JPH0583909A - Ac generator for car - Google Patents

Abstract

PURPOSE:To provide an AC generator for a car, mandays for machining of which are decreased, and eddy current loss in a magnetic pole of which is reduced and which has excellent power generation efficiency. CONSTITUTION:In an Ac generator for a car composed of a Randel type rotor 1 and a stator 3, grooves 21 interrupting eddy currents are formed in its path on the surface of the magnetic pole 11 of the rotor 1 in the axial direction of the magnetic pole 11. The pitches R of the grooves 21 are set to the quarter or less of the slot pitches T of the stators 3. The grooves take an arbitrary shape such as a V shape, a U shape, a square shape, etc. The depth of the grooves is set to 0.5mm or more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alternator used in a vehicle, and more particularly to a structure of a magnetic pole surface of a rotor.

[0002]

2. Description of the Related Art Generally, it is known that in a rotary electric machine, a harmonic magnetic field is generated by an armature reaction in a gap between a stator and a rotor. Also, with respect to the rotation angle, small magnetic flux pulsation called slot ripple occurs.
This pulsation is due to the change in the porcelain resistance between the facing surfaces between the stator and the rotor. These alternating magnetic fields have almost no adverse effect on the stator composed of laminated plates, but cause eddy current loss and hysteresis loss on the rotor magnetic poles composed of steel ingot. Further, in recent years, there has been a demand for lower fuel consumption of vehicles, and there is a demand for higher efficiency and lower eddy current loss in vehicle alternators. And
In order to meet the above requirements, a vehicle AC generator has been proposed in which the surface of the magnetic pole is provided with an uneven surface that interferes with the passage of the eddy current (Japanese Patent Laid-Open No. 3-139149).
issue).

[0003]

[Problems to be Solved] However, in the above-described conventional vehicle alternator, although a temporary effect on the eddy current loss is recognized, a significant power generation effect cannot be obtained despite the large number of processing steps. was there. The present invention is
In view of the above-mentioned conventional problems, it was made as a result of repeated studies on the relationship between the slot pitch of the stator and the surface structure of the rotor. An object of the present invention is to provide an automotive alternator which has a small number of processing steps, reduces eddy current loss in magnetic poles, and has excellent power generation efficiency.

[0004]

The present invention provides a vehicular AC generator comprising a so-called Lundell type rotor having claw-shaped magnetic poles made of low carbon steel and a stator arranged facing the so-called Lundell type rotor. The surface of the magnetic pole is provided with a groove in the axial direction of the magnetic pole in the path of the eddy current, and the pitch of the groove is 1/4 or less of the slot pitch of the stator. A vehicle AC generator characterized in that the depth is 0.5 mm or more. What is most noticeable in the present invention is that the pitch of the grooves provided on the magnetic pole surface is 1/4 or less of the slot pitch of the stator.

When the slot pitch exceeds 1/4,
Generation of eddy currents increases and power generation efficiency decreases (see FIG. 5 described later). Here, the slot pitch of the stator means the arrangement interval (pitch) of the stator. Also,
The groove pitch of the rotor is 1 of the stator slot pitch.
It is preferably / 4 or less and 17/4 or more of the width of the groove. If the groove pitch is less than 17/4 of its width,
The area of the surface of the magnetic pole excluding the groove is too small, and the power generation efficiency is reduced (see FIG. 5).

The groove is provided in the axial direction of the magnetic pole. The shape of the groove is, as shown in FIG. 3, a V-shaped groove having an acute angled bottom, a U-shaped groove having an arcuate bottom as shown in FIG. 6, and a rectangular groove having a right angled bottom. , Or a combination of these. Further, even if the groove pitches are not the same, they can be formed arbitrarily within the above range (see FIG. 8).

From the characteristic diagram of FIG. 9, it is preferable that the depth of the groove is 0.5 mm or more, which is 0.5 to 1.0 m.
It is preferably m. If it is less than 0.5 mm, the eddy current preventing effect is small, while if it exceeds 1.0 mm, the eddy current preventing effect is saturated. Further, the grooves can be provided at the above-mentioned pitch only in the magnetic pole side edge portion where the magnetic flux changes drastically, and can be formed at a large pitch in other portions. In this case, the number of man-hours for processing the groove is reduced.

[0008]

As described above, when the rotor of the vehicular AC generator rotates, an eddy current is generated in parallel with the magnetic pole surface due to the pulsation of the magnetic flux in the gap between the rotor and the stator. The eddy current becomes smaller as the electric resistance of the magnetic pole material becomes larger. However, in the present invention, the magnetic pole surface is provided with a groove having a predetermined pitch determined in relation to the slot pitch. Therefore, the flow line of the eddy current is divided by the groove. Therefore, the eddy current loss is reduced. Further, since the groove on the surface of the magnetic pole is set to 1/4 or less of the slot pitch, the number of processing steps can be reduced. Therefore, according to the present invention, it is possible to provide an AC generator for a vehicle, which has a small number of processing steps, reduces an eddy current loss in a magnetic pole, and is excellent in power generation efficiency.

[0009]

EXAMPLE 1 FIG. 1 shows an AC generator for a vehicle according to an example of the present invention.
~ It demonstrates by FIG. As shown in FIGS. 1 to 3, the vehicle alternator of this example has an excitation winding 12 in which a coil is wound.
And a rotor 1 composed of a magnetic pole 11 provided so as to wrap the surface thereof, and a stator 3 arranged on the outer periphery of the rotor 1 (see FIG.
(Fig. 3). The surface of the magnetic pole 11 of the rotor 1 is provided with a groove 21 in the path of the eddy current (FIG. 4) that interferes with the eddy current in the axial direction of the magnetic pole 11.

The rotor 1 has a fan 15 behind the magnetic pole 11. The magnetic pole 11 is a substantially trapezoidal claw-shaped magnetic pole whose width decreases toward the tip. The magnetic pole is a so-called Lundell-type multipolar claw-shaped magnetic pole, which is made of a low carbon steel ingot, and the surface thereof faces the inside of the stator core 3. The stator is usually made of a laminated plate having a thickness of 0.5 to 1 mm in which three-phase armature windings are concentratedly wound. 0.6 mm in this example
Is. The gap between the stator and the surface of the magnetic pole is usually 0.3 to 0.5 mm, and in this example, the average is 0.35 m.
m.

The groove 21 is formed in a spiral shape in the rotating direction. As shown in FIGS. 1 and 2, the spiral groove 21 has a pitch R so as to form one spiral along the rotation direction for each magnetic pole 11 that is alternately inserted from the left and right directions.
It is provided in. The groove depth is 0.8 mm. Further, as shown in FIG. 1, the relationship between the groove pitch R and the slot pitch T of the stator 3 is R ≦ T / 4. Further, as shown in FIG. 3, the relationship between the groove pitch R and the groove width W is W ×
17/4 ≦ R.

Next, the relationship between the rotation of the rotor 1 and the eddy current will be described with reference to FIG. In the vehicle alternator of this example, when the rotor 1 rotates with respect to the stator 3, the air gap magnetic flux distribution due to the combined magnetomotive force existing in the air gap between the two is a distortion having an odd-order harmonic magnetic flux component. Become a wave.
The air gap magnetic flux distribution is generated by a substantially sinusoidal magnetomotive force distribution given to the stator core from the magnetic poles 11 and a substantially rectangular magnetomotive force distribution given to the rotor core by the stator core. The odd-order harmonic magnetic flux enters the surface of the magnetic pole 11, but at that time, an eddy current 17 is generated as shown in FIG. 4, so that the harmonic magnetic flux causes eddy current loss near the magnetic pole surface. It will be impatient.

Further, since the above-mentioned approximately rectangular magnetomotive force is applied to the rotor core from the stator core, its cycle becomes a repetition time of one slot pitch, and therefore the cycle of the harmonic magnetic flux and its magnetic flux density B is also one. It is the repetition time of the slot pitch. Also, in the rotor circumferential direction (θ direction), 1
The magnetic flux density B is distributed in the period of the slot pitch. Therefore, the eddy current 17 generated near the magnetic pole surface is
As shown in (dB / dθ) ² [or (dB / dt)
It can be said that it is also ² ], so it occurs at a pitch of T / 2 in the θ direction. In addition, the eddy current generated near the magnetic pole surface is
Since it tries to flow with the minimum length (low resistance) with respect to the area that receives the magnetic flux that is generated, it becomes a perfect circle. Therefore, the pitch in the axial direction is also T / 2. After all, eddy current 1
7 is T on the surface of the magnetic pole 11 as shown in FIG.
It will occur every / 2 block.

In the present embodiment, the groove 21 is provided on the surface of the magnetic pole core so that R≤T / 4.
However, as mentioned above, the streamline of the eddy current generated on the surface must be divided. As a result, eddy current loss is reduced. On the other hand, when the groove width W is constant and the groove pitch R becomes smaller, the remaining area S of the magnetic pole surface excluding the groove portion becomes smaller. Then, the magnetic flux density B (= Φ / S) increases. Since the eddy current loss Z is represented by Z∝B ² , the eddy current Z becomes large. Therefore, it is preferable to consider the lower limit of the groove pitch.

This point will be described below. When the gap between the stator and the magnetic pole surface is 0.3 to 0.5 mm, the maximum magnetic flux density on the magnetic pole surface is usually about 13 K gauss. The average magnetic flux density inside the magnetic pole is usually about 17 K gauss. Therefore, if the magnetic pole surface area in the case where there is no groove is So, then S / So ≧ 13/17. When the remaining width between the grooves on the magnetic pole surface is D (FIG. 3), D / R = (1-w / R) ≧ 13/17. When rewritten, w × 17/4 ≦ R.

Therefore, w = 0.3 mm = 3.4 × 10 ^-2
Regarding the eddy current reduction effect in the case of × T, FIG. 5 shows the relationship between the groove pitch R of the AC generator and the power generation efficiency.
FIG. 5 is a 100 A class alternator with a stator inner diameter of 102 mm, so T = 102π / 36 = 8.9.
(36 is the number of slots), W = 3.4 × 10 ⁻² × 8.9 =
It is 0.3 mm. From the figure, it can be seen that the power generation efficiency is high when the groove pitch R of the magnetic pole is ¼ (0.25) or less of the slot pitch T of the stator. Also, the groove pitch R
Is the groove width W (W = 0.3 mm = 3.4 × 10 ⁻² ×
17/4 times T), that is, 3.4 × 10 ⁻² × T × 17/4
It can be seen that the power generation efficiency is lower than 59% when less than 0.145T.

As is known from this, when R ≦ T / 4 and w × 17/4 ≦ R, that is, 0.145T
In the case of ≤R≤T / 4, it can be seen that the power generation efficiency is superior to that of the comparative AC generator (bar graph in Fig. 5) having no groove in the magnetic pole. Further, it is understood that if the grooves are formed within the above range, the pitch and the groove depth are limited, so that the maximum effect can be obtained with less labor of processing.

Embodiment 2 This embodiment shows grooves 21 of various shapes as shown in FIGS. 6 (a) to 6 (c). That is, FIG. 6A shows a U-shaped groove 21 having a circular arc bottom, and FIG. 6B shows a rectangular groove 21 having a square bottom. Also, FIG. 6 (c)
Is a combination of the V-shaped groove having an acute bottom, the above-mentioned rectangular groove, and the U-shaped groove. Others are the same as in the first embodiment. According to this example, the same effect as that of the first example can be obtained.

Example 3 In this example, as shown in FIG. 7, on the surface of the magnetic pole 11,
The groove 21 having a predetermined pitch similar to that of the first embodiment is formed only on the side edge of the magnetic pole where the magnetic flux changes drastically, and the groove 21 having a pitch twice as large as that of the groove 21 is provided in the other portions. Others are the same as in the first embodiment. According to this example, the same effect as that of the first example can be obtained. Further, in this example, the grooves having the predetermined pitch are provided only on the side edge portions, so that the groove processing is easy.

Embodiment 4 In this embodiment, as shown in FIG. 8, each groove 21 has various pitches R1.
To R4. However, these pitches R1 to R4 are within the scope of the present invention. Thus, if the groove pitch is within the range of the present invention, the effect of the present invention can be obtained even if the groove pitch varies. Therefore, even if the cutting tool is damaged during the groove processing, it is not necessary to perform accurate pitch alignment again during the continuous processing, and the processing is easy. Further, even when using a cutting tool for a multi-thread spiral, even if there is a slight deviation in the pitch of the cutting tool, it can be ignored. Therefore, it is possible to lower the processing accuracy and reduce the processing cost. Also, in this example, the same effect as that of the first embodiment can be obtained.

[Brief description of drawings]

FIG. 1 is a development explanatory view of a rotor and a stator in a vehicle AC generator according to a first embodiment.

FIG. 2 is a perspective view of a main part of the vehicle AC generator according to the first embodiment.

FIG. 3 is an explanatory cross-sectional view of a rotor and a stator of the vehicle AC generator according to the first embodiment.

FIG. 4 is an explanatory diagram of an eddy current on a magnetic pole surface in a vehicle AC generator.

FIG. 5 is a diagram showing the relationship between groove pitch ratio with respect to slot pitch and power generation efficiency in Example 1.

FIG. 6 is an explanatory diagram of various grooves according to the second embodiment.

FIG. 7 is an explanatory diagram of a groove on a magnetic pole according to the third embodiment.

FIG. 8 is an explanatory diagram of a groove pitch according to the fourth embodiment.

FIG. 9 is a diagram showing the relationship between the groove depth of magnetic poles and the eddy current loss of the vehicle AC generator according to the present invention.

[Explanation of symbols]

 1. ． ． Rotor, 11. ． ． Magnetic pole, 17. ． ． Eddy current, 21. ． ． Groove, 3. ． ． Stator, D. ． ． Remaining width, R. ． ． Groove pitch, T.S. ． ． Slot pitch, W. ． ． Groove width,

Claims (2)

[Claims] 1. A vehicle alternator comprising a so-called Lundell-type rotor having a low-carbon steel claw-shaped magnetic pole and a stator arranged so as to face the rotor, wherein a surface of the magnetic pole of the rotor is provided. A groove is provided in the passage of the eddy current to hinder the magnetic pole in the axial direction of the magnetic pole, the pitch of the groove is 1/4 or less of the slot pitch of the stator, and the groove depth is 0. An alternator for vehicles, which is at least 0.5 mm. 2. The alternating current for vehicles according to claim 1, wherein the pitch of the rotor groove is 1/4 or less of the slot pitch of the stator and 17/4 or more of the groove width. Generator.