MXPA96005183A - Alternate current generator for vehic - Google Patents

Abstract

The present invention relates to an alternating current generator for a vehicle, characterized in that it comprises: a stator, having a stator core with a plurality of teeth that are formed in the lower periphery thereof and a winding of the stator; rotor positioned in the lower part of the stator and having a polar core which has a plurality of toothed poles on an outer periphery thereof to provide magnetic poles and a wound portion, an inductor coil placed in the devanand portion and a permanent magnet placed between the gear poles, where a ratio between a cross-sectional area for each magnetic pole of a magnetic path of the wound portion and the area of the peripheral surface of each of the tooth poles facing the teeth, is between 70% and 12

Description

ALTERNATE CURRENT GENERATOR FOR VEHICLE BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to an AC generator for a vehicle, which is driven or activated by a motor and supplies an AC power.

Description of the related art A conventional AC generator for a vehicle has an inductor or magnetic field rotor with a so-called Lundell-type polar core and an inductor coil. A part of the magnetic flux generated in the polar nuclei leaks through the adjacent toothed poles. Therefore, a quantity of the magnetic flux passing through the magnetic path of the rotor is usually larger than a quantity of the magnetic flux passing through the peripheral surface of the toothed poles. In general, the relationship between the cross-sectional area of the magnetic path of the wound portion of the gear poles REF: 23344 and the area of the peripheral surface of the gear poles is approximately 140% because the cross-sectional area of the magnetic path is designed to be proportional to the amount of magnetic flux considering the reduction of the weight of the rotor and increasing the output power by the weight of the same. To increase the output power, the magnets or permanent magnets are placed between adjacent toothed poles thus reducing leakage or loss of magnetic flux. However, if the magnetic flux of the permanent magnets is added to the stator, excessive voltage can be generated, even when the inductor coil is not energized. To solve this problem, an optimum relationship between the area of the tooth poles where the permanent magnet is in contact with the base cross-sectional area of each of the toothed poles, has been proposed in Patent Application JP 4255451. However, if this ratio between the cross-sectional area of the wound portion and the area of the peripheral surface of the tooth poles is applied to the rotor having the permanent magnet between the tooth poles, the cross-sectional area of the magnetic path it is not formed properly because the magnetic flux of the permanent magnet is not taken into account. Therefore, the weight of the rotor is not reduced and the energy by weight of the rotor does not become maximum. On the other hand, even if the rotor has the permanent magnet between the toothed poles, the cross-sectional area of the magnetic path only includes the portion of the toothed poles in contact with the permanent magnet and the base portion of the toothed poles, and the weight of the gear poles is smaller than that of the stator. Therefore, the weight of the rotor can not be reduced sufficiently.

BRIEF DESCRIPTION OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an economical alternating current generator, for a vehicle, which has a rotor with a permanent magnet between the gear poles, generating an energy increased by the weight of the rotor with less amount of material. According to one aspect of the invention, a cross-sectional area of the magnetic path of the polar core for each pole is between 70% and 120% of the area of the peripheral surface of each of said toothed poles, which face the teeth . Therefore, the density of the magnetic flux for each of the magnetic paths becomes uniform. According to a test, when the ratio of the above areas exceeds 120%, the increase of the rotor energy by weight is reduced in a sudden manner. On the other hand, when this decrease is less than 70%, the excessive voltage of the generator with the field not excited increases sharply. Therefore, the effective magnetic flux is maintained at the same level as the conventional generator and the rotor weight is reduced, or the weight of the rotor is maintained at the same level as the conventional generator and the effective magnetic flux is increased, leading to the increase in energy by weight. In accordance with another aspect of the present invention, magnets or sintered ferrite magnets, which are widely available, are used. In accordance with another aspect of the present invention, a generator resistant to centrifugal force is provided to use a molded ferrite magnet because of the low specific gravity thereof. The molten ferrite magnet forms a circular element having a plurality of magnetized poles and positioned between the gear poles. Therefore it is easily assembled.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects, aspects and features of the present invention as well as the functions of the related parts of the present invention will become apparent from a study of the following detailed description, the claims and the accompanying drawings. In the drawings: Figure 1 is a cross-sectional view illustrating an AC generator for a vehicle; Figure 2 is a schematic diagram showing the magnetic flux generated by an inductor coil and the magnetic flux generated by a permanent magnet; Figure 3 is a schematic cross-sectional view illustrating a rotor with magnetic dispersion or leakage flow; Figure 4 is a graph showing the relationship between the output power of the rotor per pole, as well as the effective magnetic flux that reaches the stator when the inductor current is not supplied, and the relationship between the cross-sectional area of the trajectory magnetic and the peripheral surface of the gear poles; Figure 5 is a cross-sectional view illustrating a magnetic path of a protruding portion per pole; and Figure 6 is a schematic view showing a relationship between a gear pole and the teeth of the stator core.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES An AC generator for a vehicle in accordance with the present invention is described below. The AC generator 1 for a vehicle, according to one embodiment of the present invention, is composed of a front structure 2, a rear structure 3, a final cover 4, a rotor and a stator. The front structure 2, and the rear structure 3, are made of aluminum castings and joined together at the outer open ends. They are fixed by a plurality of fixed screws 5 and nuts 6. The final cover 4 is fixed to the rear structure 3 and covers a brush unit attached or fixed to an outer portion of the rear structure 3, a regulator of voltage (not shown) and a rectifying unit 7.

The rotor is composed of a shaft 9, to which the motor rotation is transmitted through a pulley 8, a pair of pole cores of the Lundell 10 type, snapped into the shaft 9, an inductor coil 11 wound on the polar cores 10, and a plurality of permanent magnets 12, installed inside the cores 10. The shaft 9 is rotatably supported through the bearings 13 and 14, by the respective protruding portions 2a and 3a of the front structure 2 and the structure rear section 3. The pulley 8 is adapted to one end of the outer shaft of the front structure 2, and held by a nut 15. A pair of pole cores 10 have a cylindrical protruding portion 10a, a plurality of tooth poles-two 10b and portions of disc 10c connecting the protruding portions 10a and each of the toothed poles 10b. The polar cores 10 are snapped into the shaft 9 from the opposite sides in the axial direction so that each toothed pole of one of the pole cores extends between two toothed poles of the other core of the pole, on the inductor coil. Each of the toothed poles has a trapezoidal peripheral surface tapering towards the edge as shown in figure 6. Two cooling fans 16, are fixed by hard-solder or other means similar to the opposite axial ends of the polar cores 10, to generate cold air when it rotates. The inductor coil 11 is electrically connected to a pair of slip rings 17, which are carried by the shaft 9, through lead wires lia and 11b and are supplied with the inductor current from a battery (not shown) to through a pair of brushes 18 which slide over the slip rings 17. When the inductor current is provided to the inductor 11, all the toothed poles 10b of one of the polar nuclei 10A are magnetized towards the South pole and all the poles teeth 10b of the other polar core 10B are magnetized towards the North pole. The rubbing unit is composed of the escobi-lias 18, the springs 19, the inclination of the brushes 18 against the outer periphery of the sliding rings 17, a brush holder 20 holding the brushes or brushes 18 and the spring 19, therein, and a cover 21 of the sliding ring , which covers the circumference of the sliding ring 17. The stator is composed of a core 22 of the stator snapped into the inner periphery of the front structure 2 and a winding or winding of the armature placed in the core 22 of the stator. The core 22 of the stator is composed of annular, laminated steel plates having numerous teeth 22a as shown in FIGS. 5 and 6 formed in the inner periphery thereof to face the outer peripheries of the toothed poles 10b. The winding 23 of the stator has three separate coils connected to or connected to A, placed in slots between the teeth 22a of the stator core 22 as shown in FIGS. 5 and 6 and which generate an alternating current voltage when the rotor rotates. . The permanent magnets 12 are magnets or sintered ferrite magnets and are placed between the surfaces of the opposite side 10d of the adjacent toothed poles 10b in the rotary direction by a joint or the like. They are magnetized to have the same pole as the lateral surface facing the toothed poles as shown in figures 5 and 6. As shown in figure 2, because the main magnetic flux Jl is generated in the portion protruding 10a by the inductor coil 11 in a direction opposite to that of the magnetic flux id2 generated by the permeant magnets 12, the magnetic flux $ a (ie $ 1 - 352) passing through the protruding portion 10a reaches be smaller than the main flow íl. In this way, the cross-sectional area Sa of the pole-pole magnetic path of the protruding portion 10a can be made smaller than the cross-sectional area of the same magnetic path without the permanent magnets. Meanwhile, the number of magnetic poles corresponds to the number of toothed poles 10b in this mode. That is, if the nuclei 10 of the Lundell type have six toothed poles, the number of poles is "6". On the other hand, an effective magnetic flux Fd reaches the teeth 22a of the core 22 of the stator from the peripheral surface 10O of the tooth poles 10b. The magnetic flux before it reaches the teeth is reduced from the main magnetic flux by the dispersion or leakage flow (L) (the magnetic leakage or dispersion flux between the lOe portion of the rim as well as the lower periphery lOf of the toothed poles 10b and the outer periphery of the protruding portion 10a) and increased by the magnetic flux $ 3 of the permanent magnet 12. In this way, a quantity of the magnetic flux passing on the peripheral surfaces 10O of the toothed poles 10b or the effective magnetic flux? d is larger than the quantity without the permanent magnets 12. Therefore, the area of the peripheral surface Sd of the toothed poles 10b facing the teeth 22a is designed to be wider than the surface area peripheral without the permanent magnets 12. A relationship between the cross-sectional area Sa of the magnetic path of the protruding portion 10a per pole and the peripheral surface area Sd of one of the toothed poles 10b facing the teeth 22a, is described below with reference to figures 4, 5 and 6. The graph shown in Figure 4 is obtained using two kinds of permanent magnets and a polar core having the following characteristics, permanent magnet material: (1) Br sintered ferrite magnet: 440 mT, Hrt.:259 kA / m and BHMA ?: 36.7kT / m3 (2) Molded ferrite magnet of Br: 140 mT, HfB : 100 kA / m and BHMA ?: 3.6 kT / m3 size of the permanent magnet: 7.7 mm in width (placed between the gear poles), 16 mm in length and 10 mm in depth number of poles: 12 core material of the pole: steel cold forged from Bc.f,: 1.68 T, He: 200 kA / m external diameter of the core of the pole: 90 mm axial length of the core of the pole: 40 mm As the cross-sectional area Sa of the magnetic flux of the protruding portion 10a becomes relatively smaller as soon as to the area of the peripheral surface Sd, the output energy by weight of the rotor is increased excessively if the sectional relation (Sa / Sd) is not greater than 120%. The critical sectional ratio of 120% is valid either with the sintered ferrite magnets or with the molded ferrite magnets. The modalities with the sintered ferrite magnets provide a maximum output power when the sectional ratio is 100%, which is 45% larger than the output power of a generator that has a conventional rotor which does not have a permanent magnet. -nente. On the other hand, it is necessary to prevent excessive voltage caused by the magnetic flux 53 of the permanent magnets 12 when no inducing current is supplied because such excess damages the battery. For this purpose, the degree of magnetic saturation of the protruding portion 10 is designed to be smaller than the degree of magnetic saturation of the peripheral surface area Sd of the toothed poles 10b. To reduce the magnetic flux $ 3, the ratio of the cross-sectional area Sa of the magnetic path to the cross-sectional area Sd of the toothed poles 10b, ie, (Sa / Sd), should not be less than 70%. Because the modalities have 100% ratio of cross-sectional areas, such excessive voltage is not generated. Therefore, the output energy of the rotor by weight increases and the excessive voltage with the non-inducing current is prevented. In the above description of the present invention, it has been described with reference to the specific embodiments of said invention. However, it will be evident that various modifications and changes can be made in the specific embodiments of the present invention, without departing from the spirit and broad scope of the invention as described in the appended claims. Accordingly, the description of the present invention is this document, is to be considered in an illustrative sense rather than in a restrictive sense.

It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it relates.

Having described the invention as above, property is claimed as contained in the following

Claims (5)

R E I V I N D I C A C I O N S

1. An AC generator for a vehicle, characterized in that it comprises: a stator, having a stator core with a plurality of teeth that are formed in the lower periphery thereof and a winding of the stator; and a rotor positioned in the inner part of the stator and having a polar core which has a plurality of toothed poles on an outer periphery thereof to provide magnetic poles and a wound portion, an inductor coil positioned in the wound portion and a permanent magnet placed between the jagged poles; wherein a ratio between a cross-sectional area for each magnetic pole of a magnetic path of the wound portion and the area of the peripheral surface of each of the toothed poles facing the teeth, is between 70% and 120% .

2. An AC generator according to claim 1, characterized in that the ratio is approximately 100%.

3. An alternating current generator according to claim 1, characterized in that the permanent magnet comprises a magnet or sintered ferrite magnet.

4. An AC generator according to claim 1, characterized in that the permanent magnet comprises a molded ferrite magnet.

5. An alternating current generator according to claim 1, characterized in that each of the toothed poles of the polar core comprises an approximately trapezoidal peripheral surface facing the teeth.