A pressure-sensor system having a sensor element and a hermetic housing for the sensor element has a particularly uncomplicated installation, in particular even under aggressive ambient conditions. The housing of this pressure-sensor system includes a first housing part having a housing bottom, and at least one additional housing part. The sensor element is installed on the housing bottom, and the pressure is supplied via an opening in the housing bottom. The at least one additional housing part is disposed above the sensor element and is connected to the first housing part. Apart from this, connecting pins for the electrical contacting of the sensor element are provided. The connecting pins are guided through the additional housing part.

FIELD OF THE INVENTION

The present invention relates to a pressure-sensor system having a sensor element and a hermetic housing for the sensor element. The housing of this pressure-sensor system includes a first housing part having a housing bottom, and at least one additional housing part. The sensor element is installed on the housing bottom, and the pressure is supplied via an opening in the housing bottom. The at least one additional housing part is disposed above the sensor element and connected to the first housing part. Furthermore, the pressure-sensor system includes connecting pins for the electrical contacting of the sensor element.

BACKGROUND INFORMATION

Sensor systems are used for pressure detection in liquid and gaseous media, where they are frequently subjected to aggressive ambient conditions.

In this connection, the sensor element is disposed in a hermetic steel housing, which is made up of a relatively thick-walled base and a relatively thin-walled cover. Base and cover are welded together. An opening is formed in the base, above which the sensor element is installed. Together with a tube connector that connects to the outer side of the housing, this opening forms the hydraulic connection of the sensor system. The electrical connections are implemented in the form of connecting pins, which are likewise guided through the housing base and connected to the sensor element via bonding wires. Accordingly, the electrical connection of the known pressure-sensor system is located on the same housing side as the hydraulic connection.

For this concept, particular precautions must be taken to prevent the electrical connections from coming into contact with the measured medium and thus being chemically attacked. In practice, to this end, the hydraulic connection is extended using a small tube or the like, which is relatively complex in terms of construction and which requires additional components.

SUMMARY OF THE INVENTION

The present invention provides a pressure-sensor system of the type mentioned at the outset, which is distinguished by a particularly uncomplicated installation, in particular, even under aggressive ambient conditions.

According to the present invention, for this purpose, the connecting pins are guided through the additional housing part of the pressure-sensor system, while the pressure is applied via an opening in the housing bottom.

By disposing the connecting pins in this manner, the hydraulic connection and the electrical connection of the pressure-sensor system are formed on different sides of the housing. Therefore, the pressure-sensor system according to the present invention is provided with a hydraulic connection side and an electrical connection side that is separated from the hydraulic connection side. Additional construction elements for the spatial separation of the hydraulic and the electrical connections, such as a small tube for the pressure connection, are therefore unnecessary.

To construct a pressure-sensor system of the type mentioned at the outset, first the sensor element is installed on the housing bottom, namely above the pressure connection opening. Afterward, the other housing parts, such as a cover, are disposed above the sensor element, and connected to the first housing part in order to hermetically seal the housing. If the connecting pins are guided through the cover of the housing according to the present invention, then particular measures are necessary in order to produce an electrical connection between the sensor element and the connecting pins.

To this end, a preferred specific embodiment of the pressure-sensor system according to the present invention includes a circuit substrate, for example, in the form of a printed-circuit board, which is disposed together with the sensor element in the housing. In this variant, the electrical connections of the sensor element are guided to the circuit substrate. If the circuit substrate is installed on the housing bottom along with the sensor element, the electrical connections may simply be guided to the circuit substrate with the aid of bonding wires, before the housing is closed. Additional connecting means are provided for the electrical connection between the circuit substrate and the connecting pins in the housing cover.

In principle, there are different options for implementing an electrical connection between the connecting pins and such a circuit substrate, it being important to note that this connection is established only when the housing parts are joined together or the assembly achieves its final constructive form.

In a first variant, a flex foil is guided from the circuit substrate to the connecting pins as a connecting means. In this case, the electrical connection between the circuit substrate and the connecting pins is produced, i.e., the flex foil is installed, before the housing parts are joined together and mechanically connected to each other. In the process, the flex foil is then folded into the housing.

According to another variant of the present invention, a spring is used as electrical connecting means. The one end of such a spring engages with a connecting pin, and thus is also in electrical contact with the connecting pin. The other end of the spring is then pressed against a corresponding contact surface on the circuit substrate when the housing parts are assembled, thereby producing an electrical contact. For this purpose, as a rule the spring has to be fixed on at least one side. As a connecting means, a leaf spring is advantageously cemented or soldered to the connecting pin and/or to the contact surface, whereby a particularly low-resistance connection is produced.

In a particularly advantageous specific embodiment of the present invention, a spiral spring is used as a connecting means, which is dimensioned in accordance with the connecting pin. The one end of the spiral spring is slipped onto the connecting pin, thereby contacting the outer surface of the connecting pin in a form-locking manner. On the one hand, this press fit fixes the spiral spring, and on the other hand, it produces the electrical contact. The free spring end is pressed against the contact surface on the circuit substrate during assembly of the housing parts. In the process, the spiral spring is compressed over the connecting pin, so that the connecting pin functions as a guide for the spiral spring.

Apart from being used for re-contacting, the circuit substrate may also advantageously be used for disposing additional circuit parts or elements, in particular an EMC capacitor, within the housing. Apart from this, contact surfaces, e.g., needle contact surfaces, may be formed on the circuit substrate for a sensor adjustment. In this case, a sensor adjustment may be performed even before the assembly or closure of the housing, that is, on a lower level of value creation, which means that the number of connecting pins may be reduced.

The use of a metallic housing, in particular of steel, for the pressure-sensor system according to the present invention, proves to be advantageous in several regards. The metallic surface of the housing bottom allows for the sensor element to be installed by soldering or welding. The high-strength connection that results in the process withstands well even the tensile loads that normally occur under the effect of pressure. Apart from this, a reliable, leak-proof connection between the individual housing parts may be produced simply by soldering or welding. In this context, a defined reference pressure, such as a vacuum, for example, may be enclosed in the housing.

DETAILED DESCRIPTION

Pressure-sensor system10shown inFIG. 1includes a sensor element1in the form of a sensor chip11having a glass base12. A diaphragm13is formed in sensor chip11, which diaphragm13is acted upon by pressure via a pressure supply opening14in glass base12. Sensor element1is disposed in a hermetically sealed steel housing2, which in the exemplary embodiment shown here is made up of a housing bottom15and a cover16as an additional housing part. In housing bottom15, a recess17is formed as an installation surface for sensor element1. An opening3is located in the bottom region of recess17. Glass base12of sensor element1is disposed and soldered in this recess17, so that pressure supply opening14is situated above opening3in housing bottom15. Accordingly, housing bottom15forms the hydraulic connection side of pressure-sensor system10. However, the interior of housing2is hermetically sealed due to the pressure-resistant installation of sensor element1above opening3.

Apart from this, a printed-circuit board4is disposed on housing bottom15, which is used for re-contacting sensor element1. For this purpose, the electrical connections of sensor element1are guided to printed-circuit board4with the aid of bonding wires18. Cover16of housing2is disposed above sensor element1and printed-circuit board4, and welded to housing bottom15.

According to the present invention, connecting pins5for the electrical contacting of sensor element1are guided outside through cover16. To this end, connecting pins5were glazed in a pressure-resistant manner. In this instance, the electrical connection between connecting pins5and printed-circuit board4is produced with the aid of a flex foil19, which is guided from printed-circuit board4to connecting pins5. Prior to the assembly of the two housing parts15and16, this flex foil19was on the one hand connected to printed-circuit4and on the other hand to connecting pins5, and during the joining of the two housing parts15and16, it was folded inside housing2, which is illustrated byFIG. 1.

The variant of a pressure-sensor system20according to the present invention shown inFIG. 2also includes a sensor element1having a pressure sensor chip11on a glass base12, which is disposed in a hermetically sealed steel housing2. This housing2is made up of two housing parts21and22. Bottom region211of first housing part21is designed as an installation surface for sensor element1, and has an opening3for applying pressure to sensor diaphragm13. Glass base12of sensor element1is connected to installation surface211in a pressure-resistant manner via a soldered connection23, so that pressure may be applied to sensor diaphragm13via opening3in first housing part21and via pressure supply opening14of glass base12.

Apart from this, an installation surface212for a printed-circuit board4is designed in first housing part21. The electrical connections of sensor element1are guided via bonding wires18to printed-circuit board4, where they also may already be connected to additional circuit elements. Thus, in the exemplary embodiment shown here, printed-circuit board4functions as a substrate for an EMC24. Furthermore, a contact surface25is formed on printed-circuit board4.

Second housing part22forms a cover, which is disposed above sensor element1and printed-circuit board4, and welded to first housing part21. Through holes are formed in this cover22, into which connecting pins5for the electrical contacting of sensor element1are glazed. A leaf spring26is soldered onto the end of a connecting pin5that projects into the interior of the housing. During the assembly of the two housing parts21and22, this leaf spring26is pressed against contact surface25on printed-circuit board4, which is shown inFIG. 2. An electrical connection between connecting pin5and printed-circuit board4is thus produced, via which sensor element1is electrically contacted.

FIG. 2shows pressure-sensor system20in an application as a transmission pressure sensor. In this instance, pressure-sensor system20is installed between base plate41and hydraulic plate42of a transmission. The hydraulic connecting side of pressure-sensor system20is installed in a pressure-resistant manner with the aid of a high-pressure seal43on hydraulic plate42, on which the measured pressure or the measured medium is applied. Due to the structural concept according to the present invention, the electrical connecting side of pressure-sensor system20faces opposite base plate41. Accordingly, in the installed state, connecting pins5may be accessed only from base plate41, where they cannot come into contact with the measured medium. The structural concept according to the present invention thus allows for a simple spatial separation between the hydraulic and the electrical connecting sides in the application.

The structure of pressure-sensor system30shown inFIG. 3corresponds to a large extent to that of pressure-sensor system20inFIG. 2, except for the contacting of connecting pins5. In the case of pressure-sensor system30, a contact surface25is likewise formed on printed-circuit board4disposed in housing2. However, in this instance the electrical connection between connecting pin5and printed-circuit board4is produced with the aid of a spiral spring31, which is slipped onto connecting pin5and fixed on its upper end to connecting pin5in a press fit. A contact region32is formed on the lower free flexible end of spiral spring31, which contact region32is pressed against contact surface25on printed-circuit board4during the assembly of the two housing parts21and22. Thus, an electrical connection between connecting pin5and printed-circuit board4is produced, via which sensor element1is ultimately contacted. In this variant, connecting pin5is thus also used as a support and guide for spiral spring31, in that it fixes spiral spring31and absorbs the lateral force occurring during the compression, in order to avoid a buckling.