CS240236B1 - Position sensor, especially for stepper motors - Google Patents

Abstract

A design of a stepper motor position sensor using the gearing of the reaction, mostly moving part of the motor. Perpendicular to the yoke on which the excitation coil is mounted, pole pairs are attached at both ends, which are equipped with toothed pole extensions at the ends. The mutual position of the teeth of the pole extensions of the same pole pair is determined by the relationship == -rz (kt + 0.5), where τζ denotes the tooth pitch in the direction of movement, τζ the tooth pitch and (k) a non-negative integer. The mutual position of the teeth of the identical pole extensions relative to the axis of the yoke of both pole pairs is determined by the relationship τ2 = τ2 (k2 + 0.25), the meaning of the symbols is the same as in the previous relationship. A sensing coil is placed on at least one pole extension of each pole pair.

Description

The present invention relates to a position sensor particularly suitable for stepper motors. It consists of a magnetic circuit, excitation coil and sensing coils.

Optoelectronic incremental encoders are used to sense the position of the moving portion of a linear or reaction stepper motor. When a position is shifted by a certain section, they generate a pulse, the total number of which is a measure of the travel path. In some applications it is necessary to measure 1 motor load angle, ie the difference between the magnetic voltage vector of the fixed part and the magnetic voltage vector (tooth axis) of the moving part. This can only be done with complex electronic circuits with simultaneous synchronization of the pulses with the position of the teeth of the moving part using the incremental encoder.

The above-mentioned disadvantages are eliminated by the embodiment of the position sensor according to the invention, which is characterized in that the magnetic circuit is formed by a yoke, at the ends of which the first and second pole pairs are fixed such that the tooth axes of the first, second, third and fourth pole pieces the pairs are perpendicular to the yoke axis, with one pole piece of each pole pair located on one side of the axis and a second pole piece of each pole pair on the other side of the axis. The teeth of the first and second pole pieces of the first pole pair and the teeth of the third and fourth pole pieces of the second pole pair are offset relative to each other by an integral multiple of the tooth pitch increased or decreased by half the tooth pitch. The teeth of the first and third pole pieces on the same side of the axis of the first and second pole pair are spaced apart by an integral multiple of the tooth pitch increased or decreased by one quarter of the tooth pitch. An excitation coil is located on the mule and a sensing coil is located on at least one opposite pole piece of each pole pair.

1 shows the relative position of the teeth of the reaction part of the motor and the teeth of the individual poles of the sensor; FIG. 2 shows an embodiment of the position sensor of a linear stepper motor.

FIG. 1 shows the relative position of the sensor teeth and the reaction part of the motor necessary for proper operation. The tooth pitch 50 of the engine reaction section 5 is equal to τ _ζ . The relative position τ _{χ of the} teeth 110, 120 of the first and second pole pieces 11, 12, respectively. of the teeth 130, 140 of the third and fourth pole pieces 13, 14 is equal to an integral multiple of the tooth pitch τ _ζ, increased or decreased by half of the tooth pitch τ _ζ . The relative position τ _{2 of the} teeth 110, 130 of the first and third pole pieces 11, 13, respectively. of the teeth 120, 140 of the second and fourth pole pieces 12, 14 is equal to an integral multiple of the tooth pitch τ _ζ increased or reduced by 1/4 of the tooth pitch τ _ζ .

FIG. 2 shows an example of a sensor structure. The magnetic circuit 1 consists of a yoke 15 with an excitation coil 2, a first and a second pole pair 16, 17 with four pole pieces 11, 12, 13, 14 provided with teeth 110, 120, 130, 140. For each pole pair 16, 17 there is at least one opposite pole piece 11, 14 is located a pick-up coil 3, 4. The teeth 110, 120, 130, 140 of the first, second, third and fourth pole pieces 11, 12, 13, 14 occupy the position shown with respect to the teeth 50 1. Thus, the first and second pole pieces 11, 12 of the first pole pair 16 as well as the third and fourth pole pieces 13, 14 of the second pole pair 17 are offset relative to each other in the axis direction o so as to achieve the respective tooth configuration 110, 120, 130, 140 of all pole pieces 11, 12, 13, 14 with their same shape. The first and second pole pieces 11, 12 and the third and fourth pole pieces 13, 14 of the first and second pole pairs 16, 17 are located on both sides of the axis and in order to ensure the same magnetic flux path for both pole pieces 11 and 12, 13, 14 of each pole pair 16, 17.

The excitation coil 2 is supplied with alternating current of constant amplitude. A voltage proportional to the magnitude of the magnetic flux is induced in the sensing coils 3, 4. The sum of the conductivities of the first and second pole pieces 11, 12 and the third and fourth pole pieces 13, 14 does not change, only the distribution of the magnetic flux in them changes. Due to the phase shifts of all pole pieces 11, 12, 13, 14, a voltage uy = U sin ω t is induced in the first sensing coil 3. sin x -—τ _ζ and on the second sensing coil 4 the voltage u ₃ = U sin ω t. cos x ---- ^τ ζ

By evaluating these voltages, we obtain an indication of the instantaneous relative position of the fixed and moving parts of the motor, from which the value of the loading angle can be determined.

Claims (1)

PfiEDMST Position sensor, in particular for stepper motors, comprising a magnetic circuit, an excitation coil and a sensing coil, characterized in that the magnetic circuit (1j is formed by a yoke (15) at the ends of which a first and a second pole pair (16, 17J) are mounted. that the tooth axes (110, 120, 130, 140) of the first, second, third and fourth pole pieces (11, 12, 13, 14) of the first and second pole pairs (16, 17J) are perpendicular to the axis (yoke yoke (15)) wherein one pole piece (11, 13) of each pole pair (16, 17) is located on one side of the axis (o) and a second pole piece (12, 14 J of each pole pair (16, 17) on the other side) axes, (drawbar, teeth (110, 120) of the first and second pole pieces) BACKGROUND OF THE INVENTION (11, 12), the first pole pair (16) and the teeth (130, 140) of the third and fourth pole pieces (13, 14) of the second pole pair (17) are offset relative to each other by an integral multiple of the tooth pitch (τ _ζ ) or reduced by half of the tooth pitch (τ _ζ ) and the teeth (110, 130) of the first and third pole pieces (11, 13) on the same side of the axis (o) of the first and second pole pairs (16, 17) are spaced apart a multiple of the tooth pitch (r _z ) increased or decreased by one quarter of the tooth pitch (τ _ζ ), the yoke (15) having an excitation coil (2) and at least one opposite pole piece (11, 14) of each pole pair (16) 17) a sensing coil (3, 4) is provided.