GB2422305A

GB2422305A - Vehicle seat assembly

Info

Publication number: GB2422305A
Application number: GB0600738A
Authority: GB
Inventors: Daniel Frost; Barry Connolly; Chris Smart; Andrew Bradley
Original assignee: Nissan Motor Manufacturing UK Ltd
Current assignee: Nissan Motor Manufacturing UK Ltd
Priority date: 2005-01-19
Filing date: 2006-01-16
Publication date: 2006-07-26
Anticipated expiration: 2026-01-16
Also published as: WO2006077385A1; EP1841618A1; GB0600738D0; GB0501168D0; GB2422305B

Abstract

A vehicle seat assembly comprises a seat (10), at least one rail (18) to which the seat (10) is slidably connected allowing the seat (10) to slide in a longitudinal direction forward and backward along the rail (18), a locking mechanism to retain the seat (10) at a selected desired position along the rail (18), and at least one biasing device (22) that applies a permanent force to the seat (10) such that the seat (10) is urged in a forward direction when the locking mechanism is disengaged. The biasing device may be a gas spring which expands to assist the forward seat movement and emulate the electronic seat assist mechanisms used in other vehicles.

Description

VEHICLE SEAT ASSEMBLY

The present invention relates to a seat assembly for use in a vehicle, and in particular to an assembly for assisting movement of a vehicle seat to a selected position.

Most vehicles on the road today have adjustable front seats which allow limited movement of the seats in a forward or rearward direction, primarily for the purpose of achieving a comfortable driving position for the driver but also, for example, to allow more or less legroom for any passengers in the rear seats or to facilitate access to the rear seats in three-door cars.

Commonly, the seat is slidably connected to at least one rail, usually a pair of rails, secured to the floor of the vehicle. For example, the underside of the seat may be provided with co-operating rails which slide along and are retained by the floor rails to prevent the seat from lifting off the floor. The seat can move longitudinally along the rail(s), either forwards or backwards, between two extreme positions. A locking mechanism is also provided to enable the seat to be secured in a selected position, for example, in the forwardmost position, the rearwardmost position or a position in between. The locking mechanism is of course disengageable to permit adjustment of the seat position.

Movement of the seat to a desired position is generally achieved in one of two ways.

At the higher end of the vehicle market, seat movement may he powerassisted using electronic control and there may even be memory facilities to record the optimum driving position for one or more drivers of the vehicle. Movement can be initiated by applying light pressure to a lever on the side of the seat or simply by pressing a button to achieve a preselected position. In such vehicles, the seat slides to the chosen position in a smooth, steady fashion as a result of the electronic control.

Away from the luxury or executive vehicle market, seat movement is usually achieved manually. Typically, a handle or lever will be provided close to or beneath the front seat cushion which the driver or passenger operates to release the locking mechanism.

Once released, the driver or passenger must then push the seat forwards or backwards himself This can often require a reasonable amount of physical effort, especially if the rail(s) on which the seat slides are sloped down towards the back of the car as is often the case or if the car is parked nose-up on a hill. Additionally, when the driver or passenger is sitting in the seat, his/her weight must be overcome in order to displace the seat and this usually results in a jerky, uncontrolled movement. This can make it difficult to set the seat in the desired position at the first attempt.

It is therefore an object of the invention to provide a vehicle seat assembly that requires little effort to propel the seat in a forward direction. It is a further object of the invention to provide a vehicle seat assembly that creates the sensation of the controlled, smooth adjustment achieved by an electronic seat assist system, yet does not incur the significant cost of installing such a system.

Accordingly, the invention resides in a vehicle seat assembly comprising a scat having a seat back and a seat cushion, at least one rail to which the seat is slidably connected allowing the seat to slide in a longitudinal direction forward and backward along the rail, a locking mechanism to retain the seat at a selected desired position along the rail, and at least one biasing device that applies a permanent force to the seat such that the seat is urged in a forward direction when the locking mechanism is disengaged.

Advantageously, the arrangement permits the seat to be urged forward under the influence of the biasing device without adjustment of the relative positions of the seat back and seat cushion By means of the invention, when the locking mechanism is released, forward movement of the seat is achieved or at least assisted by the biasing device such that little or no effort is required by the driver or passenger to adjust the seat position, even when the vehicle is facing up hill. Moreover, because the force applied by means of the biasing device is ever-present, forward movement of the seat is always assisted irrespective of the longitudinal position of the seat relative to the rail.

The biasing device that forms part of the assembly of the invention is desirably selected to provide a sufficient forward force to propel the seat forwards when the seat is occupied, yet at the same time should not be so strong as to prevent the seat being pushed back when the seat is required to be adjusted, for example, to accommodate a taller person. As will be appreciated, moving the seat back against the forward force requires additional effort by the user, but generally backward motion is easier to achieve than forward motion, especially when the seat is occupied with the occupant being required merely to push back against the vehicle floor with his/her feet.

Aside from the benefits in requiring less effort to adjust the seat to a forward position, the assembly of the invention is able to convey a similar sensation to that provided by an electronically controlled seat assist mechanism. In other words, customers' perception of the vehicle will be enhanced because it appears to share features in common with vehicles at the executive or luxury end of the market.

The biasing device is preferably installed beneath the seat both to reduce the opportunity for damage when passengers are getting in and out of the vehicle and also to enhance the aesthetic appeal of the vehicle. Ideally, the biasing device should not be visible or be barely visible from the rear seats.

Typically, one part of the biasing device is attached, directly or indirectly, to the seat and another part is attached, directly or indirectly, to the vehicle body, such as the floor. Whilst the biasing device may be located centrally underneath the seat, it is preferred to locate the device adjacent to one of the rails. Indeed, in one embodiment of the invention, the rails provide a convenient location for anchoring one part of the biasing device.

Positioning a single biasing device adjacent one of the rails may produce a slight twisting action on the seat as it is propelled forwards. However, this may be overcome by providing a pair of biasing devices, each rail being associated with one of the pair of devices, to balance any twisting effect. Alternatively, or in addition thereto, one or both parts of the biasing device may be pivotally mounted. Pivotably mounting the biasing device is particularly beneficial when the fixing locations for the biasing device do not lie in a horizontal plane, as will often be the case when one part is mounted on the vehicle floor and the other on the seat.

In order to achieve the permanent forward force on the scat, the biasing or force- generating device may take several different forms. For example, the device may comprise a spring, such as a coil tension spring in which the spring is stretched as the seat is moved backwards. In this way, the spring acts to store elastic energy which aids the seat to move forwards when the locking mechanism is released.

Other types of spring suitable for use in the invention include a geared, watch-type spring. In this type, a rotary spring is attached to the seat and a gear is provided in the rail which turns as the seat is moved. As the seat is moved backwards, the gear winds the spring thereby storing elastic energy. When the locking mechanism is unlocked, the stored energy is released thereby propelling the seat forward.

A yet further type of spring that may be used in the biasing device of the invention is a lever action watch-type spring. Such a spring operates in a similar fashion to the geared spring above, except that the spring is wound as the seat is moved back by a system of levers attached between the spring (attached to the seat) and a fixed point on the vehicle.

A preferred form of biasing device is a gas spring, also known as a gas strut or damper. The gas spring is installed so that it is compressed when the seat is moved backwards. In this way, the gas pressure pushes the seat forward again when the locking mechanism is released.

All of the aforementioned springs offer the advantage of not requiring a vehicle harness or electric power to operate and all are substantially silent in operation.

However, the gas spring offers a number of advantages over the mechanical springs described. In particular, the use of a gas spring allows greater control over the rate of release of the stored energy. For example, it is well known that gas springs can provide a rate of extension (controlled release of the stored energy) that can be set to a prescribed velocity.

A further advantage of gas springs is that they can have multiple extension rates, typically two, one through the majority of the extension stroke and another at the end of the extension stroke to provide dampening. This dampening effect can be conveniently used when the seat approaches its forwardmost position.

Gas springs have been around for many years and indeed their use in vehicles is also well known, for example, they are commonly used in the tailgate mechanism to raise the tailgate in a smooth, controlled manner. Accordingly, a detailed description of the construction and mode of operation of gas springs is not necessary for the purpose of understanding the present invention.

As described above, one part of the gas spring may be attached to the seat and the other part to the vehicle body, most conveniently the vehicle floor. In a preferred arrangement, the gas spring is accommodated alongside the inboard rail in a hollow in the seat squab. in such a position, the gas spring is unlikely to foul any of the seat workings and may be positioned in a substantially flat attitude parallel to the seat rail so that the force it applies does not change depending on the position of the seat.

The gas spring may be fixed to the vehicle body and seat by means of brackets or other such fixing means. Separate brackets may be used to fix the spring to the seat frame and the vehicle body but it is preferred that the brackets be formed integrally with the relevant part to reduce production costs. The gas spring is attached to the vehicle body in a position that permits the seat to be fully pushed back to the extent that the rail permits on a compression stroke of the spring. Equally, the spring must be capable of projecting the seat to its forwardmost position on an expansion stroke.

Typically, one end of the gas spring is fixed close behind the rear end of the rail and the other end is fixed to the underside of the seat frame towards the front of the seat.

In a preferred arrangement, the piston rod of the gas spring is fixed to the floor towards the rear of the floor rail and the cylinder is fixed towards the front of the underside of the seat, though the opposite arrangement will also work.

The dimensions of the spring and the spring rate, that is the velocity at which the spring "expands" under a defined load, may be selected as appropriate according to the vehicle in which the system is to be installed. As an example, if the system of the invention is selected to assist smaller individuals, having a maximum weight of 64 kilos (1 0 stone), then the spring force required to move the seat forward at a suitably steady speed may be in the region of 1 7kgf. So, if the model of vehicle to which the assembly is to be fitted has a seat with a stroke of about 234mm, then a variable pressure gas spring providing a force range of 10-65 kgf and a stroke length of 250mm would meet the system requirements. Such a gas spring is available from RS Components Ltd under part no. 686-991.

The locking mechanism, which retains the seat in a desired position along the rail, may take any convenient form. Conventional locking mechanisms must be sufficiently robust to hold the seat at a fixed position in extreme situations, for example, during emergency braking and on impact. Accordingly, existing mechanisms will generally exhibit ample strength to withstand the permanent force exerted by the biasing device when the locking mechanism is engaged. This means that little or no modification of conventional locking mechanisms is required in order to put into effect the present invention.

A typical example of a locking mechanism suitable for use in the present invention comprises a latch member mounted underneath the seat and adapted to engage one of a number of engaging holes or slots formed in the rail secured to the vehicle floor, and a coil spring which urges the latch member towards the rail. The latch member can he released by operation of a handle so that the latch member disengages from the engaging hole to allow the seat to move. The handle typically extends towards the front of the underside of the seat so that it is accessible to the driver when seated and also when leaning in to the vehicle from outside.

The present invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is an exploded perspective view of a seat assembly in accordance with one embodiment of the invention; Figure 2a is an enlarged cross-section of the floormounted rail of the seat assembly shown in Figure 1; Figure 2b is an enlarged cross-section of the seat-mounted rail of the seat assembly shown in Figure 1; Figure 3 is an enlarged side view of a part of the seat assembly shown in Figure 1; and Figure 4 is an enlarged plan view of the part of the seat assembly shown in Figure 3.

Figure 1 shows a vehicle seat assembly in accordance with one embodiment of the invention. The assembly comprises a vehicle seat (10) having a backrest (12) and a seat cushion (14) to the underside of which is affixed a pair of seat rails (16, 16'). The seat rails (16, 16') are disposed in co-operation with a pair of floor rails (18, 18') mounted on the floor (not shown) of the vehicle such that the seat rails (16, 16') can slide along and be guided by the floor rails (18, 18').

Figures 2a and 2b show seat rail (16) and floor rail (18) in enlarged cross-section.

Floor rail (18) in use is secured to the floor (28) of the vehicle and has a generally box-like section with an open channel (42) extending along its upper surface (44).

Seat rail (16) in use is secured to the seat cushion frame (36) on the underside of the scat and has a generally inverted U-shape cross-section. The inverted U- shape cross- section of seat rail (16) is dimensioned such that it fits inside the box- like section of the floor rail (18) and can glide smoothly within it but without much "play" so that the seat does not wobble. Extending from the inverted U-shape section along the length of the scat rail (16) is flange (46) which projects into open channel (42) of the floor rail (18) and provides a fixing location for mounting the rail (16) to the seat cushion frame (36). The floor rail (18) and seat rail (16) co-operate so that the seat rail (16) can slide along the floor rail (18) until the desired position of the seat is reached and at the same time the seat (10) is prevented from lifting off the vehicle floor (28).

Referring again to Figure 1, lever (20) underneath the seat cushion (14) at its forward end and accessible to the driver of the vehicle actuates the locking mechanism (not shown) to lock one or both seat rails (16) in any selected position with respect to the floor rails (18) thereby enabling the seat position to be adjusted to suit the driver.

Gas spring (22) is pivotably attached at one end to bracket (24) via bolt (26) and the bracket (24) in turn is secured to the floor (28) of the vehicle body by bolt (30). At the opposite end, gas spring (22) is pivotably attached to bracket (32) via bolt (34), the bracket (32) being secured to the seat cushion frame (36) by bolt (38).

The gas spring (22) is installed so that whenever the locking mechanism (not shown) is disengaged by operation of lever (20), the spring force urges the seat (10) forwards along the rails (18). When the driver has reached a desired driving position, he releases lever (20) which in turn causes the locking mechanism to re-engage at the new position. The seat (10) is then held at the new position by the locking mechanism against the continuous forward force exerted by the gas spring (22).

if the driver wishes to move the seat (10) backwards then he simply has to operate the lever (20) to disengage the locking mechanism again and push back against the floor of the vehicle with his feet against the forward force exerted by the gas spring (22).

As before, when the driver has reached the new, rearward position he simply has to release the lever (20) to re-engage the locking mechanism.

Enlarged side and plan views of the gas spring (22) and mounting brackets (24, 32) are shown in Figures 3 and 4 respectively. Bolt (38) affixes the bracket (32) to the underside of the seat cushion frame (36) and bolt (30) affixes bracket (24) to the vehicle floor (28) just behind the mounting surface (48) for the floor rail (18). The fixing point for the seat bracket (32) is higher with respect to the fixing point for floor bracket (24), however the differential height remains substantially the same irrespective of the position of the seat (10) along the rails (18). For this reason, the gas spring (22) is pivotably mounted to the brackets (24, 32) via bolts (26, 34) thus allowing the angle of inclination of the gas spring (22) to alter as the spring expands and compresses.

The gas spring (22) is mounted such that the piston rod (50) attaches to the rear, floor- end bracket (24) whereas the gas spring cylinder (52) attaches to the scat cushion frame. In this way, when the lever (20) is released to disengage the locking mechanism, the cylinder (52) is moved forwards as the gas spring expands thereby also moving the seat (10) in a forward direction.

Although the invention has been particularly described, it should be appreciated that the invention may be embodied in other specific forms without departing from its essential attributes. Accordingly, reference should be made to the appended claims rather than the foregoing specific description as indicating the scope of the invention.

Claims

CLAIMS: I. A vehicle scat assembly comprising a seat (10) having a seat

back (12) and a seat cushion (14), at least one rail (18) to which the seat (10) is slidably connected allowing the seat (10) to slide in a longitudinal direction forward and backward along the rail (18), a locking mechanism to retain the seat (10) at a selected desired position along the rail (18), and at least one biasing device (22) that applies a permanent force to the seat (10) so as to urge the seat (10) in a forward direction when the locking mechanism is disengaged without adjustment of the relative positions of the seat back (12) and the seat cushion (14).

2. An assembly according to claim 1, wherein the biasing device (22) comprises first and second parts (50, 52), the first part (50) being attached to the vehicle body and the second part (52) being attached to the seat (10).

3. An assembly according to claim 2, wherein the rail (18) is secured to the vehicle floor (28) and the first part (50) of the biasing device (22) is attached to the floor (28) close to rear end of the rail (18) and the second part (52) of the biasing device (22) is attached to the underside of the seat (36) towards the front end of the seat (10).

5. An assembly according to any one of claims 2 to 4, wherein the first and second parts (50, 52) of the biasing device (22) are pivotably attached.

6. An assembly according to any preceding claim, wherein the biasing device (22) comprises a spring.

7. An assembly according to claim 6, wherein the spring comprises a gas spring (22).

8. An assembly according to claim 7, wherein the gas spring (22) is positioned parallel to the rail (18).

9. An assembly according to claim 7 or claim 8, wherein the gas spring piston rod (50) is fixed to the vehicle floor (28) and the gas spring cylinder (52) is fixed to the underside (36) of the seat (10).

10. An assembly according to any of claims 7 to 9, wherein the gas spring (22) is tuneable to adjust the force applied according to the weight of the seat occupant.

11. An assembly according to any of claims 7 to 9, wherein the gas spring (22) applies a predetermined, fixed force.

12. An assembly according to any of claims 7 to 11, wherein the gas spring (22) is set to provide multiple extension rates.

13. An assembly according to claim 12, wherein the gas spring (22) is set to expand at a first extension rate throughout the majority of the expansion stroke and at a second extension rate at the end of the expansion stroke to provide dampening when the seat (10) approaches its forwardmost position.

14. An assembly substantially as hereinbefore described with reference to Figure 1 and Figures 3 and 4 of the accompanying drawings.