GB2040472A - Apparatus for Measuring the Rate of Flow of a Medium - Google Patents

Apparatus for Measuring the Rate of Flow of a Medium Download PDF

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Publication number
GB2040472A
GB2040472A GB8000176A GB8000176A GB2040472A GB 2040472 A GB2040472 A GB 2040472A GB 8000176 A GB8000176 A GB 8000176A GB 8000176 A GB8000176 A GB 8000176A GB 2040472 A GB2040472 A GB 2040472A
Authority
GB
United Kingdom
Prior art keywords
temperature
protective layer
polymerization
flow
rate
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB8000176A
Other versions
GB2040472B (en
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Robert Bosch GmbH
Original Assignee
Robert Bosch GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Robert Bosch GmbH filed Critical Robert Bosch GmbH
Publication of GB2040472A publication Critical patent/GB2040472A/en
Application granted granted Critical
Publication of GB2040472B publication Critical patent/GB2040472B/en
Expired legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D1/00—Processes for applying liquids or other fluent materials
    • B05D1/62—Plasma-deposition of organic layers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F2/00—Processes of polymerisation
    • C08F2/46—Polymerisation initiated by wave energy or particle radiation
    • C08F2/52—Polymerisation initiated by wave energy or particle radiation by electric discharge, e.g. voltolisation
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/18—Circuit arrangements for generating control signals by measuring intake air flow
    • F02D41/187—Circuit arrangements for generating control signals by measuring intake air flow using a hot wire flow sensor
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/68—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using thermal effects
    • G01F1/684—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow
    • G01F1/688—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow using a particular type of heating, cooling or sensing element
    • G01F1/69—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow using a particular type of heating, cooling or sensing element of resistive type
    • G01F1/692—Thin-film arrangements
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P5/00—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft
    • G01P5/10—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft by measuring thermal variables
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P5/00—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft
    • G01P5/10—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft by measuring thermal variables
    • G01P5/12—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft by measuring thermal variables using variation of resistance of a heated conductor

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Aviation & Aerospace Engineering (AREA)
  • Organic Chemistry (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Health & Medical Sciences (AREA)
  • Fluid Mechanics (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Measuring Volume Flow (AREA)
  • Testing Resistance To Weather, Investigating Materials By Mechanical Methods (AREA)

Abstract

An apparatus for measuring the rate of flow of a medium especially for measuring the rate of flow of air inducted through the intake duct by an internal combustion engine comprises at least one temperature-dependent resistor (3) formed as a layer (coating) resistor provided with a dielectric, corrosion-resistant, hydrophobic, pinhole-free protective layer (18) which is as thin as possible. The protective layer (18) comprises an organic substance which is precipitated from the vapour phase by polymerization under the action of energy. <IMAGE>

Description

SPECIFICATION Apparatus for Measuring the Rate of Flow of a Medium The present invention relates to an apparatus for measuring the rate of flow of a medium and a method of providing a protective layer on temperature resistor for use in such apparatus.
A measuring probe is known in which a temperature-dependent resistor formed as a layer is in direct contact with a flowing medium. The resistance layer is subject to corrosive attack from the medium and measurement errors are caused by any electrical conductivity of the medium and/or change in the heat transfer resistance.
According to the present invention there is provided an apparatus for measuring the rate of flow of a medium, comprising means defining a flow path, an elongate support extending along the flow path and provided with a coating having a temperature-dependent resistance, and means responsive to variations in the resistance of the coating to provide a signal indicative of the rate of flow of the medium, the coating being provided with a thin corrosion resistant hydrophobic protective layer of dielectric material.
The protective layer may comprise an organic substance which has been precipitated by one of glow polymerization and thermionic emission polymerization from a vapour phase.
The protective layer may comprise a siliconorganic substance.
According to another aspect of the present invention there is provided a method of providing a corrosion resistant hydrophobic protective layer of dielectric material on a temperature-dependent resistor, comprising subjecting the temperaturedependent resistor to a monomeric vapour which is polymerized on the surface of the temperaturedependent resistor from a vapour phase with the assistance of energy from an electrical gas discharge.
The polymerization may be provided by a non self-maintaining gas discharge which is sustained by thermionic emission electrons.
The polymerization may be provided by a selfsustaining glow discharge.
The method may comprise interrupting polymerization at least once.
A thin, such as about 0.1 to 2 4m thick, closed layer possessing extremely small heat transfer resistance can be produced, which inhibits deposits by hydrophoby and therefore provides long-term stability of the measuring probe.
By interrupting, at least once, the polymerization process, nucleus formation (seed formation) during the condensation is repeatedly promoted, so that a pinhole-free layer is formed.
An embodiment of the present invention will now be more particularly described by way of example and with reference to the accompanying drawing in which: Fig. 1 shows a circuit diagram for a measuring probe comprising a temperature-dependent resistor, and Fig. 2 shows a measuring probe provided with a protective layer and disposed in a duct through which medium flows.
In Fig. 1, reference 1 denotes an induction duct of an internal combustion engine, not otherwise shown, into which the air inducted by the internal combustion engine flows in the direction of the arrows 2. In the induction duct 1 there is disposed a temperature-dependent resistor 3, for example a hot-layer resistor, through which the output variable of a controller flows and which at the same time supplies the input variable for the controller. The temperature of the temperaturedependent resistor 3 is set (regulated) by the controller to a fixed value which is higher than the mean air temperature. If the flow rate, that is the quantity of air inducted per unit time, rises, then the temperature-dependent resistor 3 cools down.
This cooling is signalled to the input of the controller, so that the latter raises its output variable in such a way that once again the established temperature becomes set at the temperature-dependent resistor 3. The output variable of the controller regulates the temperature of the temperature-dependent resistor 3 to the predetermined value each time changes occur in the inducted air flow rate, and represents a measure of the inducted air flow rate which is supplied as a measurement signal to a metering circuit for adapting the required fuel flow rate to the quantity of air inducted per unit time.
The temperature-dependent resistor 3 constitutes, together with a resistor 4, a first arm of a bridge, to which there is connected in parallel a second arm of the bridge comprising two fixed resistors 5 and 6. Between the resistors 3 and 4 is a tapping point 7 and between the resistors 5 and 6 a tapping point 8. The two arms of the bridge are connected in parallel at points 9 and 10. The diagonal voltage of the bridge across the points 7 and 8 is supplied to the input of an amplifier 11, to the output terminals of which the points 9 and 10 are connected, so that its output variable supplies the bridge with operating voltage and operating current. The output variable hereinafter designated as actuating variable Us can be tapped across the terminals 12 and 13, as shown in the Figure.The actuating variable Us regulates the metering of the fuel necessary for the sucked-in air in a fuel metering circuit, not shown, of the internal combustion engine. The temperaturedependent resistor 3 is heated by the current flowing through it up to a value at which the input voltage of the amplifier 11, the bridge diagonal voltage, becomes zero or assumes a predetermined value. A specific current then flows from the output of the amplifier into the bridge circuit. If, as a consequence of a change in the flow rate of the inducted air, the temperature of the temperature-dependent resistor 3 changes, then the voltage at the bridge diagonal changes and the amplifier 11 regulates the bridge supply voltage and bridge current to a value for which the bridge is again balanced or detuned in a predetermined manner.The output variable of the amplifier 11 , the control voltages Us, like the current in the temperature-dependent resistor 3, represents a measure of the inducted air flow rate.
For compensating the influence of the temperature of the inducted air on the measured result, it may be advisable to connect into the second arm of the bridge a second resistor 14, around which the inducted air flows. The magnitude of the resistors 5, 6 and 14 should be so selected that the output loss of the temperature-dependent resistor 14 produced by the arm current flowing through it is so small that the temperature of this resistor 14 practically does not change with the changes in the bridge voltage, but is always substantially equal to the temperature of the inducted air flowing past it.
As shown in Fig. 2, the temperature-dependent resistor 3 may be formed as a resistance layer or coating, which is applied by a known process onto one or both sides of a support 17. If the support 17 is made from an electrically conducting material, then an insulating layer, not shown in the drawing, is incorporated between the resistor 3 and the support 1 7. A dielectric, corrosionresistant, pinhole-free, hydrophobic protective layer 1 8 is applied onto the resistance layer 3. The protective layer 18 should if possible, not be thicker than 4,us, preferably 0.5 ym so that the heat transfer between the medium and the resistance layer 3 shall be impeded as little as possible and the measuring probe will therefore respond rapidly to temperature changes.The protective layer preferably is of organic substance, in particular of silicon-organic substance, which is precipitated all round from the vapour phase by radiation polymerization. Hexamethyl disiloxane or hexafluoro-propylene may be used as starting monomers for such polymerization. Starting materials of such a type for the production of a protective layer by polymerization are disclosed in for example DE-OS 2 263 480, DE-AS 2 537 416 and DE-OS 2 625 448. Also disclosed in these specifications are methods for precipitating a layer by polymerization from the vapour phase by means of energy from an electric gas discharge.
Thus the polymerization can be effected by a non self-maintaining gas discharge sustained by thermionic emission electrons, or by a selfsustaining glow discharge. It is particularly advantageous for the polymerization operation to be interrupted at least once, causing nucleus formation to be promoted afresh during condensation and a pinhole-free layer to be formed by multiple condensation.
The above described embodiment has the advantage that the resistance layer, virtually without heat transfer resistance, is protected from corrosive attack by the medium and that measurement errors arising from any electrical conductivity of the medium or from a change in the heat transfer resistance due to deposits are avoided.

Claims (9)

Claims
1. An apparatus for measuring the rate of flow of a medium, comprising means defining a flow path, an elongate support extending along the flow path and provided with a coating having a temperature-dependent resistance, and means responsive to variations in the resistance of the coating to provide a signal indicative of the rate of flow of the medium, the coating being provided with a thin corrosion resistant hydrophobic protective layer of dielectric material.
2. An apparatus as claimed in claim 1, wherein the protective layer comprises an organic substance which has been precipitated by one of glow polymerization and thermionic emission polymerization from a vapour phase.
3. An apparatus as claimed in claim 2, wherein the protective layer comprises a silicon-organic substance.
4. An apparatus for measuring the rate of flow of a medium substantially as hereinbefore described with reference to the accompanying drawings.
5. A method of providing a corrosion-resistant hydrophobic protective layer of dielectric material on a temperature-dependent resistor, comprising subjecting the temperature-dependent resistor to a monomeric vapour which is polymerized on the surface of the temperature-dependent resistor from a vapour phase with the assistance of energy from an electrical gas discharge.
6. A method as claimed in claim 4, wherein the polymerization is provided by a non selfmaintaining gas discharge which is sustained by thermionic emission electrons.
7. A method as claimed in claim 5, wherein the polymerization is provided by a self-sustaining glow discharge.
8. A method as claimed in any one of claims 5 to 7, comprising interrupting polymerization at least once.
9. A method of providing a corrosion-resistant hydrophobic protective layer of dielectric material on a temperature-dependent resistor, substantially as hereinbefore described with reference to the accompanying drawing.
GB8000176A 1979-01-04 1980-01-03 Apparatus for measuring the rate of flow of a medium Expired GB2040472B (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE19792900200 DE2900200A1 (en) 1979-01-04 1979-01-04 MEASURING PROBE WITH PROTECTIVE LAYER AND METHOD FOR PRODUCING A PROTECTIVE LAYER ON A MEASURING PROBE

Publications (2)

Publication Number Publication Date
GB2040472A true GB2040472A (en) 1980-08-28
GB2040472B GB2040472B (en) 1983-05-25

Family

ID=6060045

Family Applications (2)

Application Number Title Priority Date Filing Date
GB8000176A Expired GB2040472B (en) 1979-01-04 1980-01-03 Apparatus for measuring the rate of flow of a medium
GB08215541A Expired GB2108133B (en) 1979-01-04 1982-05-27 Electrical gas discharge polymerization method of coating a resistor

Family Applications After (1)

Application Number Title Priority Date Filing Date
GB08215541A Expired GB2108133B (en) 1979-01-04 1982-05-27 Electrical gas discharge polymerization method of coating a resistor

Country Status (4)

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JP (1) JPS5593021A (en)
DE (1) DE2900200A1 (en)
FR (1) FR2445952B1 (en)
GB (2) GB2040472B (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2179161A (en) * 1985-08-13 1987-02-25 Nippon Soken Direct-heated flow measuring apparatus
EP1083412A1 (en) * 1999-09-07 2001-03-14 Endress + Hauser Gmbh + Co. Device for determining a physical quantity of a fluid or a solid material

Families Citing this family (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6013220A (en) * 1983-07-04 1985-01-23 Esutetsuku:Kk Gas flow sensor and manufacture thereof
DE3326376A1 (en) * 1983-07-22 1985-01-31 Siemens AG, 1000 Berlin und 8000 München METHOD FOR PRODUCING GLIMP POLYMERISATE LAYERS
DE3326377A1 (en) * 1983-07-22 1985-01-31 Siemens AG, 1000 Berlin und 8000 München METHOD FOR PRODUCING GLIMP POLYMERISATE LAYERS
JPS60236025A (en) * 1984-05-09 1985-11-22 Nippon Soken Inc Air flow rate sensor
DE3606849A1 (en) * 1986-03-03 1987-09-10 Vdo Schindling ARRANGEMENT FOR MEASURING THE FLOW RATE
DE3838466C2 (en) * 1988-01-16 1995-11-16 Bosch Gmbh Robert Air mass measuring device and method for producing an air mass measuring device
JP2860126B2 (en) * 1989-12-26 1999-02-24 メージャーメント・テクノロジー・インターナショナル Fluid flow meter
JP2740620B2 (en) * 1993-06-01 1998-04-15 シーケーディ株式会社 Thermal flow meter
ATE316593T1 (en) 1997-06-14 2006-02-15 Secr Defence SURFACE TREATMENT
GB9712338D0 (en) 1997-06-14 1997-08-13 Secr Defence Surface coatings
DE10083897T1 (en) 1999-02-26 2002-06-27 Trikon Holdings Ltd Process for processing a polymer layer
CN1185694C (en) 1999-06-26 2005-01-19 特利康控股有限公司 Method and apparatus for forming film on substrate
JP3782669B2 (en) * 2001-02-28 2006-06-07 株式会社日立製作所 Thermal flow meter
GB0406049D0 (en) 2004-03-18 2004-04-21 Secr Defence Surface coatings

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1010304B (en) * 1955-12-19 1957-06-13 Vyzk A Zkusebni Letecky Ustav Measuring body for measuring the flow velocities of a medium
CH510873A (en) * 1969-07-08 1971-07-31 Mettler Instrumente Ag Electric resistance thermometer
NL7202331A (en) * 1972-01-24 1973-07-26
US3991613A (en) * 1975-03-10 1976-11-16 Corning Glass Works Sensing element for flow meter
DE2625448C3 (en) * 1976-06-05 1986-11-13 Robert Bosch Gmbh, 7000 Stuttgart Method and device for producing a protective layer on the surface of optical reflectors
DE2537416B2 (en) * 1975-08-22 1977-06-30 Robert Bosch Gmbh, 7000 Stuttgart METHOD AND DEVICE FOR THE PRODUCTION OF A PROTECTIVE LAYER ON THE SURFACE OF OPTICAL REFLECTORS

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2179161A (en) * 1985-08-13 1987-02-25 Nippon Soken Direct-heated flow measuring apparatus
US4843882A (en) * 1985-08-13 1989-07-04 Nippon Soken, Inc. Direct-heated flow measuring apparatus having improved sensitivity response speed
GB2179161B (en) * 1985-08-13 1990-04-04 Nippon Soken Direct-heated flow measuring apparatus
EP1083412A1 (en) * 1999-09-07 2001-03-14 Endress + Hauser Gmbh + Co. Device for determining a physical quantity of a fluid or a solid material
US6435025B1 (en) 1999-09-07 2002-08-20 Endress + Hauser Gmbh + Co. Apparatus for determining a physical variable of a liquid or solid medium

Also Published As

Publication number Publication date
DE2900200A1 (en) 1980-07-17
FR2445952A1 (en) 1980-08-01
GB2108133B (en) 1983-10-05
FR2445952B1 (en) 1986-03-14
JPS5593021A (en) 1980-07-15
GB2040472B (en) 1983-05-25
GB2108133A (en) 1983-05-11

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Date Code Title Description
PCNP Patent ceased through non-payment of renewal fee

Effective date: 19930103