DE3543047A1 - DC motor without a commutator - Google Patents

Abstract

In order to accelerate and to brake a stepping motor (when used as an actuating drive) at maximum speed, the stepping frequency must be predetermined in a ramp function. This results in the following disadvantages: - the ramp function must be matched to the load torque, - the torque of the motor may not be fully utilised owing to stepping losses, - a high level of electronics complexity for implementing the ramp function. When using a DC motor for an actuating drive, a high level of control-engineering complexity and additional measurement devices for position detection are necessary for exact positioning. The present circuit for a motor combines the advantages of DC motors and stepping motors without the disadvantages mentioned above. The essential element is the changeover between internal and external commutation, which is achieved in the case of a DC motor of known type in that the drive signals PHI 1-4 which are formed from the sensor signals phi 1, phi 2 in switching logic 3 are connected to the switching transistors 7 directly or in a clock-pulse dependent manner (clock signal TJ) with any desired delay time. In the first case, the motor operates as a DC motor and can thus move to a required position at high speed, while the clock control is used for exact setting of the required position. The clock control can be made to act as a function of the difference between the actual and required positions.

Description

State of the art

The invention is based on a collectorless DC motor the genus of the main claim. Such a motor is known (DE-PS 29 00 547).

In such a known motor, the position sensors Position of the rotor tapped and then via a switching logic and a driver circuit sequentially the individual motor coils controlled. The speed is controlled by a voltage regulator Setpoint set. If such a motor is intended for example for one Actuator is used, then there is a large dynamic range necessary, d. H. for the exact setting of a target position, the Speed can be continuously reduced to zero. For quick Adjustment requires the highest possible speed. For this is the sole voltage control is no longer suitable because the engine torque if possible kept constant over the entire speed range must become.

But it has also been shown that stepper motors for one Actuator can only be used to a limited extent as they accelerate and deceleration work very heavily depending on the load and then the entered  Step impulses no reliable information about the rotor position allow. Acceleration and deceleration are possible here based on a guide size; however, this requires an increased expenditure on electronics.

Advantages of the invention

The collectorless DC motor with the characteristic features The main claim has the advantage that with little effort a position control can be carried out. The circuit described with the control of the control signals via clock pulses fulfills two Conditions:

With very high frequency clock pulses, i. that is, the frequency is one Multiple of the frequency of the control signals, the motor works like a DC motor.

At a clock frequency that is lower than the frequency of the control signals the motor works like a stepper motor. Here the motor is turned one step further with every clock pulse. The step size is defined by the number of pole pairs and is, for example in a two-pole motor, 90 ° mechanically.

It is also advantageous to additionally switch the switching logic via a torque direction signal to influence. This is a very simple one Reversal of the torque possible.

Finally, it is advantageous to use the actual position of the motor of a counter. A position control can thus be used a target-actual comparator. Thus the DC motor to a servomotor with high positioning accuracy. Additional advantages the invention result from the description and from the Subclaims.  

drawing

An embodiment of the invention is shown in the drawing and explained in more detail in the following description.

Show it:

Fig. 1 shows the circuit configuration in block form,

Fig. 2 is a timing diagram showing the high frequency clock pulses,

Fig. 3 is a timing diagram with low-frequency clock pulses.

The block diagram shown in FIG. 1 shows a two-phase motor 1 . A sensor device 2 coupled to the motor generates two signals ϕ ₁ , ϕ ₂ , from which four control signals are formed in a switching logic 3 . The linking of the sensor signals to form the control signals is carried out in a known manner and is shown for example in DE-PS 29 00 547.

The switching logic 3 is also supplied with a torque direction signal M _{R / L.} The sensor signals ϕ ₁ , ϕ ₂ are fed via the signal line L / R (direction of rotation signal) and step (sensor pulses) to a counter 4 , which thus generates a position signal. This position signal is transmitted via a position output 5 , for example to an actual value display, not shown here. The control signals Φ _1-4 formed by the switching logic 3 are fed to a buffer memory 6 , which transmits these signals α _1-4 to the power transistors (block 7 ) in synchronism with a clock pulse. The drive currents formed by the power transistors reach the motor coils (not shown here) via lines 8 .

The operation of the buffer 6 is explained below with reference to FIGS. 2 and 3. Fig. 2 shows the signal formation at a high frequency of the clock pulse, while Fig. 3 shows the signal formation at a low clock pulse frequency.

In principle, the buffer memory 6 works in such a way that each clock pulse transmits the drive signals Φ _{1-4 present} in the output signals without conversion. As shown in Fig. 2, the clock pulse has 50-100 times the frequency of the drive signals Φ _1-4 . As a result, the delay time T _d between control signals and output signals is only approx. 1-2% of the control phase and thus has practically no influence on the output signals.

In this case, the motor works as a normal DC motor and thus fulfills the requirement to carry out a rapid rotary movement close to a target position. If this proximity to the target position is reached, or if the motor has to travel only a small angle of rotation, then the frequency of the clock pulses according to FIG. 3 is set. For a better representation, the time axis has been compressed here, the time span t ₁ - t ₂ corresponds to the time shown in FIG. 2 between the points t ₁ , t ₂ . The control signals Φ _{1-4 present} at the buffer memory 6 are switched through to the output at a time on the clock signal T _J at time t ₁ . The motor switches one phase. The sensors recognize this rotary movement, the combination of the sensor signals ϕ ₁ , d ₂ by means of the switching logic 3 forms the control signals Φ _1-4 shown at the time t ₂ . These control signals are only switched through again on a rising edge of the clock signal T _J , ie at time t ₃ , whereupon the motor is turned one step further. It can be seen that the step angle of the motor in this operating mode depends on the number of motor phases and can therefore be chosen as desired.

Likewise, the engine speed in cyclical operation can be arbitrary can be set, for example, with a decreasing Clock frequency of the motor an actuator with a defined delay bring a target position.

Claims (5)

1. Collectorless DC motor, in particular for use as an actuator with non-contact commutation sensors for forming commutation signals, a switching logic forming control signals from these signals by logic combination and a power stage for exciting the motor windings, characterized in that an intermediate memory ( 6 ) is provided, the the control signals ( Φ ) are supplied and the frequency variable clock pulses ( T _J ) are also supplied, the control signals being connected to the power stage ( 7 ) in synchronism with the clock pulses. 2. Collectorless DC motor according to claim 1, characterized in that a two-phase winding with four winding phases and two commutation sensors is provided, the signals ( ϕ ₁ , ϕ ₂ ) of the commutation sensors are linked by means of the switching logic ( 3 ) such that four control signals ( Φ _1-4 ). 3. Collectorless DC motor according to claim 1 or 2, characterized in that the switching logic ( 3 ) a torque direction signal ( M _{R / L} ) is supplied, which controls the logical combination of the signals of the commutation sensors. 4. Collectorless DC motor according to one of the preceding claims, characterized in that a counter ( 4 ) is provided which determines the actual position of the motor position from the signals of the commutation sensors and from the direction of rotation. 5. Collectorless DC motor according to claim 4, characterized in that a target-actual comparator, the actual position and a target value is supplied and the output signal controls the direction of the torque ( M _{R / L} ) and the clock pulses ( T _J ).