Regulator for heating and air conditioning appliances in motor vehicles

A regulator for heating and air-conditioning appliances in motor vehicles, having a suction fan which is driven by an electrically commutated DC motor and in whose induction air flow a temperature measurement sensor is arranged. A disturbance in motor running which may lead to an incorrect temperature measurement is detected at an early stage by providing measurement means which, in two time intervals, determine measurements that are proportional to the frequency of the motor voltage, and compare these measurements with one another.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates generally to field of automated controls.
 More specifically, the present invention is directed to a regulator for
 heating and air-conditioning appliances in motor vehicles. The device
 employs a suction fan which is driven by an electrically commutated DC
 motor and a temperature measurement sensor arranged in the induction air
 flow.
 2. Description of the Related Art
 Regulators for heating and air-conditioning appliances are used to
 determine the interior temperature in motor vehicles. In these devices, an
 electrically powered suction fan is used to suck air out of the interior
 of the vehicle and to move it past a temperature measurement sensor. The
 temperature measured by the temperature measurement sensor is used to
 regulate the heating and air-conditioning appliance. Since only a small
 amount of air is sucked out of the passenger compartment, low-power
 electrically commutated DC motors are used to drive the suction fan, and
 also have the advantage that they produce little noise.
 In order to ensure that the electrically commutated DC motor starts
 reliably, it is known for appropriate motors to be used whose starting is
 ensured by means of an integrated Hall sensor. However, Hall sensors are
 relatively expensive components. German Patent Application DE 43 40 580
 furthermore discloses a regulator for heating and air-conditioning
 appliances, in which there is no Hall sensor.
 In order, nevertheless, to ensure that the electrically commutated DC motor
 starts reliably, this invention proposes that an interrupter be arranged
 in the circuit of the DC motor. The interrupter is actuated by a timer and
 is used to interrupt the motor supply voltage cyclically, in a pulsed
 manner. As a result of this measure, when the supply voltage is built up
 once again in the starting phase, the motor receives rotation impulses at
 regular time intervals, which ensure starting by virtue of their continual
 repetition.
 The mass inertia of the rotating fan bridges the current interruption,
 which lasts for only fractions of a second, so that there is no reduction
 in the measured air flow sufficient to adversely affect the measurement
 results in any way, and the motor is not overloaded. However, if the motor
 fails to start despite these measures, or if the motor remains stationary
 during operation for any reason whatsoever, then this results in no air
 being conveyed out of the interior of the vehicle or past the temperature
 measurement sensor. Consequently, the air-conditioning regulating process
 is based on an incorrect actual value of the internal temperature.
 SUMMARY OF THE INVENTION
 The present invention overcomes these shortcommings and provides an
 improved regulator for heating and air-conditioning appliances in motor
 vehicles, in which the lack of any drive for the suction fan from the DC
 motor is identified at an early stage. A further object of the invention
 is to provide a method for operating an electrically commutated DC motor
 which can be used in the abovementioned regulator. Other objects and
 advantages will be apparent from the following description set forth
 below.
 At the very least, the first-mentioned object is achieved, for a regulator
 of this generic type for heating and air-conditioning appliances in motor
 vehicles wherein the regulator has measurement means, which are connected
 to the actuation electronics and to the drive winding of the motor for
 determining a first and a second measurement. In this embodiment, the
 first measurement is proportional to a first frequency f1 of the cyclic
 voltage on the drive winding of the DC motor in a first time interval
 .DELTA.t1, and the second measurement is proportional to a second
 frequency f2 of the cyclic voltage on the drive winding of the DC motor in
 a second time interval .DELTA.t2.
 In this case, the expression "measurements proportional to a frequency"
 also means those which are inversely proportional to the frequency.
 With the regulator according to the invention, a cyclically varying voltage
 occurs on the drive winding during operation, in a manner known per se. As
 is known from DE 43 40 580, this motor voltage may be briefly interrupted.
 After the end of the interruption, the motor thus receives a new pulse
 when the voltage starts once again, which acts as a starting pulse on a
 stationary motor. However, in an equivalent manner, it is also possible
 not to interrupt the voltage, but to leave it briefly at a constant
 voltage level. This once again results in the motor briefly receiving no
 drive energy. With this process as well, the motor then receives starting
 pulses as a result of the subsequent voltage change. In accordance with
 the invention, it is possible to make a determination of measurements
 which are proportional to the frequency of the voltage on the drive
 winding at different times. The invention provides a reliable means to
 identify whether the motor is being supplied with drive energy.
 One alternate exemplary embodiment of the regulator according to the
 invention provides for the motor voltage to be briefly and cyclically
 interrupted throughout the entire motor running time, or cyclically to be
 briefly kept at a constant voltage level. In this case, the first time
 interval .DELTA.t1 preferably directly follows the time interval when the
 voltage on the drive winding of the DC motor is briefly switched off or
 constant, and measurements proportional to the frequency are determined
 and evaluated at different time intervals .DELTA.t1 and .DELTA.t2.
 If the frequency in the second time interval .DELTA.t2 is greater than the
 frequency in the first time interval .DELTA.t1, then it can be assumed
 that the motor is running reliably. If this condition is not satisfied,
 then starting pulses can be supplied to the motor once again, in the known
 manner.
 Furthermore, a comparator is provided for comparison of the
 frequency-proportional measurements, and thus may be used for evaluation.
 The comparator supplies an output signal which is a function of the
 comparison of the frequency-proportional measurements in the time
 intervals .DELTA.t1 and .DELTA.t2. Starting pulses for the DC motor can
 then be generated, if necessary, as a function of the output signal from
 the comparator.
 In the regulator according to the invention, it is not only possible to use
 the known electrically commutated DC motors with an integrated Hall
 sensor, but also to use electrically commutated DC motors without a Hall
 sensor, which have an auxiliary winding in addition to the drive winding.
 The method according to the invention for operating an electrically
 commutated DC motor, in which the DC motor is supplied with a cyclically
 varying voltage and the cyclic variation of the voltage is briefly
 switched off at times is distinguished by a first measurement being
 determined in a first time interval .DELTA.t1. This measurement is
 proportional to the frequency f1 of the voltage in the time interval
 .DELTA.t1. A second measurement is determined in a subsequent time
 interval .DELTA.t2. The second measurement is proportional to the
 frequency f2 of the voltage in the time interval .DELTA.t2.
 The first and second measurements, which are proportional to the
 frequencies f1 and f2, are preferably compared with one another. A
 starting signal is supplied to the motor when the second measurement,
 which is proportional to the frequency f2, is less than or equal to the
 first measurement, which is proportional to the frequency f1. In the case
 of measurements which are inversely proportional to the frequency, the
 same statements apply in the opposite sense.
 In one preferred embodiment, the invention provides for the rotation speed
 of the DC motor to be determined from at least one of the measurements
 which are proportional to frequency f1 or f2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
 FIG. 1 shows, schematically, the electrically commutated DC motor 1
 together with the corresponding electrical components. The motor 1 is
 electrically actuated by actuation electronics 2. The voltage on the drive
 winding of the motor 1 is tapped off, and is supplied to the measurement
 means 3, 4, which generate a measurement, proportional to the frequency of
 the motor voltage, within a time interval .DELTA.t1 or .DELTA.t2.
 There are various operations for doing this, which are known per se. For
 example, the time from one maximum of the voltage profile to the next
 maximum of the voltage profile can be recorded. Alternatively, it is
 possible to record the time from one voltage maximum to the next voltage
 minimum. Alternatively, it is possible to start from any desired voltage
 value and to record the time until this particular voltage value is
 reached once again. In order to improve the measurement accuracy, the
 measurement may also be extended over a number of cycles. Furthermore, a
 time interval .DELTA.t1 or .DELTA.t2 may also be split into subintervals,
 and the measurements may be averaged over the individual sub-intervals.
 In all cases, an integrator which integrates a DC voltage may be started,
 for example at the commencement of a time interval. The integration is
 ended at the end of the time interval. The reciprocal of the integrated DC
 voltage is then proportional to the frequency of the voltage applied to
 the motor. It is also possible to dispense with forming the reciprocal.
 There is no need to know the absolute frequency value, since all that is of
 interest is how the frequency changes as the time duration increases.
 Thus, to do this, it is sufficient to know the frequency-proportional
 signals obtained in the time intervals .DELTA.t1 and .DELTA.t2.
 The means for determining the frequency-proportional measurements may also
 include a single measurement means as well as a storage element for
 storing the measurements in the time interval .DELTA.t1 or .DELTA.t2.
 Furthermore, a comparator 5 is provided to compare the
 frequency-proportional signals obtained by the measurement means 3, 4. The
 output signal from the comparator 5 is supplied to the actuation
 electronics 2. Depending on the output signal from the comparator 5, the
 actuation electronics 2 generate a starting voltage, when required. To do
 this, the cyclically varying voltage is briefly interrupted or is kept at
 a constant voltage level. The subsequent voltage pulse leads to the DC
 motor being started.
 FIG. 2 shows the voltage profile on the drive winding of the motor 1. The
 cyclically varying voltage is interrupted for a short time period
 .DELTA.tPause, or is kept at a constant value. The motor receives a
 starting pulse from the voltage pulse at the end of the time interval
 .DELTA.tPause. A measurement that is proportional to the voltage frequency
 is then determined in a first time interval .DELTA.t1. The same applies to
 a subsequent time interval .DELTA.t2. The measurements determined in the
 two time intervals provide information as to whether the motor is running
 correctly. If the frequency in the time interval .DELTA.t2 is greater than
 the frequency in the time interval .DELTA.t1, then it can be assumed that
 the motor is running correctly. On the other hand, if the frequency in the
 time interval .DELTA.t2 is less than or equal to the frequency in the time
 interval .DELTA.t1, then this means that the rotation speed of the motor
 is decreasing, and it is not running correctly. If this situation is
 detected, then the actuation electronics 2 can output another starting
 pulse to the motor at an early stage. Starting pulses are likewise output
 if the frequencies detected in the two time intervals are the same. To do
 this, the voltage on the drive winding of the motor is once again briefly
 interrupted, or set to a constant value. This early action allows any
 disturbance in the motor running to be prevented at an early stage as
 well, thus preventing corruption of the measurements on a temperature
 measurement sensor.
 FIG. 3 shows the complete regulator. It is comprised of the electrically
 commutated DC motor 1, which is supplied from the actuation electronics 2.
 An impeller 6 is mounted on the shaft of the motor 1 and moves air past a
 temperature measurement sensor 7, from the interior of the motor vehicle.
 The DC motor 6 and impeller 6 in this case form a suction fan. The
 temperature measurement sensor 7 is connected to a microprocessor 8, which
 is used to control the air-conditioning system. The complete regulator is
 arranged, for example, behind a front panel 9 of the controller of the
 heating and air-conditioning system, with the front panel 9 having an
 opening 10 through which the air is sucked out of the interior of the
 motor vehicle.
 FIG. 4 shows an actuation circuit for the electrically commutated DC motor.
 The actuation circuit supplies the drive winding W1 of the DC motor with a
 voltage that varies with time. An auxiliary winding W2 is required to
 produce this voltage. The drive winding W1 is set in motion by applying a
 voltage to it. This induces a voltage in the auxiliary winding W2 which,
 via the illustrated circuit comprising transistors T, resistors R and
 capacitors C, now produces the voltage, which varies with motor rotation,
 on the drive winding W1 in a manner known per se. A corresponding circuit
 is used, for example, to operate the S 2000 sensor fan from Pabst-Motoren
 GmbH, Sankt Georgen. The illustrated circuit, which is known per se, is,
 according to the invention, connected to the comparator 5 via an
 intelligent switch 11, which can briefly interrupt the voltage on the
 drive winding of the motor in order to generate a starting pulse.