Patent Application
20130082564
The present invention relates to an alternator for a vehicle which is mounted on a passenger automobile, a truck or the like.
Recently, an alternator for an automobile is required to satisfy a demand for the miniaturization and the enhancement of power generating ability while keeping the same frame. That is, there has been a demand for providing a miniaturized high-output alternator for a vehicle at a reasonable cost.
An alternator for a vehicle described in patent document includes a rotor having a rundel-type core which is constituted of a cylindrical portion, a yoke portion, and claw-shaped magnetic pole portions. This patent document 1 proposes the alternator for an automobile where a length of a stator core in the axial direction is set larger than a length of the cylindrical portion of the rotor in the axial direction, and a cross-sectional area of a root of the claw-shaped magnetic pole portion is set narrower than an area of the cylindrical portion and a cross-sectional area of the yoke portion. Due to such a constitution, a portion of a magnetic flux directly flows into the stator core from the yoke, and a coil cross section of a field coil is ensured by decreasing a cross-sectional area of roots of the claw-shaped magnetic pole portions.
PTL 1: Japanese patent publication 3381608
However, in making the cross-sectional area of roots of the claw-shaped magnetic pole portions narrower than an area of the cylindrical portion and a cross-sectional area of the yoke portion as in case of the rotor core described in the above-mentioned patent document 1, it is necessary to study such decrease of the cross-sectional area in more detail by taking into account the magnetic saturation in the vicinity of the roots of the claw-shaped magnetic pole portions. For example, when the cross-sectional area of roots of the claw-shaped magnetic pole portions is excessively small, the magnetic resistance is increased and is saturated at the roots of the claw-shaped magnetic pole portions so that it is difficult to enhance an output current to an expected level.
In this manner, the way how to enhance an output current has been the task that an alternator for a vehicle has to achieve. Under such circumstances, it is an object of the present invention to achieve the further enhancement of performance of an alternator for a vehicle having a rundel-type rotor by improving a shape of a rotor core.
To overcome the above-mentioned drawbacks, one desirable aspect of the present invention is as follows.
In an alternator for a vehicle which includes: a rundel-type rotor which includes a cylindrical portion around which a field coil is wound, first and second plate-shaped end plate portions which are arranged such that the end plate portions face both end surfaces of the cylindrical portion in the axial direction in an opposed manner, a plurality of first claw portions which extend parallel to a rotary axis in the direction from the first end plate portion to the second end plate portion, and a plurality of second claw portions which extend parallel to the rotary axis in the direction from the second end plate portion to the first end plate portion, and are arranged alternately in the circumferential direction with respect to the plurality of first claw portions; and a stator which is arranged on an outer peripheral side of the rundel-type rotor with a rotary gap therebetween so as to face the rundel-type rotor in an opposed manner, and has a laminated core on which an armature coil is wound, a size of a gap between a claw magnetic pole of the first claw portion and a claw magnetic pole of the second claw portion which are arranged adjacent to each other is set to a value which falls within a predetermined optimum gap range including a size of the gap between the claw magnetic poles where an output current becomes maximum.
According to the present invention, the further enhancement of an output current of an alternator for a vehicle can be realized.
Hereinafter, the best mode for carrying out the present invention is explained in conjunction with drawings.
Slip rings 9 for supplying electricity to a field coil 12 are mounted on a rear end of the shaft 18. Both ends of a coil conductor which constitutes the field coil 12 extend along the shaft 18 and are connected to the slip rings 9 respectively. Electricity for generating a magnetic field is supplied to the field coil 12 from a battery mounted on the vehicle via brushes 8 which are brought into contact with the slip rings 9.
A front fan 7F and a rear fan 7R each having a plurality of blades on an outer peripheral side thereof are mounted on both front and rear end surfaces of the rotor 112 in the rotary axis direction. These fans 7F, 7R are integrally rotated with the rotor 112, and circulate air from an inner peripheral side to an outer peripheral side. Here, the front-bracket-14-side front fan 7F has blades smaller than blades of the rear-bracket-15-side rear fan 7R, and a flow rate of air which the front fan 7F can circulate is smaller than a flow rate of air which the rear fan 7R can circulate.
The stator 4 is constituted of a stator core 21 and a stator winding 5, and is arranged to face the rotor 112 in an opposed manner with a slight gap therebetween. The stator core 21 is held in a state where the stator core 21 is sandwiched between the front bracket 14 and the rear bracket 15 from front and rear sides. The stator winding 5 is constituted of three-phase windings, and lead wires of the respective windings are connected to a rectifying circuit 11. The rectifying circuit 11 is constituted of a rectifying element such as a diode, and constitutes a full-wave rectifying circuit. For example, when a diode is used as the rectifying element, a cathode terminal of the diode is connected to a terminal 6, and an anode-side terminal is electrically connected to a body of the alternator for a vehicle. Here, a rear cover 10 in which an air hole is formed for cooling plays a role of a protection cover for the rectifying circuit 11.
Each of the rotor cores 112F, 112R has the cylindrical portion 112a around which the field coil 12 is wound, an end plate portion 112b which is perpendicular to the rotary axis, and a plurality of claw portions 112c which are formed on an outer-peripheral-side end surface of the end plate portion 112b and extend parallel to the rotary axis. As shown in
As shown in
The field coil 12 which is wound around a coil bobbin 17 is arranged between outer peripheries of the cylindrical portions 112a and inner peripheries of the claw portions 112c. The coil bobbin 17 is fitted on the cylindrical portions 112a of the rotor cores 112F, 112R, and the field coil 12 is wound around a barrel portion of the coil bobbin 17 about the rotary axis. The insulation of the field coil 12 is ensured by the coil bobbin 17 which is interposed between the rotor cores 112F, 112R and the field coil 12.
Stator windings 5 of a U phase, a V phase and a W phase are connected to each other by the three-phase Y-connection, and terminals of the stator windings 5 on a side opposite to neutral point side of the stator windings 5 are connected to joints of the diodes 111 which are connected in series. The upper-side (plus-side) diodes 111 have a common cathode, and the common cathode is connected to a plus terminal of a battery 99. Anodes of the lower-side (minus-side) diodes 111 are connected to a minus terminal of the battery 99.
In this embodiment, although the explanation is made by taking the double-star winding shown in
Next, the explanation is made with respect to the power generating operation. As described above, the pulley 1 and the engine-side pulley are connected to each other by the belt, and the rotor 112 is rotated along with the rotation of the engine. The rotor 112 is magnetized when an electric current flows through the field coil 12 so that a magnetic path which goes around the periphery of the field coil 12 is formed in the rotor 112. On the other hand, a magnetic flux which is emitted from the claw portions 112c of one rotor core enters the stator core 21 and, thereafter, enters the claw portions 112c of the other rotor core. Then, when the rotor 112 is rotated, a rotating magnetic field is formed thus generating a three-phase induced electromotive force in the stator windings 5. The full-wave rectification is applied to a voltage of the three-phase induced electromotive force by the above-mentioned rectifying circuit 11 so that a DC voltage is generated. A plus side of the DC voltage is connected to the terminal 6 and is further connected to the battery 99.
Although the detailed explanation is omitted, a field current which is supplied to the field coil 12 is controlled such that a DC voltage immediately after the rectification becomes a voltage suitable for charging the battery 99 and, further, is controlled corresponding to a state of the battery 99 such that the charging is started when a power generation voltage becomes higher than a battery voltage of the vehicle. An IC regulator (not shown in the drawing) which is provided as a voltage control circuit for adjusting a power generation voltage is arranged in the inside of the rear cover 10 shown in
a) is a view showing an equivalent magnetic circuit of this embodiment, and
On the other hand, an outer peripheral surface shape of a claw magnetic pole of a conventional rundel-type rotor has a shape as shown in
In the equivalent magnetic circuit shown in
As can be understood from
1/r345=1/(r3+r4)+1/r5 r345=r5(r3+r4)/(r3+r4+r5) (1)
Here, it is considered that magnetic resistance r2 is formed of the series connection of magnetic resistance r20 and magnetic resistance r21 shown in
r2=r20+r21 (2)
The magnetic path cross-sectional areas S20, S21 are simply expressed by following formulae (3), (4). Symbol P indicates the number of poles, and symbol W indicates a width of the claw portion 112c as shown in
S20=X2·(πDy/P/2+πDe/P/2)/2 (3)
S21=W·X2 (4)
In this embodiment, to enhance the efficiency of an alternator for a vehicle, a shape of the rundel-type rotor is studied by performing simulations by making use of a three-dimensional electromagnetic field analyzing technique. In this three-dimensional electromagnetic field analysis, adopted is an analyzing method where a set of alternator for a vehicle which includes the stator, the rundel-type rotor and an air layer around the stator and the rundel-type rotor is divided into minute blocks having a proper size (although the minute block is referred to as a minute space block constituted of a node and an element analytically, actually, one set of alternator for a vehicle is divided into several hundreds of thousands number of blocks) by taking into account the magnetic flux distribution and the magnetic flux density on respective portions, and the degree of magnetic saturation, magnetic permeability and magnetic flux density for every minute block are calculated and analyzed in accordance with a distribution constant.
To obtain an alternator for a vehicle having a large output current without changing a frame, it is important for the rotor 112 to generate a larger induction voltage by efficiently introducing a magnetic flux generated by the field coil 12 into a stator core side. In view of the above, in this embodiment, following measures (a) to (c) are taken.
(a) Optimization of a gap size between claw magnetic poles
(b) Improvement of a shape (outer peripheral surface shape) of the claw portion 112c
(c) Improvement of a side surface shape of the claw portion 112c
[a. Optimization of a Gap Size Between Claw Magnetic Poles]
In case of the rotor 112 as shown in
On the other hand, when the gap size G between claw magnetic poles (see
In general, the increase of the claw magnetic pole surface area increases an effective magnetic flux, while the increase of a leakage magnetic flux causes the decrease of the effective magnetic flux. The claw magnetic pole surface area depends on the gap size between claw magnetic poles unless a shape of an outer peripheral surface of the claw magnetic pole is changed. In this embodiment, a simulation calculation of an output current is performed using the gap size between claw magnetic poles as a parameter so as to obtain a gap size between claw magnetic poles where an output current becomes a peak value, that is, a gap size between claw magnetic poles where an effective magnetic flux becomes the maximum.
[b. Improvement of an Outer Peripheral Surface Shape of the Claw Portion 112c]
In this embodiment, the outer peripheral surface shape of the claw portion 112c is set such that a width size W (see
[c. Improvement of Side Surface Shape of the Claw Portion 112c]
In the conventional rundel-type rotator, as shown in
Due to such a shape, a gap size between the neighboring claw portions of the rotor 112, that is, a gap size between the claw portion 112c of the rotor core 112F and the claw portion 112c of the rotor core 112R is held at a fixed value from the outer diameter side to the inner diameter side. This structure is adopted so as to prevent a gap between the claw portions 112c from being decreased even at a position closer to the inner diameter side in an attempt to prevent the increase of a leakage magnetic flux between the claw portions 112c.
However, according to result which inventors of the present invention have acquired by analyzing an electromagnetic field, as shown in
Firstly, the φ128 alternator is explained. Specific sizes of the rotor core are, by making use of representative design constants of the φ128 alternator manufactured conventionally, set such that the number of poles=12 poles, Dy=54 mm, Ds=17 mm, Dr=99.4 mm, and δ=0.3 mm. A thickness X2 of the end plate portion 112b is also set such that X2=13.5 mm in the same manner as a conventional alternator. Further, values of Ly, Ls in
The simulation result (output current) shown in
Such a characteristic may be considered as follows. In a region where the gap size between claw magnetic poles G is smaller than approximately 9.7 mm, when the gap size between claw magnetic poles G is increased, the increase of an effective magnetic flux due to the decrease of a leakage magnetic flux is larger than the decrease of the effective magnetic flux due to the decrease of a claw magnetic pole surface area and hence, an output current exhibits an increasing tendency. On the other hand, in a region where the gap size between claw magnetic poles G is larger than approximately 9.7 mm, the gap size between claw magnetic poles G is large and hence, the influence of the leakage magnetic flux becomes small. Accordingly, the influence brought about by the decrease of the claw magnetic pole surface area becomes dominant so that the effective magnetic flux is decreased leading to the decrease of the output current.
Further, the simulation of an output current is performed not only with respect to the case where the claw shape S1 shown in
The claw shape S2 has a shape shown in
As shown in
Further, although the peak position when the claw shape S2 is adopted is slightly shifted toward a left side compared to a case where the claw shape S1 is adopted, it is considered that such shifting is brought about by the increase of a gap on a claw inner diameter side due to narrowing of the width of the claw portion toward a claw inner diameter side so that the gap G between claw magnetic poles G on which the influence of a leakage magnetic flux is exerted is shifted toward a left side.
On the other hand, an output current curve when a claw shape S3 is adopted and an output current curve when the claw shape S4 is adopted intersect with each other between the gap size between claw magnetic poles G =9 mm and the gap size between claw magnetic poles G=10 mm. When the gap size between claw magnetic poles G is smaller than a value of the size G at an intersecting point, an output current when the claw shape S4 is adopted is larger than an output current when the claw shape S3 is adopted and, to the contrary, when gap size between claw magnetic poles G is larger than a value of the size G at an intersecting point, the output current when the claw shape S3 is adopted is larger than an output current when the claw shape S4 is adopted. Such a characteristic can be considered as follows.
That is, to compare the claw shape S3 and the claw shape S4 on a condition that the gap size G between claw magnetic poles is equal, the claw shape S3 has the same claw width size on an outer diameter side and an inner diameter side and hence, an actual gap size on an inner diameter side is set smaller than the gap size G between claw magnetic poles on an outer diameter side. Accordingly, the claw shape S3 exhibits a larger claw cross-sectional area and a larger leakage magnetic flux than the claw shape S4. That is, the claw shape S3 has a larger effective magnetic flux attributed to the claw cross-sectional area than the claw shape S4 by an amount corresponding to the difference in claw cross-sectional area and, to the contrary, the claw shape S3 has a smaller effective magnetic flux attributed to a leakage magnetic flux than the claw shape S4 by an amount corresponding to the difference in a leakage magnetic flux. Which one of an output current when the claw shape S3 is adopted and an output current when the claw shape S4 is adopted becomes larger is decided based on whether this differential (=the increase of the effective magnetic flux attributed to the difference in claw cross-sectional area)−(the decrease of the effective magnetic flux attributed to the difference in leakage magnetic flux)) is positive or negative.
In a region where the gap size between claw magnetic poles G is small, the influence of a leakage magnetic flux is large and hence, it is considered that the decrease of the effective magnetic flux attributed to the difference in a leakage magnetic flux becomes larger than the increase of an effective magnetic flux attributed to the difference in a claw cross-sectional area. That is, the difference becomes smaller than 0 and hence, an output current when the claw shape S4 is adopted becomes larger than an output current when the claw shape S3 is adopted. On the other hand, when the gap size G between claw magnetic poles is increased to some extent, the influence of the leakage magnetic flux becomes small and hence, it is considered that the increase of the effective magnetic flux attributed to the difference in the claw cross-sectional area becomes larger than the decrease of the effective magnetic flux due to the difference in a leakage magnetic flux. That is, the difference becomes larger than 0 and hence, an output current when the claw shape S3 is adopted becomes larger than an output current when the claw shape S4 is adopted. In a graph shown in
Here, an output current when the claw shape S1 is adopted and an output current when the claw shape S2 is adopted (both claw shapes S1, S2 having a trapezoidal shape as an outer peripheral surface shape of the claw portion 112c) are compared to each other. In this case, the output current when the claw shape S1 is adopted where the claw side surfaces are not made to come closer to each other toward an inner diameter side is always larger than the output current when the claw shape S2 is adopted so that the reversal between the output currents which is brought about when the claw shapes S3, S4 are adopted shown in
An output current curve of the φ139 alternator also exhibits the substantially same tendency as the φ128 alternator. That is, an output current when the claw shape S1 is adopted is, as a whole, larger than an output current when the claw shape S2 is adopted, and an output current curve when the claw shape S3 is adopted and an output current curve when the claw shape S4 is adopted intersect with each other.
In both cases where the claw shapes S1, S2 are adopted, the peak position of an output current falls between G=9 mm and G=11 mm, while the gap size G between claw magnetic poles where an output current when the claw shape S2 is adopted becomes a peak value is smaller than a gap size G between claw magnetic poles where an output current when the claw shape S1 is adopted becomes a peak value. In this manner, also in case of φ139 alternator, when a shape of the outer peripheral surface of the claw portion 112c is a trapezoidal shape, the output current can be enhanced by abandoning the narrowing of the width of the claw portion 112c toward an inner diameter side.
Further, to compare the case where the claw shape S3 is adopted with the case where the claw shape S4 is adopted, the gap size G between claw magnetic poles at an intersecting point of the output current curves is approximately G=9 mm. When the gap size G between claw magnetic poles is smaller than G=9 mm, the output current when the claw shape S4 is adopted is larger than the output current when the claw shape S3 is adopted. To the contrary, when the gap size G between claw magnetic poles is larger than G at the intersecting point, the output current when the claw shape S3 is adopted is larger than the output current when the claw shape S4 is adopted.
When the simulation results shown in
As described above, with respect to the enhancement of an effective magnetic flux in the alternator for a vehicle provided with the rundel-type rotor, the magnitude of a leakage magnetic flux generated by the adjustment of the gap size between claw magnetic poles and the magnitude of the claw magnetic pole surface area have the trade-off relationship. Accordingly, in this embodiment, by carrying out the simulation calculation explained in detail with respect to the output current when the gap size between claw magnetic poles is changed, it is possible to set the gap size between claw magnetic poles between the first claw portion and the second claw portion arranged adjacent to each other to a value which falls within a predetermined optimum gap range including the gap size between claw magnetic poles at which the output current becomes maximum. To summarize the above-mentioned simulation results, the following is obtained.
When only the gap size G between claw magnetic poles is changed to various values without changing the shape of the claw portion 112c, there is a size where an output current value becomes a peak value. To classify optimum ranges of the output current, the optimum range is a range from 8 mm or more to 11 mm or less in case of the φ128 alternator having 12 poles, and the optimum range becomes a range from 8 mm or more to 12 mm or less in case of the φ139 alternator having 12 poles. Further, when the number of poles is 16, the optimum range of the output current becomes a range from 6 mm or more to 8 mm or less in case of the φ128 alternator, and becomes a range from 6 mm or more to 9 mm or less in case of the φ139 alternator. By setting the gap size G between claw magnetic poles in this manner, the output current can be enhanced even when any one of the claw shapes S1 to S4 is adopted.
(Outer Peripheral Surface Shape of the Claw Portion 112c)
In this embodiment, two shapes shown in
With respect to the case where the side surface shapes of the claw portion 112c are set to a shape where a width size is equal between an inner diameter side and an outer diameter side as shown in
Further, in the case where the side surface shape of the claw portion 112c is formed into a shape where the side surfaces are made to come closer to each other as shown in
Although the description of the output current relating to the claw shapes S2, S3 is omitted with respect to the case where the number of magnetic poles is 16, the relationship of the output current between the claw shape S1 and the claw shape S3 and the relationship of the output current between the claw shape S2 and the claw shape S4 in case where the number of magnetic poles is 16 are substantially equal to the corresponding relationships of the output current in case where the number of poles is 12.
In this manner, with respect to the outer peripheral surface shape of the claw portion 112c, the output current can be enhanced by adopting the trapezoidal shape irrelevant to whether or not the side surface shape of the claw portion 112c are formed into a shape where the side surfaces are made to come closer to each other. In other words, it is desirable to increase a width size of the claw portion 112c in the circumferential direction on a cross section perpendicular to the extending direction of the claw portion 112c such that the outer peripheral surface shape of the claw portion 112c has a trapezoidal shape ranging from the distal end to the end-plate-side end portion of the claw portion in the claw portion extending direction thus increasing a surface area of an outer peripheral surface of a claw root portion.
The purpose of forming the outer peripheral surface shape of the claw portion 112c into a trapezoidal shape lies in the improvement of an output current by increasing the surface area of the outer peripheral surface which is a surface through which a magnetic flux permeates, and a trapezoidal shape is a desirable shape when easiness of working or the like is taken into account. However, the shape may be deformed within a category of a trapezoidal shape. For example, a case where rounding is applied to the outer peripheral surface shape also falls within the category of the trapezoidal shape as shown in
(Side Surface Shape of Claw Portion 112c)
To summarize the relationship between the side surface shape of the claw portion 112c and the output current, that is, the relationship between the presence and the non-presence of the narrowed shape and the output current, they are as follows. In this case, as shown in
Firstly, an output current when the claw shape S1 is adopted and an output current when the claw shape S2 is adopted (both claw shapes S1, S2 having a trapezoidal shape as an outer peripheral surface shape of the claw portion 112c) are compared to each other. In both cases of the φ128 alternator and the φ139 alternator, irrespective of a value of the gap size G between claw magnetic poles, the output current when the claw shape S1 is adopted is larger than the output current when the claw shape S2 is adopted. That is, an output current is larger when the narrowed shape is not adopted.
On the other hand, output currents of the claw shape S3 and the claw shape S4 having a conventional shape as an outer peripheral surface shape of the claw portion 112c are compared to each other. In both cases of the φ128 alternator and the φ139 alternator, it is understood that the relationship between the magnitudes of the output currents is reversed. In case of the φ128 alternator shown in
When all of the gap size G between claw magnetic poles, the outer peripheral surface shape of the claw portion 112c, and the side surface shape of the claw portion 112c described above are taken into consideration, in both cases of the φ128 alternator (12 poles) and the φ139 alternator (12 poles), it is preferable that a claw shape is set to the claw shape S1 shown in
The above-mentioned respective embodiments may be used in a single form or in combination. This is because the advantageous effects of the respective embodiments can be acquired individually or synergistically. The present invention is not limited to the above-mentioned embodiments unless the characteristic of the present invention is impaired.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2010/059200 | 5/31/2010 | WO | 00 | 11/12/2012 |
