Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F25/00—Testing or calibration of apparatus for measuring volume, volume flow or liquid level or for metering by volume
• • 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
  • 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
• • 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
  • G01F1/696—Circuits therefor, e.g. constant-current flow meters
  • G01F1/6965—Circuits therefor, e.g. constant-current flow meters comprising means to store calibration data for flow signal calculation or correction
• • 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
  • G01F1/696—Circuits therefor, e.g. constant-current flow meters
  • G01F1/698—Feedback or rebalancing circuits, e.g. self heated constant temperature flowmeters
• • 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
  • G01F1/72—Devices for measuring pulsing fluid flows
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F25/00—Testing or calibration of apparatus for measuring volume, volume flow or liquid level or for metering by volume
  • G01F25/10—Testing or calibration of apparatus for measuring volume, volume flow or liquid level or for metering by volume of flowmeters

Definitions

• the invention relates to a device for determining a gas mass flow with a first sensor unit having at least a first temperature measuring element and a first heating element, a second sensor unit having a second temperature measuring element and a second heating element and a control unit, by means of which the at least one temperature measuring element controlled Overtemperaturen is controllable and a method for recalibration of a device for determining a gas mass flow, in which the first heating element of the first sensor unit is controlled to a controlled excess temperature and then calculates a mass flow of the heat dissipation of the at least one heating element of the first sensor unit in dependence of the temperature of the temperature measuring element becomes.
• Devices for gas mass flow measurement are mainly known from the field of intake air mass measurement in internal combustion engines. Particularly good results are achieved with air mass meters, which operate on the principle of hot film manometry. This means that a heating element of the sensor is heated, wherein the generated heat of this heating element is delivered to the flowing medium by convection. The resulting temperature change or the additional power consumption to obtain the heating element temperature form a measure of the existing mass flow.
• Modified mass flow sensors are also used in recent years for measuring the exhaust gas mass flow, as described for example in DE 10 2006 058 425 AI. This device for determining the mass flow has two separate sensor units, of which a first is used for mass flow calculation by determining a power loss and the second is used to determine the temperature of the exhaust gas flow.
• the heating element of the first sensor unit is then either regulated to an excess temperature, which has a constant difference to the temperature measuring element or regulated to a constant excess temperature. From the additional power required for this purpose can be concluded that the exhaust gas mass flow. However, soiling must be avoided, which falsify the measurement result, which is why the temperature measuring element has a heating element with which, in particular, soot deposits on the substrate can be burned off. In addition to the problem of pollution occurring when used in the exhaust system, the problem is to obtain representative measurement results with occurring pulsations and turbulences, as they increasingly occur in the exhaust system. For this purpose, it is proposed in DE 10 2006 058 425 AI to arrange two temperature measuring elements in succession, whereby a direction detection due to the existing heat transfer from the upstream to downstream region is possible, which can be included in the calculation of the exhaust gas mass flow.
• This object is achieved by a device for determining a gas mass flow with the features of claim 1 and by a method for recalibrating a device for determining a gas mass flow with the features of claim 5.
• control unit is connected to the heating element of the second sensor unit such that the heating element can likewise be regulated to a controlled excess temperature
• the control unit switches and the heating element of the second sensor unit is controlled to a controlled excess temperature and a mass flow of the heat dissipation of the at least one heating element of the second sensor unit depending on the temperature of the temperature measuring element first calculated and finally the two values of the gas mass flow are compared with each other and recalibrated according to a stored in the control unit correction table, the first sensor unit.
• the coverings which change the measured value are not present in the reverse measurement.
• the heating elements are arranged meandering or omega-shaped on the substrates.
• a uniform, constant temperature distribution on the substrate can be achieved, whereby measuring errors between the determined values of the measuring elements on a substrate are avoided by an inhomogeneous temperature distribution.
• the first sensor unit has two temperature measuring elements which are connected to the control unit. The difference of the measured temperature of the two temperature measuring elements on the first sensor unit is then used for flow direction detection.
• Such an arrangement and the method described enables the detection of occurring pulsations and thus temporary flow reversals, which can then be taken into account correspondingly. For this purpose, one makes use of the fact that a heat radiation to the respective downstream temperature measuring element is present.
• the second sensor unit has two temperature measuring elements, which are connected to the control unit. Accordingly, by comparing the two measured temperatures, pulsations can also be taken into account during the recalibration and errors in the individual measuring elements can be inferred.
• the control unit switches in a following step again, so that the heating element of the first sensor unit is controlled to the controlled excess temperature. Thus, the normal operating state is automatically restored after the recalibration.
• the second sensor unit is burned free before recalibration by means of the second heating element, so that the actual measured values of the sensor units are used in the recalibration.
• Figure 1 shows a side view of an inventive device for determining a mass flow in a channel in a schematic representation.
• Figure 2 shows a schematic plan view of the first sensor unit of the device for determining a mass flow.
• FIG. 3 shows a schematic plan view of the second sensor unit of the apparatus for determining a mass flow.
• the inventive device for determining a mass flow is arranged in a channel 10, which is traversed by exhaust gas and is limited by walls 12.
• a perpendicular to a channel axis 14 extending opening 16 is formed, through which a housing 18 of a device for determining an exhaust gas mass flow extends into the channel 10.
• first sensor unit 20 and a second sensor unit 22 in the channel 10 which are formed by mostly multilayer ceramic substrates 24, 26, on which platinum thin-film resistors and conductor tracks 28 are arranged in a known manner.
• the sensor units 20, 22 are usually arranged parallel to each other in the main flow direction of the exhaust gas lying one behind the other, wherein the main extension direction of each sensor unit 20, 22 is also parallel to the main flow direction in the channel 10. Due to the parallelism of the connecting line of the sensor units 20, 22 to the main flow direction of the exhaust gas, these are not frontal flows but only flows over, which significantly reduces deposits on the support body.
• the device operates in a known manner according to the principle of H adoptedfllmanemometrie and has, in addition to the two sensor units 20, 22 on the sensor units 20, 22 opposite end of the housing 18, a plug part 30, via which the sensor units 20, 22 by means of a connecting cable 32 with a Control unit 52 are connected, which is shown only schematically and can be arranged alternatively either in the housing 18 or in the engine control unit.
• the connecting cable 32 is used accordingly Power supply and data transmission.
• the upstream second sensor unit 22 forms a temperature sensor, by means of which the respective exhaust gas temperature is measured. This is done via a temperature measuring element 36, which may for example consist of two platinum thin-film resistors with different resistance.
• the temperature measuring element 36 is electrically connected to the control unit 52 via the conductor tracks 28 and contact lugs 38. This sensor unit 22 is used in normal operation for measuring the temperature of the gas stream to be measured.
• a heating element 50 is arranged on the substrate 24, which has the shape of an omega, in order to produce a uniform temperature distribution on the substrate 24 can.
• the downstream first sensor unit 20 has two temperature measuring elements 40, 42 on the substrate 26, which are both connected to the control unit 52 independently of one another via conductor tracks 28 and contact lugs 38.
• a heating element 44 is either heated to a constant excess temperature during operation or heated to a constant temperature difference to the temperature measuring element 36 of the second sensor unit. Due to the existing flow, a cooling of the heating element 44 takes place, so that this requires a constant power consumption in order to obtain the controlled excess temperature.
• This power consumption or the heat dissipation can be converted in the control unit 52 via a stored map into an exhaust gas mass flow as a function of the exhaust gas temperature which is present and measured via the sensor unit 22. So that an influence of the temperature sensor so the second Sensor unit 22 is eliminated by the heating of the first sensor unit 20 via heat transfer in the direction of the main exhaust gas flow, the first sensor unit 20 downstream of the second sensor unit 22 is arranged.
• the use of two temperature measuring elements 40, 42 on the substrate 26 serves the determination and consideration of occurring exhaust gas pulsations thus a temporary reversal of the exhaust gas flow, as expected in the exhaust region of a reciprocating engine due to the intake and Ausschubamba.
• the respectively downstream temperature measuring element 42 measures a higher temperature than the upstream temperature measuring element 40, since the heat transfer of the upstream temperature measuring element 40 is transported by the exhaust gas flow in the direction of the downstream temperature measuring element 42.
• the respective upstream temperature measuring element 40 is representative of the exhaust gas flow flowing in the corresponding direction or if a characteristic map is stored in which different flow states and power consumption of the two temperature measuring elements 40 , 42 an exhaust gas mass flow from both available power consumption is deposited.
• the heating element 44 of the first sensor unit 20 is omega-shaped to allow uniform heating of the substrate 26.
• the second sensor unit 22 and in particular the heating element 50 are connected to the control unit 52 in such a way that this second sensor unit 22 is connected in the same way. This means that in a stationary engine load state, the functions of the two sensor units 20, 22 are exchanged and now the heating element 50 alshe increased to a temperature of the exhaust gas flow upper temperature
• the necessary additional power consumption for maintaining the excess temperature is a measure of the existing exhaust gas mass flow.
• the value determined in this way for the exhaust gas mass flow is compared with the value determined by the first sensor unit 20 for the exhaust gas mass flow, and a new calibration of the first sensor unit 20 is carried out according to the deviation by means of a characteristic field stored in the control unit 52 or a correction table.
• the correction table is previously determined by tests with known operating states upon reversal of the mode of operation of the two sensor units 20, 22. Before this routine is carried out for recirculation, in each case both heating elements 44, 50 of the sensor units 20, 22 should be heated to burn off the surfaces in order to avoid measurement errors due to soot deposits.

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• 2012
  • 2012-03-13 DE DE102012102094A patent/DE102012102094A1/de not_active Withdrawn
• 2013
  • 2013-01-22 US US14/384,689 patent/US20150020570A1/en not_active Abandoned
  • 2013-01-22 EP EP13701603.6A patent/EP2825855A1/de not_active Withdrawn
  • 2013-01-22 WO PCT/EP2013/051086 patent/WO2013135405A1/de active Application Filing
  • 2013-01-22 CN CN201380011823.8A patent/CN104136894A/zh active Pending
  • 2013-01-22 JP JP2014561332A patent/JP5955420B2/ja not_active Expired - Fee Related

Non-Patent Citations (1)

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