This application is based on and incorporates herein by reference Japanese Patent Application No. 2005-080804 filed on Mar. 22, 2005.
1. Field of Application
The present invention relates to an AC generator for installation in a motor vehicle such as a passenger automobile, truck, etc.
2. Description of Related Art
In recent years, due to the increased level of electrical load that is imposed on the AC generator (sometimes referred to as the alternator) of a motor vehicle by the use of safety control equipment etc., a requirement has arisen for increased generating capacity of such an AC generator. Types of rotary electric machine are known, designed to provide a higher level of operating capacity, in which each phase coil of the stator winding is formed of a plurality of conductor segments connected in series, each conductor segment basically formed in a U-shaped configuration. In that way each of the stator slots can be substantially completely filled by these conductor segments, so that the occupancy factor of each slot is higher than can be achieved with a conventional form of stator winding, and a higher operating capacity can thereby be achieved. In particular, a higher output power generating capability can be achieved. Such a rotary electric machine is described for example in Japanese patent publication No. 2001-204151 (pages 2-5, FIGS. 1-4).
With such a type of stator winding, tip portions of the control signal generating section are bent to an appropriate shape such that pairs of the conductor segments can be connected in series by attaching together respective tip portions (e.g., by welding). These pairs of connected protrude axially at one end of the stator core.
Such a rotary electric machine is generally provided with a pair of cooling fans, mounted at axially opposing ends of the rotor, for producing outward-directed flows of cooling air within the interior of the rotary electric machine. However when the stator winding is formed as described above from such successively connected U-shaped conductor segments, with the connection portions are disposed adjacent to the outer circumference of one of the fans, the connection portions (i.e., pairs of connected tip portions) of the conductor segments obstruct the flow of cooling air from the adjacent cooling fan.
This is a significant problem, since achieving effective cooling of the interior of the rotary electric machine is an important factor in attaining increased operating capacity.
Moreover, as a result of the flow of cooling air over the connection portions of the stator winding, an increased level of audible noise is generated, by comparison with a conventional type of stator winding which does not incorporate such connection portions.
It is an objective of the present invention to overcome the above disadvantages of the prior art by providing an AC generator for installation in a motor vehicle (referred to in the following simply as a vehicle AC generator) having a stator winding formed of sets of basically U-shaped conductor segments as described above, but whereby the degree of obstruction of a flow of cooling air due to the presence of the connection portions of the stator winding conductor segments can be substantially reduced, and the level of noise due the cooling air passing over the connection portions can also be reduced.
To achieve the above objectives, the invention provides a vehicle AC generator comprising a rotor (in general, rotated by the vehicle engine), a stator having a stator iron core fixedly disposed opposing the stator, a stator winding disposed in the stator iron core, and a frame which supports the rotor and stator. The stator winding is made up a plurality of conductor segments, each basically formed in a U-shaped configuration having two linear portions that are connected by a turn portion and that extend to respective tip portions, with pairs of the tip portions of respective conductor segments being connected together. According to a first aspect of the invention, such a pair of connected tip portions are oriented along a direction that is inclined with respect to a radial direction of the stator. More specifically, a line (in a plane at right angles to the stator axis) extending between respective centers of such a pair of connected tip portions is inclined with respect to a radial direction of the stator.
In that way, when a flow of cooling air is generated by utilizing rotation of the rotor and passes through the pairs of connected tip portions of the conductor segments, with the air flow being along a direction which is angularly displaced from a radially outward direction, it can be ensured that the amount of resistance presented to the cooling air flow by the tip portions of the conductor segments is reduced, while in addition the level of audible noise resulting from the flow of cooling air over the tip portions of the conductor segments.
From another aspect, each of the conductor segments preferably has a cross-sectional shape that is substantially rectangular, and each connected pair of adjacent tip portions has a pair of substantially circumferentially opposing faces which are respectively flat and are each oriented along the aforementioned direction that is inclined with respect to a radial direction of the stator.
Typically, such an AC generator comprising a cooling fan mounted on an (axial) end face of the rotor, for producing the aforementioned flow of cooling air, i.e. by drawing a flow of cooling air from the exterior, towards inner parts of the rotor, and impelling the cooling air axially outward, along a direction that is inclined with respect to a radial direction of the rotor. With the present invention, the orientation direction of each connected pair of tip portions of the conductor segments is set in accordance with the direction in which the flow of cooling air is impelled outward (i.e., with that flow direction being measured as an angular deviation from a radial direction of flow).
From another aspect, when such a type of fan is utilized then in each pair of connected tip portions of conductor segments, the radially outer tip portion of the pair is preferably positioned ahead of the radially inner tip portion of the pair, with respect to the direction of rotation of the rotor. The resistance to the flow of cooling air can thereby be further decreased.
From another aspect, the frame of such a vehicle AC generator is preferably formed with a plurality of ventilation apertures such as an annular array of ventilation apertures, that are disposed radially outward from the pairs of connected tip portions (for example, with each of the ventilation apertures being located in correspondence with and closely adjacent to a space between two circumferentially adjacent pairs of the connected tip portions), and with each of respective circumferentially opposing faces of each of the ventilation apertures being oriented along a substantially identical direction to an orientation direction of a corresponding one of the radially adjacent pairs of tip portions.
In addition, each of the ventilation apertures preferably has the shape of an outward extension of a space formed between two circumferentially adjacent pairs of the radially adjacent connected tip portions, when that space is extended along a direction that is inclined by the aforementioned angular amount from a radial direction of the stator.
An embodiment of a vehicle AC generator will be described referring first to the overall configuration shown in the cross-sectional view of
The rotor shaft 6 has a pulley 20 fixedly mounted axially thereon, which is coupled to the engine (not shown in the drawings) of a vehicle in which the vehicle AC generator 1 is installed, to drive the rotor shaft 6 for rotation. The Lundel pole core 7 is configured with a set of pole cores. The angled-flow fan 11, which is located at the same end of the rotor shaft 6 as the pulley 20, is fixedly attached to an end face of the Lundel pole core 7, for example by welding. The angled-flow fan 11 has vanes which are oriented at an acute angle with respect to the corresponding end face of the Lundel pole core 7.
The centrifugal fan 12, which is located at the opposite end of the rotor 3 from the pulley 20, is fixedly attached to an end face of the Lundel pole core 7, e.g., by welding, and has vanes that are oriented at right angles to that end face.
The frame 4 is made up of a front frame 4a and a rear frame 4b, with ventilation intake apertures 41a, 41b being respectively formed in axially opposing side walls of the front frame 4a and rear frame 4b respectively. A set of ventilation exhaust apertures 42a (in this embodiment, configured as an annular array of apertures arranged at regular circumferential spacings) is formed in a shoulder portion of the front frame 41a, disposed radially outward from the ventilation intake aperture 41a and adjacent to a first coil end group 31a (described hereinafter), while ventilation exhaust apertures 42b are similarly formed in the rear frame 41b.
The rotor 3 and stator 2 are respectively supported by the frame 4.
A stator iron core 32 of the stator 2 is fixedly attached to the front frame 4a, and has a stator winding 31 mounted therein, with the stator winding 31 being formed of series-connected basically U-shaped conductor segments as described hereinafter. A first coil end group 31a of the stator winding 31, containing connection portions (described hereinafter) between respective conductor segments, protrude axially outward from one end of the stator iron core 32 as shown, while an axially opposing second coil end group 31b (made up of respective continuous curved portions of the conductor segments, referred to herein as the turn portions) protrude from the opposite end of the stator iron core 32. The coil end group 31a are located to receive a flow of cooling-air from the angled-flow fan 11, with the air flow exiting through the ventilation apertures 42a. The centrifugal fan 12 similarly induces a flow of cooling air through the second coil end group 31b, which exits through the ventilation apertures 42b.
The stator 2 will be described in greater detail in the following.
Each stator slot 35 is an axially extending slot formed in the inner periphery of the stator iron core 32, having a substantially rectangular cross-sectional shape as shown in
In this embodiment, linear portions of a total of four conductor segments are accommodated in each stator slot 35, i.e., the conductor portions 331a, 332a, 332b′, 331b′ in the example of
The second coil end group 31b is made up of the continuous curved portions 331c, 332c (referred to herein as turn portions) of respective conductor segments 33, as shown in
It can thus be understood that each conductor portion disposed as an innermost layer within a stator slot 35 (e.g., the portion 331a of the conductor segment 331 as seen in
As shown in
Also as can be understood from
It will be understood that the term “connection” as used herein, applied to an attachment between two tip portions of respective conductor segments, has the significance of both electrical connection and mechanical connection, e.g., as achieved by welding the two tip portions together.
In addition, each conductor portion 332a, forming an inner center layer of a stator slot 35, is paired with a conductor portion 331a′ (not shown in the drawings)), that is the innermost layer within a stator slot 35 that is spaced apart by 1 pole pitch (moving in the clockwise direction of the stator iron core 32). Similarly, each conductor portion 331b′, forming an outermost layer in a stator slot 35, is paired with a conductor portion 332b, that is the outer center layer within a stator slot 35 that is spaced apart by 1 pole pitch (moving in the clockwise direction of the stator iron core 32).
As can further be understood from
As can be understood from
More precisely, (in general, irrespective of the cross-section shape of the conductor segments) a line (in a plane at right angles to the stator axis) that connects respective centers of a pair of tip portions constituting a connection portion is inclined with respect to a radial direction of the stator, for example by the angle θ shown in
With this embodiment, each of the conductor segments has a substantially rectangular cross-section, as shown in
As shown in
A more detailed description of the stator winding 31 and of the connection portions 33d, 33e, will be given in the following. Referring to the partial oblique view of
As shown in
In addition, respective opposing faces (with respect to the circumferential direction) of the tip portions 331d, 332d, 332e, 331e, are flat and mutually parallel, with each of these flat faces being oriented along a direction that is angularly displaced by the aforementioned angle θ from a radial direction of the stator iron core 32. As a result, each of the connection portions 33d, 33e is formed with substantially flat opposing faces (with respect to the circumferential direction), e.g., the opposing faces Ff, Fg indicated in
The extent of this of inclination with respect to radial direction of the stator iron core 32 is by the extent to which the position of the outer tip portion (e.g., the tip portion 331e) in each connection portion is advanced with respect to the position of the inner tip portion (e.g., the tip portion 331d) of that connection portion, in relation to the direction of rotation of the rotor 3 (indicated by the arrow line C in
Alternatively, the extent of this inclination (i.e., the value of the angle θ) can be can be considered as being determined by the extent to which the position of the outer connection portion (e.g., the connection portion 33e) in each radially adjacent pair of connection portions connection is advanced with respect to the position of the inner connection portion (e.g., the connection portion 33d) of that pair of connection portions, in relation to the direction of rotation of the rotor 3.
As partially illustrated in
Furthermore with this embodiment, as partially shown in
As can also be understood from
Furthermore with this embodiment, each of the ventilation apertures 42a is circumferentially positioned in correspondence with such a region Sj.
In that way, due to the manner in which each pair of radially adjacent connection portions 33d, 33e are oriented at an appropriate angle with respect to a radial direction, a significant reduction can be achieved in the amount of resistance that is presented by the connection portions 33d, 33e to a correspondingly oriented outward flow of cooling air from the angled-flow fan 11.
Furthermore in addition to this lowering of air flow resistance, the amount of audible noise that results from the flow of air past the connection portions 33d, 33e can be substantially reduced. Hence, the AC generator can have improved cooling performance, together with a lower level of audible noise.
Moreover with this embodiment, due to the fact that each of the conductor segments 33 (in particular, each of the tip portions 331d, 331e, etc.) is formed with a substantially rectangular cross-sectional shape, each of the connection portions 33d, 33e can have circumferentially opposing faces that are substantially flat and are each oriented at an appropriate angle with respect to a radial direction of the stator. The resistance to the flow of cooling air can thereby be further decreased.
As described above, the orientation direction of each pair of radially adjacent connection portions 33d, 33e is determined in accordance with the direction of the flow of cooling air that is produced by the angled-flow fan 11 of the rotor 3. Specifically, that orientation is such that the position of the outermost connection portion (33e) of a radially adjacent pair (or the outermost tip portion 331e in the outermost connection portion 33e) is advanced along the direction of rotation of the rotor 3, in relation to the inner connection portion 33d of that pair, as illustrated in
Furthermore as described above, each of the ventilation apertures 42a is oriented along a direction having the same angular difference from a radial direction as each of the connection portions 33d, 33e, and has the shape of a radially outward extension of a space formed between two circumferentially adjacent pairs of the connection portions 33d, 33e. Hence there is a lowered level of resistance to a flow of cooling air that passes from the interior of the front frame 4a, through the stator winding 31 and the apertures 42a to the exterior.
It should be noted that the present invention is not limited to the above embodiment, and that various modifications could be envisaged to that embodiment. For example, each of the connection portions 33d, 33e could be covered by layer of electrical insulation material such as synthetic resin, etc. In that case also, the principles of the present invention described above can be applied to the gap between each pair of circumferentially adjacent connection portions 33d and each pair of circumferentially adjacent connection portions 33e.
Number | Date | Country | Kind |
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2005-080804 | Mar 2005 | JP | national |