JPH0139311B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vehicle alternator having a field pole shape that reduces ripple in the DC output voltage.

With the advent of car electronics in recent years, the quality of vehicle generators as a power source has become increasingly important. A "high-quality power source" means that (1) the average output voltage of the generator does not fluctuate due to fluctuations in vehicle engine rotation or sudden changes in vehicle electrical load;
(2) Items such as instantaneous voltage pulsations such as rectification ripples should be minimized as much as possible. former
Regarding item (1), the voltage regulator
Although considerable improvements have been made through high-precision control based on ICs, the reality is that the latter (2) has hardly been studied at present. If the ripple is large, the specifications of the input power circuit sections of all the electronic devices loaded on the vehicle will become complicated and costly, and the cumulative cost of the entire vehicle will be significant. On the other hand, even if the voltage regulator becomes extremely accurate, if the ripple in the detected voltage is large,
The control accuracy does not improve that much.

Therefore, it has become a particularly important issue to reduce ripple in vehicle alternators and bring them as close to ideal direct current as possible.

FIG. 1 shows a conventionally known vehicular alternator.
A pulley 1 is driven by a V-belt by a vehicle engine (not shown). This driven rotational speed varies depending on the effective diameter of the pulley 1 and the engine rotational speed, but conventional generators have a maximum rotational speed.
It is within the range of 12000 [rpm] to 14000 [rpm].
When the Landel type field rotor 2 directly connected to the pulley 1 rotates while being DC-excited by the field winding 3, field magnetic poles 4a and 4b are alternately located on the outer diameter of the field rotor 2. etc., the armature core 5 receives a rotating magnetic field, and the three-phase armature windings 6a, 6b, 6c provided on the core receive symmetrical three-phase electromotive forces e _a , e _b ,
e _c occurs.

FIG. 2 is a circuit diagram of the vehicle alternator shown in FIG. 1. Note that the voltage regulator, which does not require explanation, is omitted. The three-phase electromotive force e _a , e _b , e _c is the main diode
It is three-phase full-wave rectified by D ₁ , D ₂ , D ₃ , ₁ , ₂ , and ₃ and is supplied to an external vehicle electrical load battery (not shown) as a DC output via the generator output terminal 5 . Ru. On the other hand, armature windings 6a, 6
The armature current flows through b and 6c, and the field flux distribution between the field poles and the armature core becomes a distorted waveform containing a large amount of third harmonic electromotive force due to armature reaction. A third harmonic electromotive force appears at the neutral point 7 of the child winding. As shown in Fig. 3, the potential 8 at the neutral point 7 fluctuates slightly around a potential of about 1/2 of the generator output voltage 9 in the region where the output current and rotation speed of the generator are low. However, in a region where the output current and rotational speed are high, the potential at the neutral point exhibits a large fluctuation 8' exceeding the output voltage 9 and the ground potential (0 [V]). For this purpose, the auxiliary diode D ₀ , ₀ connected to the neutral point in FIG. 2 begins to conduct current. In other words, the third harmonic electromotive force is added to the three-phase full-wave rectified output from the main diodes D ₁ , D ₂ , D ₃ , ₁ , ₂ , ₃ as a DC output through the diodes D ₀ , ₀ . reach.

4a and 4b are expanded views of the armature core, field poles, etc. shown in FIG. 1. The slot pitch arc dimension τ _s on the magnetic pole face shown in Fig. 4b
With ⌒ as one unit, the sides 5a, 5 of the armature core 5
b Arc dimension of the base of the trapezoidal magnetic pole face directly below A⌒
was in the range of 2.8 to 3.3 in these conventional examples.

Conventionally, when the third harmonic electromotive force appearing at the neutral point exceeds the output terminal voltage or drops below the ground potential, it is alternately half-wave rectified and added to the DC output voltage. Therefore, the DC output based on this third harmonic electromotive force has a pulsation rate of 100%. Therefore, although the auxiliary diode D _0,0 is added to the circuit to improve the overall output of the generator, the ratio of the output based on this third harmonic electromotive force to _the overall output is large. Naturally, the ripple also increases. As is well known, the output based on this third harmonic electromotive force increases linearly until the generator rotation speed reaches the maximum rotation speed because it is not affected by armature reaction. The output derived from the three-phase full-wave rectifier circuit reaches saturation in a rectangular hyperbolic shape as the rotation speed increases due to armature reaction. In other words, as the rotational speed of the generator increases, the proportion of the output based on the third harmonic electromotive force in the total output increases in proportion to the rotational speed. Based on this, the ripple in the output voltage increases as the rotational speed increases. The problem was that the number increased linearly.

At the same time, this was an obstacle to high-speed drive systems known as a means of improving the output per unit weight of automotive alternators.

The present invention creates a magnetic pole shape that makes it difficult to generate third-order harmonic electromotive force at high speeds and high outputs. The object of the present invention is to provide an alternator for a vehicle that prevents the ripple, which is largely relied upon, from increasing beyond a predetermined degree in a high-speed, large-output region.

An embodiment of the present invention will be described with reference to FIGS. 5 and 6.

As mentioned above, conventional generators have a maximum rotation speed of 12,000
14,000 [rpm], but this generator has a maximum rotation speed of 18,000 [rpm] due to the use of a poly V pulley 1' as shown in FIG. The basic structure of the generator is the same as that of a conventional generator, so a description thereof will be omitted.

FIG. 6 is a developed view of the armature core 5 and the field rotor 2 corresponding to FIG. 4, with the field pole plane as a reference. The magnetic pole shape of the conventional generator explained in FIGS. 1 and 4 is such that the A⌒ dimension is in slot pitch units, as shown by the two-dot chain line in FIG. 6a.
The diameter was approximately 2.8 to 3.3, but in this embodiment, the dimension A⌒ is 2.5 times the slot pitch, and the shape is sloped or two-step tapered.

Next, although the results given to the ripple by the magnetic pole shape according to the present invention were confirmed through experiments,
The reason why this effect occurs can be considered as follows.

As mentioned above, the main diodes D ₁ , D ₂ , D ₃
The three-phase full-wave rectified output due to... etc. reaches saturation on a rectangular hyperbola as the rotational speed increases. As shown in FIG. 7, this means that the armature reaction magnetomotive force distribution 1 caused by the armature current is against the field magnetomotive force distribution 10 applied to the armature core 5 of the magnetic poles in the field rotor 2.
1 coincides in phase and cancels out the former magnetomotive force distribution (large demagnetizing effect). The armature reaction magnetomotive force distribution 11 is a trapezoidal distribution based on the structure of the armature core and field magnetic poles. The present invention attempts to make this trapezoid shape more similar to a sine wave.
On the other hand, since the field magnetic flux distribution 10 is sinusoidal and is close to the shape of a magnetic pole, the resulting magnetic flux distribution 12 (the difference between distributions 10 and 11) generated in the gap is as shown by the broken line in FIG. It probably contains the third harmonic, and the third spatial harmonic _component of this magnetic flux distribution is the source of the output derived from the auxiliary diode _D0,0 mentioned above, and at the same time it is also a factor that determines the ripple size. It is becoming.

The effect of the magnetic pole shape according to the present invention will be explained. 6th
As shown in the figure, by setting the A⌒ dimension to about 2.5 in slot pitch units and making the magnetic pole shape slope-like or double-tapered, the field magnetic pole shape becomes slender, and the shape is slender in the direction of the arrow shown in Fig. 6. The magnetic flux distribution changes so that the magnetic flux flowing between the magnetic poles decreases.
That is, compared to the conventional state shown in FIG. 7, the armature reaction magnetomotive force distribution 11 changes from the trapezoidal shape shown in FIG. 7 to a sine wave due to the narrower magnetic pole shape. 10 is slightly deformed from the waveform of FIG. 7 in a direction that projects more sharply.

Since the magnetomotive force distributions 10 and 11 are modified as described above, the third harmonic corresponding to the combination of both magnetomotive force distributions has a gentle wave height. In other words, when the dimension A⌒ is set to about 2.5 in terms of slot pitch, the ripple will be reduced. The above is the effect that occurs when the field magnetomotive force distribution and the armature reaction magnetomotive force distribution overlap at high speed and large output, that is, in a state of so-called demagnetization effect. At low speed rotation, the reactance of the stator coil is small and the delay in the current is small, so that the field magnetomotive force distribution and the armature reaction magnetic flux distribution have a phase difference unlike in Figure 7, which is similar to the so-called cross magnetization effect. state. For this reason, the above-mentioned magnetic pole shape has no effect of reducing the third spatial harmonic with respect to the rectangular magnetomotive force distribution 11 due to armature reaction.

According to the magnetic pole shape of the present invention, in a relatively low speed range, the output addition due to the third harmonic electromotive force is ensured, and in the high speed range, the rate of increase of the third harmonic electromotive force with respect to the rotational speed is reduced. Based on this, the output due to the third harmonic electromotive force increases in a saturated nonlinear manner with respect to the rotational speed, and the slot pitch is similarly limited in a saturated manner with respect to the rotational speed.

FIG. 8 shows the results of actual measurement of changes in the third harmonic electromotive force and changes in ripple with respect to the rotational speed for the generator according to the present invention shown in FIGS. 5 and 6. As mentioned above, this is a high-speed drive generator, and when the magnetic pole shape dimension A⌒ is slot pitch unit, which is the same as the conventional one and A⌒=3.0, it is 7500 [rp
The rated output at [m] is 13.5 [V] and 105 [A]. At this time, the third harmonic electromotive force 13 and the ripple 14 increase linearly as shown by the broken line in the figure, and the ripple shows a very large value of 7 [V] at the maximum rotation speed of 18,000 [rpm]. Therefore, if A⌒=2.5 is applied to this generator as the magnetic pole shape dimension A constituting the present invention, the third harmonic electromotive force 1 with respect to the rotation speed as shown by the solid line in the figure.
5 and ripple 16 have a saturated nonlinear shape, and at the maximum rotation speed of 18000 [rpm], the ripple becomes 5.
It became [V].

In the above embodiment of the present invention, the gap between the magnetic poles and the armature core was explained as a so-called uniform gap, but the same effect can be obtained in other embodiments in which the gap between the magnetic poles and the armature core is an unequal gap as shown in FIGS. 9a and 9b. can get.

In this case, the average gap length 1/2 (δmin +
The arc dimension A'⌒ between the two intersections formed by the virtual magnetic pole surface 18 and the real magnetic pole surface 17 formed by δmAx) corresponds to the magnetic pole dimension A.

As described above, in the present invention, by reducing the magnetic pole shape dimension A⌒, the third harmonic electromotive force and the ripple based thereon can be made to change in the form of a nonlinear saturation curve with respect to the rotational speed. That is, in the low-speed range where ripples are originally small, sufficient DC output addition due to the third harmonic electromotive force is ensured, while in the high-speed range, ripples are limited in a nonlinear saturation manner. As a result, a high-speed drive system for a generator, in which ripple has been an obstacle in the past, can be put to practical use as shown in the embodiments shown in FIGS. 5, 6, and 7.

Finally, with reference to FIG. 10, the magnitude of the magnetic pole shape dimension A⌒ according to the present invention and the magnitude of the effect thereof will be explained.

FIG. 10 shows the ripple 19 and rating at the maximum rotational speed of 18000 [rpm] when the magnetic pole shape dimension A⌒ of the slot pitch unit is changed for the generator according to the present invention shown in FIGS. 5 and 6. Actual measurement of output 20 at rotation speed 7500 [rpm],
It is expressed as a percentage. When A⌒=3.0, the output 105 [A] is 100 [%], and the ripple is 7.0 [V]
is set as 100 [%]. From Fig. 10, the ripple reduction is larger than the output reduction, and as shown in curve 21, A
It can be seen that there is a mountain-shaped peak for ⌒.
That is, the conventional A⌒ dimension range was A⌒≧2.8, but when it became 2.6≧A⌒≧1.8, a ripple reduction effect was observed by changing the magnetic pole shape according to the present invention, and more preferably 2.5⌒⌒≧A. It was found that the effect is particularly large when ⌒≧2.0.
Note that the above embodiment is located at points 22, 23, and 24.

Note that the ripple reduction effect for the above A⌒ is 30 [A] to 110 [A], 13.5 [V] used for vehicles, even if the basic dimensions of the generator, maximum driving speed, and excitation ampere turns are different. If the generator has a rated output of about 100 yen, the results almost match those shown in FIG.

[Brief explanation of drawings]

Figure 1 is a sectional view of a conventionally known vehicle AC generator, Figure 2 is an electrical circuit diagram of the generator in Figure 1, and Figure 3 is a sectional view of a conventionally known vehicle AC generator.
The figure is an explanatory diagram of neutral point potential fluctuation, Figures 4a and 4b are the magnetic pole shapes of a conventional generator, and Figure 5 is a cross-sectional view of a high-speed drive type vehicle alternator having the magnetic pole shape of the present invention. Figures 6a and b are magnetic pole shape diagrams according to the present invention, Figure 7 is a diagram explaining the origin of the third harmonic, and Figure 8 is the fifth harmonic.
Figures 9a and 9b are diagrams showing the third harmonic electromotive force and ripple in the embodiment shown in Figure 6 and Figure 6.
10 shows other embodiments of the magnetic pole shape according to the present invention, and FIG. 10 shows the magnetic pole shape according to the present invention,
An explanatory diagram of the effect. 2... Field rotor, 3... Field winding, 4a, 4
b... Field magnetic pole, 5... Armature core, 6a, 6
b, 6c...armature winding, A⌒...arc dimension,
D ₀ ,. ...Single-phase half-wave rectifier, D ₁ , D ₂ , D ₃ ;
₁ , ₂ , ₃ ...Three-phase full-wave rectifier, _τs ...Slot pitch.

Claims (1)

[Claims] 1. A rotating shaft driven by an engine, a holding part provided on the rotating shaft and holding a field winding, and a plurality of shafts extending in the axial direction from the holding part and each having a tapered tip. a Lundell-type rotor having a plurality of claws; a stator core disposed at a position facing the plurality of claws of the rotor and having a plurality of slots; and a stator core having a three-phase Y-connection wound in the slot. a three-phase full-wave rectifier that rectifies fundamental wave electromotive force induced in the armature winding to generate a main DC output; a single-phase half-wave rectifier that rectifies the third-order harmonic electromotive force induced at the magnetic point and adds a DC output to the main DC output; An alternator for a vehicle, wherein the circumferential arc dimension of the outer peripheral surface of the child's claw portion is 1.8 to 2.6 times the pitch between the slots of the stator.