Measuring and testing – Vehicle drive train – Rear end
Patent
1991-10-29
1994-10-11
Raevis, Robert
Measuring and testing
Vehicle drive train
Rear end
G01M 1500
Patent
active
053536339
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a pressure sensor. More particularly, the present invention relates to a pressure sensor for detecting pressure in a combustion chamber in an internal combustion engine, more particularly in a motor vehicle, in which there is a sensor with a piezoelectrically acting work material, an electrically conducting contact disc, a plunger, an abutment, a diaphragm closing a housing and contacting the plunger and an electrical evaluating circuit in the housing. In such a pressure sensor, which is known from U.S. Pat. No. 4,620,438, the electronic components are arranged on a ceramic plate which is fastened after the abutment in the housing in the longitudinal direction of the pressure sensor. The piezoelectric elements are located on the other side of the abutment. The piezoelectric elements and the electronic components must accordingly be connected with one another in an expensive manner by means of insulated filaments. The overall size of the pressure sensor is accordingly additionally lengthened.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a pressure sensor of the above mentioned general type which avoids the disadvantages of the prior art.
In keeping with these objects and with other which will become apparent hereinafter, one feature of the present invention resides, briefly stated, in that the sensor block and the electrical components of the evaluating circuit are arranged on a ceramic plate which at least partially contacts the abutment, and the components are located on the side of the plate facing the diaphragm.
When the pressure sensor is designed in accordance with the present invention, it has the advantage over the prior art that the electronic components, the piezoelectric element or elements and the plunger located between the piezoelectric elements and the diaphragm are located on a single ceramic plate, a hybrid. Accordingly, simple standard bond techniques which have been proven in practice can be used for connecting the electronic components and the piezoelectric elements. The entire hybrid, including the electronic components and the piezoelectric elements, can be tested already before installation in the sensor housing. Accordingly, a simple assembly of the pressure sensor is possible. In particular, its overall length is shortened. The pressure sensor can accordingly be produced inexpensively. Due to the spatial arrangement, particularly the arrangement on the same hybrid in immediate proximity to one another, practically the same temperature prevails at the electronic components and the piezoelectric elements. Costly steps for temperature compensation can accordingly be dispensed with. In contrast, it is possible to compensate for the systematic temperature curve of the piezoelectric ceramic materials used as piezoelectric elements by means of electronic components. Moreover, there is no conductive electrical connection between the piezoelectric element and the housing, so that a potential-free construction of the sensor is possible and the measurement signal is accordingly transmitted so as to be virtually free of errors.
In accordance with another feature of the present invention the electrical components and the contact discs of the sensor block are connected by means of wire bonds and thick-film conductor paths.
The connection surfaces between the plate, the piezoelectric work material and the contact disc can be glued.
The plate can be composed of Al.sub.2 O.sub.3 and the abutment can be pressed into the housing.
In accordance with still a further feature of the present invention, the abutment can be provided with a bore hole for guiding through an electrical line of the evaluating circuit. The abutment can be provided with a flattened segment for guiding through electrical lines as well.
The plunger can be composed of glass ceramic. The housing can be sealed with a sealant in the area of the sensor block and the electronic components.
The novel features which are considered a
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Benedikt Walter
Herden Werner
Konrad Johann
Kusell Matthias
Schmidt Wolfgang
Raevis Robert
Robert & Bosch GmbH
Striker Michael J.
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