FR2612013A1 - Improvement to disengageable linear stepper motors - Google Patents

Abstract

Disengageable linear stepper motor of the type comprising a multipole stator provided with a cylindrical bore, inside which can roll a cylindrical rotor, of smaller diameter. In addition to a threading, the stator includes longitudinal grooves which improve the passage of the flux in favoured zones and the positioning of the rotor.

Description

The invention relates to disengageable linear stepper motors. In engines of this type. a multipolar stator is provided with a cylindrical bore inside which can roll, in a cycloidal manner. a cylindrical rotor of smaller diameter.

When the stator coils are successively excited. the rotor turns according to angular steps, the number of which, on 3600. is defined by the number of poles of the stator.

To transform this angular movement into a linear translation step by step, the cylindrical bore of the stator and the rotor, also cylindrical. are threaded at the same pitch.

As a variant, the threading of the rotor may not be helical but consist of parallel circular grooves.

These motors are often used to control the regulating device and their linear movement must be done with precise and repetitive steps.

To do this, it is known, as described in European patent N "078 740 in the name of the applicant, to channel the flux of the stator towards the rotor in precise zones in space, by creating the saturation of the interpolar zones of the stator by reducing the section of the magnetic material.

Despite this, the position of the rotor is not always well defined in the stator due to small air gap differences when the bore of the stator and the diameter of the rotor are close.

The purpose of the motor according to the invention is to avoid this drawback. In it indeed the bore of the stator, in addition to the helical thread. has internal longitudinal grooves. of any shape. but each generating two longitudinal edges. that is to say along generators of the cylindrical bore. These grooves are arranged in the interpolar zones, they have the effect. on the one hand to deviate. by saturation the magnetic flux towards the rotor in the interpolar zones and on the other hand it ensures a precise and repetitive positioning of the rotor which is pressed at each step on the two edges created by the existence of these longitudinal grooves.

The accompanying drawing illustrates, by way of example. an embodiment of an engine according to the present invention.

As shown. the motor comprises a cylindrical carcass 1 in which are adjusted four magnetic poles 10, 11, 12 and 13 intended to receive the four excitation coils 110 - 111 - 112 and 113
A rotor 3 can rotate while rolling. by magnetic attraction in the bore 14 of the stator. The four stator poles are arranged 900 from each other and the motor is characterized in that in the bore 14 four grooves, for example semi-cylindrical 20 - 21 - 22 and 23 were made in the bisector planes of the four stator poles . These grooves generate longitudinal edges in the stator bore.

Besides the fact that these notches, the 21 in the case of the drawing, deflect the magnetic flux t towards the rotor 3 when the coils 110 and 111 are excited, the presence of the longitudinal edges 210. 211 imposes a precise position on the rotor.

This type of motor is particularly suitable for controlling servo devices such as valve control for flow regulation.

Claims (1)

1 - Disengageable linear stepper motor whose rotor rolls inside the bore of a multipolar stator characterized in that the bore (14) has internal grooves C2O - 21 - 22 - 23), longitudinal available in the interpolar areas of the stator.