Measuring and testing – Engine detonation – Specific type of detonation sensor
Reexamination Certificate
1999-06-02
2001-06-19
Kwok, Helen (Department: 2856)
Measuring and testing
Engine detonation
Specific type of detonation sensor
C073S654000
Reexamination Certificate
active
06247351
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a vibration pickup with a pressure sleeve.
Vibration pickups of the above mentioned general type are known in the art. One of such vibration pickups with a pressure sleeve is disclosed for example in the German patent document DE 195 24 147.9. It is formed as a knock sensor for monitoring the operation of an internal combustion engine in a motor vehicle. The pressure sleeve is joined through an abutment region fixedly to a component which causes vibrations, for example a motor block of the internal combustion engine.
The vibrations to be detected are knock noises of the internal combustion engine during the operation. They are transmitted through a pressure sleeve to a piezo-ceramic disk as a sensor element, with intermediately located contact disks and insulating disks which allow picking up of the signal, so as to form an evaluatable electrical output signal.
This type of mounting or clamping of the sensor element on the pressure sleeve and the mounting of the pressure sleeve on the vibrating component has a great influence on the manufacture. The clamping of the sensor element together with a plurality of individual components, for example with a spring and a seismic mass is performed in the known vibration pickup with a threaded ring which is screwed on the corresponding thread of the pressure sleeve and directly abuts on the seismic mass.
This known threaded ring and the thread is a substantial cost factor on the pressure sleeve and alternative mounting possibilities are needed. All components must be firmly compressed during the occurring accelerations with a defined mechanical pretensioning and must remain this way. When the pretensioning changes, also the characteristic line changes and evaluation becomes more difficult.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a vibration pickup with a pressure sleeve which avoids the disadvantages of the prior art.
In keeping with these objects and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated, in a vibration pickup with a pressure sleeve, in which the seismic mass in a non dismounted condition abuts only partially against the arrangement with the sensor element, and in predetermined ring-shaped regions a distance for arrangement with the sensor element is provided, and after the mounting with overcoming of the distance with the substantially plane abutment of the seismic mass against the arrangement with the sensor element, the axial pretensioning is produced.
When the vibration pickup is designed in accordance with the present invention, it has the advantage that with dispensing with a spring, the required above mentioned axial pretensioning can be provided with optimal pressure distribution on the clamped sensor element of the pressure sleeve of the vibration pickup.
In accordance with the present invention, the seismic mass in non-mounted condition has, in predetermined ring-shaped regions, a simply arrangable distance, such as for example by a conical contour, with respect to the sensor element, or with respect to the intermediately located insulating disk and the contact disk. Since for example with the threaded ring during screwing a pressure for reducing of this distance is applied, the required pressing force for a clamping of the sensor element is produced.
After the mounting, or in other words, after the performed screwing of the threaded ring on the corresponding thread on the pressure sleeve, this side of the seismic mass is located substantially plane. The now applied axial pretensioning for the sensor element is provided by flat relatively identically distributed pressing forces, since first the seismic mass is applied in the regions without a distance, and then under pressure of the threaded ring, the distance must be covered.
With the inventive vibration pickup, the disadvantages of the prior art are avoided with a plane abutment of the seismic mass in the non-mounted condition on the arrangement with the sensor element. In the prior art a high force is applied on the pressure introducing point of the threaded ring or a spring during mounting. After the mounting this can lead to a non uniform force distribution on the abutment surface of the seismic element on the arrangement of the sensor element.
In accordance with a preferable embodiment of the present invention, the seismic mass in the non-mounted condition on the side which is opposite to the arrangement with the sensor element, is provided with an inclined contour in a radial section. The inclined contour has radially inner and radially outer portions.
In order to obtain a uniform pressure distribution in the sensor element, in some cases it is important where a ring-shaped abutment of the threaded ring on the seismic mass is performed. It has to be taken into consideration that the vibration pickup is produced with different long radial expansion of the seismic mass. In many vibrations pickups the radial expansion of the seismic mass is relatively long. Therefore there is a so-called lever action during the ring-shaped abutment of the nut on the seismic mass. If the ring-shaped abutment is somewhat exactly centrally performed on the seismic mass, then the edge regions of the piezo-ceramic disk are somewhat lifted. For this reason, it is advantageous when with a ring-shaped abutment the engagement of the threaded ring on the seismic mass is performed off-center. In particular, it can be performed with offset in direction to the conical formation, or in other words the distance.
In accordance with a further embodiment of the present invention, the seismic mass in the non-mounted condition has a concave corner in the radial section at the side which is opposite to the arrangement of the sensor element. Here in a simple manner also a central abutment of the threaded ring against the seismic mass can be performed. For further averaging of the force transmission the seismic mass can be provided with a corresponding incline or a corresponding contour at the side facing the threaded ring.
The inventive vibration pickup with a conical or concave but same formation of the non mounted seismic mass on the upper and the lower side moreover provides a safety effect. The reason is that a false mounting of the seismic mass during the mounting process is reliably prevented. The abutment of the threaded ring against the seismic mass can be designed differently. The threaded ring can be both plane, or in other words flat, or also ring-shaped and abut against the seismic mass. The objective of the conical or concave formation of the seismic mass is a uniform pressure distribution in the sensor element, for example in a piezo-ceramic disks.
The shape end size of the conical or concave formation of the upper surface of the seismic mass can be determined in a simple manner in connection with the pretensioning to be produced by the threaded ring. With the knock sensor which is utilized in the process, as the vibration pickup, it can be advantageous to provide at the inner side, or in other words in the region of the opening in a pressure sleeve, a height of approximately 0.2 mm.
In accordance with a preferable embodiment of the invention, the component which causes vibration is a motor block of international combustion engine in a motor vehicle.
The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
REFERENCES:
patent: 4944179 (1990-07-01), Komurasaki
patent: 5398540 (1995-03-01), Entenmann et al.
patent: 5440933 (1995-08-01), Brammer et al.
patent: 5739418 (1998-04-01), Hackel et al.
patent: 5798453 (1998-08-01), Brammer et al.
patent: 5872307 (1999-02-01)
Brammer Hartmut
Krebs Holger
Kwok Helen
Robert & Bosch GmbH
Striker Michael J.
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