DE102005057574A1 - Hot-film air mass sensor for measuring air mass flow, has sensor surface, and gradient field producing device that is formed to produce electric field with field gradient, where electric field partially penetrates air mass flow - Google Patents

Hot-film air mass sensor for measuring air mass flow, has sensor surface, and gradient field producing device that is formed to produce electric field with field gradient, where electric field partially penetrates air mass flow

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Publication number
DE102005057574A1
DE102005057574A1 DE200510057574 DE102005057574A DE102005057574A1 DE 102005057574 A1 DE102005057574 A1 DE 102005057574A1 DE 200510057574 DE200510057574 DE 200510057574 DE 102005057574 A DE102005057574 A DE 102005057574A DE 102005057574 A1 DE102005057574 A1 DE 102005057574A1
Authority
DE
Germany
Prior art keywords
air mass
electrode
gradient
film air
mass meter
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.)
Pending
Application number
DE200510057574
Other languages
German (de)
Inventor
Axel Franke
Christoph Gmelin
Bernhard Opitz
Erhard Renninger
Klaus Reymann
Ulrich Wagner
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
Priority to DE200510057574 priority Critical patent/DE102005057574A1/en
Publication of DE102005057574A1 publication Critical patent/DE102005057574A1/en
Pending legal-status Critical Current

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Classifications

    • GPHYSICS
    • G01MEASURING; TESTING
    • G01FMEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through the meter in a continuous flow
    • G01F1/68Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through the meter in a continuous flow by using thermal effects
    • G01F1/684Structural arrangements; Mounting of elements, e.g. in relation to fluid flow
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01FMEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through the meter in a continuous flow
    • G01F1/68Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through the meter in a continuous flow by using thermal effects
    • G01F1/684Structural arrangements; Mounting of elements, e.g. in relation to fluid flow
    • G01F1/6842Structural arrangements; Mounting of elements, e.g. in relation to fluid flow with means for influencing the fluid flow
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01FMEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F15/00Details of, or accessories for, apparatus of the preceding groups insofar as such details or appliances are not adapted to particular types of such apparatus
    • G01F15/12Cleaning arrangements; Filters

Abstract

It becomes a hot film air mass meter (110) for measuring an air mass flow, in particular in the intake tract (112) of an internal combustion engine proposed. The hot-film air mass meter (110) has a sensor surface (132) which can be overflowed by the air mass flow on. Furthermore, the hot film air mass meter (110) has a gradient field generating device (134), wherein the gradient field generating device (134) is configured, around an air mass flow at least partially enforcing electric field (148) with a field gradient.

Description

  • State of technology
  • at many processes, for example in the field of process engineering, Chemistry or mechanical engineering, must define a gas mass, in particular an air mass fed become. Which includes in particular combustion processes, which under controlled conditions expire. An important example is the combustion of fuel in internal combustion engines of motor vehicles, in particular with following catalytic emission control. For measuring the air mass flow rate Different types of sensors are used.
  • One type of sensor known from the prior art is the so-called hot film air mass meter (HFM), which is used, for example, in US Pat DE 196 01 791 A1 in one embodiment. Such a hot-film air mass meter usually uses a sensor chip which has a thin sensor membrane, for example a silicon sensor chip. On the sensor membrane is typically arranged at least one heating resistor, which is surrounded by two or more temperature measuring resistors (temperature sensors). In an air flow, which is guided over the membrane, the temperature distribution changes, which in turn can be detected by the temperature measuring resistors and can be evaluated by means of a control and evaluation circuit. Thus, for example, from a difference in resistance of the temperature measuring resistors, an air mass flow can be determined. Various other variants of this type of sensor are known in the art.
  • An example from DE 101 11 840 C2 The known problem with this type of sensor is that frequent contamination of the sensor element may occur, for example contamination by oil, other liquids or other types of contaminants. The sensor chip is usually used directly in the intake tract of the internal combustion engine or in a bypass to the intake tract of the internal combustion engine. In this case, oil may be deposited on the sensor chip and in particular on the sensor membrane during operation of the internal combustion engine. This oil precipitate can lead to an undesired influence of the measurement signal of the sensor, in particular since an oil film acts on the surface of the sensor on the thermal conductivity of the surface, which leads to the falsification of the measurement signals.
  • The oil contamination can continue also during or shortly after switching off the internal combustion engine, For example, a diesel engine occur. This is special then the case, if after switching off the internal combustion engine one in a crankcase existing overpressure over one Crankcase ventilation in the intake of the internal combustion engine (and thus, for example also in the bypass channel of the hot film air mass meter) degrades. In this case, oil vapor or oil mist is often carried. This oil mist beats at least partially on the sensor chip as a contamination film down and thus causes in particular when turning on the internal combustion engine again a significant measurement signal interference.
  • The DE 101 11 840 C2 proposes a method of preventing soiling on a sensor chip using an auxiliary heater. The sensor chip has a sensor area and an additional heater arranged outside the sensor area. This additional heater is electrically heated so that in the area of the additional heater thermal gradient vortices occur, which lead to precipitation of the contaminants of the flowing medium in the region of the additional heater away from the region of the sensor area.
  • The in the DE 101 11 840 C2 However, the arrangement disclosed and the method disclosed are only of limited suitability for solving the problem of contamination which, as described, is based on several effects. In particular, there is the problem that the oil precipitates now predominantly occur away from the sensor area, but still on the sensor chip itself. If large amounts of contamination accumulate, they can be driven onto the sensor area, for example by air turbulence. Furthermore solves the in the DE 101 11 840 C2 described arrangement also not the above problem that contaminations form especially after switching off the internal combustion engine.
  • epiphany the invention
  • It Therefore, a hot-film air mass meter for Measurement of an air mass flow, in particular in the intake tract of a Internal combustion engine, which proposed the disadvantages prevents the known from the prior art devices. The hot film air mass meter is universally applicable, but is particularly optimized for Measurement of an air mass flow with a flow velocity between 0 and 60 m / s.
  • The hot-film air mass meter has a sensor surface overflowed by the air mass flow, for example a chip surface of a sensor chip as known from the prior art. In principle, various types of Heißfileinuftmassenmessern and sensor can be insert chips.
  • One The basic idea of the present invention is an oil contamination the sensor surface by applying an electric field with a field gradient to reduce or avoid. This is done by a gradient field generating device, which is an air mass flow at least partially enforcing generated electric field with a field gradient. Especially this electric field should be arranged with the field gradient in the vicinity of the sensor surface be.
  • In the electric field, oil droplets contained in the air mass flow are electrically polarized. If the oil droplet is polarized, it acts like a dipole. On an electric dipole with a dipole moment p → the force acts in an electric gradient field
    Figure 00030001
  • Here, E → denotes the electric field vector and the components p x , p y , p z the individual space components of the electric dipole moment of the oil droplet. Overall, therefore, a net force acts on the oil droplet when an electric field gradient is present. The stronger this electric field gradient is, the greater is this force. The net force can be exploited to drive away oil droplets from the sensor surface to prevent contamination.
  • If the air mass flow flows with a main flow direction is so it is advantageous, the electric field substantially perpendicular to the main flow direction align. That way to use the power to the electric dipoles optimally.
  • The Gradient field generating device may in particular at least Have a capacitor, in particular a capacitor with at least one large-area electrode and at least one small electrode. The electrode surface of the at least one large-area electrode should to be taller as the electrode surface the at least one small electrode, preferably at least a factor 2, more preferably at least a factor of 3. This can be done, for example, that the at least one small electrode at least one point-shaped electrode, in particular an electrode tip, and / or at least one line-shaped electrode, in particular a wire electrode, whereas the at least a large-area electrode for example, one of the at least one small electrode opposite Electrode area, can have.
  • Becomes a sensor chip with an at least partially electrically conductive chip carrier (z. B. a carrier plate) used, so also the chip carrier itself an electrode of the form at least one capacitor. This chip carrier opposite then arranged, for example, a point or line-shaped counter electrode be. That way directly above the sensor surface form an electric field with a strong field gradient.
  • In In practice, the field gradient is due to the boundary conditions of the hot film air mass meter, in particular by given geometries, as well as by the available ones be limited to manageable voltages. In this respect, an indication of a minimum field gradients not possible and a design of a theoretically optimized gradient field generation device is difficult in practice.
  • In In practice, a geometry has proven itself in which at least two oppositely charged electrodes of a capacitor at a distance between 1 and 10 mm, in particular between 2 and 5 mm are. Between the oppositely charged electrodes is an electric Voltage in a range between 10 V and 10 kV, in particular between 100 V and 5 kV, and more preferably between 1 kV and 2.5 kV, applied. For example, the Heißfileinuftmassenmesser a flow channel comprise, in particular a bypass channel, wherein at least one of Electrodes are applied to a wall of the flow channel is. Under the above-mentioned "main flow direction" is respectively the main transport direction of the air mass flow at the respective location in the flow channel to understand, taking into account each local turbulence should stay. For example, conductive coatings, For example, silver conductive paint, or used as separate metals be, for example, metal foils. Also, for example Use plastic components, which are subsequently metallized, for example by means of an MID technique (MID: molded interconnect device, injection-molded circuit carriers) such as z. As laser structuring or hot stamping.
  • The hot-film air mass meter according to the invention in one of the variants described has proven to be well suited in practice to keep contamination away from the sensor surface. The problems of the prior art devices described above do not occur with the hot film air mass meter of the present invention. In particular, in the hot-film air mass meter according to the invention, no oil deposits are deposited in the vicinity of the sensor surface, which are then exposed to the air flow through the air mass flow Sensor surface could be worn. In this way, a particularly robust and reliable prevention of contamination is given.
  • Of the hot-film air mass meter according to the invention let yourself both during use the operation of the internal combustion engine as well (alternatively or additionally) after switching off the internal combustion engine. So be in operation the internal combustion engine oil contamination efficiently kept away from the sensor surface in the air mass flow. To the above-described problem of oil diffusion after shutdown to counter the internal combustion engine, will continue to be a process proposed, which uses the Heißfileinuftmassenmesser invention. In the method according to the invention becomes the gradient field generation device during a tracking period after switching off the internal combustion engine further actuated. Consequently is also after switching off the internal combustion engine, an electric Field generated with a field gradient.
  • there can also the electric fields and / or the field gradients during the Operation of the internal combustion engine and after switching off the internal combustion engine differ. Other schemes are conceivable, for example a scheme in which exclusively after switching off an electric Field is generated with a field gradient, whereas during the Operation of the internal combustion engine generates no such field becomes. The duration of the follow-up period is preferably between 5 Seconds and 10 minutes, especially between 5 seconds and 5 Minutes, and more preferably between 10 seconds and 3 minutes. Such trailing periods have proven to be suitable, an oil contamination effectively counteract by the described diffusion effects.
  • drawing
  • Based the drawing, the invention is explained in more detail below.
  • It shows:
  • 1 a Heißfileinuftmassenmesser used in the intake of an internal combustion engine;
  • 2 an open Heißfileinuftmassenmesser in plan view;
  • 3 a section through a bypass channel of the Heißfileinuftmassenmessers according to 2 with a wire-shaped small electrode as seen from below;
  • 4 the device according to 3 in the direction of the side;
  • 5 a lid part of the Heißfileinuftmassenmessers according to the embodiment in the 3 and 4 ; and
  • 6 one to the 3 to 5 alternative embodiment with an electrode tip.
  • Ausführungseispiele
  • In 1 is an example of a hot film air mass meter 110 shown, which in an intake 112 an internal combustion engine is used. Such hot film air mass meter 110 are commercially available. The hot film air mass meter 110 is designed to detect the flow direction of an exhaust gas flow in pulsating flow and is designed for load detection in internal combustion engines with gasoline or Dieselkraftstoffein injection. The installation of the hot film air knife 110 Usually takes place between an air filter and a throttle device and is usually as a preassembled module in the form of a plug-in sensor including a measuring housing 114 ,
  • In 2 is a hot film air mass meter 110 with opened measuring housing 114 shown. It can be seen that in this embodiment, the measuring housing 114 is divided into a flow area 116 and an electronics area 118 , In the flow area 116 , which, as in 1 visible, in the installed state of the Heißfileinuftmassenmessers 110 in the intake tract 114 is plugged in, is a flow channel 120 in the form of a bypass channel 122 added. During operation of the hot film air mass meter 110 the air flows in the main flow direction 124 , what a 2 symbolized by an arrow, through the bypass channel 122 , After switching off the internal combustion engine, oil mist can, as described above, along the diffusion paths 126 , what a 2 symbolically represented by arrows, diffuse.
  • From the electronics sector 118 a chip carrier protrudes with a sensor chip embedded in it 130 with a measuring surface 132 in the bypass channel 122 , The chip carrier 128 For example, it can be designed as a metallic component, for example as a sheet-metal component (floor panel), or it can also be a plastic component, for example an injection-molded component. The chip carrier is usually at one in the electronics area 118 recorded, in 2 not shown electronic circuit board attached (for example, molded), wherein the electronic board may include an evaluation and control circuit of the Heißfileinuftmassenmessers. During operation of the hot film air mass meter and after switching off the internal combustion engine occurs on the sensor surface 132 the contamination problem described above due to oil precipitation.
  • In the 3 to 5 is a first embodiment according to the invention of a realization of a gradient field generating device 134 shown, which reduces the contamination problem or avoids completely. It shows 3 a cross section through the bypass channel 122 , where the cutting plane in 2 horizontally through the chip carrier 128 runs. 4 shows a section through the bypass channel 122 with an in 2 vertically extending cutting plane. 5 shows a lid part 136 , which by flaps around a vertical axis on the open measuring housing 114 according to 2 is attached to the bypass channel 122 close. This cover part 136 thus forms an integral part of the measuring housing 114 ,
  • The gradient field generating device 134 is in this case as a capacitor 138 constructed, which consists of a large-area electrode 140 and a small electrode 142 composed. In this embodiment according to the 3 to 5 is the chip carrier 128 at least partially made of conductive material, so in particular designed as a floor panel. As a small electrode 142 becomes a wire electrode in this embodiment 144 used, which on the cover part 136 of the measuring housing 114 is attached and which, as in 5 to recognize, in a partial area along the bypass channel 122 is guided.
  • As based on 5 and 3 to recognize, has the bypass channel 122 along its longitudinal extension no constant cross-section, but tapers in the area of the chip carrier 128 , This rejuvenation is also called a convergence ramp. The air mass flow, which in the main flow direction 124 through the bypass channel 122 flows, hits a leading edge 146 (please refer 3 ) on the chip carrier 128 and is characterized by the rejuvenation of the bypass canal 122 (Convergence ramp) along the sensor surface 122 directed.
  • Between the electrodes 140 . 142 of the capacitor 138 In this embodiment, an electrical voltage of about 2.5 kV is applied. This forms between the electrodes 142 . 144 an electric field 148 out, which in 4 symbolically represented in the form of field lines. Due to the very different expansion of the electrodes 142 . 144 has this electric field 148 a strong field strength gradient. From the air mass flow entrained oil droplets 150 , which typically have an extension in the micron range, are, as described above, in the electric field 148 polarize and experience a force due to the field strength gradient 152 towards the small electrode 142 , ie in the direction of the higher field strength. In this way, oil droplets 150 , which are carried by the air mass flow, in the region of the sensor chip 130 from the sensor surface 132 deflected, so that during operation of the Heißfileinuftmassenmessers 110 an oil contamination of the sensor chip 130 is avoided. Also charged oil droplets 150 , so oil droplets 150 with a net charge, be in the electric field 148 distracted.
  • As described above, preferably after switching off the internal combustion engine is an electric field 148 generated, so that even oil diffusion, which occur after switching off the internal combustion engine, not on the sensor surface 132 knock down.
  • In 6 is a second embodiment of a gradient field generating device 134 represented, wherein the sectional plane analogous to 3 is selected. Instead of in the embodiment according to 3 used wire electrode 144 is in the embodiment according to 6 however, an electrode tip 154 as a small electrode 142 used, which in the lid part 136 of the bypass channel 122 is admitted. As a large-area electrode 140 acts also in this embodiment, analogous to 3 , the chip carrier 128 , which in the second embodiment according to 6 at least partially made of conductive material. Due to the sharp electrode tip 154 can be with the gradient field generating device 134 according to the embodiment in 6 even an even stronger field gradient of the electric field 148 generate as in the embodiment according to the 3 to 5 ,
  • It should be noted that as a large-area electrode 140 instead of a conductive chip carrier 128 also a separate large-area electrode 140 can be used. For example, this separate large-area electrode can be independent of the chip carrier 128 in the bypass channel 122 be arranged, for example on the wall of the bypass channel 122 or as a separate component.

Claims (10)

  1. Hot film air mass meter ( 110 ) for measuring an air mass flow, in particular in the intake tract ( 112 ) of an internal combustion engine, wherein the hot film air mass meter ( 110 ) a sensor surface which can be overflowed by the air mass flow ( 132 ), characterized by a gradient field generating device ( 134 ), wherein the gradient field generating device ( 134 ) is designed to be an air mass flow at least partially passing through electric field ( 148 ) With to generate a field gradient.
  2. Hot film air mass meter ( 110 ) according to the preceding claim, characterized in that the air mass flow with a main flow direction ( 124 ), the electric field ( 148 ) substantially perpendicular to the main flow direction ( 124 ) runs.
  3. Hot film air mass meter ( 110 ) according to one of the two preceding claims, characterized in that the gradient field generating device ( 134 ) at least one capacitor ( 138 ), wherein the at least one capacitor has at least one large area electrode ( 140 ) and at least one small electrode ( 142 ), wherein an electrode surface of the at least one large-area electrode ( 140 ) an electrode surface of the at least one small electrode ( 142 ) exceeds.
  4. Hot film air mass meter ( 110 ) according to the preceding claim, characterized in that the electrode surface of the at least one large-area electrode ( 140 ) the electrode surface of the at least one small electrode ( 142 ) in at least one dimension perpendicular to the main flow direction by at least a factor of two, preferably by at least a factor of three exceeds.
  5. Hot film air mass meter ( 110 ) according to one of the two preceding claims, characterized in that the at least one small electrode ( 142 ) at least one point-shaped electrode, in particular an electrode tip ( 154 ), and / or at least one line-shaped electrode, in particular a wire electrode ( 144 ), having.
  6. Hot film air mass meter ( 110 ) according to one of the three preceding claims, characterized by a sensor chip ( 130 ) and a chip carrier ( 128 ), whereby the sensor chip ( 130 ) in the chip carrier ( 128 ) is embedded, wherein the chip carrier ( 128 ) has at least partially electrically conductive properties and wherein the chip carrier ( 128 ) an electrode of the at least one capacitor ( 138 ).
  7. Hot film air mass meter ( 110 ) according to the preceding claim, characterized in that compared to the large-area electrode ( 140 ) acting, at least partially electrically conductive chip carrier ( 128 ) a point or line-shaped counterelectrode ( 144 . 154 ) as a small electrode ( 142 ) is provided.
  8. Hot film air mass meter ( 110 ) according to one of the five preceding claims, characterized in that at least two oppositely charged electrodes ( 140 . 142 ) are arranged at a distance between 1 mm and 10 mm, preferably between 2 mm and 5 mm, wherein between the oppositely charged electrodes ( 140 . 142 ) is applied an electrical voltage in a range between 10 V and 10 kV, in particular between 100 V and 5 kV, and particularly preferably between 1 kV and 2.5 kV.
  9. Hot film air mass meter ( 110 ) according to one of the six preceding claims, characterized by a flow channel ( 120 ), in particular a bypass channel ( 122 ), wherein at least one electrode ( 144 . 154 ) on a wall ( 136 ) of the flow channel ( 120 ), in particular metallized, is.
  10. Method for measuring an air mass flow of an internal combustion engine using a hot-film air mass meter ( 110 ) according to one of the preceding claims, characterized in that the gradient field generating device ( 134 ) during an after-running period after switching off the internal combustion engine an electric field ( 148 ) is generated with a field gradient, wherein the duration of the trailing period between 5 seconds and 10 minutes, preferably between 5 seconds and 5 minutes and more preferably between 10 seconds and 3 minutes.
DE200510057574 2005-12-02 2005-12-02 Hot-film air mass sensor for measuring air mass flow, has sensor surface, and gradient field producing device that is formed to produce electric field with field gradient, where electric field partially penetrates air mass flow Pending DE102005057574A1 (en)

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Applications Claiming Priority (1)

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DE200510057574 DE102005057574A1 (en) 2005-12-02 2005-12-02 Hot-film air mass sensor for measuring air mass flow, has sensor surface, and gradient field producing device that is formed to produce electric field with field gradient, where electric field partially penetrates air mass flow

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2011061148A1 (en) * 2009-11-17 2011-05-26 Mahle International Gmbh Intake manifold section and intake system
DE102013212162A1 (en) 2013-06-26 2014-12-31 Robert Bosch Gmbh Sensor device for detecting at least one property of a fluid flowing in a channel
WO2016165868A1 (en) 2015-04-15 2016-10-20 Robert Bosch Gmbh Sensor for determining at least one parameter of a fluid medium flowing through a measurement channel

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2011061148A1 (en) * 2009-11-17 2011-05-26 Mahle International Gmbh Intake manifold section and intake system
US8991352B2 (en) 2009-11-17 2015-03-31 Mahle International Gmbh Intake manifold section and intake system
DE102013212162A1 (en) 2013-06-26 2014-12-31 Robert Bosch Gmbh Sensor device for detecting at least one property of a fluid flowing in a channel
US10006793B2 (en) 2013-06-26 2018-06-26 Robert Bosch Gmbh Sensor device for detecting at least one property of a fluid medium flowing in a channel
WO2016165868A1 (en) 2015-04-15 2016-10-20 Robert Bosch Gmbh Sensor for determining at least one parameter of a fluid medium flowing through a measurement channel
DE102015206708A1 (en) 2015-04-15 2016-10-20 Robert Bosch Gmbh Sensor for determining at least one parameter of a fluid flowing through a measuring channel

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