin length of the vehicle.

This cabin length saving is achieved whilst still accommodating an optimum seating position for a full range of anthropometric body types from JFO5 through to AM99. The horizontal adjustment in the longitudinal direction of the vehicle required to achieve this is over a range of about 200 mm which is a reduction in that required in a conventional seating assembly of around 40 mm. This also contributes to the saving in cabin length.

A further advantage of a more elevated seating position is that it is much easier for a driver to enter and exit the vehicle. In conventional seating arrangements a driver will often have to pull himself up out of the seating position, which is relatively low in the vehicle, and this can lead to discomfort or injury. For frequent entry-exit vehicles such as delivery vans and the like, the seating assembly of the present invention provides a particular advantage that the entry and exit manoeuvre is much easier. For elderly, infirm or disabled drivers, the elevated seating position provides a particular benefit.

In the more elevated, forwardly located seating position provided by the present embodiment, the driver is seated with a more upright posture, closer to the front of the vehicle cabin. Back support for the driver is provided by the seat back 12 which is tilted backwards at an angle of around 10° to the vertical. This is a shallower tilt than conventional seat backs. In typical commercial vehicles such as LGV5 and larger haulage vehicles, a seat back is commonly tilted back at an angle of around 15°. In cars the seat back is typically tilted further back at an angle of up to around 25°, with the driver in a semi-recumbent position, relatively low in the vehicle and further away from the vehicle controls.

With a more upright seating position, positional comfort is provided for the driver whilst contributing to a cargo length saving in the longitudinal direction of the vehicle.

For optimal positional comfort of the driver in the more upright seating position, the vertical length of the seat back 12 of the present embodiment is around 50 mm longer than a conventional seat back. This longer seat back 12 provides improved back support to the driver in this upright seating position.

Furthermore, since the seating position of the driver is elevated compared with a conventional seating position, the driver is seated naturally with a wider gait. To accommodate this natural seating position, the seat base 10 of the present embodiment is increasingly widened towards the front of the seat base 10 compared with a typical seat assembly, as though triangular inserts had been inserted into the seat base 10 with a wedge end of the triangle at the front of the seat. Furthermore, the horizontal length of the seat base 10 in the longitudinal direction of the vehicle is around 70 mm, which is shorter than a conventional seat base 10. This provides positional comfort to the driver in the more elevated seating position and enables the driver's knee angle to open up to facilitate ease and comfort of access to the foot-operated vehicle controls.

The seat base 10 and seat back 12 are suppoited by a frame of the seat assembly which is arranged to accommodate the specific shape and dimensions of the seat base 10 and seat back 12 of the present embodiment.

Both manually and electronically operable versions of the seat adjustment mechanism are envisaged. For example, the fore-aft adjustment along the iunners 22, 24 need not be achieved by a combined motor-driven and gas strut-driven arrangement, but could alternatively be entirely motor-driven, entirely driven by a biasing means such as a gas strut, achieved through a mechanical mechanism, or any othei combination of these arrangements. Similarly, the height adjustment need not be a weight-off lift driven by a gas strut, but could for example be at least partially motor driven. Furthermore, the height adjustment mechanism need not involve a curved trajectory of the seat through different height positions, but could be achieved by a straight vertically up and down motion implemented using a lead screw and nut arrangement as described above in relation to the fore-aft adjustment along the runners 22, 24.

It will be appreciated by a person skilled in the art that the invention could be modified to take various alternative forms to those described herein, without departing from the scope of the appended claims.

Claims

Claims 1. A seat adjustment mechanism for providing fore-aft adjustment of a vehicle seat, the adjustment mechanism comprising: a runner (18, 20) for rigid fixing to the vehicle floor; and a slider (22, 24) for rigid fixing to a frame of the seat and being arranged for cooperating with the runner (18, 20) to provide fore-aft adjustment of a position of the vehicle seat, wherein the runner (18, 20) is inclined upwardly towards the rear of the vehicle.
2. A seat adjustment mechanism according to claim 1, wherein the incline of the runner (18, 20) is at an angle in the range 150 to 45° to the horizontal.
3. A seat adjustment mechanism according to claim 1 or claim 2, further comprising a motor (36) arranged to drive the fore-aft adjustment.
4. A seat adjustment mechanism according to claim 3, further comprising a first member (30, 32) for coupling to the seat, and a second member (26, 28) coupled to the runner (18, 20), wherein the first and second members (30, 32, 26, 28) are movable relative to one another, and the motor (36) is arranged to drive cooperation between the first and second members (30, 32, 26, 28) for propelling the first member (30, 32).
5. A seat adjustment mechanism according to claim 4, wherein the first member (30, 32) comprises a lead screw, the second member (26, 28) comprises a threaded nut, and the motor (36) is arranged to drive rotation of the first member (30, 32) for propelling the first member (30, 32) with respect to the second member (26, 28).
6. A seat adjustment mechanism according to any preceding claim, further comprising a biasing means (38) for urging the slider (22. 24) along the runner (18, 20) in an upward direction of the runner incline.
7. A seat adjustment mechanism according to claim 6, wherein the biasing means (38) comprises a gas strut.
8. A seat adjustment mechanism for providing height adjustment of a vehicle seat, the adjustment mechanism including a user-operable locking means comprising a recline mechanism assembly (42).
9. A seat adjustment mechanism according to claim 8, wherein the recline mechanism assembly (42) comprises: first and second plates arranged for relative motion, and a locking member, wherein each of the first and second plates has a formation for receiving the locking member such that when the locking member is received by both formations, the recline mechanism assembly (42) is placed into a locked configuration for locking a position of the seat.
10. A seat adjustment mechanism according to claim 9, wherein the relative motion is a relative rotation.
11. A seat adjustment mechanism according to claim 10 wherein the first and second plates are disks and the formations are holes in the disks.
12. A seat adjustment mechanism according to any of claims 8 to 11, further comprising a biasing means (48, 50) arranged to urge the seat upwards when the recline mechanism component (42) is unlocked.
13. A seat adjustment mechanism according to claim 12, wherein the biasing means (48, 50) comprises a gas-strut.
14. A seat adjustment mechanism according to any of claims 8 to 13, wherein the adjustment mechanism further comprises a handle (44) and a cable (46) for remote operation of the recline mechanism assembly (42).
15. A composite seat adjustment mechanism comprising a seat adjustment mechanism for fore-aft adjustment according to any of claims 1 to 7 and a seat adjustment mechanism for height adjustment according to any of claims 8 to 14.
16. A seat assembly comprising a seat base (10), a seat back (12). and a seat adjustment mechanism according to any preceding claim, wherein the seat back (12) is tilted back from the vertical at an angle in the range 5° to 15°.
17. A seat assembly according to claim 16, wherein the seat back (12) has a vertical length in the range 650 mm to 750 mm.
18. A seat assembly according to claim 16 or 17, wherein the seat base (10) increases in width in a direction towards the front of the vehicle for accommodating a seating position in which a seat occupant is seated with a relatively wide gait.
19. A seat assembly according to any of claims 16 to 18, wherein the length of the seat base (10) in a longitudinal direction of the vehicle is in the range 300 mm to 400 mm.