GB2205654A

GB2205654A - Pressure measuring device

Info

Publication number: GB2205654A
Application number: GB08811543A
Authority: GB
Inventors: Raymond Ciarlitti; Francois Henry
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1987-06-13
Filing date: 1988-05-16
Publication date: 1988-12-14
Anticipated expiration: 2008-05-16
Also published as: DE3719842A1; GB8811543D0; FR2616543A1; JPS649333A; FR2616543B1; GB2205654B

Description

Pressure measuring device

Prior art

The invention proceeds from a pressure measuring device according to the generic concept of the m ain cLaim. It'is normaL to use resistance strain gauges in pressure measuring devices, but difficuLties often arise in accommodating them. Moreover, it is known to use pres sure ceLLs in thickor thin-fiLm technoLogy, which are based on,the capacitive measuring principLe. They, too, are expensive to use and assembLe.

Advantages of the invention By contrast, the pressure measuring device according to the invention, which has the characteristic features of the main cLaim, has the advantage of being very simpLe and posing no difficuLties concerning its assembLy. Moreover, it works very accurateLy.

Further advantageous forms of the invention foL- Low from the sub cLaims.

D r a w i n g An iLLustrative embodiment of the invention is given in the foLLowing description and drawing. The

Latter shows in Figure 1 a cross section through a pres sure measuring device, in Figures 2 and 3 modifications of the iLLustrative embodiment according to Figure 1, and in Figure 4 an appLication of the pressure measuring device.

Description of the Mustrative embodiments

Figure 1 shows the cross section through a pipe section having a fLat 11. At a certain distance from, and paraLLeL to, the fLat a capacitor eLectrocle 12 is 2 Located, which forms the active pLate of the capacitor (positive poLe). As in this iLLustrative embodiment, it can be composed of a metaL fiLm deposited by vacuum evap oration on a ceramic body 13. This unit is secured by means of an insuLating body 14 which enveLops the unit in a pressure-tight fashion and secures it to the fLat 11.

The fLat produces a thinning A of the pipe waLL on one - side, so that, when a pressure medium fLows through the concentric bore 15 under high pressure, the waLL is clefLected a LittLe. so that the capacitive resistance of the capacitor changes, doing so in proportion to the pressure. The change in the capacitance produced by the sLight clefLection is evaLuated, for exampLe. by a high frequency osciLLating circuit. It is possibLe and expedient to assembLe the osciLLating circuit on the spot from highLy integrated eLectronic components. Such a type of pressure measuring device has a very smaLL design size, onLy one connecting Lead, attaching it is very simpLe. and it is insensitive to temperature and magnetic fieLds and resistant to ageing.

In the Mustrative embodiment according to Fig- ure 2, the active pLate 12 has no ceramic Layer, and is Located much cLoser to the fLat 11. In this way, the sensitivity of the pressure measuring device is inc reased. In the Mustrative embodiment according to Figure 3, the active pLate 12 is stiLL nearer to the fLat, thus producing a stiLL higher sensitivity.

The Mustrative embodiment according to Figure 4 shows an injection nozzLe 20, which is secured to a hoLder 21. On the outer surface of the injection nozzLe are provided two fLats, 11A and 11B, which correspond to the fLat 11 according to the previous Mustrative embodiment. An evaLuation Lead 22 Leads from the active capacitor pLates 12 at each fLat to an eLectronic evaLu ator 23 which is composed, for exampLe. of an osciLLating circuit 24, an osciLLator 25 and a clemoduLator 26.

C L a i m s Pressure measuring device having a cyLindricaL body with a concentric passage through which a pressure medium fLows, especiaLLy a tubuLar body, characterized in that in the region where the pressure measuring device (12 to 14) is Located the cyLindricaL body (10) has a fLat (11) on its outer surface, and that a metaL membrane (12) is Located at a distance to the fLat and forms the active pLate of the pressure measuring device, which takes the form of a capacitor.

2. Device according to CLaim 1, characterized in that the membrane is heLd fast hermeticaLLy in a hoLder (14).

3. Device according to CLaim 1 and/or 2, character- ized in that the membrane takes the form of a metaL fiLm deposited by vacuum evaporation on a ceramic body.

4. Device according to one of CLaims 1 to 3, characterized in that it is Located on an injection noz zLe (20).

5. Device according to one of CLaims 1 to 4, characterized in that there are two fLats (11A and 11B) opposite one another on the tubuLar part, a capacitor being Located at each of them.

6. Device according to one of CLaims 1 to 5, characterized in that the capacitor is connected to an eLectronic evaLuator (23)f having, for exampLe, a high frequency osciLLating circuit (24), an osciLLator (25) and a demoduLator (26).

Any of the pressure measuring devices substantially as herein described with reference of the accompanying drawing.

Published 19S8 at TI.e Patent Of!,A..tae House. eF,72 F.gt Hclbcr;-. London WC1R 4TP P=ther copies meZ,, be obtained frcm The Patent Office, Sales Branc-. St Ya::; Orpington- Kent, BT-t5 3RD Primed by Milltzplex techniq7,;es ltd. SI Maz:,, Cray. Keia. Con. 187.