FOLDING ROOF CONTROLLER

Field of the invention

The present invention relates to the field of folding roof structures for vehicles. In particular, the invention relates to a controller for a roof structure and a method of operating a controller for a roof structure.

Background to the invention

Vehicles, particularly automobiles, having retractable or folding roof structures are well known and are commonly referred to as 'convertibles' or 'cabriolets'. The latter term will be used herein for brevity. There are two main types of cabriolet: the 'soft-top' cabriolet and the 'hard-top' cabriolet.

The more common type of cabriolet is the soft-top cabriolet which has a roof structure comprising a flexible fabric material stretched over a folding frame. The frame is collapsible or extendable between folded and unfolded states of the roof, the flexible material folding or creasing as the frame collapses into the folded state. The folded roof structure is stored in a roof storage compartment behind the seats of the vehicle, most commonly ahead of or above a luggage compartment in front-engine vehicles. The roof storage compartment may then be closed by a rigid movable cover or by a soft cover removably attachable over the folded roof structure.

The hard-top cabriolet is rapidly gaining in popularity due to its superior insulation, safety and security characteristics. Hard- top cabriolets include a so-called 'retractable hard-top' (RHT), this being a roof structure formed of two or more rigid panels that are connected together for relative movement. Linkages, such as pivots or parallelogram linkages, support the panels and permit movement of the panels between a first, unfolded state of the roof structure and a second, folded state.

In the unfolded state, the RHT roof structure covers the passenger compartment or cabin of a hard-top cabriolet giving the appearance of a conventional fixed-roof vehicle. In the folded state, the roof structure is folded such that the panels lie beside each another as compactly as possible. During movement between the unfolded and folded states, each panel moves relative to each other about the linkages between them, often in a 'clamshell' pivoting movement.

Again, the folded RHT roof structure is stored behind the seats of the vehicle in a roof storage compartment. Most commonly in front-engine vehicles, that compartment is an upper region of a luggage compartment whose lid, hatch, door or tailgate is arranged to open to permit access of the folded roof structure thereto. Such hard-top cabriolet vehicles are well known: an example of a vehicle having a RHT, and the operation thereof, is described in US Patent No. 6,299,234.

Substantially all hard-top cabriolets and many soft-top cabriolets employ actuators such as hydraulic rams to cycle the roof between the folded and unfolded states and to move associated vehicle panels during that movement of the roof, such as a roof storage compartment cover. A roof control system responds to user input to co-ordinate the numerous actions necessary to fold or to unfold the roof and to latch the roof in the desired state. For example, the roof control system may be operated by a driver pressing a roof-up or roof-down switch located in the vehicle cabin, or on a remote-control key fob.

When partially unfolded during operation, a folding roof is vulnerable to wind damage due to vehicle motion if the vehicle accelerates to excessive speeds. A partially unfolded roof may also adversely affect handling characteristics by raising the centre of gravity of the vehicle or by damaging its aerodynamics. Consequently, roof control systems routinely include a deactivation or warning means that prevents roof motion or that gives a warning such as sounding a buzzer when the vehicle is moving, or when the

vehicle speed exceeds a predetermined threshold of up to say 50 kph. The deactivation or warning means may be directly responsive to vehicle speed or motion, for example by acting on information from the vehicle transmission, speedometer or engine management system. Alternatively, the deactivation or warning means may simply respond to whether or not the vehicle is capable of motion, for example if an attempt is made to move the roof when the parking brake is off or when a gear has been selected in the vehicle transmission.

So, present roof control systems either stop roof motion or notify the vehicle user in some manner (e.g. by sounding a buzzer) that operation of the roof is inappropriate.

Unfortunately if roof motion is stopped in mid-transit while a vehicle is moving, that perpetuates the reason for stopping the roof, i.e. the possibility of roof damage and vehicle instability. Moreover, paradoxically, it does so when the roof and the vehicle may be at their most vulnerable to those threats. Also, the vehicle occupants may be soaked by a sudden downpour of rain if the roof movement stops before the roof is fully unfolded and closed.

If the driver chooses to accelerate despite the roof being partially unfolded, the roof could be damaged and the vehicle may become unstable. However, there may be instances where the driver has to accelerate for safety reasons or simply because traffic flow makes it undesirable for the vehicle to remain stationary, or below a deactivation threshold speed, while waiting for the roof to complete its movement.

As noted above, conventional roof control systems are limited to a certain control response and furthermore take no account of the fact that the vehicle's speed and the position of the roof structure can alter whether roof movement is allowable.

It is an object of the present invention to provide a folding roof control arrangement that substantially overcomes or mitigates some of the above mentioned problems.

According to a first aspect of the present invention, there is provided a cabriolet roof movement controller, the controller comprising inputs for receiving data representing the vehicle speed and data representing the position of the roof; a processor programmed to determine roof movement responses in dependence on the position of the roof and the vehicle speed; and outputs for outputting a roof movement response signal as determined by the processor.

The present invention recognises that the position of the roof, as well as the speed of the vehicle, has an effect on whether a folding roof may be operated. The present invention, therefore, provides a roof controller that determines whether operation of the roof structure is allowable based on both the speed of the vehicle and also the position of the roof structure between its first and second positions.

In use, the processor within the controller determines the position of the roof structure and also the speed of the vehicle . Based on these two factors the controller then determines whether movement of the roof structure is allowable and so derives an appropriate roof movement response. This decision will be based on predetermined factors such as effect of roof movement on vehicle handling characteristics, likelihood of wind damage or other effects on the roof structure, or other effects on the vehicle. Once the roof movement response has been determined by the processor an appropriate roof movement response is output by the controller. Depending on the mode of operation of the controller the response signal may take a variety of forms such as a notification signal, a vehicle speed control signal, a roof movement control signal to move the roof structure etc.

In the event that the controller determines that roof movement is allowable, given the current vehicle speed and roof position, then the response signal output by the roof controller will conveniently comprise a roof movement control signal. Such a response

signal may conveniently be output to a roof drive mechanism that is used to raise and lower the roof.

Conveniently, the present invention may also act to modify or limit the speed of the vehicle in order to allow the roof structure to operate. This system is in contrast to prior art arrangements which seek to prevent roof movement above certain speeds. The response signal output by the roof controller may therefore comprise a vehicle speed control signal.

The vehicle speed control signal may conveniently be output to an engine management system capable of limiting vehicle speed by restricting the speed or power output of the engine. Alternatively, however, the vehicle speed control signal may be output to the transmission system of the vehicle or to its braking system in order to control the speed of the vehicle.

For a roof controller that is in communication with a roof drive mechanism and a system that can limit the speed of the vehicle , the controller can, if the vehicle is operating below a certain threshold, conveniently activate the roof drive mechanism and limit the vehicle speed until the roof structure has completed its transition. The roof controller can therefore ensure that the roof can safely be raised and lowered without risk of significant damage to either the roof structure or the vehicle.

In the case where the roof controller determines that the speed of the vehicle is below a certain value, it will output a vehicle speed control signal to limit the vehicle speed to a first speed threshold value. The controller may also additionally output a roof movement control signal to raise/lower the roof. Alternatively, the roof movement control signal may be delayed until the vehicle speed is within the first speed threshold. In this case, the first threshold value of the vehicle operating parameter is preferably equal to the first speed threshold value.

The roof controller may additionally receive data representing the acceleration of the vehicle. In this case, the roof controller will determine the acceleration of the vehicle, more specifically the acceleration requested by the driver as may be deduced from the position of the vehicle's accelerator pedal. If the acceleration is below a certain threshold value, the roof controller will output a vehicle speed control signal to limit the vehicle speed to a first speed threshold value and will output a roof control signal to raise/lower the roof.

If the vehicle user attempts to operate the roof structure above the first threshold value, then, preferably, the roof controller sends an vehicle speed control signal to limit the speed of the vehicle to a second speed threshold. Depending on the position of the roof structure, the controller may also output a roof movement control signal to stop movement of the roof structure. For example, if the roof is in a fully raised or lowered position then the controller may output a roof movement control signal to stop movement of the roof. However, if the roof structure is in transition from open to closed (or vice versa) then it may be preferable to complete the roof movement. The controller may therefore send a first roof movement control signal to complete the roof transition and then a further control signal to prevent further roof movement.

As described above, the roof controller of the present invention acts to limit the speed of the vehicle (to either a first or second speed threshold value) in order to allow the roof to operate or to prevent significant damage to the roof structure or vehicle.

It may be the case, however, that a user wishes to over-ride the speed limitation commands output from the roof movement controller. This could be because the vehicle is in an inconvenient or dangerous position and needs to exceed one or more of the speed threshold values to manoeuvre out of that position or to keep up with traffic flow.

Preferably, therefore, the roof controller further comprises override means arranged in use to override the vehicle speed control signals. Such an override means could, conveniently, be operated by a dedicated control switch or lever or, alternatively, could be linked to the position of the vehicle's accelerator pedal such that a kick-down action on the pedal activates the override means.

It is noted that, although it is preferred that roof movement is stopped or prevented when the vehicle speed exceeds one of the aforesaid thresholds, it is not essential. In some instances, e.g. when the roof is reaching the end of a transition, it may be preferable to complete the roof movement.

Conveniently, the response signal output by the controller may also comprise a notification signal which is output to indicator means within the vehicle in order to alert a user of the current roof status and/or the permitted roof actions in relation to the current vehicle operating conditions. This allows a vehicle user to be notified of the status of the roof (e.g. its position), whether roof movement is allowed, whether speed needs to be reduced to allow roof movement etc. The notification means may be any suitable type of indicator means such as audible notification, tactile or visual. In a preferred embodiment, the notification means is a visual display within the vehicle although this may be supplemented by audible feedback such as a buzzer or a synthesised voice. Conveniently, the indicator means can display a recommended maximum speed to allow for safe operation of the roof structure.

As noted above, both the position of the roof structure and also the vehicle speed affect whether the roof may be operated safely. Preferably, a look-up table may be used to store information relating to the operation of the roof as a function of vehicle speed and roof position.

The roof controller may either monitor the roof status continuously or, alternatively, may further comprise an input for receiving a user command to move the roof structure.

A user may conveniently send the user command to the controller via a user operable switch within the vehicle or by some other means (e.g. voice activation, key fob).

The data relating to the vehicle speed that is input to the roof controller may be received from any number of means. For example, an engine management system could provide data relating to various vehicle operating parameters to the roof controller or, alternatively, the roof controller could receive data input from the vehicle transmission, braking system, wheels or speedometer. The vehicle speed and other vehicle operating parameters could also be provided from an extra-vehicular positioning system such as a GPS system

The present invention extends to a method of operating a cabriolet roof movement controller, the method comprising determining the position of the roof structure between a first, unfolded position in which the roof structure substantially covers the passenger compartment of the vehicle and a second, folded position in which the roof structure is stored in a storage compartment of said vehicle; determining the speed of the vehicle; determining a roof movement response in dependence on the position of the roof structure and the vehicle speed; and outputting a response signal appropriate to the determined response.

It is noted that the preferred features described above in relation to the first aspect of the invention may also be applied to the method of the invention.

According to another aspect of the present invention, there is provided a display device for a vehicle having a folding roof structure, the display comprising a display area arranged to display, in juxtaposition, the current speed and roof position of the vehicle.

Preferably, the display device is in communication with a roof controller and comprises means for receiving a notification signal from the controller, the signal comprising

information relating to the speed of the vehicle and the position of the roof. Preferably, the roof controller is the controller according to the first aspect of the invention.

Conveniently, the display device can represent the roof-related data on a graphical plot wherein one axis represents the vehicle speed and another axis represents the roof position. The graphical plot may conveniently be divided into a plurality of distinct areas, each of which represents a different roof-related action or function (e.g. one area may define the roof position-vehicle speed area within which roof movement is allowed, another area may define the area in which the roof cannot be moved etc.).

The present invention also encompasses a display device for a vehicle having a folding roof structure, the display device comprising a display area for displaying one or more of the following: the maximum recommended speed of the vehicle for safe operation of the roof structure, whether operation of the roof structure is allowed, a notification to reduce speed in order to allow movement of the roof structure, a notification that movement of the roof structure has been stopped.

According to another aspect of the present invention, there is provided a data carrier comprising a computer program to implement the method of the second aspect of the present invention.

The invention extends to a cabriolet roof comprising a folding roof structure and a roof controller according to the first aspect of the invention, and to a cabriolet vehicle having such a roof

Brief description of drawings

The present invention will now be described, by way of example only, with reference to the following figures in which:

Figure 1 illustrates a known folding roof structure for a vehicle in its unfolded position;

Figure 2 shows the roof structure of Figure 1 in its folded position;

Figure 3 illustrates a roof control system incorporating a roof controller according to an embodiment of the present invention;

Figure 4 is a graph according to a further embodiment of the present invention illustrating how the operation of the roof controller varies in dependence upon the speed of the vehicle and the roof position.

Figure 5 illustrates a display device in accordance with an embodiment of the roof controller of the present invention; and

Figure 6 is a flow chart illustrating the operation of the system and roof controller of Figures 3 to 5.

Detailed description of the preferred embodiments of the invention

It is noted that throughout the drawings like numerals have been used to denote like features.

Referring firstly to Figures 1 and 2, a known folding roof structure for a vehicle is shown generally at 10. Figures 1 and 2 depict a hard- top cabriolet in which the roof structure is formed of two main parts, a roof part 12 and a rear-window part 14. In a first, closed or unfolded position of the roof structure 10, as illustrated in Figure 1, the roof part 12 is oriented generally horizontally and a front edge region 13 thereof engages with a frame 15 of the vehicle windscreen. In this position, the rear- window part 14 and the roof part 12 cover the cabin or passenger compartment 6 of the vehicle.

In the case of a hard-top cabriolet shown in Figure 1, both the first and second parts 12, 14 are substantially rigid and are generally formed from metal, glass or similarly rigid materials so as to give the appearance, when in the first, non-folded position, that the vehicle is a conventional fixed-roof vehicle and not a cabriolet.

In the case of a soft- top cabriolet, not shown in Figure 1, the roof structure is formed from a flexible fabric material mounted on substantially rigid but foldable frame members.

The roof structure 10 is arranged to be moved or folded from the first unfolded position shown in Figure 1 to a second, open or folded position illustrated in Figure 2. A linkage (not shown) is provided which allows the rear- window part 14 to pivot or rotate in a rearward direction (clockwise in the drawings) about a pivot point 17 over an arc of approximately 90°. This pivoting movement is achieved by a positive drive mechanism (not shown) drivingly connected to the linkage.

As the rear-window part 14 pivots upon folding the roof structure 10, it carries with it the roof part 12 (It is noted that in hard-top cabriolets, the nature of the linkage and the pivoting connection between the two parts, means that the roof part 12 remains substantially horizontal throughout the rearward movement of the roof structure 10). The folding movement of the roof structure 10 is such that, when the rear- window part 14 has pivoted through its full range of rotation, the entire passenger compartment 6 is uncovered, as illustrated in Figure 2. The roof structure 10 has now been lowered.

The roof structure is stored in its second, folded position with a roof storage compartment 18a behind the passenger compartment 6 of the vehicle. In front engined vehicles such as that illustrated, the roof storage compartment 18a is typically an upper part of the luggage compartment 18b of the vehicle, and is not separated or divided therefrom or otherwise compartmentalised. A path for movement of the folded roof structure 10 into the roof storage compartment 18a is cleared by opening a rearwardly-

hinged trunk lid or tailgate 19 which provides access to the roof storage compartment.

On folding, the folded roof structure 10 is pivoted into the roof storage compartment 18a by the aforementioned positive drive mechanism. Such roof structures, and the construction and operation thereof are well known and are described, for example, in US6,299,234 as aforesaid. As such, further details of roof structures of this type are not included herein but will be well understood by those skilled in the art.

In order to avoid damage to the roof components, a roof controller (not shown in Figures 1 and 2) controls the operation of the folding roof based on the vehicle speed. In general, the folding roof will function only when the vehicle is stationary or moving only at a low speed. A few vehicles will allow roof operation up to vehicle speeds of around 50kph. However, most folding roofs will not operate if the vehicle exceeds a slow walking pace and many folding roof systems require the vehicle to be stationary or incapable of movement before the folding roof can function.

The above described prior art roof control mechanism suffers from a number of disadvantages which has already been described in the background section above. In particular, during transition of a retractable roof from open to closed, or vice versa, the roof will be susceptible to wind damage caused by the vehicle's movement. Also, in the event that the vehicle exceeds the maximum allowed speed for roof transition, the roof may be held in a partially opened/closed state which may adversely affect vehicle handling characteristics and will further increase the risk of damage to the roof.

In response to these and other disadvantages of the prior art retractable roof systems, the present applicants have developed an improved system which alleviates or reduces some or all of these problems.

Referring to Figure 3, a roof retraction system incorporating a roof controller according to an embodiment of the present invention is shown generally at 20. The system

comprises a roof controller 22 which is operably connected to a roof motor mechanism 24 that is used to raise and lower the roof 10 between the first, unfolded position shown in Figure 1 (roof "up" or closed position) and the second, folded position shown in Figure 2 (roof "down" or open position).

The roof controller 22 is also operably connected to an engine management system 26 and a user-operable roof control switch 28. The roof controller 22 is also connected to a visible display device 30 (e.g. a light or series of lights or alternatively a message display screen) and an audible notification device 32 (e.g. a sounder such as a buzzer).

Accelerator position 34 and vehicle speed 36 are input into the engine management system 26, from which that information may be derived by the roof controller.

In use, the roof controller 22 receives a command input 38 from a user via the control switch 28 to either raise the roof 10 (if the roof is currently in its folded position as shown in Figure 2) or to lower the roof 10 (if the roof is currently in its non-folded position as shown in Figure 1). The control switch may be operated by means of a button or switch element or alternatively may comprise voice activated means.

The roof controller 22 according to this embodiment of the present invention determines, based on the position of the roof and at least one vehicle operating parameter (e.g. the vehicle speed or vehicle acceleration), whether operation of the roof structure 10 is permitted.

As shown in Figure 3, the position of the roof structure 10 is input 40 to the roof controller 22 from the roof motor mechanism 24. It is noted, however, that the roof position may be input to the roof controller by means of a separate sensor array (not shown).

As shown in the Figure, both the acceleration 34 of the vehicle and vehicle speed 36 are input (42a,b; 44a,b) to the roof controller 22 via the engine management system 26. It is noted, however, that such inputs may be provided directly to the roof controller and need not pass through the engine management system.

The present invention recognises that, as well as the vehicle speed (or acceleration), the position 24 of the roof structure 10 will also determine whether roof operation should be allowed. If the roof is near either end of its range of movement and so close to being fully open or closed, a higher speed may be safely permissible than when the roof is near the middle of its range of movement and so is relatively upright where it will catch the airflow particularly badly and may upset the balance of the vehicle.

Table 1, below, shows an example of how two different speed threshold values vary in dependence upon the position of the roof structure.

Table 1

The "first speed threshold value" in Table 1 represents the speed at which the roof structure can be moved without sustaining damage to the roof or other significant harmful effect to the vehicle due to wind effects. It is noted that, as the roof moves throughout the transition, from position 1 (roof down and passenger compartment exposed) to position 6 (roof up and passenger compartment covered), the speed at which the roof can be operated first falls and then rises.

The "second speed threshold value" in Table 1 represents the speed at which the vehicle can be driven with minimal risk of sustaining damage or adverse handling effects. It is seen that the second speed threshold value is generally higher than the first speed threshold value but that it varies with roof position in much the same way as the first speed threshold value.

Table 1 is represented graphically in Figure 4. It is noted that the maximum vehicle speed has been depicted as 100 kph although this is only for illustration purposes.

In the region below the first speed threshold line (indicated by arrow 45a) the roof controller will determine that roof movement is allowed.

In the region between the first speed threshold line and the second speed threshold line (indicated by arrow 45b) the roof controller 22 will determine that roof movement should be prevented.

In the region above the second threshold line (indicated by arrow 45c) the roof controller will determine that it is unsafe for the roof to be open.

Following a command input from a user via the control switch 28, the roof controller 22 determines the speed 36 (or alternatively the acceleration 34 of the vehicle) and also the roof position (as determined by the mechanism 24). A determination is then made as to whether the roof can be operated. Depending on the specific situation the roof controller 22 can instigate one or more of a number of actions:

1) If the roof controller 22 determines that the vehicle is stationary or moving slowly enough (i.e. it is below the first threshold value noted in Table 1) that the roof can be raised or lowered without any damage to the roof or other significant effect on the vehicle, the roof controller 22 sends a first roof control signal 46 to the roof motor mechanism 24 to either raise or lower the roof as appropriate. The position of the roof during its transition from open to closed (or vice versa) is communicated 40 by the roof motor mechanism 24 to the roof controller 22.

2) In addition to the action at (1) above, the roof controller 22 may additionally output a notification (48, 50) to the vehicle user either by means of the visible display device 30 or alternatively, or additionally, by means of the sounder 32 regarding the roof movement. The visible notification mechanism may take the form of a changing light display or alternatively a message displayed on a screen on, for example, the instrument display panel of the vehicle.

3) In addition to the actions at (1) and (2) above and in order to ensure that the vehicle user does not exceed the speed at which the roof operation can safely be operated (i.e. the first speed threshold value), the roof controller 22 may additionally send a first engine control signal 52 to the engine management system 26 to limit the vehicle speed to the first speed threshold value. It is noted that the speed to which the vehicle is limited will vary according to the position of the roof.

4) If the roof controller 22 determines that the vehicle is moving too fast for the roof structure to be moved without damage (i.e. the vehicle is moving above the first threshold value noted in Table 1), then the roof controller 22 may prevent the roof 10 from opening/closing, i.e. no signal or a "no action required" signal will be sent to the roof motor mechanism 24.

5) In addition to the action at (4) above, the roof controller 22 may additionally send an appropriate notification message to the user either via the sounder 32 or display devices 30 (or a combination of both).

It is further noted that the roof controller 22 may continually assess the vehicle speed and roof position regardless of whether the user has requested to operate the roof structure. The results of this assessment (e.g. roof motion is currently permitted, vehicle is moving too fast to permit roof motion) may then be displayed via the visual indication means 30 to the user.

Turning to Figure 5, a display device in accordance with an embodiment of the roof controller of the present invention, is shown generally as 60. The display device displays the vehicle's current status 62 as a function of vehicle speed 64 and roof position 66. The current status may be represented by an icon 62.

The display area 68 is divided into different areas (70, 72, 74) representing different roof related actions. Three separate areas 70, 72 and 74 are depicted in Figure 5. It is, however, noted that there may be any number of different areas.

The display device 60 of Figure 5 additionally comprises status buttons (76, 78, 80) each of which is related to a respective display area (70, 72, 74). For example, as depicted in the Figure, display area 70 relates to vehicle operating conditions under which roof motion is allowed. This display area 70 is associated with status button 76 which provides a textual notification to the vehicle user ("Roof Motion Allowed").

Remaining status buttons 78, 80 may indicate, for example, that roof motion is either not allowed or has been stopped (button 78 associated with area 74) or that the vehicle speed needs to be reduced (button 80 associated with area 72) in order to continue with or initiate roof motion.

It may be the case that, having initiated a roof transition below the first speed threshold value, the vehicle user decides that he needs or wishes to exceed the threshold speed. This could be for various reasons. For example, the roof transition may be initiated while the vehicle is stationary at traffic signals. If the signals change such that traffic flow resumes before the roof transition is complete, the user may decide to exceed the first speed threshold value in order not to impede traffic flow. The roof control system 20 is therefore optionally provided with override means 22a to allow the vehicle user to override the speed limit imposed by the controller/engine management system such that the vehicle may exceed the first threshold value.

The override means may be controlled by the control switch 28. However, more conveniently the override means 22a is linked to the accelerator pedal position 34. In that case, to override the first speed threshold value, the vehicle user may kick down on the accelerator pedal (e.g. by depressing the accelerator pedal past a certain threshold such as 33% of the maximum accelerator position). This over-ride action is communicated (82a, 82b) via the engine management system 26 to the roof controller 22.

Once an override of the system has been initiated by the user, the roof controller 22 sends a second roof control signal 84 to the roof motor mechanism 24 to stop the roof transition (e.g. to stop the roof transition partway between the open and closed positions). The roof controller 22 additionally sends a second engine control signal 86 to the engine management system 26 to allow the vehicle speed to exceed the first speed threshold value.

The roof controller 22 may allow the user to operate the vehicle/engine without limitation at this stage or more preferably the second engine control signal 86 sent to the engine management system 26 may instruct the management system to limit the vehicle speed to a second speed threshold value. Upon receipt of this second signal 86, the engine management system will either limit the vehicle speed to the second threshold value or allow the engine to operate without limitation depending on the requirements of the roof retraction system.

The second speed threshold value is set at a value which allows the vehicle to move, with the roof in a fixed position between the open and closed positions but with minimal risk of adverse effects to the vehicle or its handling characteristics.

The roof controller may once again send notification (48, 50) to the vehicle user of the second speed threshold value by means of one or both of the visual display means 30 and sounder 32.

If the vehicle speed is above the second speed threshold value when the vehicle user operates the control switch 28 then the roof controller 22 will prevent the roof 10 from opening/closing, i.e. no signal or a "no action required" signal will be sent to the roof motor mechanism 24. In this event, the roof controller 22 will send an appropriate notification message to the user either via the sounder 32 or display device 30 or a combination of both.

Again, it may be case that, having exceeded the first speed threshold value, the vehicle user needs or wishes to exceed the second speed threshold value. Exceeding the second speed threshold value will likely cause damage to the roof mechanism 24, roof structure 10 and also the vehicle and so it is envisaged that exceeding the second speed threshold will only occur in extreme circumstances (e.g. the vehicle is in a position of danger).

The roof retraction system 20 (and the over-ride means 22a) may therefore allow the vehicle user to over-ride the speed limitation for a second time. This second over-ride may be provided once again by means of a kick-down action on the accelerator pedal 34 distinct from the action that overrides the first speed threshold (e.g. by depressing the accelerator past 66% of its maximum position).

Once a second over-ride of the system has been initiated by the user, the roof controller 22 sends a third roof control signal 80 to the roof motor mechanism 24 to ensure that the roof transition remains stopped. The roof controller 22 additionally sends a third engine control signal 90 to the engine management system 26 to allow the vehicle speed to exceed the second speed threshold value. Upon receipt of this third roof control signal 90, the engine management system 26 will allow the engine to operate without limitation.

The transition from the second speed threshold operating condition to the unlimited operating condition may be notified 48, 50 to the user by the roof controller 22 via the visual display means 30 or sounder 32.

Referring to Figure 6, a flow diagram is shown depicting the processes described above in relation to Figures 3-5.

Roof movement is initially requested 92 by the user (by operating the control switch 28). Assuming the vehicle speed is below the first speed threshold value, then the roof controller 22 will open the roof 10 and signal the engine management system 26 to limit the vehicle speed to the first threshold value (Stage 1).

If the vehicle speed is greater than the first speed threshold value when the user requests a roof transition or if alternatively the user over-rides the speed limitation imposed in

Stage 1 (e.g. by depressing the accelerator past 33% of its full acceleration position), then the system moves 94 to Stage 2 in which the vehicle is limited to a second speed

threshold value and the roof transition is stopped or prevented. Additionally a warning is notified to the user by either the sounder 32 or the visual display device 30 (or alternatively by both devices).

If the vehicle speed is greater than the second speed threshold value when the user requests a roof transition or alternatively if the user over-rides the speed limitation imposed in Stage 2 (e.g. by depressing the accelerator past 66% of its full acceleration position), then the system moves 96 to Stage 3 in which vehicle speed is not limited. In Stage 3, roof movement is preferably prevented and a second level of warnings is notified to the user.

If the system is in Stage 3 and the accelerator position 34 drops below the threshold value that initiates the second over-ride or alternatively if the vehicle speed drops below the second speed threshold then the roof retraction system 20 returns 98 to Stage 2.

If the system is in Stage 2 and the accelerator position 34 drops below the threshold value that initiates the first over-ride or alternatively if the vehicle speed drops below the first speed threshold then the roof retraction system returns 100 to Stage 1.

It will be understood that the embodiments described above are given by way of example only and are not intended to limit the invention, the scope of which is defined in the appended claims. It will also be understood that the embodiments described may be used individually or in combination.

As an example of variants within the broadest concept of the invention, it is preferred that roof movement is stopped or prevented when the vehicle speed exceeds one of the aforesaid thresholds, but this is not essential. For example, there may be advantages in permitting roof movement to continue once the driver has chosen to exceed a vehicle speed threshold with knowledge of the risks involved. This may apply particularly if the roof has already moved past its most vulnerable position such that continued movement

would have the effect of decreasing rather than increasing the risks arising from vehicle movement while the roof is in transition

The preceding description of some of the above preferred embodiments requires that vehicle speed is known to and derived from the engine management system. However it is possible to deduce vehicle speed by other means, such as from sensors associated with the vehicle transmission, braking system, wheels or speedometer. It is even possible to deduce vehicle speed from extra-vehicular positioning systems such as satellite-based global positioning systems or roadside beacons. Any such means of speed measurement is contemplated within the broad inventive concept.

Similarly, whilst it is preferred to use the engine management system to limit vehicle speed by restricting the speed or power output of the engine, this is not essential to the invention in its broadest sense. For example, speed may be limited by the transmission system of the vehicle or by its braking system.