Electricity: motor control systems – Specific feedback condition or device – Thermal condition
Reexamination Certificate
2000-03-13
2001-12-04
Nappi, Robert E. (Department: 2837)
Electricity: motor control systems
Specific feedback condition or device
Thermal condition
C388S912000, C318S471000
Reexamination Certificate
active
06327425
ABSTRACT:
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 f
1
of the cyclic voltage on the drive winding of the DC motor in a first time interval &Dgr;t1, and the second measurement is proportional to a second frequency f
2
of the cyclic voltage on the drive winding of the DC motor in a second time interval &Dgr;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 &Dgr;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 &Dgr;t1 and &Dgr;t2.
If the frequency in the second time interval &Dgr;t2 is greater than the frequency in the first time interval &Dgr;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 &Dgr;t1 and &Dgr;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 &Dgr;t1. This measurement is proportional to the frequency f
1
of the voltage in the time interval &Dgr;t1. A second measurement is determined in a subsequent time interval &Dgr;t2. The second measurement is proportional to the frequency f
2
of the voltage in the time interval &Dgr;t2.
The first and second measurements, which are proportional to the frequencies f
1
and f
2
, are preferably compared with one another. A starting signal is supplied to the motor when the second measurement, which is proportional to the frequency f
2
, is less than or equal to the first measurement, which is proportional to the frequency f
1
. 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 f
1
or f
2
.
REFERENCES:
patent: 4376894 (1983-03-01), Vogler
patent: 5966001 (1999-10-01), Maehara et al.
patent: 6021252 (2000-02-01), Faris et al.
patent: 6054823 (2000-04-01), Collings et al.
Depke Robert J.
Leykin Rita
Mannesmann VDO AG
Mayer Brown & Platt
Nappi Robert E.
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