KR102466025B1 - Sensor for determining at least one parameter of a fluid medium flowing through a measuring channel - Google Patents

Abstract

The invention relates to a sensor (10) for determining at least one parameter of a fluid medium flowing through a measuring channel (30), in particular of an intake air mass flow of an internal combustion engine. The sensor 10 comprises a sensor housing 12, in particular a sensor inserted or insertable into the flow tube, and at least one sensor chip 42 disposed in the measuring channel 30 for determining a parameter of the fluid medium. ), and a channel structure 22 having a main channel 24 and a measurement channel 30 is formed in the insertion sensor. The sensor housing 12 is at least partly made of plastic. The sensor 10 includes at least one electrode 48 , 60 , 64 , and the electrode 48 , 60 , 64 is disposed within the sensor housing 12 to be covered by plastic.

Description

A sensor for determining at least one parameter of a fluid medium flowing through a measuring channel

The present invention relates to a sensor for determining at least one parameter of a fluid medium flowing through a measurement channel.

The prior art has disclosed many methods and devices for determining the flow properties of fluid media, ie liquids and/or gases. The flow properties can be essentially any physically and/or chemically measurable property that qualifies or quantifies the flow of a fluid medium. In particular, it may be flow rate and/or mass flow and/or volume flow.

The present invention is hereinafter described in particular in relation to a so-called hot film air mass meter, disclosed for example in Konrad Reif (publisher): Sensoren im Kraftfahrzeug, Vol. 1, 2010, pages 146-148. These hot-film air mass meters are generally based on micromechanically manufactured silicon sensor chips with a sensor chip, in particular a sensor film capable of overflowing by a flowing fluid medium, as the measuring surface or sensor area. The sensor chip usually comprises at least one heating element and at least two temperature sensors, which are arranged, for example, on the measuring surface of the sensor chip. From the asymmetry of the temperature profile detected by the temperature sensors and influenced by the flow of the fluid medium, the mass flow and/or volume flow of the fluid medium can be estimated. Hot-film air mass meters are usually designed as implantable sensors that can be fixed or replaceable inserted into the flow tube. For example, the flow pipe may be a suction pipe of an internal combustion engine.

In this case, a partial flow of the medium flows through at least one main channel provided in the hot film air mass meter. Behind the inlet, the flow is split to flow through the main and bypass channels. Fluid discharge is through at least one outlet. In particular, the bypass channel is formed to include a bent section for changing the direction of a partial flow of the medium introduced through the inlet of the main channel, and the bent section subsequently leads to a section where the sensor chip is disposed. The section mentioned later forms the actual measurement channel in which the sensor chip is placed. In this case, means are provided in the bypass channel for guiding the flow and preventing separation of the flow of the medium partial flow from the channel walls of the measuring channel. In addition, the inlet region of the main channel comprises sloped or curved faces in the region of its opening facing away from the direction of the main flow, said faces guiding the medium entering the inlet region away from the part of the main channel extending to the sensor chip. formed so that This allows liquid particles or solid particles contained in the medium to be guided along with the main flow due to their mass inertia.

In practice, these hot-film air mass meters must meet a number of requirements and boundary conditions. With the goal of reducing the pressure drop in the hot film air mass meter as a whole by means of suitable flow technology design, one of the main requirements is the signal quality and oil droplets and water droplets and carbon black particles, dust particles and other solid particles. to further improve the stiffness of these devices against contamination by Said signal quality relates, for example, to the mass flow of the medium through a measuring channel extending towards the sensor chip and possibly to a reduction in signal drift and an improvement in the signal-to-noise ratio. The signal drift relates in this case to a deviation of the mass flow of, for example, a medium in the sense of a fluctuation of the characteristic curve relationship between the mass flow actually occurring and the signal to be output determined in the range of calibration during manufacture. When determining the signal-to-noise ratio, the sensor signal output in a rapid time sequence is taken into account, while the characteristic curve or signal drift is related to the fluctuation of the mean value.

In conventional hot-film air mass meters of the type described above, a sensor chip usually attached to or inserted into the sensor support protrudes into the measurement channel. For example, the sensor chip can be glued into or glued to the sensor support. The sensor support can form a unit together with a bottom plate made of metal, to which electronic devices, for example control and evaluation circuits in the form of a printed circuit board, can be glued. For example, the sensor support can be formed as an injection molded plastic part of an electronic module. The sensor chip and the control and evaluation circuit can be connected to each other, for example by means of bonding connections. The electronic module thus formed can be glued into the sensor housing, for example, and the entire inserted sensor can be closed with a cover.

DE 10 2010 020 264 A1 discloses a hot-film air mass meter of this type with a housing made of plastic. A flow channel is formed within the housing. A sensor element is disposed in the flow channel, and the sensor element detects an air mass flowing in the flow channel. At least a portion of the flow channel has static dissipative properties. Electrostatic dissipation refers to the range having a surface resistivity less than 10 ¹² Ohm for all references. Thus, the surface resistance is small enough to discharge electrostatically charged particles in air and protect the sensor element from deposition of the particles.

The improvements used in the sensor still have room for improvement. These sensors are often installed in automobiles so that they can be placed under the direct influence of very strong electric fields. These electric fields can directly or indirectly affect the sensor's function.

The object of the present invention is to avoid at least substantially the disadvantages of the known sensors, and to provide at least one fluid medium flowing through a measuring channel suitable for modifying an electric field that may occur in the vicinity of the sensor and which directly or indirectly affects its function. It is to provide a sensor for determining the parameter. Due to this, the life of the sensor can be significantly extended.

This problem is solved by the features of claim 1 .

A sensor according to the invention for determining at least one parameter of a fluid medium flowing through a measuring channel, in particular of an intake air mass flow of an internal combustion engine, comprises a sensor housing, in particular an insertable sensor inserted or insertable into a flow tube, and said measuring channel and a sensor chip for determining a parameter of the fluid medium, and a channel structure having a main channel and a measurement channel is formed in the inserted sensor. The sensor housing is at least partially made of plastic. The sensor includes at least one electrode, which is disposed within the sensor housing so as to be covered by plastic.

For example, electrodes are coated with plastic. Preferably the electrodes are embedded in plastic. For example, the first electrode is arranged in the area of the measuring channel. The first electrode can be arranged upstream of the sensor chip with respect to the main flow direction of the fluid medium within the measurement channel. The first electrode may extend parallel to the measurement channel. The second electrode may be disposed within the region of the main channel. The sensor housing may include an inlet into the channel structure, the inlet facing opposite to the direction of the main flow of the fluid medium at the point of the sensor. A third electrode may be disposed around the inlet. The electrode may be in electrical connection with a fixed potential. The fixed potential may be the sensor ground.

The main flow direction means within the scope of the present invention the direction of the local flow of the fluid medium at the point of the sensor or sensor device, local deformations such as turbulence for example may not be taken into account. In particular, the main flow direction may refer to the local mean transport direction of the flowing fluid medium. Thus, the main flow direction can on the one hand relate to the direction of flow at the point of the sensor device or to the direction of flow in a channel inside the sensor housing, for example at the point of the sensor support or sensor chip, which In this case, the two main flow directions may be different. Therefore, in the scope of the present invention it is always indicated to which point the main flow direction is concerned. If no detailed instructions are given, the main flow direction is relative to the point of the sensor device.

Downstream arrangement means, within the scope of the present invention, the arrangement of a component at a point where the fluid medium arrives later in time than the reference point in the direction of the main flow.

Similarly, upstream placement of a component in the context of the present invention means placement of the component at a point at which the fluid medium flowing in the direction of the main flow arrives in time earlier than the reference point.

Within the scope of the present invention, the sensor support may be formed wholly or partly as a circuit support, in particular as a printed circuit board, or may be part of a circuit support, in particular a printed circuit board. For example, a circuit support, in particular a printed circuit board, may include an extension that forms a sensor support and protrudes into a channel, for example a measurement channel of a hot film air mass meter. The remaining part of the circuit support, in particular the printed circuit board, can be accommodated, for example, in an electronics chamber, a circuit device or a housing of an insertion sensor of a sensor device.

A printed circuit board means, within the scope of the present invention, a substantially plate-like member, which plate-like member can be used as a support for an electronic structure, for example a conductor track, a connecting contact or the like, preferably comprising one or a plurality of such structures. include Basically, at least a slight deviation from the plate shape should be taken into account and conceptually understood together. The printed circuit board can be made of, for example, a plastic material and/or a ceramic material, for example an epoxy resin, in particular a fiber-reinforced epoxy resin. In particular, the printed circuit board can be formed, for example, as a printed circuit board (PCB) with conductor tracks, in particular printed conductor tracks.

Due to this, the electronic module of the sensor device can be very simple, eg a bottom plate and a separate sensor support can be omitted. The bottom plate and sensor support can be replaced by a single printed circuit board, on which board the control and evaluation circuits of the sensor device, for example, can be completely or partially arranged. The control and evaluation circuit of the sensor device is used for controlling at least one sensor chip and/or for evaluating a signal generated by said sensor chip. Accordingly, by integrating the above members, the manufacturing cost of the sensor device can be significantly reduced and the installation space for the electronic module can be significantly reduced.

The sensor device may in particular include at least one housing, wherein the channel is formed in the housing. For example, the channel may include a main channel and a bypass channel or measurement channel, and the sensor support and sensor chip may be disposed in the bypass channel or measurement channel, for example. Further, the housing may include an electronics chamber separate from the bypass channel, and the electronic module or printed circuit board is substantially housed within the electronics chamber.

The sensor support may be formed as an extension of the printed circuit board protruding into the channel. This arrangement is technically relatively simple to implement, in contrast to the complicated electronic modules known in the prior art.

In particular, where a printed circuit board is used as the sensor support and also in other cases and/or using other media as the sensor support, the sensor support can be at least partially formed as a multilayer sensor support. The sensor support may be formed in so-called multi-layer technology and may include two or multiple interconnected support layers. For example, the support layers may be made of a metal, plastic or ceramic material or a composite material and may be connected to one another by means of a connection technique, for example gluing.

In the above case where a multi-layer technology with a plurality of sensor layers of the sensor support is used, the inlet edge can be realized at least partially stepped opposite to the main flow direction of the fluid medium by different dimensional design of the support layers. Due to this, the profile can be implemented at least approximately in a stepped shape. For example, this can result in a rectangular or - approximately stepped - at least approximately rounded, rounded or wedge-shaped profile in cross section perpendicular to the extension plane of the sensor support. The sensor chip can be placed on or in the sensor support to be aligned perpendicular to the local main flow direction. For example, the sensor chip may be formed as a rectangle, one side of the rectangle being arranged perpendicular or substantially perpendicular to the local main flow direction, for example with a deviation of less than 10 degrees from the vertical. do.

The sensor chip may be in electrical contact through at least one electrical connection. For example, a sensor carrier, in particular a printed circuit board or an extension of said printed circuit board forming the sensor carrier, may comprise one or more conductor tracks and/or contact pads, said conductor tracks and/or contact pads comprising the sensor Corresponding contacts on the chip are connected, for example by bonding methods. In this case, the electrical connection can be protected by at least one covering and separated from the fluid medium. The covering can in particular be formed as a so-called globe-top covering electrical connections, for example bonding wires, for example as a plastic drop and/or as a drop of glue. Because of this, since the globe-top has a smooth surface, the influence of the flow by the electrical connection can also be reduced.

Also, the sensor chip may include at least one sensor area. The sensor area can be a sensor surface and/or in particular a sensor membrane, for example made of a porous ceramic material. As a sensor area or measuring surface, the sensor membrane can be saturated by a flowing fluid medium. The sensor chip comprises for example at least one heating element and at least two temperature sensors, said temperature sensors being arranged for example on a measuring surface of the sensor chip, one temperature sensor upstream of the heating element and the other temperature sensor. A temperature sensor may be installed downstream of the heating element. From the asymmetry of the temperature profile influenced by the flow of the fluid medium and detected by the temperature sensor, the mass flow and/or volume flow of the fluid medium can be estimated.

The basic idea of the present invention lies in the attachment of electrodes in the immediate vicinity of the sensor chip. The electrode is attached so that it can be connected by electrical contact to a suitable potential, for example sensor ground. Thus, areas connected to a defined suitable potential, eg sensor ground, can be implemented, whereby existing flux lines deviate preferably from the flight path of the flying particles determined by the kinematics and the electric field. roll, bend Since the electrodes are arranged in the plastic or below the surface of the plastic, no surface discharge can occur, as in DE 10 2010 020 264 A1. Instead, the external electric field is shielded by the insertion of electrodes of a defined shape and of a defined potential, or, in some cases, the existing electric flux lines are affected so that the charged particles are guided through their kinematics and not through electrostatic forces. receive In contrast, in DE 10 2010 020 264 A1 the particles strike an electrical conductor track and discharge there.

Other optional details and features of the invention are presented in the following description of a preferred embodiment shown schematically in the drawings.

1 is a plan view of a sensor according to a first embodiment of the present invention;
2 is a perspective view of an electronic module;
3 is a plan view of a sensor according to a second embodiment of the present invention;
4 is a plan view of a sensor according to a third embodiment of the present invention;
5 is a plan view of a sensor according to a fourth embodiment of the present invention;

1 shows a perspective view of a sensor 10 for determining a parameter of a fluid medium. The sensor 10 is designed as a hot-film air mass meter and comprises a sensor housing 12 designed as an insertion sensor, which sensor housing can for example be inserted into a flow tube, in particular the intake tube of an internal combustion engine. The sensor housing 12 is made of plastic. The sensor housing 12 includes a housing body 14, a measurement channel cover 16, an electronics chamber 18 and an electronics chamber cover 20 for closing the electronics chamber. A channel structure 22 is formed within the sensor housing 12 . The channel structure 22 includes a main channel 24 and a bypass and measurement channel 30 branched off from the main channel 24, the main channel 24 of the sensor housing 12 in FIG. The bypass or measurement channel 30 communicates with the main flow outlet 26 on the lower face 28 as viewed from the illustration and is disposed on the end face 32 of the sensor housing 12. (34) It leads to me. The channel structure 22 allows a representative amount of the fluid medium to flow through the inlet 36 oriented opposite to the main flow direction 38 of the fluid medium at a point in the sensor housing 12 in the inserted state. Sensor 10 also includes an electronics module 40 .

2 shows a perspective view of the electronic module 40 . The electronic module 40 includes a sensor support 41 . In the inserted state of the electronic module 40, the sensor support 41 protrudes into the measuring channel 30 in the form of a blade (this arrangement is not clearly shown in the drawings). The sensor chip 42 is inserted into the sensor support 41 so that the micromechanical sensor film formed as the sensor area of the sensor chip 42 can be swollen by the fluid medium. The sensor support 41 is a constituent part of the electronic module 40 together with the sensor chip 42 . The electronic module 40 also comprises a printed circuit board 44 with a curved bottom plate 43 and attached, eg glued, control and evaluation circuitry 46 thereon. The sensor chip is electrically connected to the control and evaluation circuit 46 via electrical connections 47 which can be formed as wire bonding. The thus formed electronic module 40 is inserted, for example glued, into the electronics chamber 18 in the housing body 14 of the sensor housing 12 . In this case, the sensor support 41 protrudes into the channel structure 22 , more precisely into the measuring channel 30 . Then, the electronics chamber 18 is closed by the electronics chamber cover 20 .

The sensor 10 also includes at least one electrode 48 disposed within the sensor housing 12 such that the electrode 48 is covered by the plastic of the sensor housing 12 . As shown in FIG. 1 , the sensor 10 of the first embodiment includes a first electrode 48 disposed in the area of the measurement channel 30 . Electrode 48 is coated with the plastic of sensor housing 12 . Electrode 48 is preferably embedded in plastic. With respect to the main flow direction 50 of the fluid medium in the measurement channel 30 , the first electrode 48 is arranged upstream of the sensor chip 42 . The first electrode 48 is electrically connected to the fixed potential 54 by a conductor track 52. Preferably fixed potential 54 is sensor ground 56 .

3 shows a top view of a sensor 10 according to a second embodiment of the present invention. In the following, only differences from the preceding embodiment are described, and like parts are denoted by like reference numerals. In the sensor 10 of the second embodiment, the first electrode 48 runs parallel to the measuring channel 30 . For example, the first electrode 48 is disposed on the wall 58 of the measurement channel 28 remote from the electronics chamber 18 .

4 shows a plan view of a sensor according to a third embodiment of the present invention. In the following, only differences from the preceding embodiment are described, and like parts are denoted by like reference numerals. In the sensor 10 of the third embodiment, in addition to the first electrode 48, a second electrode 60 is disposed in the area of the main channel 24, and the second electrode 60 is located on the conductor track 62. connected to the first electrode 48 and thus to the sensor ground 56 by

5 shows a plan view of a sensor according to a fourth embodiment of the present invention. In the following, only differences from the preceding embodiment are described, and like parts are denoted by like reference numerals. In the sensor 10 of the fourth embodiment, a third electrode may be provided as an alternative to or in addition to the foregoing embodiments. A third electrode 64 is disposed at least partially around the inlet 36 . Preferably, the third electrode 64 completely surrounds the inlet 36 .

10 sensor
12 sensor housing
22 channel structure
24 main channels
30 measurement channels
42 sensor chip
48, 60, 64 electrodes

Claims (10)

A sensor (10) for determining at least one parameter of a fluid medium flowing through a measurement channel (30), the sensor (10) being disposed within a sensor housing (12) and the measurement channel (30) to measure the flow of the fluid medium. It includes at least one sensor chip 42 for determining a parameter, and a channel structure 22 having a main channel 24 and a measurement channel 30 is formed in the sensor housing, and the sensor housing 12 ) is at least partially made of plastic, in the sensor 10,
wherein the sensor (10) includes at least one electrode (48, 60, 64), the electrode (48, 60, 64) disposed within the sensor housing (12) to be covered by plastic;
The sensor housing (12) comprises an inlet (34) into the channel structure (22), which inlet (34) is connected to the main flow direction (38) of the fluid medium at the point of the sensor (10). Sensor (10), characterized in that oppositely oriented, a third electrode (64) is arranged around the inlet (34). The sensor (10) according to claim 1, characterized in that the electrodes (48, 60, 64) are coated with plastic. 3. Sensor (10) according to claim 1 or 2, characterized in that the electrodes (48, 60, 64) are embedded in plastic. 3. Sensor (10) according to claim 1 or 2, characterized in that the first electrode (48) is arranged in the area of the measuring channel (30). Sensor according to claim 4, characterized in that the first electrode (48) is arranged upstream of the sensor chip (42) with respect to the main flow direction (50) of the fluid medium in the measuring channel (30). (10). 5. Sensor (10) according to claim 4, characterized in that the first electrode (48) extends parallel to the measurement channel (30). 3. Sensor (10) according to claim 1 or 2, characterized in that the second electrode (60) is arranged in the region of the main channel (24). delete 3. Sensor (10) according to claim 1 or 2, characterized in that the electrodes (48, 60, 64) are electrically connected to a fixed potential (54). 10. The sensor (10) according to claim 9, characterized in that the fixed potential is sensor ground (56).

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