Abstract:
A motor vehicle with a movable convertible top includes a control device for controlling a convertible top motion and a device for the recognition of the convertible top position. The device for convertible top position recognition continuously monitors the position of the convertible top. The position of a defined element of the convertible top is determined by means of at least one acceleration sensor that measures the current acceleration in relationship to the acceleration of free fall.

Description:
FIELD OF THE INVENTION 
   The invention relates to a motor vehicle with a movable convertible top and a device for the recognition of the convertible top position. 
   BACKGROUND OF THE INVENTION 
   Convertibles are often equipped with a movable convertible top, which can be automatically moved for example from an open to a closed position or vice versa with the press of a button. The movement of the convertible top is usually effected by a hydraulic drive, which in turn drives a convertible top mechanism, which includes a convertible top linkage. The convertible top linkage may be a carrying device for a textile roof as well as a so-called hard-top folding roof with mainly rigid roof elements, and may include a cover for a convertible top compartment as well as all elements that are being moved in the process. To control the movement of the convertible top it is necessary to obtain information on the current position of the convertible top. 
   German Patent Application DE19842337A1 describes an operating mechanism for a folding top of a convertible vehicle, comprising a hydraulic gear with a hydraulic pump and hydraulic motors that are linked to the foldable top, whereby the operating mechanism comprises a position transmitter for generating electric signals according to positions of the folding top and control electronics for creating the planned movement of the convertible top and for sensing the electric signals of the position transmitter. Limit switches are positioned at the ends of the range of motion of the convertible top as well as within the range of motion of the convertible top; they are used to sense the convertible top position. The limit switches transmit a signal to the control electronics as soon as the convertible top has reached the final position switch. In the process, a constant rotational speed or a constant power output of the electric motor that drives the hydraulic pump is allocated to each area between the two final position switches. 
   The limit switches are used as terminal points for position recognition. To determine the position of the convertible top between these terminal points it is suggested to integrate the rotational speed of the motor over time and to interpolate the convertible top position. To avoid a high quantity of limit switches, the DE19842337A1 application proposes to calculate the approximate position of the convertible top with the help of the control equipment using the number of revolutions of the electric motor and the average displacer volume of the hydraulic pump. 
   However, the disadvantage of using this method is that only the theoretical, mathematically calculated information on the convertible top position is available between the terminal points with limit switches. The information does no longer corresponds to the actual convertible top position for example after a change in speed of the convertible top movement. Moreover, the disadvantage of this solution is that a number of end switches have to be provided in the range of motion of the convertible top to enhance the accuracy of the information in regard to the current convertible top position and that this involves an accordingly higher amount of expense. 
   According to the DE19842337A1, also sensors for sensing the positioning angle or travel distance of the convertible top linkage may be used in order to accurately calculate the current position of the convertible top, whereby the sensors create an analog signal or they scan and count marks on the linkage like a potentiometer for example. 
   However, these types of sensors that are designed as potentiometers and are used to continuously scan the displacement have to be directly attached to the pivot point of the convertible top section that is to be scanned, whereby it is problematic that the cumbersome size of the potentiometer, because of its physical properties, can not fall below a certain limit. As a result, there is the danger of collision between the sensors and other convertible top segments when these types of sensors are being used. 
   Moreover, this type of sensor that is designed as a potentiometer is a manual part, which is subject to wear when it is used, and to a drift in temperatures, which can lead to errors in regard to the information on the current convertible top position. 
   It is also known from practical applications that the convertible top position can be calculated with the aid of the measurement of the retraction travel of the cylinders of a hydraulic system of the convertible top drive. However, it has to be taken into account with this method, that this type of solution requires a comparably large installation space and does not provide any information on the position of the convertible top inherently, but merely on the distance of cylinder travel. Therefore, a possibly defective connection point, that is, a disruption of the connection between a cylinder and the convertible top linkage, cannot be detected. 
   The fact that the currently known installations for the recognition of convertible top positions are highly prone to errors is disadvantageous in particular in regard to the detection of an obstruction situation, since possible problems during the sequence of the convertible top motion, such as a decelerated motion or the blocking of the convertible top, which can be indications that an object or a body part is caught in the convertible top mechanism, may not be detected or not detected until very late. 
   SUMMARY OF THE INVENTION 
   It is the object of the present invention to provide a motor vehicle with an automatically movable convertible top, which is equipped with a device for the recognition of a convertible top position, which provides reliable information on the actual position of the convertible top. 
   In accordance with the invention, this object is solved with a motor vehicle that comprises a movable convertible top according to the features of described herein. 
   The advantage of the solution in accordance with the invention is that the continuous monitoring of the convertible top position and an accurate position recognition of the convertible top are possible at any time, whereby at least one acceleration sensor, which measures the actual acceleration in relationship to the acceleration of free fall, is used to calculate the position of a defined convertible top element. 
   With the aid of these types of acceleration sensors that are also called G-sensors, which sense two axes in one plane, the longitudinal acceleration and the lateral acceleration, it is possible to determine the longitudinal inclination, and the transversal inclination of the convertible top. The angle to the surface of the earth can be resolved to approximately 0.2 degree with the aid of a very high possible resolution of the acceleration. 
   In addition to the high accuracy in the recognition of the convertible top position, the use of G-sensors offers the additional advantage of high freedom in the design of their disposition, since this type of convertible top position recognition can be implemented independently from convertible top kinematics. 
   Furthermore, these types of acceleration sensors offer the advantage that they can also be used for other functionalities in the vehicle, such as for roll-over detection. 
   Of particular advantage is the device for convertible top position recognition according to the invention that operates with high accuracy when it interacts with a detection device that recognizes an interference into the range of motion of the convertible top mechanism, which can for instance feature a sensor system with sensors that carry out measurements based on different measurement principles, whereby the convertible top movement is controlled in a safety mode after a fault has been detected in the detection equipment or after an obstruction situation has been recognized. 
   The provision of information on the exact current convertible top position permits a reaction that is geared toward the particular operating situation. The reaction can consist of continuing the convertible top motion with reduced speed or stopping or reversing the convertible top motion. 
   Additional advantages and advantageous features of the invention will be readily understood after reading the description, the drawings, and the patent claims. 
   The drawings show schematically an example of the invention, which will be explained in further detail in the following description. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic perspective view of a movable convertible top of a convertible vehicle with a device for the recognition of the convertible top position according to the invention, whereby the convertible top that is shown individually is closed; and 
       FIG. 2  is a schematic top view of another convertible top of a convertible vehicle with the device for convertible top position recognition according to  FIG. 1 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  shows only a movable convertible top  1  of a convertible vehicle, which includes a convertible top mechanism  2  that may be covered with a textile roof, whereby the convertible top mechanism can be moved between an open and a closed position by means of a control device  3  representing a convertible top control unit and an electro-hydraulic convertible top drive  4 , of which only sections are shown in  FIG. 1 . 
   The control device  3  is designed so as to interact with a rain sensor and a key transmitter, and to start an automatic convertible top motion upon the request of the driver with the aid of a button in the vehicle or through the key transmitter, as well as when precipitation is recognized by the rain sensor. 
   A device  5  for the recognition of the convertible top position is provided in order to recognize the current position of the convertible top  1  or its convertible top mechanism  2 . The device  5  is equipped with several acceleration sensors  6 ,  7 ,  8 . In the embodiment according to  FIG. 1 , a first acceleration sensor  6  is located on a front linkage section  9 , adjacent to a vehicle window; a second acceleration sensor  7  is located on a linkage section  10  which is located centrally in regard to the vehicle length and adjacent to a vehicle window, and a third acceleration sensor  8  is located on a rear window frame  11 . 
   Only three acceleration sensors are shown in the drawings both in  FIG. 1  and in  FIG. 2 ; however, any number of acceleration sensors can be used depending on the application. The location of the acceleration sensors  6 ,  7 ,  8  in  FIGS. 1 and 2  is only to be regarded as an example and can be changed depending on the type of convertible top design. 
     FIG. 2  shows an application of the device  5  for the recognition of the convertible top position for a convertible top  1 ′, which is designed as a hard top folding roof, and for which the acceleration sensors  6 ,  7 ,  8  are located on different roof segments, such as the first acceleration sensor  6  on a front roof segment  12 , the second acceleration sensor  7  on a center roof segment  13 , and the third acceleration sensor  8  on a rear roof segment  14 . 
   The acceleration sensors  6 ,  7 ,  8  can be positioned anywhere on convertible top  1  or  1 ′, whereby attention is to pay only to the orientation in a defined co-ordinate system. 
   The acceleration sensors  6 ,  7 ,  8  represent so-called G-sensors, which measure and show the current acceleration in relationship to the acceleration of fall or normal g force. The earth&#39;s acceleration of free fall of 9.81 m/s 2  corresponds to 1 G (G=gravitation). The acceleration sensors  6 ,  7 ,  8  not only measure the acceleration of the element to which each of them is attached, but also the incline in relationship to the earth&#39;s surface. The acceleration sensors  6 ,  7 ,  8  that are used here operate in a range of 0 G up to a maximum of 10 G and provide an output voltage, which is linear to the acceleration value. 
   As appears from  FIG. 2  in particular, the acceleration sensors  6 ,  7 ,  8  on the convertible top  1  or  1 ′ are connected via a suitable wiring harness or a highly-flexible microstrip to an electronic analysis unit  15 , which analyzes the sensor signals and calculates a relative position using the individual positions. The calculated relative position of the acceleration sensors  6 ,  7 ,  8  or the components that carry them is transmitted to the convertible top control unit  3  by an electronic analysis unit  15  via a bus system such as a CAN bus  16 . 
   In the embodiment described here, a further acceleration sensor  17  that is designed as a G-sensor is located in the convertible top control unit  3 ; the sensor determines the location or incline of the motor vehicle in the defined co-ordinate system, to which the acceleration sensors  6 ,  7 ,  8  are allocated as well. The convertible top control unit  3  uses the relative position and the present information on the vehicle incline to calculate the current position of the convertible top  1  or  1 ′. 
   The current convertible top position is also transmitted to an electronic analysis unit of an automatic detection device  18 , which recognizes an intervention into the range of motion of the convertible top mechanism  2 , and which is here integrated into the convertible top control unit  3  in regard to its electronic analysis unit, and which is only shown schematically in  FIGS. 1 and 2 . The detection device  18 , which may comprise for instance a sensor system with optical and/or capacitive sensors, can recognize an obstruction situation with high accuracy since it knows the current convertible top position, whereupon the convertible top control unit  3  can initiate an adequate reaction. 
   Advantageously, the typical convertible top final position switches are no longer required when the device  5  for convertible top position recognition according to the invention is used, since a corresponding pulse is put out by the acceleration sensors  6 ,  7 ,  8 , when the convertible top  1  or  1 ′ has reached a limit stop, in other words when it is fully closed or open, whereby the sensors are subject to powerful negative acceleration. 
   Moreover, with the present continuous convertible top position recognition it is possible to implement an adaptive self-learning control of the convertible top motion, which may be realized for instance by manually driving to individual defined convertible top positions one time.