DE102008033868A1 - Direct current commutator motor for adjustment system for adjustment of e.g. headrest, in vehicle, has set of brushes for short-circuiting adjacent lamellas at same time when small change of brush angle is produced - Google Patents

Abstract

The motor (1) has a set of brushes (8) provided for power supply of armature windings (5). A motor shaft (4) and a magnet set (3) form a four poled magnetic field. The armature windings and a commutator (6) are attached on the motor shaft as a rotatable stator. A set of lamellas (7) is arranged such that number of lamellas is not equal to multiples of four. The set of brushes is arranged each other on the commutator by a brush angle. The brushes short-circuit the two adjacent lamellas at a same time when a small change of the brush angle and/or small angular misalignment is produced. An independent claim is also included for a motor arrangement coma direct current commutator motor.

Description

The The invention relates to a DC commutator motor, in particular for adjusting a vehicle component, z. B. a vehicle seat component is.

at Electric motors for adjusting different components in the Vehicle is partially provided, a previously stored position or To find the starting position again. There are engines on the one hand with position sensors, z. B. a Hall sensor or a potentiometer, which directly determine the respective position. Furthermore, electric motors Known with ripple counter technology where the position is sensorless is determined.

at Commutator motors, the current from the power supply or the Control device over to brush supplied the at the divided into several slats, serving for current application commutator issue. The lamellae are at the periphery of the commutator against each other be isolated and turn off the armature windings, motor shaft and commutator formed according to the succession of the rotor to brush energized. Here comes each brush from a lamella following the isolated intermediate region or the groove between two lamellae, being the two adjacent ones Slats simultaneously contacted and shorted or bridged, resulting in a change in the current signal leads, which is read by the control device. Thus, the generate permanently energized electric motors in operation according to their Groove on the commutator Current ripple coming from the control device ge for position detection can be used without sensors for this purpose required with the appropriate wiring.

at bipolar motors are generally used a brush angle of 180 °. In engines with an even number of grooves or lamellae spaces and thus even an even number of slats results in a Frequency of the ripple current, which is determined by the speed of the motor multiplied by the number of commutator blades results. at Motors with odd numbers are the slats through the two to brush not shorted at the same time, so that the frequency off the speed multiplied by twice the number of commutator bars results. For the evaluation of both variants of bipolar motors is available corresponding evaluation algorithms.

at many commutator motors with two pole pairs, d. H. four stator poles, become two pairs of brushes with four brushes used. Furthermore, commutator motors with two pole pairs, but only two brushes known. Non-symmetric lamellae numbers result in a more complex one Behavior according to the bipolar motors with an odd Number of slats. Here partly the problem arises that the control unit to evaluate a relatively high number of rippels or high ripple frequency has, especially with simpler and cheaper built control devices to delays or errors.

Of the Invention is based on the object, a DC commutator motor to create, even with a non-symmetric slat number one safe evaluation in ripple counter method allows.

These Task is achieved by a DC commutator according to claim 1 solved. The under claims describe preferred developments. Here are in particular also the entire motor assembly from the commutator and the Control device for implementation the ripple counter method, as well as an adjustment system for adjustment a vehicle component provided.

The Invention is based on the idea, the brush angle of the two brushes of the four-pole motor opposite the ideal arrangement of 90 ° something to change, so that the number of ripples is reduced. Here it is recognized that already a relatively small change in the brush angle or a small angular offset opposite the 90 ° arrangement by a fraction of a slat angle to a geometric Arrangement can lead at the two brushes each simultaneously shorting two adjacent lamellae or over the Groove between two slats. Thus, the short-circuit signals become and generates the resulting current ripple at the same time, so that the Rippelfrequenz or Rippelzahl per revolution clearly reduced, in particular can be halved.

Thus, according to the invention especially opposite the 90 ° arrangement an angular misalignment of a fraction of the fin angle (less as a whole slat angle), e.g. B. half of a slat angle be made, the change in principle to Reduction or enlargement of the brush angle can be used.

According to the invention here is It has been recognized that the relatively small angular offset to none significant influence on the engine characteristics. This results in particular in a four-pole motor with a number of slats above 12, in particular a lamella number of 14, since here the angular offset of half a slat angle is very low.

Consequently can the controller enable safe detection of the motor position.

The Motor assembly according to the invention in particular for adjusting a seat component, z. B. for longitudinal adjustment, Backrest tilt adjustment or height adjustment the headrest used become. Furthermore, uses are z. B. as a window possible.

The Invention will be described below with reference to the accompanying drawings explained in more detail on an embodiment. It demonstrate:

1 an electric motor for a seat adjustment in axial section;

2 a view of the commutator of the electric motor 1

3 a current-time diagram of the electric motor according to the invention.

An electric motor 1 according to 1 a cylindrical housing 2 , a serving as a stator magnet set 3 with two pole pairs and thus four by the magnet set 3 permanently excited stator poles as well as a rotor, which consists of a shaft 4 , Armature windings 5 and a commutator 6 is formed. At the commutator 6 are according to 2 fourteen louvers 7 arranged distributed in the circumferential direction, where two brushes 8th issue. To the two brushes 8th is from a controller 12 over two lines 10 a DC voltage U, z. B. applied as a PWM signal, so that sets a current I. The lamella brush system thus serves in a known manner as a mechanical commutation of the commutator 1 , The two brushes 8th are at this four-pole motor on the commutator 6 not opposite or at an angle of 180 °, but arranged substantially at right angles to each other.

The slats 7 are even over the circumference of the commutator 6 arranged distributed, with the brushes 8th during the rotational movement of the rotor 4 . 5 . 6 glide on them. Here comes each brush 8th thus periodically on a groove 7a or gap between two slats 7 , causing the two adjacent slats 7 shorts. This periodic short circuit leads to the formation of current ripples Ir in the current-time diagram of the 3 in which the current intensity I is plotted as a function of the time t, where T indicates the period or circulation time; the current ripples Ir are shown schematically in shape and size. The of the armature windings 5 generated current ripple Ir are from the controller 12 measured and evaluated by means of ripple counter technology. As a result, the control device 12 the position of the rotor 4 . 5 . 6 without an additional position sensor such. B. Hall sensor or a potentiometer determine.

In the embodiment shown, there are fourteen fins 7 at the commutator 6 intended. Each lamella 7 with an adjacent groove 7a thus extends over a fin angle γ of 360 °: 14 = 25.71 °.

According to the invention, the two brushes 8th arranged at a brush angle α ≠ 90 ° to each other, ie there is an angular displacement β = 90 ° - α ≠ 0 relative to the right angle of 90 ° before. Here it is recognized that, although initially a 90 ° arrangement of the energization of the armature windings 5 would be the most effective, a small angular displacement β, however, does not affect the engine characteristics or not relevant.

The angular offset β is chosen such that the two brushes 8th at the same time two adjacent lamellae 7 short. Thus, the angular offset β in this embodiment corresponds to half the fin angle γ, ie, γ / 2.

Because the two brushes 8th always two slats at the same time 7 short-circuit, here results in a behavior or a current-time diagram with a number of current ripples Ir, as is to be expected in a four-pole commutator motor with a brush angle α = 90 ° and a fin number n, which is divisible by four, or also like a two-pole motor with a brush angle of 180 ° and even number of slots.

In the fourteen-pole commutator motor 1 with the slat angle γ = 360 °: 14 = 25.71 °, the brush angle α is thus increased according to the invention to 4 × 25.71 ° = 102.9 °, so that in each case two adjacent slats 7 be short-circuited at the same time and gives a pulse number m with m = 14 pulses or current ripples Ir per revolution, which corresponds to the number of lamellae n.

The control unit 12 thus counts at a speed of z. B. 3000 revolutions per minute corresponding to 50 revolutions per second 700 ripples per second.

alternative to the embodiment shown the brush angle α also on 3 × 25.71 ° ≈ 77.14 ° set be, d. H. a half Lammelenwinkel less than 90 °. The shown Training with α = 4 × 25.71 ° will be here but chosen as advantageous.

at of a lamination number n = 13 and thus γ = 360 °: 13 = 27.69 °, the brush angle α can be set to 3 × γ = 83.08 ° become.

Claims (8)

DC commutator motor, in particular for a vehicle seat adjustment, wherein the commutator motor ( 1 ): armature windings ( 5 ), a commutator ( 6 ) with circumferentially distributed slats ( 7 ), two on the slats ( 7 ) adjacent brushes ( 8th ) for the power supply of the armature windings ( 5 ) and for receiving in the armature windings ( 5 ) generated ripple signals (Ir), a motor shaft ( 4 ), and a magnet set ( 3 ) for forming a four-pole magnetic field, wherein the armature windings ( 5 ) and the commutator ( 6 ) on the motor shaft ( 4 ) are mounted as a rotatable stator, characterized in that a number of lamellae (s) of the lamellae ( 7 ) of the commutator ( 6 ) is not equal to a multiple of four, the two brushes ( 8th ) at a brush angle (α) to each other on the commutator ( 6 ), which has an angular offset (β) from 90 °, and the two brushes ( 8th ) always two adjacent slats ( 7 ) short circuit. DC commutator motor according to claim 1, characterized in that the brush angle (α) is an integer multiple of a fin angle (γ), which is a subdivision of the circumference of the commutator ( 6 ) in the lamella number (s). A DC commutator motor according to claim 1 or 2, characterized in that the brush angle (α) with respect to 90 ° to a Part of the slat angle (γ) is reduced or increased. DC commutator motor according to claim 3, characterized characterized in that with an even number of lamellae (n) the brush angle (α) compared to 90 ° by half of Slat angle (γ) is reduced or increased. DC commutator motor according to claim 4, characterized characterized in that the number of fins (n) is fourteen. Motor assembly comprising: a DC commutator motor ( 1 ) according to one of the preceding claims, and a control device ( 12 ) for applying the two brushes ( 8th ) with a DC voltage (U) and for receiving and evaluating the current ripple signals (Ir) by a ripple counter method for determining a position of the electric motor ( 1 ). Motor arrangement according to claim 6, characterized in that the control device ( 12 ) in determining the position of the electric motor ( 1 ) determines a motor revolution as a number of current ripple signals (Ir) corresponding to the number of slats (n). Adjustment system for a vehicle, in particular for adjusting a vehicle seat component or as part of a window lift, wherein the adjustment system a Motor arrangement according to claim 6 or 7 and to the on-board voltage the vehicle is connected.