WO2006106004A1

WO2006106004A1 - Sensor module, in particular for an air conditioning system

Info

Publication number: WO2006106004A1
Application number: PCT/EP2006/050746
Authority: WO
Inventors: Michael Arndt; Gerd Lorenz; Daniela Winkler
Original assignee: Robert Bosch Gmbh
Priority date: 2005-04-07
Filing date: 2006-02-08
Publication date: 2006-10-12
Also published as: DE102005016002A1

Abstract

The invention relates to a sensor module, in particular for an air conditioning system, preferably a vehicle air conditioning system, comprising at least the following: a housing (2), a humidity sensor (4), a temperature sensor (3), and an infra-red optical gas sensor (5) for measuring at least one gas concentration, the temperature sensor (3), humidity sensor (4) and infra-red gas sensor (5) being located in the housing (2). The invention provides a compact sensor module (1), which is cost-effective to produce and permits an autonomous switch between an exhaust air mode and a circulating air mode. Preferably, the sensor module also comprises an evaluation unit (6), which receives the signals of the sensors and which is preferably also located in the housing. In addition, one or more gas sensors (8) for detecting additional gas components, in particular nitrogen oxides, and a pressure sensor (9) are preferably located in the housing (2), said sensors being read by the common evaluation unit, which is preferably an ASIC (6).

Description

Sensor module, in particular for an air conditioning system

The invention relates to a sensor module, in particular for an air conditioner, for. B. a vehicle air conditioning.

In the field of air conditioning and ventilation, vehicles use humidity sensors, temperature sensors and gas sensors to detect nitrogen oxides (NOx) and carbon monoxide. They are usually used in different measuring systems. Vehicle air conditioning systems typically use a temperature sensor and a humidity sensor. They are generally formed separately from each other and z.T. attached via appropriate socket or housing on a common substrate.

The vehicle air conditioning systems can generally be used in an exhaust air operation and a recirculation mode. In exhaust air operation or normal operation fresh air is constantly sucked in, cooled and dehumidified. In recirculation mode, when the recirculation flap is closed, initially only the air of the vehicle interior is cooled, so that the energy requirement can be reduced and fuel can be saved in continuous operation. Since in recirculation mode, however, the concentration of CO2 gas in the air by the breathing air of the occupants increases rapidly and thereby fatigue of the vehicle occupants can occur, such regulations are currently not unproblematic in recirculation mode. Furthermore, the manufacturing costs of a conventional sensor module are high.

DE 197 31 420 A1 shows a device for detecting the pressure and the temperature in the suction chamber of an internal combustion engine, in which a pressure sensor is accommodated in a metallic chip housing. This me- metallic chip housings and a temperature sensor are mounted in separate chambers of an overall housing. Metallic chip packages are expensive, as are ceramic chip packages.

In contrast, the sensor module according to the invention and the method for its production have some advantages.

According to the invention, at least one temperature sensor, a moisture sensor and, in particular infrared-optical, gas sensor are accommodated in a single housing. This will be a small size of the

Sensor module achieved at low production costs. The sensor module according to the invention thus provides on the one hand for the operation of the air conditioning required measurements of the temperature of humidity and determined in addition to the particular infrared optical gas sensor, the CO2 concentration in the ambient air, so that the air conditioner by comparing the determined CO2 content with a preset limit can switch automatically between an exhaust air operation and a recirculation mode.

Advantageously, the sensors are provided by a common evaluation device, e.g. an ASIC, which is preferably also accommodated in the housing. Thus, the processing of the signals of the sensors can already take place in the housing of the sensor module, so that evaluation signals are already output by the sensor module.

According to a preferred embodiment, an additional, in particular physical or chemical, gas sensor for measuring additional gas concentrations, in particular carbon monoxide and / or nitrogen oxides, and preferably also a pressure sensor for measuring the ambient pressure and advantageously also an air mass sensor for

Measurement of air flow provided. They can be inserted into the housing and read out by the same evaluation device. In the housing, the temperature sensor and the humidity sensor are advantageously mounted in separate chambers in order to achieve a rapid, unaffected measurement independently of the other detectors.

The infrared-optical sensor, the temperature sensor and advantageously also the moisture sensor, the air mass sensor and possibly the pressure sensor and the one or more gas sensors can be designed as micromechanical components that deliver reliable measurement results with a small size.

For the infrared optical gas sensor, one or more IR detectors with filters - e.g. a measuring chip with two thermopile structures for a first measurement channel for determining the CO2 content and a second measurement channel for a reference measurement in another wavelength range - be used, wherein the optical path between the IR radiation source and the one or more IR detectors an attached reflector is set, so that a large measuring section can be evaluated with a resulting strong measurement signal.

In addition to the advantageous use in vehicle air conditioning systems z. B. also possible to use in other air conditioners, i. generally in air conditioning systems for recording the measured values of humidity, temperature and gas concentration, whereupon suitable, controlled variables can be determined in particular, but not necessarily, from the measured variables.

The invention will be explained below with reference to the accompanying drawings of some embodiments. Show it:

1 shows a block diagram of a sensor module according to the invention according to a first embodiment; 2 shows a block diagram of a sensor module according to a further embodiment with additional ASIC;

3 shows a temperature sensor used in the sensor module in a) top view and b) vertical section through the membrane;

4 shows a plan view of a microstructured moisture sensor;

FIG. 5 shows the IR-optical gas sensor accommodated in the sensor module in an exploded view; FIG.

6 shows a section through a microstructured pressure sensor used in the sensor module;

Fig. 7 is a section through a in a spectroscopic

Gas sensor used microstructured IR detector; and

Fig. 8 shows a sensor module according to a further embodiment with representation of the chambers in the housing.

A sensor module 1 has a housing 2, preferably plastic housing 2, in which a temperature sensor 3, a humidity sensor 4, an infrared optical gas sensor 5, serving as an evaluation ASIC 6, and advantageously also a further gas sensor 8 -. B. a chemical gas sensor 8 - and a pressure sensor 9 are added. The infrared-optical gas sensor 5 detects the CO2 content in the ambient air; the further gas sensor 8 serves to detect at least qualitatively more gas concentrations, in particular of NOx. Furthermore, an air mass sensor 10 is provided, which measures an incoming air mass flow.

At terminals 12 of the housing 2, a supply voltage Uv is applied, with which the sensors 3, 4, 5, 8, 9, 10 and the ASIC 6 are operated. In the housing 2 is further a gas supply 13th provided, for example, as a free opening or as provided with a gas-permeable membrane opening. In contrast, FIG. 2 shows a further embodiment in which a microcontroller 14 is additionally provided as a control device.

The sensors 3, 4, 5, 8, 9 and 10 measure the introduced through the gas supply 13 into the housing 2 ambient air and give signals S3, S4, S5, S8, S9 and S10 respectively to the ASIC 6, the temperature, a moisture content, the gas concentration of at least a gas portion, the chemical composition, the pressure and the mass air flow measures and outputs an output signal Sa. According to FIG. 1, the ASIC 6 can determine the relevant values directly from the measurement signals or, in accordance with FIG. 2, use the microcontroller 14 for this purpose. The microcontroller 14 may continue to be e.g. serve to integrate the sensor module 1 in a data bus and thus store a bus address and receive signals transmitted via the data bus, or, if necessary, be used for wireless transmission of the signals.

In order to ensure a short response time of the temperature sensor 3, a separate chamber 15 within the housing 2 is preferably provided for the temperature sensor 3. Fig. 8 shows such a configuration in a sensor module 1 with Temperautrsensor 3, moisture sensor 4 and infrared optical gas sensor 5; In this case, a separate chamber 16 is provided in the housing 2 for the moisture sensor 4 in this embodiment; Alternatively, however, the moisture sensor 4 may also be provided in the chamber 15. The infrared-optical gas sensor 5 and the ASIC 6 are correspondingly provided in a further chamber 17 in the housing 2. By the separate chambers 15 16, 17 mutual influences are avoided by in particular the heating of the internal air of the chamber concerned. The chambers 15, 16, 17 are each connected to the external space via gas supply lines 13, the gas supply lines 13 being closed in each case by a porous membrane 18 which prevents the penetration of the gas. prevents dirt and water, but ensures a rapid exchange of air. The internal dimensions of the chambers 15, 16 or the common chamber 15 are advantageously chosen to be small in order to enable a rapid response of the temperature sensor. Since the relevant sensor element is primarily responsible for the chamber size, a micromechanically constructed temperature sensor with main dimensions smaller than, for example, 15 mm × 15 mm × 15 mm offers the possibility of forming a small chamber volume.

The internal structure of the sensor module 1 can be realized in different ways. As a temperature sensor 3 is advantageously provided an element with response times none than 300 ms. For this, the temperature sensor 3 may be e.g. be formed as a micromechanical device in which a membrane 24 is formed on a silicon substrate 20 by forming a cavity 22 from the underside on the upper side, on which a resistance conductor track 26 is formed, eg a metal trace 26 or polysilicon trace. The conductor track 26 runs from contacting pads 28 to the membrane 24 and on the membrane 24 in a meandering or comb-shaped fashion to form a large diaphragm 24 on the membrane 24

To train length. Such a temperature sensor 3 allows response times in the range t <0.1 s.

For the production of the temperature sensor 3 shown in Fig. 3a, b, a thermally well insulating layer package 29, for example of silicon nitride and / or silicon oxide, produced on the silicon substrate 20 by deposition and patterning process, on which the resistance conductor 26 is deposited as a meandering path, for example , The resistance conductor 26 may be made of platinum, aluminum or doped polysilicon, for example. Subsequently, a cavity 22 is etched on the underside of the silicon substrate 20 below the meander-shaped structure of the resistance conductor 26, for example by means of KOH etching, until a thermally insulating carrier membrane 24 is provided middle part of the layer package 29 is formed. Due to the low thermal mass of the membrane 24, the resistance conductor 26 reacts quickly to changes in ambient temperature. In addition, resistance paths can also be generated away from the membrane, which then react with greater time delay to temperature changes. Alternatively, conventional NTC (negative temperature coefficient conductor, thermistor) or PTC (positive temperature coefficient conductor, PTC thermistor) sensors of small size can be used.

The humidity sensor 4 may be e.g. be formed as a capacitive humidity sensor element and according to FIG. 4, a capacitor 30, between the capacitor surfaces 30a, 30b, a gas volume or air volume depending on the moisture provides different Dikektrizi- tätswerte. By z. B. applying an AC voltage and measuring the reactance can thus be determined, the moisture content of the ambient air.

The infrared-optical (or IR spectroscopic) gas sensor 5 can in turn be embodied in different configurations; it preferably has an IR radiation source 52, one or more IR detectors 54 and optionally a reflector 55. According to FIG. 4, an incandescent lamp operated in the low-current range is provided as IR radiator 52, the bulb of which has a high transmission at wavelengths between 3.8 and 4.3 μm. In this case, the light bulb 52 is inserted from below through a printed circuit board 56, on the upper side of which the IR detector 54 designed as a measuring chip is fastened directly or by means of a housing. The reflector 55 comprises a measuring space between the printed circuit board 56 and its reflective inner side and allows a gas exchange through, for example, an opening in its side. The IR radiation emitted by the IR radiation source 52 is reflected on the inner side of the reflector 55 and focused on the IR detector 54; For this purpose, the IR detector 54, for example, a first measuring channel 54a for the optical or spectroscopic measurement in an absorption band of CO2 and a second measurement channel 54b for a reference measurement in a different wavelength range.

The ASIC 6 provides both the means for the control of the sensors 3, 4, 5, 8, 9, 10 and the means for further processing and in particular the amplification of the sensor signals S3, S4, S5, S8, S9 and S10. It also serves as an interface to the outside world, e.g. as a digital interface, e.g. a Local Interconnect Network (LIN) interface or a Serial Peripheral Interface (SPI) interface, or as a wireless interface, e.g. B. as bluetooth interface.

The housing 2 is preferably a molded plastic housing with an integrated plug into which the one or more boards with the detectors, the evaluation electronics 6 and the reflector 55 are mounted by pressing.

The gas supply can preferably take place via one or more openings 62 or an opening in the housing 2 and / or in the reflector 55, which are closed with a gas-permeable, but water-repellent and / or oil-repellent membrane 18, or via a labyrinth-like feed, which Ingress of water and dirt prevented.

The microcontroller 14 can be used to perform preprocessing, e.g. Linearization, threshold monitoring, calculation of signal slopes of the sensor signals to realize. Furthermore, a dew point calculation from the temperature signal S3 and the moisture signal S4 can also be carried out via the microcontroller 14. Furthermore, the microcontroller 14 can also be used to provide a respective desired interface.

The further gas sensor 8 can -. B. as a chemical gas sensor 8 - are used in particular for the monitoring of infrared optical unmeasurable substances such as vapors or gases. For example, he can tion of carbon monoxide (CO) or nitrogen oxides (NOx) can be designed and formed as a thin conductor or conductor layer on a substrate, for example. In this case, the conductor track or layer is covered by a chemically reactive paste whose resistance value changes as a function of gas molecules absorbed on its surface. Furthermore or alternatively, for detection of gases other than CO2, a further optical gas sensor having basically the same construction as the gas sensor 5 but deviating the absorption band used for the measurement can also be used. Depending on the target gas to be detected, other physical evaluation principles, eg. As chemically reactive field effect transistors (ChemFETs), evaluation of a thermal conductivity measurement, opto-acoustic evaluation or sound velocity measurement possible. Depending on the requirement, this allows a qualitative or quantitative determination of other gases.

The pressure sensor 9 can be used for monitoring the ambient air pressure. Here, advantageously, a micromechanical pressure sensor element is used, which is known as such and e.g. 6, a substrate 70 having a cavity 74 and an epitaxial layer 75 (or epitaxial layer stack 75) deposited on the substrate, which forms a membrane 76 above the cavity 74. Piezo resistors 78 formed in the membrane 76 serve as sensor elements.

The IR detector 54 of the infrared optical gas sensor 5 may preferably be formed thermoelectric, pyroelectric or photoelectric and have a bandpass filter for filtering a relevant wavelength range. It is advantageously produced according to FIG. 7 in microstructure technology, for example with a measuring chip 80, a cap chip 82 and two filter chips 84 a, b spaced at a laterally latitudinal distance, which correspond to the measuring channels 54 a, b of FIG. 5. On the measuring chip 80, a membrane 86 is formed above a cavity 88. On the membrane 86, a thermopile structure 90 is applied from at least two contacted conductor tracks, which consist of materials with different Seebeck coefficients, for example a metal, in particular aluminum, and polycrystalline silicon. On the thermopile structure 90, an absorber layer 92 is applied. In the cap chip 82, a cavity 96 is formed on the underside, in which the absorber layer 92 is accommodated. The cap chip 82 is attached to the sensor chip 80 in a vacuum-tight manner by means of a seal glass connection 100. The filter chips 84a, b are fixed on the top side of the cap chip 82 by means of IR-transparent adhesive layers 102. Infrared radiation incident from above is thus filtered in the cap chips 82a, b and passes through the cap chip 82 into the cavern 96 and onto the absorber layer 92, which heats up accordingly, whereby the thermopile structure 90 delivers a measurement signal corresponding to the heating which is advantageously proportional to the intensity of the filtered incident IR radiation.

Claims

claims

Sensor module, in particular for an air conditioner, comprising at least: a housing (2), a humidity sensor (4), a temperature sensor (3), and a particular infrared optical gas sensor (5) for measuring at least one gas concentration, wherein the temperature sensor (3 ), the humidity sensor (4) and the

Gas sensor (5) are accommodated in the housing (2).

2. Sensor module according to claim 1, characterized in that it has an evaluation device (6, 6, 14), the measurement signals (S3, S4, S5) from the humidity sensor (4), the temperature sensor (3) and the gas sensor (5). receives and outputs evaluation signals (Sa).

3. Sensor module according to claim 2, characterized in that the evaluation device (6, 14) in the housing (2) is accommodated.

4. Sensor module according to one of the preceding claims, characterized in that it comprises a pressure sensor (9) which is accommodated in the housing (2).

5. Sensor module according to one of the preceding claims, characterized in that it comprises a further gas sensor (8) for measuring a further gas concentration, which is accommodated in the housing (2).

6. Sensor module according to claim 5, characterized in that the further gas sensor (8) is a chemical gas sensor (8) for a qualitative or quantitative measurement of the further gas concentration.

7. Sensor module according to claim 6, characterized in that the chemical gas sensor (8) is formed as a micromechanical device with an electrically conductive thin film and a thin film applied to the material, the resistance value changes depending on at least one gas concentration.

8. Sensor module according to claim 6, characterized in that the chemical gas sensor (8) is designed as a chemically reactive field effect transistor.

9. Sensor module according to one of the preceding claims, characterized in that it comprises an air mass sensor (10) for measuring an air mass flow, which is accommodated in the housing (2)

10. Sensor module according to one of the preceding claims, characterized in that the evaluation device (6; 6, 14) has an ASIC (6).

11. Sensor module according to claim 10, characterized in that the evaluation device (6, 14) has a microcontroller (14) which receives signals from the ASIC (6) and outputs output signals (Sa).

12. Sensor module according to one of the preceding claims, characterized in that the temperature sensor (3) is formed as a micromechanical device having a substrate (20) and at least one formed on or above the substrate (20) th resistance path (26), e.g. made of platinum, aluminum or doped

Polysilicon.

13. Sensor module according to claim 12, characterized in that on an upper side of the substrate (20) of the temperature sensor (3), a membrane (24) is formed, on which the resistance path (26) extends at least partially.

14. Sensor module according to one of claims 1 to 11, characterized in that the temperature sensor (3) is designed as a non-micromechanical NTC or PTC.

15. Sensor module according to one of the preceding claims, characterized in that the in particular infrared-optical gas sensor (5) is formed micromechanically and comprises: a measuring chip (80) with a membrane (86) and a below the membrane (86) formed cavern (88) a cap chip (82) having a formed on its underside

Cavern (96), and at least one filter chip (84a, b), wherein on the upper side of the membrane (86) a thermopile structure (90) of at least two contacted interconnects of different borrowed materials and a thermopile structure at least partially covering Absorber layer (92) are formed, wherein the cap chip (82) in vacuum-tight connections (100) is mounted on the measuring chip (80) such that its cavity (96) receives the absorber layer (92).

16. Sensor module according to claim 15, characterized in that on the cap chip (82) one or more filter chips (84a, b) are fastened by means of infrared-permeable adhesive bonds (102).

17. Sensor module according to one of the preceding claims, characterized in that in the housing (2) a gas supply (13) is provided.

18. Sensor module according to one of the preceding claims, characterized in that the in particular infrared-optical gas sensor (5) is formed with two channels with a measuring channel (54a) for measuring a CO2 concentration and a reference channel (54b).

19. Sensor module according to one of the preceding claims, characterized in that it in the housing (2) recorded circuit board (56) from below through the printed circuit board (56) plugged through, operated in low-voltage operation light bulb (52), an infrared

Detector (54) and a on the circuit board (56) set reflector (55) which reflects the light bulb (52) emitted IR radiation to the IR detector (54).

20. Sensor module according to one of the preceding claims, characterized in that the temperature sensor (5) in a separate chamber (15) of the housing (2) is arranged.