Convertible top assembly with hydraulic actuating device

Land vehicles: bodies and tops – Tops – Let-down type top

Reexamination Certificate

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C296S117000, C060S352000

Reexamination Certificate

active

06299233

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a hydraulically actuated convertible top assembly for a vehicle having a passenger compartment. Said convertible top assembly comprises a convertible top which is displaceable between a closed position, in which said convertible top covers the passenger compartment of the vehicle, and an open position, in which the passenger compartment is open. Said convertible top assembly further comprises a hydraulic actuating device for actuating one or more components of the convertible top assembly. The hydraulic actuating device comprises a hydraulic pump with an associated drive motor and a reservoir for hydraulic fluid, as well as one or more hydraulic actuators, the hydraulic actuators acting on said convertible top assembly. The pump is connectable to said hydraulic actuators for supplying pressurized hydraulic fluid to said hydraulic actuators.
BACKGROUND OF THE INVENTION
Convertible top assemblies with one or more hydraulically driven components are generally known, e.g from EP 0 425 156. In a known simple design, the hydraulic actuating device comprises a single hydraulic actuator for moving the convertible top, but in many cases there are a plurality of components which are each driven by one or more associated hydraulic actuators, for example the convertible top (which may comprise either a foldable cover or one or more rigid cover parts), the tonneau cover, one or more latches and, in the case of convertible tops with a foldable cover, the bow for tensioning the fabric.
One of the functions which is often carried out hydraulically is the movement of the convertible top itself from the open position to the closed position and vice versa. The hydraulic pressure which is required in order to carry out these movements is relatively low throughout most of these movements. However, in the vicinity of the end positions of the convertible top, it is often necessary to supply a greater force, for example in order to compress a sealing strip between the convertible top and the header above the windscreen, or owing to the relatively unfavourable engagement of the convertible top actuators on the convertible top in the open position. It may also be desirable
ecessary to supply a greater force at other moments during the movement. Furthermore, some actuators have only a small active piston surface, so that a relatively great hydraulic pressure is required in order for these actuators to be able to drive the associated component. For example, in a number of convertible top assemblies one or more latches are hydraulically actuated, and the actual hydraulic actuators associated with these latches are often extremely small, in particular owing to the limited fitting space, and therefore require a high hydraulic pressure in order to drive the latch.
A significant drawback of the known hydraulically actuated convertible top assemblies is that it takes an undesirably long time to open and close the convertible top, while the market demands convertible top assemblies which work increasingly quickly.
OBJECT OF THE INVENTION
The object of the present invention is to provide measures which allow a rapidly operating convertible top assembly to be produced.
SUMMARY OF THE INVENTION
The present invention provides a convertible top assembly of the above kind wherein the actuating device comprises control means which are adapted to regulate the volumetric output of the pump while the convertible top assembly is being hydraulically actuated.
In the known convertible top assemblies the pump and the associated electric drive motor of the hydraulic actuating device are adapted to the highest pressure level which has to be delivered by the pump in order to actuate the actuators of the convertible top assembly. The known pumps which are used for this purpose are of the type which have a constant volumetric output per revolution of the pump shaft, the so-called fixed displacement type, despite the fact that, partly owing to leakage losses in the pump, this volumetric output is often not entirely constant, but rather decreases as the hydraulic pressure to be delivered increases. The electric motor is usually a small low-voltage DC motor able to deliver a limited maximum power for driving the pump. This limitation stems, inter alia, from the electric current taken up, the cost, the volume of the motor and the weight of the motor.
Since the pump/motor combination is adapted to those moments during actuation of the convertible top assembly at which the highest hydraulic pressure is required, in the known convertible top assemblies functions (movements of hydraulically driven components) which require a relatively lower pressure than the maximum pressure required are carried out with incomplete utilization of the available drive motor power. This is because the power required by the pump can be seen as the arithmetic product of the outputted hydraulic pressure and the hydraulic output (volumetric flow rate).
The convertible top assembly according to the invention provides for the pump volumetric output to be controlled, making it possible to vary the volumetric output during actuation of the convertible top assembly, in steps and/or continuously, between various values. As a result, the speed at which the hydraulic actuators carry out their driving movement can be controlled. It is thus possible for the volumetric output to be set to one value for the actuation of one specific actuator and for the volumetric output to be set to a different value for the subsequent actuation of a different actuator. However, it is also possible for the volumetric output to be controlled continuously during the actuation of one or more actuators, in particular as a function of the hydraulic pressure. The volumetric output control makes it possible to control the speed at which the functions are carried out, which is advantageous, for example, if a plurality of movements of components of the convertible top assembly are to take place.
Preferably, the control means are designed such that the speed of the hydraulic actuation of the one or more hydraulically driven components of the convertible top assembly, in particular of the movement of the convertible top itself, is optimized on the basis of the maximum power which the drive motor can deliver. With a volumetric output control of this nature, it is possible to carry out each function at the maximum possible speed within the range of the motor power which can be delivered. As a result, a specific (electric) motor can be utilized optimally, and it has been found that, by using the same electric motor as that currently used, it is possible for a convertible top assembly to operate many tens of percents more quickly.
Preferably, the control means are designed such that, if the hydraulic pressure required for the hydraulic actuation of an actuator is lower than a maximum hydraulic pressure which is required during the actuation of the convertible top assembly, the pump volumetric output is set to a higher value than the volumetric output of the pump at the maximum hydraulic pressure. As a result, a function, or a part of a function, of the convertible top assembly which requires a relatively low hydraulic pressure can be performed with a greater volumetric pump output than a function or another part of this function which requires a higher pressure.
The volumetric output control may also be used to protect the (electric) motor from overload, if the control means are designed in such a manner that the arithmetic product of the hydraulic pressure and the volumetric output by the pump is at most equal to the maximum motor power which can be delivered. In the same way, the control can be used to limit the pressure of the hydraulic system by reducing the volumetric output at high pressures, thus preventing a further pressure increase. In one embodiment thereof, it is possible for the pump volumetric output to be set to zero, if the pressure has reached a maximum permissible value.
In order to achieve the as rapid actuation of the convert

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