DE10254855B4 - Air quality sensor and air quality detection method with one sensor - Google Patents

Abstract

sensor for recording air quality parameters, which is connectable or connected to a control unit (42), characterized in that the sensor (41) has a control input (411) and a matching unit (45) connected thereto via which the sensitivity of the sensor (41) is adjustable.

Description

The The invention relates to a sensor for detecting the air quality and a Method for detecting the air quality with a sensor. The proposed sensor for the detection of the air quality is in motor vehicles (automotive), for example, to control a Recirculation damper or an activated carbon filter, which or which part An air conditioner is, can be used.

In In modern vehicles, air quality sensors control the recirculation flap the air conditioning. If there is bad outside air, the recirculation damper will be closed and opened, when the outside air is better again. Bad outside air is, for example, when the concentration of polluted air for the Vehicle occupants is too high. This is measured, for example the NOx concentration and / or the concentration of hydrocarbons in the air surrounding the vehicle.

If The recirculation damper should be closed or opened, thus depends from the quality the ambient air of the vehicle. These are constantly determined Guiding gases monitored in the air. Increases the concentration of a guide gas above a predefined level or shift gradient, the interior of the vehicle must be against the in the surrounding area of the vehicle located harmful gas, hereinafter also referred to as noxious gas, protected become. For this, the air conditioner can cause the recirculation damper to close, if others for the air conditioning relevant data allow this.

Of the Switching level, the switching gradient and the closing time are in the known Air quality sensors stuck in the air quality sensor deposited. Therefore, these parameters are not on the respective motor vehicle adjustable. In addition, you can these parameters are not set by the user and are not adaptable to the respective environment.

From the DE 196 38 204 C1 a device for air quality measurement with an air quality sensor is known, to which a sensor resistance belongs, which changes depending on the pollutant concentration in the air to be monitored in terms of their quality. In a signal processing of this sensor, a resistance change of the resistance of the sensor is converted into an output signal, this output signal being designed as a time period. A certain resistance value of the sensor resistance leads to a certain period duration. This sensor is realized by means of a comparator, to whose inverting input a capacitor c is connected to a reference potential, wherein a resistor is connected to the output of the comparator. At the non-inverting input of the comparator, a sensor resistor is connected to reference potential. At the output of the comparator, the output signal of the sensor is tapped against the reference potential.

The DE 43 33 194 A1 shows air quality sensors that function as part of building air conditioning systems. These building air conditioning systems each include a variety of other measuring units, actuators, etc. Depending on specific objectives, such as air flow, temperature, etc., the active components of these air conditioning systems, eg. B. fan controlled. In one embodiment of the in the DE 43 33 194 A1 described building air conditioning systems, it is possible to change a control unit of the building air conditioning system So that the supply air device is operated manually.

Of the inventive sensor for the detection of the air quality and the method according to the invention for the detection of the air quality with a sensor offer in contrast the advantage that the sensitivity at any time and without further ado is adjustable.

advantageously, the parameters can be adapted to the needs of the vehicle occupants to adjust.

Of the inventive sensor for the detection of the air quality has the features according to claim 1 on.

The inventive method for the detection of air pockets with a sensor has the features according to claim 7.

advantageous Further developments of the invention will become apparent from the specified in the dependent claims Features.

at an embodiment the invention is the sensitivity of the sensor over a Tax byte specifiable.

at a further embodiment The invention is a memory, in particular a read-only memory provided, in which at different sensitivity levels one or several corresponding sensor parameters are stored. As read-only memory For example, an EEPROM can be used. So that can individual sensor parameters via the control byte applied as the address to the EEPROM is selected. That is, the individual values of the control byte are corresponding sensor parameters assigns.

Advantageously, a setting means is also provided, via which the sensitivity can be predetermined by a user. It is thus created a possibility which allows the user, the switching frequency and closing times to his personal perception and personal to adapt to their needs.

Farther can in an additional embodiment be provided of the invention that the control input of the sensor connected to a control output of a control unit of an air conditioner is. This will be the possibility opened, that the air conditioning influence the behavior of the sensor can.

Of the inventive sensor can be used in a motor vehicle to record the air quality in the environment be used of the motor vehicle.

Favorable Way is in a development of the invention one of the sensor parameters a certain slope in the measurement signal, wherein the overshoot this transconductance causes the sensor to switch its signal state on Sensor output changes.

at a further advantageous embodiment of the invention gives a the sensor parameter to a threshold value in the measurement signal, from which it is exceeded the sensor changes its signal state at the sensor output.

Finally, can in a further embodiment of the invention one of the sensor parameters a Specify duration while the sensor retains its signal state at the sensor output.

In a development of the invention can via the sensor output signal a recirculation damper be controlled.

moreover it is possible in a further embodiment of the invention that the transfer of the control byte in series, by means of a pulse width modulated signal or by means of an analog control signal.

in the Following, the invention will be explained with reference to four figures.

1 shows in the form of a time chart the influence of the pollutant level in connection with threshold values on the output signal of the sensor.

2 shows in the form of a time chart the influence of the gradient of the measuring signal on the output signal of the sensor.

3 shows in the form of a timing diagram different output signals of the sensor with different closing times.

4 shows in the form of a block diagram in simplified form a possible embodiment of the invention.

Ways to execute the invention

At the in 1 The time diagram shown in the lower diagram shows the time in seconds on the x-axis and the amplitude on the y-axis. In the upper part of the time diagram the time is plotted on the x-axis and the amplitude on the y-axis. Depending on the amplitude of the gas concentration 15 and the thresholds 13 and 14 arise the two output signals 11 respectively. 12 of the sensor. As long as the concentration of harmful gases does not reach the first threshold 14 is reached, the level at the output of the sensor is 0. At time t11 exceeds the gas concentrations 15 the threshold 14 , which causes the sensor to raise the signal state at its output to level 1, see Signal 12 , At time t14, the level of the gas concentration decreases 15 again below the threshold 14 but the sensor signal remains at the level 1 for the time period Y2. Only then, namely at time t16, does the output signal change 12 the sensor returns to the 0 state. If the threshold is higher than the threshold 14 set what by the threshold 13 in 1 is expressed, results at the output of the sensor, the sensor output signal 11 , Only after the gas concentration 15 the threshold 13 has exceeded, which is the case at time t12, the sensor output signal changes 11 from level 0 to level 1. The gas concentration 15 indeed falls below the threshold again at time t13 13 , the sensor output signal 11 however, it remains at the level 1 for the period Y1. It is not until time t15, that is, after the time period Y1 has passed, that the level of the sensor output signal decreases 11 back to level 0.

With X1 is in 1 the period of time during which the gas concentration 15 the threshold 13 exceeds. With X2 is in 1 the period of time during which the gas concentration 15 the threshold 14 exceeds. The sum of the two time periods X1 + Y1 constitutes the time duration during which the sensor sets the sensor output to level 1 in order to cause the recirculation damper to remain closed for this period of time. The sum of X2 + Y2 also forms a period of time during which the sensor sets the sensor output to level 1 to cause the recirculation damper to remain closed for that period of time. The two sums X1 + Y1 and X2 + Y2 represent only two examples of different durations. Which time period is to be selected can be communicated to the sensor from outside via a control input at the sensor.

At the in 2 is shown timing diagram the time in seconds is plotted on the x-axis on the x-axis and the amplitude on the y-axis. The upper part of the time diagram also shows the time in seconds on the x-axis and the amplitude on the y-axis as logic level 0 or 1. At the in 2 The timing diagram shown depends on the course of the two sensor output signals 21 and 22 of the gradient, that is the slope or the steepness 23 and 24 of the measuring signal 25 from. At time t21, the increase in the gas concentration 25 greater than the slope indicated by the dashed line 23 , As a result, at time t21, the sensor output signal 21 changes from state 0 to state 1. After a certain amount of time has elapsed, the sensor output signal changes 21 at time t22. again from state 1 to state 0. Would instead of steepness 24 the steepness 23 be selected as a reference slope, would result as a sensor output signal at the output of the sensor with 22 characterized waveform, as the gas concentrations 25 at no time the steepness 23 exceeds.

With tsmin is in the time chart in 2 the minimum closing time is indicated. Out 2 it can be seen that the steepness 23 was chosen so high that, despite a significant increase in gas concentration 25 the output signal 22 the sensor does not change to state 1. The steepness 23 is therefore too steep. As maximum steepness, with the steepness of the gas concentration 25 is therefore to choose lower, namely at least so that the minimum closing time tsmin is maintainable. The steepnesses 23 and 24 are just two examples to explain the influence, the slope on the sensor output signal.

At the in 3 shown timing diagram, as well as in the 2 In the lower area on the x-axis the time in seconds and on the y-axis the amplitude is plotted. The upper part of the time diagram also shows the time in seconds on the x-axis and the amplitude on the y-axis as logic level 0 or 1. Exceeds the gas concentration 34 as they are in 3 shown in the lower part is the threshold 33 , the output signal changes 31 respectively 32 of the sensor from logic 0 to level 1. This is the case at time t31. At time t32, the gas concentration decreases 34 again below the threshold 33 , which does not immediately change the level in the output signal 31 respectively 32 of the sensor leads. Only after a period of time Y1 or Y2, the level of the output signal decreases 31 or the output signal 32 again to the logic state 0. This corresponds to the times t33 and t34. Over the time period Y1, Y2, the period of time can be set, which still has to pass until the recirculation damper is opened again after the decrease in the pollutant concentration. The durations Y1 and Y2 in 3 are only two examples for explaining the influence of the delay time on the sensor output signal.

In 4 is shown in the form of a block diagram, the principal involvement of the sensor according to the invention in an overall system. The exit 412 of the sensor 41 is with an entrance 421 a control unit 42 connected to an air conditioner. About the exit 412 of the sensor 41 becomes the sensor output signal 11 . 12 out 1 respectively. 21 . 22 out 2 respectively 31 or 32 out 3 the control unit 42 supplied to the air conditioning. About an adjustment 48 , which on the output side with another input 424 the control unit 42 can be connected by a user a desired sensitivity level of the control unit 42 be communicated. The user thus gets the opportunity, the switching frequency and closing times of the recirculation damper 43 to adapt to his personal perception. Thus the sensitivity level desired by the user is the sensor 41 can be communicated is the control unit 42 over one of their exits 422 with the control input 411 of the sensor 41 connected. Another exit 423 the control unit 42 is with an entrance 431 the recirculation damper 43 connected. About the exit 423 the control unit 42 becomes the recirculation damper 43 controlled. The sensor 41 is with a memory, in particular a read-only memory 44 , fitted. As read-only memory 44 serves an EEPROM. This in turn is an adaptation unit 45 connected by a gas-sensitive field 46 generated measurement signal to the by the control unit 42 adjusted parameters and at the sensor output 412 the sensor provides.

That from the exit 422 the control unit 42 to the control input 411 of the sensor 41 transmitted control byte contains information about the sensor parameters to be set. Thus, 256 different sensor parameters can be set via the 8 bits of the control byte.

Sensor parameters can be, for example, those in 1 shown thresholds 13 and 14 , in the 2 shown slopes 24 and 25 and / or the in 3 closing times shown to be Y1 and Y2. Based on the control byte are from the EEPROM 44 the corresponding values for the threshold, the slope and the closing time of the sensor 41 selected. The sensor 41 then forms the corresponding sensor output signal as a function of these variables and depending on the gas concentration, which then at the output 412 of the sensor 41 is applied.

Those in the cells of the EEPROM stuck behind set levels 13 and 14 , Gradients 23 and 24 and closing times Y1 and Y2 are by a transmission of a certain control byte via a serial communication, a pulse width modulated command or an analog input signal to the sensor 41 specified. In the transmitted control byte, the sensitivity level is thus coded. Depending on the transferred value, the sensitivity levels stored in the EEPROM are called up.

As mentioned, the transfer of the control byte from the control output 422 the control unit 42 to the control input 411 of the sensor 41 for example, by a serial data transfer. Alternatively, it is also possible to accomplish the transmission of the control byte by means of a pulse width modulated control signal or by means of an analog control signal. Which of the mentioned options for data transmission is to be preferred depends on the technical boundary conditions.

The specification of a specific control byte for setting the sensor parameters can also be done by the control unit without the user 42 the air conditioning done. If certain values are set via the air conditioner, these may affect the control unit 42 take the tax byte to be specified.

As adjustment 48 to adjust the sensitivity of the sensor 41 to personal needs, for example, a keyboard, in the form of two buttons for higher and lower sensitivity, or even a rotary wheel serve.

Of the Advantage of the invention is that an adaptation of the pollutant levels, the gradients and closing times to the motor vehicle, to the user and to the environment in the the motor vehicle is located is possible. In particular this without having to remove the sensor and without different Calibrations during production possible. It becomes a possibility created, which allows the user, the switching frequency and the closing times to adapt to his perception.

The when matching, that is while The sensor-specific limit values determined with the calibration can be used with changed to the control byte become. For the limits and steepness can be factors with a 1/256 resolution in the range 0-2 being represented. For the closing times the recirculation damper and the activated carbon filter are factors in the range of zero to 255.

Claims (12)

Sensor for detecting air quality parameters, which is connected to a control unit ( 42 ) is connected or connected, characterized in that the sensor ( 41 ) a control input ( 411 ) and a matching unit ( 45 ), via which the sensitivity of the sensor ( 41 ) is adjustable. Sensor according to claim 1, characterized that sensitivity over a control byte can be specified. Sensor according to one of the claims 1 or 2, characterized in that a memory ( 44 ), in particular a read-only memory, is provided in which one or more corresponding sensor parameters are stored at different sensitivity levels. Sensor according to one of the claims 1 to 3, characterized in that an adjustment means ( 48 ) is provided, via which the sensitivity can be specified by a user. Sensor according to one of the claims 1 to 4, characterized in that the control input ( 411 ) of the sensor ( 41 ) with a control output ( 422 ) an air conditioning control unit ( 42 ) connected is. Use of the sensor according to one of the claims 1 to 5 in a motor vehicle for detecting the air quality in the vicinity of the motor vehicle. Method for recording air quality parameters with a sensor ( 41 ), characterized in that via a control input ( 411 ) of the sensor ( 41 ) the sensitivity of the sensor ( 41 ) and with the sensor ( 41 ) are then detected depending on the set sensitivity air quality parameters. Method according to claim 7, characterized in that a sensor parameter has a threshold value ( 13 ; 14 ) in the measuring signal, beyond which the sensor ( 41 ) changes its signal state at the sensor output. Method according to claim 7, characterized in that a sensor parameter has a certain slope ( 24 ; 25 ) in the measuring signal, beyond which the sensor ( 41 ) changes its signal state at the sensor output. Method according to claim 7, characterized in that a sensor parameter indicates a period of time (Y1; Y2) during which the sensor ( 41 ) its signal state at the sensor output ( 412 ). Method according to one of the claims 7 to 10, characterized in that via the sensor output signal a recirculating air flap ( 43 ) is controllable. Method according to one of the claims 7 to 11, characterized in that the transmission of a control byte serially or by means of a pulse width modulated control signal or takes place by means of an analog control signal.