Abstract:
A motor vehicle door locking system and a process for controlling the locking system. A piezoelement is assigned to a stationary outside door handle and is used to detect touching and/or actuation of the outside door handle. To increase the operating reliability, to simplify troubleshooting and to minimize the power consumption, there is a monitoring device that monitors the piezoelement. The piezoelement is monitored for fracture and the occurrence of the first signal.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to a motor vehicle door locking system having a piezoelement, and a process for controlling a motor vehicle door locking system. 
   2. Description of Related Art 
   European patent application EP 1 103 432 A1 discloses a motor vehicle door locking system in which a piezoelement is used as a sensor element, the piezoelement being installed in a substantially rigid outside door handle of the motor vehicle. The piezoelement is used to detect actuation of the outside door handle by an operator. In the disclosed motor vehicle door lock, there exists a disadvantage in that when the piezoelement fails, complex troubleshooting is required and the operating safety of the motor vehicle may also be compromised. 
   The international application WO 99/28170 discloses a motor vehicle door locking system in which pulling an outside door handle initiates the starting interval of data interrogation of a so-called “passive entry” function in order to ascertain whether the operator who is actuating the outside door handle is authorized for access. Pulling of the outside door handle can be detected, among others, by deformation of the piezoelement. Here, it is also disadvantageous if the piezoelement which is assigned to the outside door handle fails. This requires complex troubleshooting since failure would be assumed to be primarily in the “passive entry” function. It is furthermore disadvantageous if continuous evaluation or monitoring of the signals of the piezoelement is required in order to be able to start data interrogation directly after actuation of the outside door handle. 
   SUMMARY OF THE INVENTION 
   Therefore, a primary object of this invention is to provide a motor vehicle door locking system and a process for controlling the door locking system so that the operating reliability is increased and troubleshooting is simplified. 
   Another object of the invention is to provide a motor vehicle door locking system and process which minimizes the closed-circuit current demand. 
   The underlying premise of this invention is to monitor the piezoelement, on the one hand, for its operation, and on the other, for the occurrence of the first signal. This leads to several advantages as described. 
   In particular, there is a monitoring device that monitors the operation of the piezoelement, preferably a current path being formed by the piezoelement so that failure or fracture of the piezoelement leads to interruption of the current path to allow detection of the failure. This allows direct detection of a failure, especially a fracture, of the piezoelement. Accordingly, the operating reliability of the motor vehicle is increased, since a failure is immediately noticed and the pertinent piezoelement can be quickly replaced. Moreover, the monitoring of the current path in accordance with the invention greatly simplifies troubleshooting since when the motor vehicle door locking system fails, the failure can readily be established by monitoring whether the piezoelement assigned to the outside door handle is working properly. 
   According to one preferred development, the monitoring in accordance with the present invention can be additionally used to modify the evaluation of signals of the piezoelement depending on the operation of the piezoelement. For example, the gain of the amplifier assigned to the piezoelement can be increased if by monitoring, it is detected that the resistance of the piezoelement has changed, especially if the resistance is increased. 
   When monitoring for the occurrence of the first signal of the piezoelement, it can be considered that the evaluation of the signals of the piezoelement with respect to the detection of touching and/or actuation of the outside door handle is comparatively complex. This applies especially when pulling and pressing on the outside door handle which results in tensile loading and pressure loading, respectively, must be distinguished. In particular, in the evaluation, the absolute value, the relative value, the behavior, the rate of change and/or the time correlation or timing of the signals of the piezoelement should be considered in order to enable clear identification or detection of touching or actuation of the outside door handle. Accordingly, the evaluation requires a certain circuitry cost and/or computer cost. This dictates relatively high power demand of evaluation 
   A signal is generally defined as the occurrence and/or change of electrical signals or characteristics of the piezoelement. The detection of the occurrence of the first signal of the piezoelement makes it possible to activate or start evaluation only, also called wakening, when the first signal of the piezoelement has occurred and has been detected by an activation device. This enables minimization of the closed-circuit current demand because an activation device or detection device which has a simple structure is optimized for a minimum closed-circuit current demand for detection of the occurrence of the first signal of the piezoelement and is continuously activated. 
   Furthermore, according to a first embodiment, it is provided that the starting interval of a “passive entry function” is initiated when the first signal of the piezoelement, or first touching or actuation of the outside door handle assigned to the piezoelement, has been detected. According to one embodiment, this detection can take place at the same time by the monitoring device for monitoring the operation of the piezoelement. 
   Furthermore, the details of distinguishing between the detection of touching and actuation of the outside door handle is not described in detail here. It depends ultimately on the evaluation whether touching of the outside door handle with, for example only very slight deformation or loading of the piezoelement on the one hand, and strong actuation on the other hand, can be distinguished, especially in order to control or trigger different functions accordingly. However, this need not be detailed here. 
   Other aspects, properties, features and advantages of this invention result from the following explanation of one preferred embodiment which is shown in the drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a schematic perspective view of a motor vehicle with a motor vehicle door locking system in accordance with an embodiment of the present invention; 
       FIG. 2  shows an outside door handle arrangement of the motor vehicle door locking system shown in  FIG. 1 ; 
       FIG. 3  shows a schematic cross section of the outside door handle arrangement; 
       FIG. 4  shows a schematic of a piezoelement with an assigned monitoring device; and 
       FIG. 5  shows a schematic block diagram of the motor vehicle door locking system in accordance with an embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Initially, it is noted that same reference numbers are used for the same or similar parts in the various drawings discussed in detail below. Therefore, corresponding or comparable advantages and properties arise for these same or similar parts, even if a repeated description is omitted in the discussion below. 
     FIG. 1  schematically shows a motor vehicle  1  with a motor vehicle door locking system  2 . The motor vehicle door locking system  2  has several vehicle door locks  3 , especially for the vehicle doors  4 , the rear hatch, the hood and the like, at the installation positions which are shown schematically in FIG.  1 . 
   Preferably, each motor vehicle lock  3  can be locked and unlocked by a motor, such as an electric motor, by central interlock system or a central interlock drive known in the art. In the embodiment where an electric lock is provided in the motor vehicle locks  3  of the vehicle side doors  4 , each motor vehicle lock  3  has the added possibility of motorized opening. Therefore, lifting of the detent pawl (not shown) may be attained by an opening drive (not shown). Locking and unlocking can also be accomplished accordingly using only the circuitry of the central interlock system or a central interlock drive. 
   The motor vehicle door locking system  2  is preferably equipped with a “passive entry” function. Here, a “passive entry” function is defined as an automatic, vehicle-side data interrogation or identification of an operator-side data medium such as a transponder  5  or the like, as indicated by signal waves  6 , in order to ascertain whether an operator approaching the motor vehicle  1  or an operator about to open the vehicle  1  or the vehicle door  4  is authorized for access. This is generally checked by the corresponding electronics of the motor vehicle  1 . With the corresponding authorization of the operator, ordinarily automatic unlocking takes place either of a central interlock system, of the door lock  3  of the driver-side door  4 , or at least of the lock  3  of the door  4  upon being approached by the operator or upon the outside door handle being touched or activated by the operator. The energy or power demand of the “passive entry” function or data interrogation is considerable. Therefore, the corresponding electronics is only turned on or activated when necessary. Since a certain time is required for turning on or activating the electronics and data interrogation, this takes place as quickly as possible after detection of the approach of an authorized individual and/or only after initial touching and/or actuation of the outside door handle. Turning on or activating the electronics for data interrogation is referred to as starting of the authorization interrogation below. 
   If necessary, one locking cylinder  7  for actuation with a mechanical key  8  is assigned to the motor vehicle lock  3  of the driver&#39;s door and the hood lock. Thus, the motor vehicle door lock  3  of the driver&#39;s door can be mechanically actuated or unlocked in an emergency with the key  8  and thereby opened. There can be the corresponding emergency unlocking or emergency opening for the locks  3  of the other doors  4  as well. 
   One outside door handle arrangement  9  is assigned to at least each motor vehicle door lock  3  of the motor vehicle side doors  4 , as shown in FIG.  1 .  FIG. 2  shows the outside door handle arrangement  9  of the driver&#39;s door with an integrated locking cylinder  7 . However, the lock cylinder can also be omitted. The outside door handle arrangement  9  also has an outside door handle  10  which is made stationary and which has no moving parts, such as a movable actuating and opening lever or the like. A bow-shaped handle is shown, however, a flap-shaped handle could likewise be used as a possible alternative. 
   The outside door handle arrangement  9  can moreover comprise an adjacent door area, as is shown in FIG.  3 . In such an embodiment, the outside door handle arrangement  9  together with this adjacent door area  11  is inserted as a unit into the assigned motor vehicle door  4 . However, this is not absolutely necessary for the stationary outside door handle  10 .  FIG. 3  shows an outside door handle arrangement  9  without the locking cylinder  7 . A sensor  12  is assigned to the outside door handle  10 . It has a deformation-sensitive, force-sensitive or pressure-sensitive sensor element in the form of a piezoelement  13 . 
   The piezoelement  13  is especially a piezocrystal which upon loading or deformation, produces an electrical voltage by crystal deformation, especially on its sides perpendicular to the direction of deformation. This voltage is tapped, preferably with high-resistance, amplified, and evaluated. However, the piezocrystal can also carry out resistive evaluation and/or optionally, capacitive evaluation of signals or of the characteristics of the piezoelement  13  for detection of loading or deformation of the piezoelement  13 . 
   The outside door handle  10  bounds or defines an “engagement space”  14  for the hand of the operator (not shown). The engagement space  14  is defined as the space in which the hand of an operator preferably fits to actuate the outside door handle  10 . 
   The piezoelement  13  can be located on the inside wall or the inner side  15  of the outside door handle  10  facing the engagement space  14 , and in particular, covers the inside  15  and/or the adjoining areas of the outside door handle  10  over a large area, preferably essentially completely. The piezoelement  13  can however, be integrated into the outside door handle  10 , especially located within or potted in a cavity. 
   The outside door handle  10  is preferably, at least in areas, made elastically deformable. The sensor  12  can detect deformation or loading of the outside door handle  10  caused by actuation, so that touching or actuation of the outside door handle  10  can be detected. 
   Evaluation electronics or evaluation device  16  is assigned to the piezoelement  13 . The evaluation device  16  is preferably at least partially, integrated into the outside door handle arrangement  9  or the outside door handle  10  itself, but it can also be housed, for example, in the assigned motor vehicle door  4 . 
   In addition or alternatively, evaluation can take place partially in a door control device which is assigned to the motor vehicle door  4  and/or central motor vehicle electronics or control electronics  17  of the motor vehicle  1  which is shown in FIG.  1 . 
   When the hand of an operator (not shown) touches and actuates the outside door handle  10 , this leads to an electrical signal or a change in electrical signals and/or characteristics of the sensor  12  or the piezoelement  13  which can be evaluated as touching or actuation of the outside door handle  10  by the evaluation device  16 . 
   In the schematic  FIG. 3 , the broken arrow  18  indicates that the evaluation device  16  can output the corresponding evaluation signals, the evaluation device  16  being connected to the central control electronics  17 , for example via a CAN bus, and/or to a door control device (not shown), for example, via a LIN bus. Of course, other connection versions are also possible here. 
   One important aspect of the present invention is that the motor vehicle door locking system  2 , in addition to the evaluation device  16 , has a monitoring device  19  which is assigned to the piezoelement  13 , as indicated in FIG.  3 . It should be noted that whereas in the illustrated embodiment described herein, specific devices are shown for the evaluation device  16  and the monitoring device  19 , other embodiments may be provided with a single device that performs these functions. In yet other embodiments, these functions may be integrated in a device which performs other functions as well. The monitoring device  19  is used to monitor the piezoelement  13  for operation, in the example of the figure, such as for fracture. 
   A simple preferred example embodiment of the monitoring device  19  is detailed below using FIG.  4 . In the example embodiment of  FIG. 4 , the basic function of the monitoring device  19  is to form a current path  20  which runs through the piezoelement  13  and to monitor the current. Preferably, the current path  20  through the piezoelement  13  is formed by a corresponding conductor arrangement of the piezoelement  13 . In particular, the conductive metal-coated surface of the piezoelement  13 , for example, is suited for this purpose. For example, the metal-coated outside surface of a ceramic body of the piezoelement  13  makes contact on opposite end areas. Regardless of this conductive through connection, the signals caused by deformation or loading of the piezoelement  13  can be detected on the piezoelement  13 , as already explained. 
   The monitoring device  19  has a power source  21  and an electrical resistor  22  which are series-connected to the piezoelement  13  in the embodiment shown. If a power supply voltage U V  is applied to the current path  20  which has been formed in this manner, an at least essentially constant current flows through the piezoelement  13  and the resistor  22 . The voltage drop U R  on the resistor  22  is monitored. In particular, this is attained, for example, through an amplifier or a comparator  23 , as indicated in FIG.  4 . For example, the comparator  23  compares the voltage drop U R  to a reference voltage. If the voltage drop U R  falls below the reference voltage or the voltage drop U R  is completely absent, a warning signal is outputted. This warning signal indicates that the resistance of the piezoelement  13  has become too high or that the current path  20  has been completely interrupted, for example, as a result of fracture of the piezoelement  13 . 
   The warning signal can be outputted, for example, to the evaluation device  16  and/or the control electronics  17 . Alternatively or additionally, the warning signal can be displayed, for example, to warn the user of the motor vehicle  1 , to indicate a failure of the piezoelement  13 , and/or facilitate troubleshooting during a repair. 
   In the example shown, a preamplifier  13  or a first amplifier  24  (shown in  FIG. 5 ) is assigned to the piezoelement  13 , as is shown schematically in FIG.  3 . In reference to  FIG. 5 , the first amplifier  24  is located especially directly adjacent to the piezoelement  13  and preferably forms an installation unit with the piezoelement. In particular, the first amplifier  24  and optionally, other electronics can be located directly on the piezoelement  13  and carried by it. For instance, the first amplifier  24  can also be regarded as part of the sensor  12 . 
   As already indicated above, functional properties are important here instead of the particular structure and devices described. Thus, it is less important whether the evaluation device  16 , the monitoring device  19 , and the first amplifier  24  are formed by separate circuits, or either fully or in part, by common circuits, integrated circuits or also common boards, conductor arrangements or the like. Optionally, these functional units can also form one or more installation units, together with the sensor  12 . 
   Functional aspects are detailed below using the block diagram shown in  FIG. 5  which illustrates one embodiment of the motor vehicle door locking system  2 . In this embodiment, the sensor  12  with its piezoelement  13  is connected to the evaluation device  16 . According to a first embodiment, the sensor  12  comprises the first amplifier  24 , therefore the first amplifier stage. The amplifier  24  is used to detect or recognize the first signal of the piezoelement  13 , as already explained above, in order to then awaken or turn on the remaining electronics, and to be able to start the evaluation and/or authorization interrogation, for example. The first amplifier  24  is connected to the battery or electrical system  25  of the motor vehicle  1 , either directly, or via a power supply device  26  to ensure continuous supply of power. 
   Preferably, the first amplifier  24  or other suitable circuit is made such that the power consumption is minimal. For example, the circuit or the amplifier  24  is made with MOSFET technology and/or has a closed-circuit current of less than 100 μA. 
   When the piezoelement  13 , as a result of initial touching or actuation of the outside door handle  10 , is deformed or loaded, this is detected by the amplifier  24  and a corresponding signal, hereinafter called the “awakening signal A”, is output to the activation or awakening circuit  27 . The awakening signal A can, if necessary, also be outputted directly to the central control electronics  17  of  FIG. 1 , or other motor vehicle electronics in order to, for example, start the authorization interrogation for the passive entry function. 
   The awakening circuit  27  can be made or defined as a holding circuit which temporarily activates or turns on the evaluation device  16  and/or the monitoring device  19 , specifically in the awakened or turned-on state after receiving the awakening signal A. In the example shown, the awakening circuit  27  forms a temporary power supply for the evaluation device  16  and the monitoring device  19 . Therefore, the awakening circuit  27  supplies the two devices  16  and  19  after receiving the awakening signal A with power, at least temporarily. 
   In addition, the awakening circuit  27 , after receiving the awakening signal A, can output a corresponding signal to the control electronics  17  and/or to other electronics of the motor vehicle  1 , for example, to start or activate the authorization interrogation of the “passive entry” function and/or other motor vehicle functions, as indicated by arrow P in FIG.  5 . 
   Another important aspect of this invention is that the motor vehicle door locking system  2  has an activation device  28 . This activation device  28  is formed by the first amplifier  24  and the awakening circuit  27  in the above described example shown. But this represents only one embodiment. In terms of circuit engineering, the activation device  28  can also be made differently. Furthermore, the activation device  28  can also be integrated into the evaluation device  16  and/or the monitoring device  19  or other components of the motor vehicle door locking system  2 . 
   One important aspect is that the activation device  28  permanently or continuously monitors the piezoelement  13  for the occurrence of a first signal and thus, for the first contact or actuation of the outside door handle  10 . Only after the occurrence of this first signal is the evaluation device  16 , activated or turned on. This takes place here by the power supply of the evaluation device  16  being turned on only after the occurrence of the first signal. 
   In the example shown, the corresponding applies here to the monitoring device  19 , i.e., the monitoring device  19  is turned on or activated only after detection or occurrence of the first signal of the piezoelement  13  by the activation device  28 . Alternatively, the monitoring device  19  can be operated permanently or continuously. This alternative embodiment makes sense especially when the monitoring device  19  and the activation device  28  are integrated into one circuit. 
   The evaluation device  16  in the embodiment shown in  FIG. 5  has its own amplifier stage such as second amplifier  29 , and a microcontroller  30  or other suitable evaluation circuit. As already explained, the monitoring device  19  can be integrated into the evaluation device  16 . Here, the evaluation device  16  and/or the activation device  28  comprises, for example, the comparator  23  of the monitoring device  19  which is not shown individually in FIG.  5 . 
   One possible mode of operation and one preferred structure of the monitoring device  19  have already been explained using FIG.  4 . As for other components of the monitoring device  19 ,  FIG. 5  shows the power source  21  which is connected to the awakening circuit  27  and accordingly supplies power to the piezoelement  13  and the current path  20  shown in  FIG. 4 , only if beforehand, the first signal of the piezoelement  13  has been detected, i.e., when the awakening circuit  27  is in the awakened or on-state. Processing of the initial signal of the monitoring device  19  made available by the comparator  23  takes place in the example shown, by the evaluation device  16  and in particular, by its microcontroller  30  or other suitable circuit. 
   Before detailing possible signal evaluation, an alternative embodiment is briefly explained. In such an example, the first amplifier  24  which is preferably directly assigned to the piezoelement  13  can be omitted. The amplifier  29  then assumes the functions of the first amplifier  24 . The amplifier  29  is then connected accordingly to a power supply, such as the power supply device  26 , as shown by the broken arrow. When the first signal of the piezoelement  13  is detected, the amplifier  29  furthermore makes available the required awakening signal A for the awakening circuit  27  as indicated by the broken arrow connection to the awakening circuit  27 . 
   In this second embodiment, of course, minimization of the power consumption is desired. Accordingly then, the amplifier  29  is made very economical in terms of power, and therefore has a low closed-circuit current of preferably less than 100 μA. Thus, the electrical system  25  of the vehicle  1  is not overloaded even when the motor vehicle  1  is stationary for a longer time. 
   When the evaluation device  16  is activated, therefore turned on, evaluation of the sensor signals takes place continuously, i.e., here the signals of the piezoelement  13  are amplified by the amplifier  29  and optionally by the amplifier  24 . Evaluation thereupon checks the signals for whether there is actuation of the outside door handle  10 , especially whether the motor vehicle door lock  3  which is assigned to the outside door handle  10  is to be opened or closed. Preferably, it is distinguished between pulling and pressing on the outside door handle  10 , especially in order to cause selectively opening or closing of the motor vehicle door lock  3  for an electric lock. Alternatively or in addition, signal evaluation can also be used to lock and unlock the assigned motor vehicle door lock  3  and/or the central interlock system of the motor vehicle  1 . 
   In the embodiment shown, preferably locking and unlocking takes place largely independent of actuation of the outside door handle  10  via the aforementioned “passive entry” function of the motor vehicle door locking system  2 . The “passive entry” function, however, can also be used only to check access authorization. Locking and unlocking as well as subsequent opening and closing then take place depending on the detected touching and/or actuation of the outside door handle  10 . 
   In the evaluation of the sensor signals, the absolute values, the relative values, the signal behavior, the rate of change and/or the time correlation of the sensor signals are considered or evaluated. For example, threshold value evaluation makes it possible to distinguished between initial touching or slight actuation, and stronger actuation for opening the motor vehicle door  4 . Moreover, it is also possible to distinguish between a tensile and pressure load, therefore, between pulling and pressing on the outside door handle  10 . 
   For example, it is possible for initial slight pressing and/or pulling on the outside door handle  10  to be necessary in order to start the aforementioned authorization interrogation of the “passive entry” function. In this case, the corresponding signal could be outputted to the passive entry function or control electronics  17 , or other electronics of the motor vehicle  1  by the monitoring device  16  or its microcontroller  30  after corresponding evaluation. Only after pressing or especially pulling a second time on the outside door handle  10  does unlocking and/or opening of the assigned motor vehicle door lock  3  take place. 
   Alternatively, pressing or pulling once with slowly increasing force on the outside door handle  10  can be enough to start or carry out the authorization interrogation on the one hand and/or to cause unlocking of the assigned motor vehicle door lock  3 , and on the other hand, to then unlock and/or open the motor vehicle door lock  3 . This continuous touching and actuation of the outside door handle  10  corresponds more to the conventional handling and is therefore, preferred. 
   The evaluation device  16  outputs the corresponding control signals so that depending on the control signal, the assigned motor vehicle door lock  3  is locked, unlocked, opened, and/or closed. Communications of the monitoring device  16  and its microcontroller  30  is shown schematically in  FIG. 5  by arrows  31 . In particular, the evaluation device  16  communicates with a central interlock system which is not detailed, the central control electronics  17  and/or other electronics of the motor vehicle  1  such as a door control device or the like (not shown) located in the assigned motor vehicle door  4 , through a bus system, individual cables, or other data or control network. 
   If the motor vehicle door locking system  2  has a “passive entry” function as in the embodiment shown, the authorization interrogation starts as early as possible. In particular, starting of the authorization interrogation can be induced on the one hand, by the awakening circuit  27 , or on the other hand by the evaluation device  16 . 
   In the embodiment shown, the evaluation device  16  moreover evaluates the monitoring signals made available by the monitoring device  19  or its comparator  23 . For example, the microcontroller  23  outputs a warning signal when the voltage drop U R  drops below a certain reference value, which may be due to interruption of the current path  20 , for instance. In this case, the evaluation device  16  outputs a failure signal which can be displayed with the display device  32  for the vehicle user as shown in FIG.  5 . The failure signal can, if necessary, also be further processed only internally in the motor vehicle electronics and, for example, displayed only for repair or service/maintenance purposes. 
   According to one embodiment, when the warning signal fails, the gain of the amplifier  24  and/or  29  changes, and is set up to enable emergency activation or emergency opening. In particular, when a warning signal occurs, the conventional evaluation can also be modified, for example, a threshold value which must be exceeded to cause opening by the sensor signals can be reduced. Therefore failure or emergency evaluation can take place instead of normal evaluation of the sensor signals, to the extent they can still occur or be detected. 
   In the embodiment shown, there is preferably continuous monitoring of the piezoelement  13 . If necessary, the monitoring however can also take place only temporarily or cyclically in certain intervals. 
   To turn off or reset the activation device  28  or the awakening circuit  27 , an internal timer may be provided, for example. The power supply to the evaluation device  16  and the monitoring device  19  or its power source  21  is turned off after a predetermined time, the time being optionally adjustable. Alternatively or in addition, turning off the power supply can also take place, for example, on the corresponding sleep signal of the control electronics  17  or other electronics of the motor vehicle  1  and/or on a locking command of the remote control or the like. 
   The evaluation device  16 , the monitoring device  19 , the activation device  28  and the other components of the motor vehicle door locking system  2 , depending on the requirement and space conditions, can be installed in the outside door handle  10 , the outside door handle arrangement  9 , and/or the assigned motor vehicle door  4 . For example, individual components or functions can be integrated into a door control device (not shown), the control electronics  17 , or other electronics of the motor vehicle  1 . In addition, it should be pointed out that the individual aforementioned functions can be implemented by the corresponding software in existing electronic components. 
   Moreover, in yet other embodiments of the present invention, instead of the piezoelement  13  or the piezocrystal, another sensor element can also be used accordingly. Preferably, the alternative sensor used is likewise a sensor element which converts a mechanical quantity, especially load or deformation, directly into an electrical signal in the initially mentioned sense. 
   While various embodiments in accordance with the present invention have been shown and described, it is understood that the invention is not limited thereto. The present invention may be changed, modified and further applied by those skilled in the art. Therefore, this invention is not limited to the detail shown and described previously, but also includes all such changes and modifications.