JP2010101887A - Mass flow sensor, and automobile including the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mass flow sensor operated with especially high reliability, and also to provide an automobile including the mass flow sensor. <P>SOLUTION: This mass flow sensor includes a sensor chip or is constituted as a sensor chip, and the sensor also has a form wherein at least one sensor heating element, at least one sensor element, and an evaluation unit are integrated in the sensor chip. The evaluation unit is constituted as follows: a mass flow of a fluid flow and a flow direction of the fluid flow are detected by at least one sensor element, and at least one sensor heating element is driven and controlled based on the detected mass flow and the detected flow direction, and the mass flow sensor is heated at least partially by at least one sensor heating element. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a mass flow sensor, particularly a mass flow sensor for an air mass sensor for automobiles.

  The mass flow sensor is suitable for detecting the mass flow of fluid in the flow channel. Such a flow channel can be, for example, an intake pipe of an internal combustion engine. For example, the operation of the internal combustion engine can be diagnosed based on the mass flow detected by the mass flow sensor, and the internal combustion engine can also be controlled. For this reason, it is important to detect the actual mass flow as accurately as possible with high reliability even under different operating conditions.

  DE 197 26 659 A1 discloses a mass flow sensor device including a sensor element. The sensor element is arranged and integrated on a dedicated chip. Further evaluation electronics are disclosed, which are configured separately but are electrically coupled to the sensor unit.

  DE 10311039A1 discloses a mass flow sensor device, in which the sensor element of the mass flow sensor is arranged in a channel into which airflow flows. This channel is configured to prevent the mass flow sensor from colliding with airflow particles and the attachment of contaminants to the muff flow sensor.

  DE 10135142 A1 discloses a mass flow sensor device comprising a housing body, in which the sensor element of the mass flow sensor is arranged. The housing body has an inlet region from which media flow flows into the measurement channel in which the sensor element is arranged. Furthermore, the casing body has a discharge opening from which liquid particles and solid particles flow and pass by the measuring channel.

DE197272459A1 DE10311039A1 DE10135142A1

  An object of the present invention is to provide a mass flow sensor that operates with particularly high reliability and a vehicle equipped with the mass flow sensor.

  The object is a mass flow sensor comprising a sensor chip or configured as a sensor chip according to the independent claim, wherein the sensor chip comprises at least one sensor heating element, at least one sensor element and an evaluation unit. In an integrated type mass flow sensor, the evaluation unit is configured as follows, that is, the mass flow of the fluid flow and the flow direction of the fluid flow are detected and detected by the at least one sensor element. Configured to drive and control the at least one sensor heating element based on the detected mass flow and the detected flow direction, and to at least partially heat the mass flow sensor by the at least one sensor heating element. Mass flow sen characterized by It is solved by. The dependent claims contain advantageous embodiments of the invention.

  According to a first aspect, the invention features a mass flow sensor that includes or is configured as a sensor chip, the mass flow sensor comprising at least one sensor heating element and at least one sensor element. And an evaluation unit are integrated. The evaluation unit is configured as follows. That is, the mass flow of the fluid flow and / or the flow direction of the fluid flow of the fluid are detected by at least one sensor element. Furthermore, this evaluation unit is configured as follows. That is, the at least one sensor heating element is controlled based on the detected mass flow and / or the detected flow direction, and the mass flow sensor is at least partially heated by the at least one sensor heating element. Yes. By heating the mass flow sensor, condensation in the at least one sensor element and condensation in another area of the mass flow sensor, for example an evaluation unit, can be reduced, thus ensuring a reliable operation of the mass flow sensor. It becomes possible. The mass flow sensor is preferably configured as a MEMS mass flow sensor (Micro-Electiric-Mechanical-System), wherein the evaluation unit and at least one sensor element are integrated in a mass flow sensor configured as a sensor chip. The evaluation unit preferably has components integrated in the sensor chip, preferably integrated in the sensor chip as fixedly wired evaluation electronics and electrically coupled to the at least one sensor element Has been. The at least one sensor heating element is separately incorporated in the sensor chip, and is configured to be driven and controlled by an evaluation unit. Advantageously, the at least one sensor heating element is not a component of the sensor element. The fluid can be configured as a gas or a liquid. The fluid is in particular air, and this mass flow sensor can be used in particular in air mass sensors. Said at least one sensor heating element is advantageously configured such that the entire sensor chip of the mass flow sensor is heated. As an alternative, it is also possible to heat the sensor chip only partially, for example to heat only the area of the sensor element. Advantageously, a plurality of sensor heating elements are integrated in the sensor chip, and a particularly uniform heating of the sensor chip can be ensured. Evaluation units can be distributed and integrated on the sensor chip around the at least one sensor element.

  In an advantageous embodiment of the first aspect, the evaluation unit is configured as follows. That is, the evaluation unit is configured to drive and control the at least one sensor heating element when the detected mass flow is equal to or less than a predetermined mass flow threshold. If the detected mass flow exceeds a mass flow threshold, the at least one sensor heating element is advantageously switched off. An absolute value of the detected mass flow that is below the muff throw threshold advantageously represents a state in which the fluid flow is very diminishing or no longer exists.

  In another advantageous embodiment of the first aspect, the evaluation unit is configured as follows. That is, the at least one sensor heating element is driven and controlled when the detected mass flow is equal to or lower than a predetermined mass flow threshold value during a predetermined first period. In this way, it can be ensured particularly reliably that the detected mass flow is not absolutely below the mass flow threshold in an absolute value for a short time. In another advantageous embodiment of the first aspect, the evaluation unit is configured as follows. That is, the evaluation unit is configured to drive and control the at least one sensor heating element when a predetermined second flow direction of the fluid flow that is opposite to the predetermined first direction of the fluid flow is detected. Has been. Advantageously, the flow direction when the detected mass flow is greater than the mass flow threshold is assigned to the first flow direction of the fluid flow, while the detected mass flow is absolutely below the mass flow threshold. The flow direction in some cases is assigned to the second flow direction of the fluid flow. This reduces condensation in the mass flow sensor, especially when heated fluid flows in the second flow direction.

  In another advantageous embodiment of the first aspect, the evaluation unit is configured as follows. In other words, when at least a predetermined second flow direction of the fluid is detected for at least a predetermined first period, the at least one sensor heating element is driven and controlled. This particularly ensures that the fluid flow does not flow in the second flow direction for a short time.

  In another advantageous embodiment of the first aspect, the mass flow sensor is heated using the at least one sensor heating element as follows. That is, the mass flow sensor is heated so that the mass flow sensor has a temperature that is at least partially higher than the temperature of the mass flow. Thus, for example, by increasing the temperature from 10 ° C. to 50 ° C., condensation can be particularly reliably prevented.

  In another advantageous embodiment of the first aspect, the evaluation unit is configured to drive and control the at least one sensor heating element for a predetermined second period. Thereby, the energy saving operation of the mass flow sensor becomes possible.

  In another advantageous embodiment of the first aspect, the at least one sensor element comprises at least one thin film comprising a heating element. The evaluation unit is configured to drive and control each heating element and the at least one sensor heating element based on the detected mass flow and / or the detected flow direction. The heating element of each sensor element is required to detect the flow direction of mass flow and / or fluid flow. Said at least one sensor heating element is advantageously not required for this purpose. Further drive control of the heating element of each sensor element continues to allow detection of mass flow and / or detection of fluid flow flow direction. This makes it possible to detect particularly easily and reliably whether it is necessary to drive and control the at least one sensor heating element or whether the at least one sensor heating element may be switched off.

  According to a second aspect, the invention features a motor vehicle having at least one mass flow sensor according to the first aspect. The motor vehicle preferably has an internal combustion engine. Here, the at least one mass flow sensor is preferably arranged in the intake pipe of the internal combustion engine and is exposed to air flow as a fluid flow in the intake pipe, especially during operation of the internal combustion engine. . Here, the evaluation unit is configured as follows. That is, the evaluation unit is configured to at least temporarily drive and control the sensor heating element when the internal combustion engine is switched off after the operation of the preceding internal combustion engine.

2 shows a mass flow sensor in a flow channel.

  Next, embodiments of the present invention will be described in detail with reference to the drawings. The only drawing shows a mass flow sensor in the flow channel.

  Constituent members having the same structure or function are denoted by the same reference numerals in all the drawings.

  In the drawing, a mass flow sensor LMM is illustrated, and this mass flow sensor can be disposed, for example, in an air mass sensor of an automobile. The mass flow sensor LMM is arranged in the flow channel FC and is exposed to a fluid flow, for example an air flow, in this flow channel. For example, the flow channel FC is configured as a bypass channel of a housing body including a mass flow sensor LMM, which is a constituent member of the mass flow sensor device, for example, an air mass sensor. The mass flow sensor device is advantageously arranged downstream with respect to the air filter in the intake pipe of the internal combustion engine of the motor vehicle. The housing body is usually configured as follows. That is, a part of the air flow in the intake pipe is supplied to the mass flow sensor LMM through a predetermined route of the bypass channel without carrying relatively large particles such as sand and dust particles together. Yes. Such relatively large particles can damage the mass flow sensor LMM and render it unusable.

  The predetermined first flow direction of the fluid flow in the flow channel FC is illustrated using arrows in the drawing. The predetermined second flow direction of the fluid flow is configured to be opposite to the first flow direction.

  The mass flow sensor LMM is advantageously configured as a MEMS mass flow sensor, in particular as a sensor chip. An evaluation unit AU and a sensor element SU are integrated on the sensor chip. Further, a sensor heating element SHU is arranged and integrated on the mass flow sensor configured as a sensor chip. Basically, a plurality of sensor heating elements SHU can be integrated on the sensor chip.

  The sensor element SU has a cantilever thin film M, which is formed, for example, as a silicon nitride layer and / or a silicon oxide layer. The thin film M is disposed within the frame of the sensor chip. The thin film M is produced, for example, by etching a silicon wafer covered with a silicon nitride layer and / or a silicon oxide layer. On the thin film M, the first temperature sensor TS1, the second temperature sensor TS2, and the heating element HU are arranged. The first temperature sensor TS1 and the second temperature sensor TS2 are configured as thermoelectric elements, for example. Each of these thermoelectric elements generates a voltage based on the Seebeck effect, and this voltage represents each temperature detected by each temperature sensor TS1, TS2. Basically, the first temperature sensor TS1 and the second temperature sensor TS2 can be other embodiments well known to those skilled in the art, such as a temperature dependent resistance. The heating element HU is configured as a resistance element, for example, and this resistance element is disposed on the thin film M along the central longitudinal axis of the mass flow sensor LMM. The resistance element includes at least one conductor path, and the at least one conductor path heats the thin film M by a current flowing through the conductor path. Advantageously, the first temperature sensor TS1 and the second temperature sensor TS2 are arranged on the surface of the thin film M, and a heating element HU is also arranged on the surface of the thin film. The first temperature sensor TS1 and the second temperature sensor TS2 are respectively arranged on different sides of the heating element HU on both sides of the heating element HU.

  The evaluation unit AU is advantageously configured as a fixedly wired electronics unit for driving and controlling the sensor element SU and the sensor heating element SHU. As an alternative, the evaluation unit AU can also comprise a microcontroller or a digital signal processor for driving and controlling the sensor element SU and the sensor heating element SHU by program control.

  The mass flow sensor LMM is advantageously arranged in the flow channel FC as follows. That is, the mass flow sensor LMM is arranged such that the plane of the sensor chip on which the sensor element SU and the evaluation unit AU are arranged is oriented substantially parallel to the flow direction of the fluid flow.

  The first operating mode of the mass flow sensor LMM is advantageously assigned to the switched-on vehicle internal combustion engine, which is set by the evaluation unit AU. During the first operation mode of the mass flow sensor LMM, the fluid flow flows in the predetermined first flow direction in the flow channel FC. In the case of the predetermined first flow direction, the first temperature sensor TS1 is arranged on the thin film M upstream of the heating element HU, while the second temperature sensor TS2 is arranged downstream of the heating element HU. Yes. In the first operating mode, the heating element HU sets a certain temperature, which is preferably higher than the temperature of the mass flow. The region allocated to the first temperature sensor TS1 in the first temperature sensor TS1 and the thin film M is cooled by the fluid flow. The second temperature sensor TS2 is heated based on heat transport from the heating element HU by fluid flow and / or based on heat transfer by the thin film M, and has a temperature different from the temperature of the first temperature sensor TS1. Each temperature detected by each temperature sensor TS1, TS2 is preferably based on the flow rate of the fluid flow. The temperature difference between the temperature detected by the first temperature sensor TS1 and the temperature detected by the second temperature sensor TS2 represents the flow speed of the fluid flow, and thus represents the mass flow. It is possible to detect the flow direction of the fluid flow based on the temperature sensors TS1 and TS2 that detect a higher temperature, and thus based on the sign of the detected temperature difference.

  The evaluation unit AU is configured to detect a temperature difference based on each temperature detected by the first temperature sensor TS1 and the second temperature sensor TS2, and is integrated on the sensor chip based on the temperature difference. The sensor signal is supplied on the output side of the connected part CONN. This sensor signal represents the detected mass flow. The connection part CONN can be configured as a bond pad, for example. Further, the evaluation unit AU is configured to detect the flow direction of the fluid flow based on the temperature difference, that is, based on, for example, the sign of the temperature difference.

  For example, if the internal combustion engine is switched off after operation, the flow speed of the fluid flow in the flow channel FC in the predetermined first flow direction decreases. Basically the flow rate can be reduced to a zero value. On the contrary, the air in the intake pipe is also heated by the heated internal combustion engine, creating buoyancy, which can even lead to a chimney effect in the intake pipe of the internal combustion engine. This reverses the flow direction, and therefore fluid flow may flow in a predetermined second flow direction. The heated fluid flow in the predetermined second flow direction may have, for example, oil or fuel vapor as well as other particles in addition to air, and these particles may condense in a cold state, for example a cold mass flow sensor LMM. It will be done. As a result, after a relatively short period of operation of the automobile, the surface of the sensor chip assigned to the sensor element SU is covered with oil or particles. Such a coating changes the thermal characteristics of the mass flow sensor LMM, which in turn hinders accurate detection of the mass flow.

  The evaluation unit AU is configured to set the second operation method of the mass flow sensor LMM based on the detected mass flow. The second mode of operation is advantageously set when the detected mass flow is below a predetermined mass flow threshold in absolute value. As an alternative or in addition, the evaluation unit AU can also be configured to set the second operating scheme based on the flow direction. At this time, the evaluation unit AU can be configured as follows. That is, the evaluation unit AU is not used for at least a predetermined first period (for example, 1-2 seconds) after the detected mass flow is equal to or lower than the mass flow threshold and / or the fluid flow is in the predetermined second flow direction. The second operation method can be set only after the flow.

  In the second operation method, the evaluation unit AU is further configured as follows. That is, the sensor heating element SHU and the heating element HU of the sensor element SU are driven and controlled in parallel so that the mass flow sensor LMM, particularly the evaluation unit AU and the sensor element SU are heated. Here, the mass flow sensor LMM is heated as follows. That is, it is heated to be especially minimized so that the risk of condensation of oil or particles in the fluid flow flowing in a predetermined second flow direction is reduced. Advantageously, the mass flow sensor LMM is heated to a predetermined temperature that is higher than the temperature of the fluid flow flowing in the predetermined second flow direction.

  Advantageously, the evaluation unit AU is further configured to set the second operating mode of the mass flow sensor LMM only for a predetermined second period (eg 5 to 10 seconds). As a result, when the automobile is parked for a relatively long time with the internal combustion engine switched off, the mass flow sensor LMM does not operate continuously, and therefore, an unnecessary load may not be applied to the battery of the automobile. Guaranteed.

  Advantageously, the heating element HU of the sensor element SU is also driven and controlled in the second operating mode, so that mass flow detection and flow direction detection can continue. Therefore, the evaluation unit AU can detect the re-switch-on of the internal combustion engine on the basis of the occurrence of a faster flow velocity and / or on the basis of the detection of the first flow direction and set the first operating mode again. can do. Advantageously, the mass flow sensor LMM can also have a data interface and can exchange data with a control device, for example an engine control device. As an alternative or in addition, the engine control device can also be configured to transmit the operating state of the internal combustion engine of the motor vehicle to the mass flow sensor LMM.

Claims (9)

A mass flow sensor (LMM) comprising or configured as a sensor chip,
In the mass flow sensor of the type in which at least one sensor heating element (SHU), at least one sensor element (SU), and an evaluation unit (AU) are integrated on the sensor chip,
The evaluation unit (AU) is configured as follows:
The at least one sensor element (SU) detects a mass flow of a fluid flow and a flow direction (FD) of the fluid flow, and based on the detected mass flow and the detected flow direction (FD), The at least one sensor heating element (SHU) is driven and controlled, and the mass flow sensor (LMM) is at least partially heated by the at least one sensor heating element (SHU).
A mass flow sensor (LMM). The evaluation unit (AU) is configured to drive and control the at least one sensor heating element (SHU) when the detected mass flow is less than or equal to a predetermined mass flow threshold.
The mass flow sensor (LMM) according to claim 1. The evaluation unit (AU) is configured to drive and control the at least one sensor heating element (SHU) when the detected mass flow is equal to or less than a predetermined mass flow threshold during a predetermined first period. Yes,
The mass flow sensor (LMM) according to claim 2. The evaluation unit (AU) drives the at least one sensor heating element (SHU) when a predetermined second direction of the fluid flow that is opposite to the predetermined first flow direction of the fluid flow is detected. Configured to control,
The mass flow sensor (LMM) according to any one of claims 1 to 3. The evaluation unit (AU) is configured to drive and control the at least one sensor heating element (SHU) when a predetermined second direction of the fluid flow is detected for at least a predetermined first period. ing,
The mass flow sensor (LMM) according to claim 4. The mass flow sensor (LMM) is heated by the at least one sensor heating element (SHU) as follows: the mass flow sensor (LMM) has a temperature at least partially higher than the temperature of the fluid. Heated,
A mass flow sensor (LMM) according to any one of claims 1 to 5. The evaluation unit (AU) is configured to drive and control the at least one sensor heating element (SHU) for a predetermined second period.
The mass flow sensor (LMM) according to claim 1, wherein the mass flow sensor is an LMM. The at least one sensor element (SU) comprises at least one thin film (M) comprising a heating element (HU);
The evaluation unit (AU) drives each heating element (HU) and the at least one sensor heating element (SHU) based on the detected mass flow and / or the detected flow direction (FD). Configured to control,
The mass flow sensor (LMM) according to claim 1, wherein the mass flow sensor is an LMM.   An automobile comprising at least one mass flow sensor (LMM) according to any one of claims 1-8.

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