WO2009083305A1 - Device for determining sluggishness or a blocked state of an electric motor - Google Patents

Abstract

The present invention relates to a device for determining sluggishness or a blocked state of an electric motor (M), wherein the device comprises the following characteristics: a power semiconductor switch (S), connected between a positive supply voltage connection (UB+) of a supply voltage source (UB) and the electric motor (M) itself, wherein the power semiconductor switch (S) is configured to control the current flowing through the electric motor (M) and wherein the power semiconductor switch (S) is further configured to acquire a current flow through the power semiconductor switch (S) and to provide a corresponding current-flow signal (l_sense / Kelvin source); and an evaluation unit (StS) configured to acquire the current-flow signal (l_sense / Kelvin source) and on the basis of the current-flow signal (l_sense / Kelvin source) to determine the presence of sluggishness or a blocked state of the electric motor (M).

Description

 description

title

Device for determining a stiffness or a blocking case of an electric motor

Technical area

The present invention relates to a device for determining a binding or a blocking case of an electric motor according to claim 1.

State of the art

For the heat dissipation and cooling of the internal combustion engines in motor vehicles, blowers or fans are used. They are mostly with

Operated DC motors, for example, are powered by a motor vehicle battery. The fan speed is adjusted with a pulse width modulated battery voltage to the DC motor to reduce the fan noise. For detecting the stiffness, blocking and for the power limitation of the fan motor usually the motor current is measured. This can be done according to a first approach by an inductive measuring method, in which, however, in particular by high currents of the electronic controller is very hot and by this type of measurement, a cooling of the controller is necessary. In addition, additional measuring elements are required for such a detection of the motor current, which is a very costly variant of the detection of the motor current. Alternatively, a detection of the motor current as well via a shunt method in which the motor current is measured by the voltage drop across a resistor. This method also causes a high loss due to the heat conversion in the shunt resistor, so that here (additional) temperature-resistant measuring components are to be used and additionally high electrical power loss occur, whereby this measuring method proves to be costly.

Another approach to current detection using a sense-FET was proposed in WO 2004/030173 A1. In EP 0998776 B1 an end stage circuit for controlling the electric motor has been proposed. However, the approaches mentioned have disadvantages in terms of the circuit arrangement for measuring the current flow through an electric motor such that the motor is not floating in the off state.

Description of the invention

It is therefore an object of the present invention to provide a way to realize the current flow through an electric motor cost and at the same time circuit technology easy.

This object is achieved by a device having the features of claim 1. Further embodiments of the invention will become apparent from the dependent claims.

The present invention provides a device for determining a gravity or a blocking case of an electric motor, the device comprising the following features: a power semiconductor switch, which is connected between a positive supply voltage terminal of a supply voltage source for the electric motor and the electric motor itself, wherein the power semiconductor switch is designed to control the current flowing through the electric motor and wherein the power semiconductor switch is further configured to detect a current flow through the power semiconductor switch and to provide a corresponding current flow signal; and an evaluation unit configured to detect the current flow signal and to determine, based on the current flow signal, the presence of a binding or a stalling event of the electric motor.

The present invention is based on the realization that the use of a power semiconductor switch with a current measuring functionality makes it possible to measure the current flow through the electric motor (which must flow through the power semiconductor switch) in a circuitically simple manner and without great losses. This is possible through the use of modern power semiconductor switches with a corresponding functionality. At the same time, a potential-free state of the electric motor and its connection cable can only be achieved in the case of a parked, switched-off vehicle by means of the high-side circuit arrangement Handling in the workshop during repair work can occur prevented.

It is also favorable if the power semiconductor switch is a field effect transistor with a current detection functionality. This offers the possibility of being able to use an already technically mature and therefore cost-effective semiconductor component for the simple current measurement of the current through the electric motor.

Also, the power semiconductor switch may comprise a parallel connection of two, three or more power semiconductor switch devices. This is advantageous in particular when control of high currents through the electric motor is to be realized, since in this case a split of the current flowing through the electric motor to a plurality of power semiconductor components can be effected by the parallel connection. This will overload the individual Power semiconductor devices reduced, which increases the life of this and at the same time offers the possibility of controlling significantly higher currents through the electric motor. In this case, the current flowing through the individual power semiconductor switch elements can also be detected (and possibly combined into a single signal) in order to be evaluated by the evaluation unit.

Also, according to another embodiment, the device may have a Verpol- protection device which is connected in parallel with the electric motor. This offers the possibility that a fuse against an incorrect connection of the supply voltage source is easy to implement and thus a possible damage to the power semiconductors can be safely excluded by such a wrong connection.

In particular, the device may also comprise a voltage buffer unit which has an electrolytic capacitor or a parallel circuit of electrolytic capacitors and which is connected in parallel with the power semiconductor switch. This is particularly favorable if further elements are fed by the supply voltage source, so that voltage fluctuations can occur.

The voltage buffer unit can then be used for smoothing voltage spikes or fluctuations so that the control unit for the electric motor still operates without errors even in the case of such voltage peaks or fluctuations or in the case of the electromagnetic contaminations and also does not emit electromagnetic interference into the motor vehicle electrical system. A parallel connection of the capacitors offers the advantage that the high currents occurring in the power electronics can be filtered by the parallel circuit, without overheating even capacitors and where individual components reach their thermal electrical limit at high currents and are not suitable for such applications become. Furthermore, the evaluation unit can be designed to control a switching on or a blocking or the clocking of a current flow through the power semiconductor switch. The evaluation unit evaluates the Motorstrommesssignalverlauf and thereby allows a simple and quick shutdown of the current flow through the power semiconductor switch in the event that a Schwergän- speed or blocking of the electric motor is detected, which in turn prevents damage to the electric motor and the control unit is prevented.

Brief description of the drawings

The invention will now be described by way of example with reference to the accompanying drawings. It shows:

Fig. 1 is a schematic circuit diagram of an embodiment of the present invention.

Any dimensions and dimensions given are exemplary only, so the invention is not limited to these dimensions and dimensions. Furthermore, the figure of the drawing, the description and the claims contains numerous features in combination. It is clear to a person skilled in the art that these features can also be considered individually or they can be combined to form further combinations not explicitly described here.

Embodiments of the invention

Fig. 1 shows a schematic circuit diagram of an embodiment of the present invention. In this case, a DC motor M, clocked via the switching device S with integrated diodes D1 and D2 (which are correspondingly arranged in the sense FET power semiconductor switching elements S1 and S2), is clocked to the supply voltage source in the form of a battery with battery voltage U _B. connected. The DC motor M with the switching device S are electrolytic capacitors C1 and C2 connected in parallel via a reverse polarity protection device in the form of an inversely operated n-channel power Mos-FETs S3 and a choke coil L.

The DC motor M is also a freewheeling diode D also connected in parallel via the Verpolschutzeinrichtung. The freewheeling diode D is connected with its cathode to the positive terminal of the DC motor and with its anode to the negative terminal of the electrolytic capacitors and the throttle connection. The drain terminal of the power MOSFET S3 and the negative terminal of the DC motor are connected in common to the negative terminal of the battery voltage. The power MOSFET S3 used as a switch is, for example, an n-channel MOSFET. For example, the sense FETs S1 and S2 are also n-channel MOSFETs with integrated current sensors. In addition to the switching function, they also have an integrated sense function for the motor current.

Furthermore, a control circuit for the MOSFET S3 and the power MOSFETs S1 and S2 according to this embodiment is necessary. This circuit section further includes the control circuit which amplifies and digitizes and evaluates the sense signals of the power sense FETs. The sense connections l_sense and Kelvin source of the power sense FETs thereby provide a current signal proportional to the motor current that can be converted into a voltage signal in the control circuit. This circuit section controls the power SenseFETs S1 and S2 at, for example, 15kHz-25kHz, and the DC drive of the DC motor is also possible for the purpose of setting the maximum power while simultaneously detecting the binding.

With the present invention, therefore, the task can be implemented to realize an electronic control circuit with integrated motor current measurement. With the proposed circuit, the binding or blocking of the fan motor can be detected to prevent damage from the electric motor (eg a fan) or from the overall system and control unit.

The core of the invention consists essentially in the current measurement in the output stage control for the "high side clocked" or switched SenseFET switch for inductive or ohmic loads.The use of a parallel connection of two or more sense FETs can increase the switching capacity At the same time, the construction and construction costs of the control unit can be reduced by reducing the component power dissipation The SenseFET switches have a current measurement integrated in the component Blocking / binding is determined by the current profile sensed in the SenseFET and, for example, by a voltage curve derived from the current profile determined.

Claims

claims Device for determining a binding or a blocking case of an electric motor (M), the device comprising the following features: - a power semiconductor switch (S), which is connected between a positive supply voltage terminal (U _B +) of a supply voltage source (U _B) and the electric motor (M) itself, wherein the power semiconductor switch is formed (S) to a (by the electric motor M) flowing current and wherein the power semiconductor switch (S) is further configured to detect a current flow through the power semiconductor switch (S) and to provide a corresponding current flow signal (l_sense / Kelvin source); and - An evaluation unit (StS), which is designed to detect the current flow signal (l_Sense / Kelvin source) and on the basis of the current flow signal (l_Sense / Kelvin source) to determine the presence of a binding or a blocking case of the electric motor (M) , 2. Device according to claim 1, characterized in that the power semiconductor switch (S) is a field effect transistor with a current detection functionality. 3. Device according to one of the preceding claims, characterized in that the power semiconductor switch (S) from a power semiconductor terschalter or a parallel circuit of at least two Leistungshalblei- terschalterbauelementen (S1, S2) or more. 4. Device according to one of the preceding claims, characterized in that the device further comprises a Verpolschutzeinrichtung (S3) up, which is connected in parallel to the electric motor (M). 5. Device according to one of the preceding claims, characterized in that the device further comprises a voltage buffer unit (C) comprising an electrolytic capacitor or a parallel circuit of a plurality of electrolytic capacitors (C1, C2, ...) and which is connected in parallel with the power semiconductor switch (S). 6. Device according to one of the preceding claims, characterized in that the evaluation unit (StS) is designed to control a switching or blocking of a current flow through the power semiconductor switch (S).