WO1991001896A1 - Pressure sensor for motor vehicle tyres - Google Patents
Pressure sensor for motor vehicle tyres Download PDFInfo
- Publication number
- WO1991001896A1 WO1991001896A1 PCT/DE1990/000381 DE9000381W WO9101896A1 WO 1991001896 A1 WO1991001896 A1 WO 1991001896A1 DE 9000381 W DE9000381 W DE 9000381W WO 9101896 A1 WO9101896 A1 WO 9101896A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- tire
- contact pin
- pressure chamber
- membrane
- sealing ring
- Prior art date
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H9/00—Details of switching devices, not covered by groups H01H1/00 - H01H7/00
- H01H9/02—Bases, casings, or covers
- H01H9/04—Dustproof, splashproof, drip-proof, waterproof, or flameproof casings
- H01H9/047—Dustproof, splashproof, drip-proof, waterproof, or flameproof casings provided with venting means
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
- B60C23/00—Devices for measuring, signalling, controlling, or distributing tyre pressure or temperature, specially adapted for mounting on vehicles; Arrangement of tyre inflating devices on vehicles, e.g. of pumps or of tanks; Tyre cooling arrangements
- B60C23/02—Signalling devices actuated by tyre pressure
- B60C23/04—Signalling devices actuated by tyre pressure mounted on the wheel or tyre
- B60C23/0491—Constructional details of means for attaching the control device
- B60C23/0498—Constructional details of means for attaching the control device for rim attachments
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
- B60C23/00—Devices for measuring, signalling, controlling, or distributing tyre pressure or temperature, specially adapted for mounting on vehicles; Arrangement of tyre inflating devices on vehicles, e.g. of pumps or of tanks; Tyre cooling arrangements
- B60C23/02—Signalling devices actuated by tyre pressure
- B60C23/04—Signalling devices actuated by tyre pressure mounted on the wheel or tyre
- B60C23/0408—Signalling devices actuated by tyre pressure mounted on the wheel or tyre transmitting the signals by non-mechanical means from the wheel or tyre to a vehicle body mounted receiver
Definitions
- the invention is based on a tire pressure sensor for motor vehicles according to the preamble of patent claim 1.
- Such a tire pressure sensor known from DE 35 43 866 A1, enables a leak check of the reference pressure chamber, in which the membrane lifts off from the contact pin used in the reference pressure chamber at the same pressure on both sides.
- the reference pressure chamber is arranged in the forwardly open housing of the tire pressure sensor so that it is completely washed by the air of the tire, so that pressure compensation can take place on the membrane through a leak in the chamber. Flushing the reference pressure chamber with the compressed air in the tire has the disadvantage, however, that moisture can get to the glass bushing of the contact pin of the reference pressure chamber and, under certain circumstances, can cause shunts, which may then bridge the switching path between the membrane and the contact pin.
- an RC resonant circuit of the tire pressure sensor connected to this switching path must be protected against moisture. This is achieved on the one hand by a cover cap with a sealing ring attached to the housing and on the other hand by additional sealing measures with a Sealing ring on the housing base and potting the connections of the reference pressure chamber.
- the aim of the present invention is to protect the RC resonant circuit and the implementation of the contact pin on the reference pressure chamber against moisture in the simplest possible manner, in order to increase the functional reliability of the tire pressure sensor.
- a tire pressure sensor in a tire pressure sensor according to the invention, it is achieved with the characterizing features of claim 1 that, in the installed state of the sensor, the reference pressure chamber is exposed to the air pressure of the tire all around for leakage monitoring, but the contact pin is carried out by a moisture barrier Shunts is protected by penetrating moisture.
- a further advantage is the structurally simplified design of the tire pressure sensor, in which additional measures for sealing the moisture in the RC resonant circuit, such as embedding the connections on the reference pressure chamber in a sealing compound, can be dispensed with.
- a particularly simple constructive solution results from the fact that the free end of the contact pin projects into a space downstream of the semipermeable sealing ring on the underside of the reference pressure chamber and is connected there with an RC oscillating circuit, the space being closed off from the outside by a cover cap , which is attached in a known manner with a simple sealing ring on the edge of the housing.
- a print and This eliminates the need for moisture-proof separation of the reference pressure chamber from the electronic components of the RC resonant circuit.
- the contact pin, toroidal coil and capacitor of the RC resonant circuit are electrically connected to one another via a printed circuit board which is used in the space which is subjected to the tire pressure and is arranged downstream of the semipermeable sealing ring .
- FIG. 1 shows the detail of a vehicle wheel with the tire pressure sensor according to the invention inserted in the rim
- FIG. 2 shows a cross section through the tire pressure sensor according to the invention in an enlarged view.
- FIG. 1 the detail of a motor vehicle wheel is shown in cross section on a reduced scale and is designated by 10. It shows a tire 11 which is attached to a wheel rim 12.
- a tire pressure sensor 13 is screwed into a threaded bore 14 of the wheel rim 12 on an inwardly directed section of the wheel rim 12.
- a signal sensor 15 is attached to the wheel suspension of the vehicle, not shown, the end face of which is directed towards the tire pressure sensor 13 and couples a high-frequency oscillation into the tire pressure sensor 13 when the tire pressure sensor 13 rotates with each revolution of the tire pressure sensor 13 Vehicle wheel 10 comes by.
- the tire pressure sensor 13 damping or no damping of the high-frequency vibration, which is determined in an evaluation circuit 16. If the air pressure is too low, a corresponding signal is output via a display 17.
- the structure of the tire pressure sensor 13 is shown in Figure 2. It consists of a sensor housing 18 made of stainless steel, which has a threaded projection 19 for attachment to the wheel rim 12.
- the sensor housing 18 is open towards the front towards the tire 11.
- a reference pressure chamber 21 is arranged in the sensor housing 18 and is closed off by an electrically conductive membrane 22 towards the tire.
- the membrane 22 acts as a pressure switch with a contact pin 23 which is fastened in the bottom of the reference pressure chamber 21 with a glass bushing 24 in a pressure-tight and electrically insulated manner.
- the contact pin 23 projects right up to the membrane 22, so that there is an air gap between the contact pin 23 and the membrane 22 for leak testing of the reference pressure chamber 21 when the pressure is equalized on both sides of the membrane 22.
- Air or nitrogen is filled into the reference pressure chamber 21 with the required reference pressure via a filling channel 25.
- the filler channel 25 is then closed in a pressure-tight manner by a ball 26 pressed or welded therein.
- a perforated protective cap 27 for protecting the membrane 22 against mechanical damage from the outside is inserted into the housing opening 28 directed towards the tire and is fixed in a ring groove 30 of the sensor housing 18 by molded locking tongues 29.
- a semipermeable sealing ring 31 is inserted, which is made of an air-permeable, moisture-proof material.
- Synthetic fibers or " porous materials whose pores are only permeable to air but do not let moisture through can be used for this purpose.
- a material such as, for example, according to DE 24 33 961 AI can be used for signal horns for moisture-proof pressure equalization.
- the reference pressure chamber 21 in the sensor housing 18 is finally carried out by a plastic support ring 33 on the back of the ring shoulder 20, in which a rotationally symmetrical fastening bracket 34 is anchored, the end of which, after the reference pressure chamber 21 has been inserted into the sensor housing 18, has a glass bushing 24 receiving collar 35 a m bottom of the reference pressure chamber 21 is welded.
- the compressed air in the tire passes through the housing opening 28 and the openings in the protective cap 27 to the membrane 22 and outside around the reference pressure chamber 21 through channels and troughs on the plastic ring 32 which cannot be recognized, to the semipermeable sealing ring 31 and from there via an annular gap between the annular shoulder 20 of the sensor housing 18 and the collar 35 of the reference pressure chamber 21 in a space 36 downstream of the sealing ring 31, in which the free end of the contact pin 23 is connected to an RC resonant circuit.
- the resonant circuit consists of an undetectable capacitor and a ring coil 37, which is arranged on a ferrite body 38.
- the ferrite body 38 is fixed by the plastic support ring 33.
- the contact pin 23, the ring coil 37 and the capacitor of the RC oscillating circuit are electrically connected to one another by connecting parts 40 via a circuit board 39 inserted in the space 36.
- a circuit board 39 inserted in the space 36.
- Outwardly the space 36 downstream of the semipermeable sealing ring 31 is covered by a plastic cover cap 41, the edge 41a of which is fastened to the sensor housing 18 by a flange ring 43 with a rubber sealing ring 42.
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Measuring Fluid Pressure (AREA)
Abstract
A pressure sensor (13) for motor vehicle tyres has a manometric switch for monitoring the tyre pressure, which is actuated by the tyre pressure. The manometric switch comprises a reference pressure chamber (21) which is sealed on the side nearer the tyre by an electrically conductive membrane (22) and carries a contact pin (23). When the air pressure in the tyre is sufficient, the central region of the membrane rests against the contact pin, closing a current circuit. To test for leaks in the reference pressure chamber, the latter is flushed with the compressed air and when the pressure is equalized on both sides of the membrane (22), the membrane (22) is lifted off the contact pin (23). Between the sensor housing (18) and the reference pressure chamber (21) is a semi-permeable sealing ring (31) made of material which is permeable to air and impermeable to moisture, and which therefore prevents moisture from entering the passage (24) through which the contact pin (23) passes into the reference pressure chamber (21).
Description
Reifendrucksensor für KraftfahrzeugeTire pressure sensor for motor vehicles
Stand der TechnikState of the art
Die Erfindung geht aus von einem Reifendrucksensor für Kraftfahr¬ zeuge nach dem Oberbegriff des Patentanspruchs 1.The invention is based on a tire pressure sensor for motor vehicles according to the preamble of patent claim 1.
Ein derartiger, aus der DE 35 43 866 AI bekannter Reifendrucksensor ermöglicht eine Leckprüfung der Referenzdruckkammer, in dem die Mem¬ bran bei beidseitig gleichem Druck von dem in der Referenzdruckkam¬ mer eingesetzten Kontaktstift abhebt. Die Referenzdruckkammer ist dabei in dem nach vorne offenen Gehäuse des Reifendrucksensors so angeordnet, daß sie von der Luft des Reifens vollständig umspült wird, so daß durch eine Leckstelle der Kaπimer ein Druckausgleich an der Membran stattfinden kann. Die Umspülung der Referenzdruckkammer mit der Druckluft im Reifen hat jedoch den Nachteil, daß Feuchtig¬ keit an die Glasdurchführung des Kontaktstiftes der Referenzdruck¬ kammer gelangen kann und unter Umständen Nebenschlüsse verursacht, die dann gegebenenfalls die Schaltstrecke zwischen Membran und Kon¬ taktstift überbrücken. Außerdem muß ein an diese Schaltstrecke ange¬ schlossener RC-Schwingkreis des Reifendrucksensors gegen Feuchtig¬ keit geschützt werden. Dies wird einerseits nach außen durch eine am Gehäuse befestigte Abdeckkappe mit Dichtring erzielt und anderer¬ seits nach innen durch zusätzliche Dichtungsmaßnahmen mit einem
Dichtring am Gehäuseboden und einem Verguß der Anschlüsse der Refe¬ renzdruckkammer bewerkstelligt.Such a tire pressure sensor, known from DE 35 43 866 A1, enables a leak check of the reference pressure chamber, in which the membrane lifts off from the contact pin used in the reference pressure chamber at the same pressure on both sides. The reference pressure chamber is arranged in the forwardly open housing of the tire pressure sensor so that it is completely washed by the air of the tire, so that pressure compensation can take place on the membrane through a leak in the chamber. Flushing the reference pressure chamber with the compressed air in the tire has the disadvantage, however, that moisture can get to the glass bushing of the contact pin of the reference pressure chamber and, under certain circumstances, can cause shunts, which may then bridge the switching path between the membrane and the contact pin. In addition, an RC resonant circuit of the tire pressure sensor connected to this switching path must be protected against moisture. This is achieved on the one hand by a cover cap with a sealing ring attached to the housing and on the other hand by additional sealing measures with a Sealing ring on the housing base and potting the connections of the reference pressure chamber.
Mit der vorliegenden Erfindung wird angestrebt, auf möglichst ein¬ fache Weise den RC-Schwingkreis und die Durchführung des Kontakt¬ stiftes an der Referenzdruckkammer gegen Feuchtigkeit zu schützen, um damit die Funktionssicherheit des Reifendrucksensors zu erhöhen.The aim of the present invention is to protect the RC resonant circuit and the implementation of the contact pin on the reference pressure chamber against moisture in the simplest possible manner, in order to increase the functional reliability of the tire pressure sensor.
Vorteile der ErfindungAdvantages of the invention
Bei einem erfindungsgemäßen Reifendrucksensor wird mit den kenn¬ zeichnenden Merkmalen des Patentanspruchs 1 erreicht, daß im mon¬ tierten Zustand des Sensors die Referenzdruckkammer wie bisher zur Lecküberwachung ringsum dem Luftdruck des Reifens ausgesetzt wird, wobei jedoch die Durchführung des Kontaktstiftes durch eine Feuch¬ tigkeitssperre gegen Nebenschlüsse durch eindringende Feuchtigkeit geschützt wird. Ein weiterer Vorteil ist die konstruktiv verein¬ fachte Ausführung des Reifendrucksensors, bei dem zusätzliche Ma߬ nahmen zur Feuchtigkeitsabdichtung des RC-Schwingkreises, wie das Einbetten der Anschlüsse an der Referenzdruckkammer in eine Dicht¬ masse entfallen können.In a tire pressure sensor according to the invention, it is achieved with the characterizing features of claim 1 that, in the installed state of the sensor, the reference pressure chamber is exposed to the air pressure of the tire all around for leakage monitoring, but the contact pin is carried out by a moisture barrier Shunts is protected by penetrating moisture. A further advantage is the structurally simplified design of the tire pressure sensor, in which additional measures for sealing the moisture in the RC resonant circuit, such as embedding the connections on the reference pressure chamber in a sealing compound, can be dispensed with.
Durch die in den Unteransprüchen angeführten Maßnahmen ergeben sich vorteilhafte Weiterbildungen und Verbesserungen der im Hauptanspruch angegebenen Merkmale. Eine besonders einfache konstruktive Lösung ergibt sich dadurch, daß das freie Ende des Kontaktstiftes in einem dem semipermeablen Dichtring nachgeordneten Raum an der Unterseite der Referenzdruckkammer hineinragt und dort mit einem RC-Schwing¬ kreis verbunden ist, wobei der Raum nach außen von einer Abdeckkappe abgeschlossen ist, welche in bekannter Weise mit einem einfachen Dichtring am Gehäuserand befestigt ist. Eine druck- und
feuchtigkeitsdichte Abtrennung der Referenzdruckkammer von den elek¬ tronischen Bauteilen des RC-Schwingkreises kann dadurch entfallen. Ferner ist es für eine weitgehend maschinelle Herstellung des Rei¬ fendrucksensors vorteilhaft, wenn Kontaktstift, Ringspule und Kon¬ densator des RC-Schwingkreises über eine Leiterplatte miteinander elektrisch verbunden werden, die in dem vom Reifendruck beaufschlag¬ ten, dem semipermeablen Dichtring nachgeordneten Raum eingesetzt ist.The measures specified in the subclaims result in advantageous developments and improvements in the features specified in the main claim. A particularly simple constructive solution results from the fact that the free end of the contact pin projects into a space downstream of the semipermeable sealing ring on the underside of the reference pressure chamber and is connected there with an RC oscillating circuit, the space being closed off from the outside by a cover cap , which is attached in a known manner with a simple sealing ring on the edge of the housing. A print and This eliminates the need for moisture-proof separation of the reference pressure chamber from the electronic components of the RC resonant circuit. Furthermore, it is advantageous for a largely mechanical manufacture of the tire pressure sensor if the contact pin, toroidal coil and capacitor of the RC resonant circuit are electrically connected to one another via a printed circuit board which is used in the space which is subjected to the tire pressure and is arranged downstream of the semipermeable sealing ring .
Zeichnungdrawing
Ein Ausführungsbeispiel der Erfindung ist in der Zeichnung darge¬ stellt und in der nachfolgenden Beschreibung näher erläutert. Es zeigen Figur 1 den Ausschnitt eines Fahrzeugrades mit in der Felge eingesetztem erfindungsgemäßen Reifendrucksensor und Figur 2 einen Querschnitt durch den erfindungsgemäßen Reifendrucksensor in ver¬ größerter Darstellung.An embodiment of the invention is shown in the drawing and explained in more detail in the following description. FIG. 1 shows the detail of a vehicle wheel with the tire pressure sensor according to the invention inserted in the rim, and FIG. 2 shows a cross section through the tire pressure sensor according to the invention in an enlarged view.
Beschreibung des AusführungsbeispielsDescription of the embodiment
In Figur 1 ist der Ausschnitt eines Kraftfahrzeugrades in verklei¬ nertem Maßstab im Querschnitt dargestellt und mit 10 bezeichnet. Er zeigt einen Reifen 11, der auf einer Radfelge 12 befestigt ist. An einem nach innen gerichteten Abschnitt der Radfelge 12 ist ein Rei¬ fendrucksensor 13 in einer Gewindebohrung 14 der Radfelge 12 einge¬ schraubt. In geringem Abstand dazu ist im Bereich des Reifendruck¬ sensors 13 an der nicht dargestellten Radaufhängung des Fahrzeugs ein Signalaufnehmer 15 befestigt, dessen Stirnseite zum Reifendruck¬ sensor 13 hin gerichtet ist und eine hochfrequente Schwingung in den Reifendrucksensor 13 einkoppelt, wenn dieser bei jeder Umdrehung des Fahrzeugrades 10 vorbeikommt. Abhängig vom Luftdruck im Reifen 11
bewirkt der Reifendrucksensor 13 eine Bedämpfung bzw. keine Bedämp- fung der hochfrequenten Schwingung, was in einer Auswerteschaltung 16 ermittelt wird. Bei zu geringem Luftdruck wird ein entsprechendes Signal über eiώe Anzeige 17 ausgegeben.In FIG. 1, the detail of a motor vehicle wheel is shown in cross section on a reduced scale and is designated by 10. It shows a tire 11 which is attached to a wheel rim 12. A tire pressure sensor 13 is screwed into a threaded bore 14 of the wheel rim 12 on an inwardly directed section of the wheel rim 12. At a short distance from it, in the area of the tire pressure sensor 13, a signal sensor 15 is attached to the wheel suspension of the vehicle, not shown, the end face of which is directed towards the tire pressure sensor 13 and couples a high-frequency oscillation into the tire pressure sensor 13 when the tire pressure sensor 13 rotates with each revolution of the tire pressure sensor 13 Vehicle wheel 10 comes by. Depending on the air pressure in the tire 11 causes the tire pressure sensor 13 damping or no damping of the high-frequency vibration, which is determined in an evaluation circuit 16. If the air pressure is too low, a corresponding signal is output via a display 17.
Der Aufbau des Reifendrucksensors 13 ist in Figur 2 dargestellt. Er besteht aus einem Sensorgehäuse 18 aus Edelstahl, das einen Gewinde- ansatz 19 zur Befestigung an der Radfelge 12 aufweist. Das Sensor¬ gehäuse 18 ist nach vorne zum Reifen 11 hin offen. Im mittleren Be¬ reich des Sensorgehäuses 18 befindet sich innen eine breite Ring¬ schulter 20. In dem Sensorgehäuse 18 ist eine Referenzdruckkammer 21 angeordnet, die zum Reifen hin durch eine elektrisch leitende Mem¬ bran 22 abgeschlossen ist. Die Membran 22 wirkt als Druckschalter mit einem Kontaktstift 23 zusammen, der im Boden der Referenzdruck¬ kammer 21 mit einer Glasdurchführung 24 druckdicht und elektrisch isoliert befestigt ist. Der Kontaktstift 23 ragt dabei bis dicht unter die Membran 22, so daß zur Leckprüfung der Referenzdruckkammer 21 bei Druckausgleich auf beiden Seiten der Membran 22 zwischen dem Kontaktstift 23 und der Membran 22 ein Luftspalt liegt. Über einen Einfüllkanal 25 wird Luft oder Stickstoff in die Referenzdruckkammer 21 mit dem erforderlichen Referenzdruck eingefüllt. Anschließend wird der Einfüllkanal 25 durch eine darin eingepreßte oder ver¬ schweißte Kugel 26 druckdicht verschlossen. Eine durchbrochene Schutzkappe 27 zum Schutz der Membran 22 gegen eine mechanische Be¬ schädigung von außen ist in die zum Reifen hin gerichtete Gehäuse¬ öffnung 28 eingesetzt und wird durch angeformte Rastzungen 29 in einer Ringnut 30 des Sensorgehäuses 18 fixiert.The structure of the tire pressure sensor 13 is shown in Figure 2. It consists of a sensor housing 18 made of stainless steel, which has a threaded projection 19 for attachment to the wheel rim 12. The sensor housing 18 is open towards the front towards the tire 11. In the middle region of the sensor housing 18 there is a wide annular shoulder 20 inside. A reference pressure chamber 21 is arranged in the sensor housing 18 and is closed off by an electrically conductive membrane 22 towards the tire. The membrane 22 acts as a pressure switch with a contact pin 23 which is fastened in the bottom of the reference pressure chamber 21 with a glass bushing 24 in a pressure-tight and electrically insulated manner. The contact pin 23 projects right up to the membrane 22, so that there is an air gap between the contact pin 23 and the membrane 22 for leak testing of the reference pressure chamber 21 when the pressure is equalized on both sides of the membrane 22. Air or nitrogen is filled into the reference pressure chamber 21 with the required reference pressure via a filling channel 25. The filler channel 25 is then closed in a pressure-tight manner by a ball 26 pressed or welded therein. A perforated protective cap 27 for protecting the membrane 22 against mechanical damage from the outside is inserted into the housing opening 28 directed towards the tire and is fixed in a ring groove 30 of the sensor housing 18 by molded locking tongues 29.
Zwischen dem Boden der Referenzdruckkammer 21 und der RjLngschulter 20 des Sensorgehäuses 18 ist ein semipermeabler Dichtring 31 einge¬ setzt, der aus einem luftdurchlässigen, feuchtigkeitsdichten Mate-
rial besteht. Verwendbar hierfür sind synthetische Faserstoffe oder "poröse Werkstoffe, deren Poren lediglich luftdurchlässig sind, Feuchtigkeit jedoch nicht durchlassen. Verwendbar ist hier auch ein Material, wie es z.B, nach der DE 24 33 961 AI bei Signalhörnern zum feuchtigkeitsdichten Druckausgleich verwendet wird. Um den semiper¬ meablen Dichtring 31 nicht zu stark zusammenzupressen, liegt die Referenzdruckkammer 21 auf einem Kunststoffring 32 an der Ring¬ schulter 20 des Sensorgehäuses 18 auf. Die Vorspannung für den ela¬ stischen Dichtring 31 ergibt sich dabei durch die geringere Stärke des Kunststoffrings 32. Das Festspannen der Re erenzdruckkammer 21 im Sensorgehäuse 18 erfolgt schließlich durch einen Tragring 33 aus Kunststoff an der Rückseite der Ringschulter 20, in dem ein rota¬ tionssymmetrischer Befestigungswinkel 34 verankert ist, dessen Ende nach dem Einsetzen der Referenzdruckkammer 21 in das Sensorgehäuse 18 mit einem die Glasdurchführung 24 aufnehmenden Kragen 35 am Boden der Referenzdruckkammer 21 verschweißt ist.Between the bottom of the reference pressure chamber 21 and the shoulder 20 of the sensor housing 18 a semipermeable sealing ring 31 is inserted, which is made of an air-permeable, moisture-proof material. rial exists. Synthetic fibers or " porous materials whose pores are only permeable to air but do not let moisture through can be used for this purpose. A material such as, for example, according to DE 24 33 961 AI can be used for signal horns for moisture-proof pressure equalization. To the semiper ¬ not to press too much together, the reference pressure chamber 21 rests on a plastic ring 32 on the ring shoulder 20 of the sensor housing 18. The preload for the elastic sealing ring 31 results from the lower thickness of the plastic ring 32. The tightening The reference pressure chamber 21 in the sensor housing 18 is finally carried out by a plastic support ring 33 on the back of the ring shoulder 20, in which a rotationally symmetrical fastening bracket 34 is anchored, the end of which, after the reference pressure chamber 21 has been inserted into the sensor housing 18, has a glass bushing 24 receiving collar 35 a m bottom of the reference pressure chamber 21 is welded.
Die Druckluft im Reifen gelangt über die Gehäuseöffnung 28 und den Durchbrüchen der Schutzkappe 27 zur Membran 22 und außen um die Re¬ ferenzdruckkammer 21 herum durch nicht erkennbare Kanäle und Mulden am Kunststoffring 32 bis zum semipermeablen Dichtring 31 und von dort über einen Ringspalt zwischen der Ringschulter 20 des Sensor¬ gehäuses 18 und dem Kragen 35 der Referenzdruckkammer 21 in einem dem Dichtring 31 nachgeordneten Raum 36, in dem das freie Ende des Kontaktstiftes 23 mit einem RC-Schwingkreis verbunden ist. Der Schwingkreis besteht aus einem nicht erkennbaren Kondensator und einer Ringspule 37, die auf einem Ferritkörper 38 angeordnet ist. Der Ferritkörper 38 wird vom Kunststofftragring 33 fixiert. Über eine im Raum 36 eingesetzte Leiterplatte 39 sind der Kontaktstift 23, die Ringspule 37 und der Kondensator des RC-Schwingkreises durch Anschlußteile 40 miteinander elektrisch verbunden. Nach außen hin
ist der dem semipermeablen Dichtring 31 nachgeordnete Raum 36 von einer Abdeckkappe 41 aus Kunststoff abgedeckt, deren Rand 41a mit einem Gu midichtring 42 am Sensorgehäuse 18 durch einen Bördelring 43 befestigt ist.
The compressed air in the tire passes through the housing opening 28 and the openings in the protective cap 27 to the membrane 22 and outside around the reference pressure chamber 21 through channels and troughs on the plastic ring 32 which cannot be recognized, to the semipermeable sealing ring 31 and from there via an annular gap between the annular shoulder 20 of the sensor housing 18 and the collar 35 of the reference pressure chamber 21 in a space 36 downstream of the sealing ring 31, in which the free end of the contact pin 23 is connected to an RC resonant circuit. The resonant circuit consists of an undetectable capacitor and a ring coil 37, which is arranged on a ferrite body 38. The ferrite body 38 is fixed by the plastic support ring 33. The contact pin 23, the ring coil 37 and the capacitor of the RC oscillating circuit are electrically connected to one another by connecting parts 40 via a circuit board 39 inserted in the space 36. Outwardly the space 36 downstream of the semipermeable sealing ring 31 is covered by a plastic cover cap 41, the edge 41a of which is fastened to the sensor housing 18 by a flange ring 43 with a rubber sealing ring 42.
Claims
1. Reifendrucksensor für Kraftfahrzeuge mit einem am Umfang einer Radfelge zu befestigenden, vom Reifendruck zu betätigenden Druck¬ schalter zur Reifendrucküberwachung, der eine Referenzdruckkammer aufweist, welche in einem zum Reifen hin offenen Sensorgehäuse so angeordnet ist, daß sie ringsum von der Druckluft im Reifen zu um¬ spülen ist und die zum Reifen hin durch eine elektrisch leitende Membran abgeschlossen ist, welche mit einem durch die Referenzdruck¬ kammer elektrisch isoliert hindurchgeführten Kontaktstift in der Weise zusammenwirkt, daß zur Leckprüfung der Referenzdruckkammer bei gleichem Druck an beiden Seiten der Membran zwischen dem Kontakt¬ stift und der Membran ein Luftspalt liegt, dadurch gekennzeichnet, daß zur Feuchtigkeitsabdichtung der Durchführung (24) des Kontakt¬ stiftes (23) ein semipermeabler Dichtring (31) aus einem luftdurch¬ lässigen, feuchtigkeitsdichten Material zwischen dem Sensorgehäuse (18) und der Referenzdruckkammer (21) eingesetzt ist.1. Tire pressure sensor for motor vehicles with a pressure switch to be attached to the circumference of a wheel rim and operated by the tire pressure for tire pressure monitoring, which has a reference pressure chamber which is arranged in a sensor housing which is open towards the tire so that it is surrounded by the compressed air in the tire is rinsed around and which is sealed towards the tire by an electrically conductive membrane which interacts with a contact pin which is electrically insulated through the reference pressure chamber in such a way that for leak testing of the reference pressure chamber at the same pressure on both sides of the membrane between the contact ¬ pin and the membrane is an air gap, characterized in that for moisture sealing the bushing (24) of the contact pin (23) a semipermeable sealing ring (31) made of an air-permeable, moisture-proof material between the sensor housing (18) and the reference pressure chamber (21) used t is.
2. Reifendrucksensor nach Anspruch 1, dadurch gekennzeichnet, daß das freie Ende des Kontaktstiftes (23) in einen dem semipermeablen Dichtring (31) nachgeordneten Raum (36) hineinragt und dort mit einem RC-Schwingkreis verbunden ist, der nach außen von einer mit einem einfachen Dichtring (42) am Sensorgehäuse (18) befestigten Abdeckkappe (41) verschlossen ist. 2. Tire pressure sensor according to claim 1, characterized in that the free end of the contact pin (23) protrudes into a space (36) downstream of the semipermeable sealing ring (31) and is connected there to an RC resonant circuit which is connected to the outside by one simple sealing ring (42) on the sensor housing (18) attached cover cap (41) is closed.
3. Reifendrucksensor nach Anspruch 2, dadurch gekennzeichnet, daß der Kontaktstift (23) sowie eine Ringspule (37) und ein Kondensator des RC-Schwingkreises über eine in den vom Reifendruck beaufschlag¬ ten, dem semipermeablen Dichtring (31) nachgeordneten Raum (36) ein¬ gesetzte Leiterplatte (39) miteinander elektrisch verbunden sind.3. Tire pressure sensor according to claim 2, characterized in that the contact pin (23) as well as a ring coil (37) and a capacitor of the RC resonant circuit via a space (36) downstream of the tire pressurized by the semipermeable sealing ring (31). inserted circuit board (39) are electrically connected to one another.
4. Reifendrucksensor nach Anspruch 3, dadurch gekennzeichnet, daß die Vorspannung des semipermeablen Dichtringes (31) durch die gerin¬ gere Stärke eines daneben angeordneten Kunststoffringes (32) be¬ stimmt ist. 4. Tire pressure sensor according to claim 3, characterized in that the bias of the semi-permeable sealing ring (31) is determined by the lower thickness of an adjacent plastic ring (32).
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE3926245A DE3926245A1 (en) | 1989-08-09 | 1989-08-09 | TIRE PRESSURE SENSOR FOR MOTOR VEHICLES |
| DEP3926245.6 | 1989-08-09 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| WO1991001896A1 true WO1991001896A1 (en) | 1991-02-21 |
Family
ID=6386759
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/DE1990/000381 WO1991001896A1 (en) | 1989-08-09 | 1990-05-25 | Pressure sensor for motor vehicle tyres |
Country Status (2)
| Country | Link |
|---|---|
| DE (1) | DE3926245A1 (en) |
| WO (1) | WO1991001896A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0636502A1 (en) * | 1993-07-29 | 1995-02-01 | Bridgestone Corporation | Air pressure sensor for tire and method of production thereof |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB0516100D0 (en) * | 2005-08-05 | 2005-09-14 | Beru F1 Systems Ltd | A wheel sensor |
| US8122765B2 (en) † | 2006-06-07 | 2012-02-28 | Kistler Holding, Ag | Membrane protection for a sensor having a membrane, and sensor having a membrane and membrane protection |
| CN110715764B (en) * | 2019-10-24 | 2021-05-25 | 中互电气(江苏)有限公司 | Sensor with strong moisture-proof capability |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2433961A1 (en) * | 1974-07-15 | 1976-02-05 | Bosch Gmbh Robert | SIGNAL HORN, IN PARTICULAR FOR MOTOR VEHICLES |
| FR2461248A1 (en) * | 1979-07-03 | 1981-01-30 | Bridgestone Tire Co Ltd | PRESSURE SENSITIVE SWITCH DEVICE FOR RESONANCE CIRCUIT OF PRESSURE DROP DETECTOR APPARATUS IN PNEUMATIC |
| DE3437901A1 (en) * | 1983-10-21 | 1985-05-15 | Kabushiki Kaisha Tokai Rika Denki Seisakusho, Aichi | PRESSURE SWITCH |
| DE3543866A1 (en) * | 1985-12-12 | 1987-06-19 | Bosch Gmbh Robert | TIRE PRESSURE SENSOR FOR MOTOR VEHICLES |
| WO1988003879A1 (en) * | 1986-11-20 | 1988-06-02 | Robert Bosch Gmbh | Inflation pressure sensor for motor vehicles |
-
1989
- 1989-08-09 DE DE3926245A patent/DE3926245A1/en not_active Withdrawn
-
1990
- 1990-05-25 WO PCT/DE1990/000381 patent/WO1991001896A1/en unknown
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2433961A1 (en) * | 1974-07-15 | 1976-02-05 | Bosch Gmbh Robert | SIGNAL HORN, IN PARTICULAR FOR MOTOR VEHICLES |
| FR2461248A1 (en) * | 1979-07-03 | 1981-01-30 | Bridgestone Tire Co Ltd | PRESSURE SENSITIVE SWITCH DEVICE FOR RESONANCE CIRCUIT OF PRESSURE DROP DETECTOR APPARATUS IN PNEUMATIC |
| DE3437901A1 (en) * | 1983-10-21 | 1985-05-15 | Kabushiki Kaisha Tokai Rika Denki Seisakusho, Aichi | PRESSURE SWITCH |
| DE3543866A1 (en) * | 1985-12-12 | 1987-06-19 | Bosch Gmbh Robert | TIRE PRESSURE SENSOR FOR MOTOR VEHICLES |
| WO1988003879A1 (en) * | 1986-11-20 | 1988-06-02 | Robert Bosch Gmbh | Inflation pressure sensor for motor vehicles |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0636502A1 (en) * | 1993-07-29 | 1995-02-01 | Bridgestone Corporation | Air pressure sensor for tire and method of production thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| DE3926245A1 (en) | 1991-02-14 |
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