Rotary electric machine

A rotary electrical machine includes a stator, a field core, a rotor, and first and second air gaps. The stator includes an AC coil that generates a rotating magnetic field with an alternating current. The field core includes a field coil excited by a direct current. The rotor is disposed on an outer circumference of a starting apparatus and held rotatably about a rotational axis relative to the stator and the field coil. The first air gap is formed between the stator and the rotor, and allows a magnetic flux to flow therebetween. The second air gap is formed between the field core and the rotor, and allows a magnetic flux to flow therebetween. The second air gap defines an interval extending along a direction that intersects an axial direction of the rotational axis on one end surface of the rotor in the axial direction of the rotational axis.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the National Phase in the United States of PCT/JP2018/002372, filed Jan. 26, 2018, which claims priority to Japanese Patent Application No. 2017-013495, filed Jan. 27, 2017 and Japanese Patent Application No. 2017-248191, filed Dec. 25, 2017. Those applications are incorporated by reference in their entireties.

TECHNICAL FIELD

The present invention relates to a brushless field winding type rotary electrical machine disposed on an outer circumference of a starting apparatus.

BACKGROUND ART

As a conventional technique disclosed in JP 3445492 B2, a rotary electrical machine shown inFIG. 18that supplies a magnetic flux from a field coil102that is stationary relative to a rotor101has been proposed. A stator103is disposed outside the rotor101in a radial direction. Such a structure makes it possible to eliminate the need for an electric power supply apparatus, the so-called slip ring using a brush conventionally required to magnetize the rotor101. This results in a brushless field winding type rotary electrical machine110. Note that a first air gap111is provided between the stator103and the rotor101, and a second air gap112is provided between the field coil102and the rotor101, both of which extend along an axial direction of a rotational axis107.

Further, as disclosed in JP 2010-516558 T, a structure in which a rotary electrical machine is disposed on an outer circumference of a starting apparatus has been proposed. Such a structure makes it possible to start an engine by connecting the engine and the rotary electrical machine and to eliminate the need for a starter and an alternator required for a conventional automobile by causing the rotary electrical machine to function as a generator during traveling.

BRIEF SUMMARY

Combining these two Patent Documents, in other words, as shown in (b) ofFIG. 7, when the brushless field winding type rotary electrical machine110is arranged on the outer circumference of the starting apparatus104, three members of the stator103fixed to a case105, the rotor101, and the field coil102are arranged in a narrow space on an inner circumferential side of the case105and an outer circumferential side of the starting apparatus104coaxially with the rotational axis107with different diameters, in a combination of the structures disclosed in the two Patent Documents. Hence, there are drawbacks that a severe restriction is imposed on a volume occupied by the rotary electrical machine110, a degree of freedom in designing is limited, and the output performance of the rotary electrical machine110is limited.

Accordingly, an object of the present invention, having been conceived to solve the problem, is to provide a rotary electrical machine that allows an increase in degree of freedom in designing and an increase in output performance.

In order to achieve the above-described object, the present invention is constructed as below.

According to one aspect of the present invention, there is provided a brushless field winding type rotary electrical machine disposed between an engine and a transmission along a rotational axis and positioned between a case housing a starting apparatus and the starting apparatus, includes:

a stator held by the case, the stator including therein an AC coil that generates a rotating magnetic field with an alternating current;

a field core held by the case, the field core including therein a field coil that is excited by a direct current;

a rotor disposed on an outer circumference of the starting apparatus and held rotatably about the rotational axis relative to the stator and the field coil;

a first air gap formed between the stator and the rotor, the first air gap being configured to allow a magnetic flux to flow between the stator and the rotor; and

a second air gap formed between the field core and the rotor, the second air gap being configured to allow a magnetic flux to flow between the field core and the rotor and being an interval extending along a direction intersecting an axial direction of the rotational axis on one end surface of the rotor in the axial direction of the rotational axis.

According to the aspect of the present invention, in a narrow space on an inner circumferential side of the case and an outer circumferential side of the starting apparatus, only the stator or the field coil other than the rotor is disposed, which only requires two members to be arranged on diameters that are coaxial with the rotational axis but different from each other, and thus allows an increase in the degree of freedom in designing and an increase in the output performance of the rotary electrical machine.

DETAILED DESCRIPTION

First Embodiment

As shown inFIGS. 1 to 2B, a rotary electrical machine according to a first embodiment of the present invention is a brushless field winding type rotary electrical machine10that is disposed between an engine8and a transmission9along a rotational axis7and is positioned between a case5housing a starting apparatus4and the starting apparatus4. The rotary electrical machine10includes at least a stator3, a field coil2, and a rotor1.

The stator3is fixedly held by the case5in a non-rotatable manner and is configured by a cylindrical member having a plurality of slots on which an AC coil14is wound. The stator3includes the AC coil14therein and generates a rotating magnetic field with an alternating current flowing through the AC coil14.

The field coil2is shifted along the rotational axis7relative to the stator3and the rotor1, fixedly held by the case5on a side adjacent to the transmission9of the stator3, and is excited by a direct current. A field core6includes the field coil2therein. Note that the field coil2can be shifted along the rotational axis7relative to the stator3and the rotor1and on a side adjacent to the engine of the stator3via a second air gap12rather than on a side adjacent to the transmission9of the stator3(see a region89enclosed by a long dashed short dashed line inFIG. 1).

The rotor1is fixedly disposed on an outer circumference of the starting apparatus4such that an outer circumferential surface of the rotor1faces an inner circumferential surface of the stator3, and an end surface adjacent to the transmission of the rotor1faces an end surface adjacent to the engine of the field coil2. The rotor1is held rotatably about the rotational axis7relative to the stator3and the field coil2.

The first air gap11is formed between the stator3and the rotor1and allows a magnetic flux to flow between the stator3and the rotor1. The first air gap11is an interval extending along an axial direction of the rotational axis7between the inner circumferential surface of the stator3and the outer circumferential surface of the rotor1.

The second air gap12is formed between the field core6and the rotor1and allows a magnetic flux to flow between the field coil2and the rotor1. The second air gap12is an interval extending along a direction intersecting the axial direction of the rotational axis7, for example, along a radial direction orthogonal to the axial direction between the field core6and the rotor1on the end surface adjacent to the transmission of the rotor1and on an end surface adjacent to the engine of the field core6in the axial direction of the rotational axis7.

Accordingly, the field coil2is shifted in the axial direction of the rotational axis7to be in parallel to the rotor1with the second air gap12interposed between the field coil2and the rotor1.

On the other hand, as shown inFIGS. 3 to 6, the rotor1is composed of a combination of a first magnetic pole21, a second magnetic pole22, and a magnetic pole holding member23. Note that a longitudinal cross-sectional view taken along line A-A ofFIG. 3corresponds to a cross-sectional view of the rotary electrical machine10, the starting apparatus4, and the like shown in the center ofFIG. 1.

The first magnetic pole21is composed of a soft magnetic material such as iron and has a plurality of claw portions21beach of which has, for example, a rectangular thin plate shape and protrude from a first annular portion21ain the axial direction of the rotational axis7. The claw portions21bare arranged at regular intervals, for example, equal intervals, in a circumferential direction thereof and all have the same length in the axial direction of the rotational axis7. An outer circumferential surface of each of the claw portions21bis flush with an outer circumferential surface of the first annular portion21a. When the first magnetic pole21and the second magnetic pole22are combined, the claw portions21bare kept from coming into contact with the second magnetic pole22, and a radial interval16is formed extending in the radial direction.

The second magnetic pole22is composed of a soft magnetic material such as iron and is disposed inside the first annular portion21awith the radial interval16interposed therebetween. The second magnetic pole22has a plurality of protrusions22beach of which has, for example, a rectangular plate shape, protrude in the radial direction, and are arranged on an outer circumferential surface of a second annular portion22aat circumferential intervals17in the circumferential direction. The second annular portion22ais disposed partially overlapping the first annular portion21a. The protrusions22bare also arranged at regular intervals, for example, equal intervals, in the circumferential direction and all have the same height in the radial direction. The protrusions22ball have the same length in the axial direction of the rotational axis7and are shorter in length than the claw portions21b. An outer circumferential surface of each of the protrusions22bis disposed on a circle coaxial with a rotation axis of the rotor1. Each of the protrusions22bextends to an end edge adjacent to the engine of the second annular portion22ato form a second leading end locking portion22cwhile extending toward but terminating short of an end edge adjacent to the transmission of the second annular portion22ato form an inserting portion22dhaving a thin annular shape without the protrusion22b. The first magnetic pole21is moved in the axial direction relative to the second magnetic pole22to insert each of the claw portions21bof the first magnetic pole21into a middle part of the circumferential interval17between the protrusions22badjacent to each other, thereby combining the first magnetic pole21and the second magnetic pole22with the claw portion21band the protrusion22balternately arranged in the circumferential direction. The first annular portion21aof the first magnetic pole21is configured to be disposed outward the inserting portion22dwith the radial interval16interposed therebetween. As shown inFIG. 5, with the first magnetic pole21and the second magnetic pole22combined with each other, an axial interval19is present between each of the protrusions22band the first annular portion21a, and, between each of the claw portions21band the second magnetic pole22, the circumferential interval17in the circumferential direction and the radial interval16in the radial direction are present. Accordingly, the first magnetic pole21and the second magnetic pole22are kept from coming into contact with each other. In order to fix the first magnetic pole21and the second magnetic pole22to each other in this state, the magnetic pole holding member23is further provided.

The magnetic pole holding member23is composed of a nonmagnetic material such as aluminum or austenitic stainless steel and is an annular member. The magnetic pole holding member23has a fitting portion23a, for example, on an outer circumferential side. To the fitting portion23a, a first leading end locking portion21cof each of the claw portions21bof the first magnetic pole21and the second leading end locking portion22cof each of the protrusions22bof the second magnetic pole22are fixedly fitted. The first leading end locking portion21cand the second leading end locking portion22care fitted to the fitting portion23aand fixed by bolting, shrink fitting, brazing, or the like, so that the first magnetic pole21and the second magnetic pole22are fixedly held by the magnetic pole holding member23with the first magnetic pole21and the second magnetic pole22kept from coming into contact with each other.

As a specific example, the first leading end locking portion21cof each of the claw portions21bof the first magnetic pole21and the second leading end locking portion22cof each of the protrusions22bof the second magnetic pole22are each formed in a step portion, and the step portion is fitted to an engaging recess of the fitting portion23aand fixedly held in the radial direction. The second leading end locking portion22cis disposed at a leading end of each of the protrusions22bas an example, but can be disposed at a leading end of the second annular portion22a. When the magnetic flux is made to flow from the field coil2to magnetize the first magnetic pole21and the second magnetic pole22, this configuration achieves efficient magnetization by causing the magnetic pole holding member23that is nonmagnetic to prevent a magnetic short, and allows the first magnetic pole21and the second magnetic pole22to be mechanically held by the magnetic pole holding member23. Further, the configuration in which the first leading end locking portion21cof each of the claw portions21bof the first magnetic pole21is fixedly fitted to and held by the fitting portion23aof the magnetic pole holding member23suppresses outward deformation of the claw portions21bdue to a rotational centrifugal force, and thus makes it possible to increase rotational strength.

In the rotary electrical machine10configured as described above, when the field coil2is energized, a field coil magnetic flux15is generated. The field coil magnetic flux15passes from the field core6through the second air gap12, the first magnetic pole21of the rotor1, the first air gap11, the stator3, the first air gap11, the second magnetic pole22of the rotor1, and the second air gap12and returns to the field core6. At this time, for example, when a direct current is made to flow through the field coil2, the field coil magnetic flux15is generated, thereby magnetizing the first magnetic pole21and the second magnetic pole22to N pole and S pole, respectively.

A description will be given of a configuration where such a rotary electrical machine10serves as a starter to perform a start function. In accordance with a command to start the engine8, an inverter (not shown) is driven to cause a three-phase alternating current flow through the stator3to magnetize the stator3and to cause a current flow through the field coil2. Causing the current flow through the field coil2excites the first magnetic pole21and the second magnetic pole22of the rotor1. As a result, the rotor1starts to rotate relative to the stator3, and an electromotive force having an induced voltage is generated in the stator3.

Thereafter, the induced voltage increases according to a rotation speed of the rotor1, and when the rotation speed reaches an initial explosion rotation speed lower than an idling speed corresponding to idling of the engine8, the driving of the inverter is stopped, and thereafter, the rotary electrical machine10automatically shifts to a power generation mode, in other words, a mode where the rotary electrical machine10serves as a dynamo to perform a power generating function, so as to hold a predetermined induced voltage (required voltage).

In the power generation mode, when the field coil2continues to excite, an excitation current is adjusted to make the induced voltage constant at a predetermined induced voltage. When the excitation current is adjusted, the excitation current is first adjusted to make a magnetizing force of the field coil2constant. This is an intention of making the field coil2function just like a permanent magnet. As described above, when the rotor1rotates in a state as if a permanent magnet is disposed, the rotary electrical machine10functions as a dynamo.

As a result, connecting the engine8and the rotary electrical machine10allows the engine to start and allows the rotary electrical machine10to function as a generator (dynamo) during traveling.

According to the first embodiment, in the brushless field winding type rotary electrical machine10disposed on the outer circumference of the automobile starting apparatus4, the second air gap12between the field coil2and the rotor1is formed on a plane perpendicular to the rotational axis7. Specifically, employed is a structure in which the first magnetic pole21of the rotor1is an annular member having a large number of the claw portions21b, the second magnetic pole22is an annular member having a large number of the protrusions22b, and the first and second magnetic poles21,22are alternately arranged in the circumferential direction and held by the magnetic pole holding member23made of a nonmagnetic material. Such a configuration can exhibit the following effects.

First, as shown in (b) ofFIG. 7as a combination example of conventional JP 3445492 B2 and JP 2010-516558 T that is a comparative example to the first embodiment, when the rotary electrical machine110is disposed outside the starting apparatus104in the radial direction, and three members of the stator103, the rotor101, and the field coil102are arranged in a space between the case105and the starting apparatus104from the outside to the inside in the radial direction, the more the number of turns of the field coil102increases to increase the magnetic flux of the field coil102, the more the thickness in the radial direction increases, which makes it unable to put the three members into the space and accordingly fails to increase the magnetic flux.

On the other hand, in the first embodiment, as shown in (a) ofFIG. 7, employed is a configuration in which the field coil2is shifted in the axial direction of the rotational axis7to be in parallel to the stator3and the rotor1. This configuration causes only the two members of the stator3and the rotor1to be present outside the starting apparatus4in the radial direction, which eliminates the need for a space for disposing the field coil2outside the starting apparatus4in the radial direction. Accordingly, it is possible to reduce the radial dimension of the outside of the starting apparatus4by at least the space for disposing the field coil2or increase the thickness of the stator3or the rotor1by the space for disposing the field coil2, for example, for effective use of the space for disposing the field coil2. Further, since the field coil2is disposed at a position shifted in the axial direction relative to the stator3and the rotor1, it is possible to increase the thickness of the field coil2in the radial direction to increase the magnetic flux of the field coil2without considering the space for the stator3and the rotor1. This makes it possible to increase the degree of freedom in designing.

Further, as shown in (b) ofFIG. 7, when the stator103, the rotor101, and the field coil102are arranged in that order from the outside to the inside in the radial direction, it is required that a dimension of an interval between the rotor101and the field coil102to be designed in consideration of the change in thickness caused by expansion or the like due to the centrifugal force applied to the rotor101and to be generally designed larger than a required dimension.

On the other hand, as shown in (a) ofFIG. 7, the field coil2is shifted relative to the stator3and the rotor1in the axial direction to form an interval radially extending between the field coil2and the rotor1as the second air gap12, which eliminates the need to take into consideration the change in thickness caused by expansion or the like due to the centrifugal force applied to the rotor1, and only requires adjustment of the interval dimension of the second air gap12along the axial direction. Therefore, the influence of the centrifugal force can be reduced.

Further, in the radial arrangement as shown in (b) ofFIG. 7, concentricity (position adjustment of concentric positions) between the rotor101that is a rotating side and the field coil102that is a stationary side is strictly adjusted; however, as shown in (a) ofFIG. 7, when the field coil102is shifted in the axial direction, there is no need to adjust the concentricity between the rotor1that is the rotating side and the field coil2that is the stationary side as strict as the configuration in (b) ofFIG. 7.

Further, in the configuration in (a) ofFIG. 7, allowing the field coil2of the rotor1to be disposed in either a space adjacent to the engine or a space adjacent to the transmission in the axial direction makes it possible to use the space effectively.

Further, the rotor1of the rotary electrical machine10is connected to the starting apparatus4that is a synchronous rotating member synchronously rotating with an output shaft (rotational shaft)7of the engine8, and the rotary electrical machine10is disposed so that the center axis of the output shaft of the engine8is aligned with a rotation axis of the rotor1, which makes it possible to surely transmit a rotational driving force of the rotary electrical machine10to the engine8even in a cold state and surely start the engine8in the cold state.

Note that the present invention is not limited to the first embodiment and can be implemented in various other modes. For example, as a modification shown inFIG. 8, in the first embodiment, an interchange in position between the stator3and the field coil2can be made to cause the field coil2to be disposed on an outer side in the radial direction of the rotor1and cause the stator3to be shifted in the axial direction of the rotational axis7relative to the rotor1. In other words, the first air gap11between the rotor1and the stator3is formed as an interval extending along a direction intersecting the axial direction of the rotational axis7, for example, along the radial direction orthogonal to the axial direction. On the other hand, the second air gap12between the field coil2and the rotor1is formed as an interval extending along the axial direction of the rotational axis7.

This configuration not only exhibits the action effect of the first embodiment, but also causes the first air gap11between the rotor1and the stator3to be formed as an interval extending along the radial direction orthogonal to the axial direction of the rotational axis7, which eliminates the need to take into consideration the change in thickness caused by expansion or the like due to the centrifugal force applied to the rotor1in designing the stator3.

Second Embodiment

As shown inFIGS. 9 to 11, a second embodiment of the present invention can have a structure in which a permanent magnet27is disposed inside the rotor1in the configuration of the first embodiment.

More specifically, the permanent magnet27having, for example, a rectangular plate shape is provided at the same circumferential position as each of the claw portions21bof the first magnetic pole21is disposed, on an inner diameter side of each of the claw portions21bof the first magnetic pole21and on an outer diameter side of the second annular portion22aof the second magnetic pole22, and is sandwiched between an inner circumferential surface of each of the claw portions21band the outer circumferential surface of the second annular portion22a. This arrangement causes, as shown inFIG. 10, a magnet magnetic flux28of the permanent magnet27to be formed between each of the claw portions21bof the first magnetic pole21and the protrusions22bof the second magnetic pole22.

The permanent magnet27is a magnet primarily made of neodymium or a magnet primarily made of ferrite. Specifically, as the permanent magnet27, various kinds of permanent magnets such as a SmCo magnet, an AlNiCo magnet, a neodymium bonded magnet, and the like can be used. The permanent magnet27is disposed entirely or partially an inner surface of each of the claw portions21b.

Such a configuration makes it possible to increase output performance by using the magnet magnetic flux28of the permanent magnet27in addition to a magnetic flux generated in the rotor1by the field coil2. Further, holding the permanent magnet27with the claw portions21bmakes it possible to increase strength of the permanent magnet27against a centrifugal force, which can prevent the permanent magnet27from being deformed due to the centrifugal force and thus increase centrifugal strength during high speed rotation.

Third Embodiment

The second air gap12is not limited to an interval extending along the radial direction orthogonal to the axial direction of the rotational axis7as described in the first and second embodiments, and can be an interval inclined from the axis direction of the rotational axis7. An example having such an interval will be described below.

As shown inFIGS. 12A to 13B, a rotary electrical machine according to a third embodiment of the present invention is a brushless field winding type rotary electrical machine10that is disposed between an engine8and a transmission9along a rotational axis7and is positioned between a case5housing a starting apparatus4and the starting apparatus4. The rotary electrical machine10includes at least a stator3, a field coil2, and a rotor1.

The stator3is fixedly held by the case5in a non-rotatable manner and is configured by a cylindrical member having a plurality of slots on which an AC coil14is wound. The stator3includes the AC coil14therein and generates a rotating magnetic field with an alternating current flowing through the AC coil14.

The field coil2is shifted along the rotational axis7relative to the stator3and the rotor1, fixedly held by the case5on a side adjacent to the transmission9of the stator3, and is excited by a direct current. A field core6includes the field coil2therein. Note that the field coil2can be disposed closer to the engine than the stator3and the rotor1along the rotational axis7, that is, on a side adjacent to the engine of the stator3via a second air gap212rather than on a side adjacent to the transmission9of the stator3(see a region89enclosed by a long dashed short dashed line inFIG. 12A).

The rotor1is fixedly disposed on an outer circumference of the starting apparatus4such that an outer circumferential surface of the rotor1faces an inner circumferential surface of the stator3, and an end surface adjacent to the transmission of the rotor1faces an end surface adjacent to the engine of the field coil2. The rotor1is held rotatably about the rotational axis7relative to the stator3and the field coil2.

The first air gap11is formed between the stator3and the rotor1and allows a magnetic flux to flow between the stator3and the rotor1. The first air gap11is an interval extending along an axial direction of the rotational axis7between the inner circumferential surface of the stator3and the outer circumferential surface of the rotor1.

The second air gap212is formed between the field core6and the rotor1and allows a magnetic flux to flow between the field coil2and the rotor1. The second air gap212is an interval inclined from the axial direction of the rotational axis7at an inclination angle α between the field core6and the rotor1on the end surface adjacent to the transmission of the rotor1and on an end surface adjacent to the engine of the field core6in the axial direction of the rotational axis7.

More specifically, as shown inFIG. 13A, the second air gap212is formed between the field core6and the second magnetic pole22of the rotor1on the end surface adjacent to the transmission of the rotor1and on the end surface adjacent to the engine of the field core6in the axial direction of the rotational axis7, and between the field core6and the first magnetic pole21of the rotor1on the end surface adjacent to the transmission of the rotor1and on the end surface adjacent to the engine of the field core6in the axial direction of the rotational axis7.

First, between the field core6and the second magnetic pole22of the rotor1, on the end surface adjacent to the transmission of the rotor1and on the end surface adjacent to the engine of the field core6in the axial direction of the rotational axis7, the second air gap212includes a first perpendicular portion212athat is an interval perpendicular to the axial direction of the rotational axis7, an inclined portion212bthat is an interval inclined from the axial direction of the rotational axis7at the inclination angle α, and a second perpendicular portion212cthat is an interval perpendicular to the axial direction of the rotational axis7in that order from a center of the rotational axis7. The first perpendicular portion212a, the inclined portion212b, and the second perpendicular portion212care continuously connected to each other. An inclination direction of the inclined portion212bis gradually inclined from the inside to the outside in the radial direction as advancing from the engine side to the transmission side. The intervals of the first perpendicular portion212a, the inclined portion212b, and the second perpendicular portion212care approximately the same.

Further, between the field core6and the first magnetic pole21of the rotor1, on the end surface adjacent to the transmission of the rotor1and on the end surface adjacent to the engine of the field core6in the axial direction of the rotational axis7, the second air gap212includes a first perpendicular portion212athat is an interval perpendicular to the axial direction of the rotational axis7, an inclined portion212bthat is an interval inclined from the axial direction of the rotational axis7at the inclination angle α, and a second perpendicular portion212cthat is an interval perpendicular to the axial direction of the rotational axis7in that order from the center of the rotational axis7. The first perpendicular portion212a, the inclined portion212b, and the second perpendicular portion212care continuously connected to each other. In contrast to the second air gap212on the second magnetic pole22side, an inclination direction of the inclined portion212bis gradually inclined from the inside to the outside in the radial direction as advancing from the transmission side to the engine side. The intervals of the first perpendicular portion212a, the inclined portion212b, and the second perpendicular portion212care approximately the same.

Consequently, when the inclination direction of the second air gap212on the first magnetic pole21side and the inclination direction of the second air gap212on the second magnetic pole22side are aligned with each other, as shown inFIG. 12B, the second air gaps212are arranged in an approximate V shape whose apex is directed from the engine side to the transmission side. This approximate V shape is an example and can be an approximate inverted V shape or a parallel shape. In other words, each of the inclination direction of the second air gap212on the first magnetic pole21side and the inclination direction of the second air gap212on the second magnetic pole22side can have any direction and any inclination angle. As an example, it is preferable that the inclination directions of the two be identical to each other from the viewpoint of balancing the magnetic flux and the axial force.

The second air gap212only needs to include at least the inclined portion212b, and can further include one or both of the perpendicular portions212aand212c.

Here, the reason why the second air gap212is inclined in this way will be described.

When the second air gap212between the rotor1and the field coil2is formed as a plane perpendicular to the axial direction of the rotational axis7, magnetic reluctance becomes high due to a small air gap cross-sectional area, which may cause an increase in field current that is required for a rotor field. Further, when the second air gap212is formed perpendicular to the axial direction of the rotational axis7, an electromagnetic attractive force is generated in the axial direction, and a large axial force can be applied to a bearing (not shown) that supports the starting apparatus4.

In particular, in a case where the second air gap212is formed perpendicular to the axial direction of the rotational axis7, an effective magnetic path width of the second air gap212in the cross section is equivalent to a thickness of the field core6and a thickness of the magnetic pole. Further, when the field core6is excited, the electromagnetic attractive force acts between the field core6and the rotor1. Therefore, when the second air gap212is formed perpendicular to the axial direction of the rotational axis7, all of the electromagnetic attractive force act as the axial force.

On the other hand, as in the third embodiment, when the second air gap212is inclined from the axial direction of the rotational axis7, compared with the case where the second air gap212is formed perpendicular to the axial direction, the effective magnetic path width of the second air gap212can be increased, and the axial force can be reduced by decomposing the electromagnetic attractive force into not only the axial force but also a radial force.

Here, inFIG. 13C, the magnetic flux and the electromagnetic force in the case where the second air gap212is formed perpendicularly are represented by a bar graph91, the magnetic flux and the electromagnetic force in the case where the second air gap212is formed obliquely as in the third embodiment are represented by a bar graph92. Here, respective magnifications 1.04 and 0.76 of the magnetic flux and the electromagnetic force in the case where the second air gap212is formed obliquely as in the third embodiment are shown when respective magnifications of the magnetic flux and the electromagnetic force in the case where the second air gap212is formed perpendicularly are defined as 1. In the case where the second air gap212is formed obliquely as in the third embodiment, as compared with the case where the second air gap212is formed perpendicularly, the magnetic flux is increased by the increase in the effective magnetic path width, and the electromagnetic attractive force, in other words, electromagnetic force, is reduced by the decomposition into the radial force.

Accordingly, the reduction in the electromagnetic attractive force in the axial direction makes it possible to reduce the axial force applied to the bearing. As a result, it is possible to reduce a drag torque and increase fuel efficiency of a vehicle.

Further, inclining the second air gap212to increase the cross-sectional area of the second air gap212makes it possible to lower the magnetic reluctance and reduce the field current. As a result, it is possible to increase the efficiency of the rotary electrical machine10and further increase the fuel efficiency of a vehicle.

In order to reliably achieve the various effects described above, the inclination angle α of each inclined portion212bis, for example, in a range from 10 degrees to 25 degrees from the axial direction of the rotational axis7.

Note that each of the inclination directions of the inclined portions212bin the first magnetic pole21and the second magnetic pole22can be an opposite direction. In other words, the inclined portion212bon the second magnetic pole22side is gradually inclined from the inside to the outside in the radial direction as advancing from the transmission side to the engine side, while the inclined portion212bon the first magnetic pole21side is gradually inclined outward from the inside in the radial direction as advancing from the engine side to the transmission side.

Further, as shown inFIG. 12C, the second air gap212can include only the inclined portion212bwithout the perpendicular portions212aand212c.

Accordingly, the field coil2is shifted in the axial direction of the rotational axis7to be in parallel to the rotor1with the second air gap212interposed between the field coil2and the rotor1.

Note that, the configuration of the third embodiment corresponding toFIGS. 3 to 6of the first embodiment is the same as the configuration of the first embodiment; thus description and illustration thereof is omitted.

In the rotary electrical machine10configured as described above, when the field coil2is energized, a field coil magnetic flux15is generated. The field coil magnetic flux15passes from the field core6through the second air gap212, the first magnetic pole21of the rotor1, the first air gap11, the stator3, the first air gap11, the second magnetic pole22of the rotor1, and the second air gap212and returns to the field core6. At this time, for example, when a direct current is made to flow through the field coil2, the field coil magnetic flux15is generated, thereby magnetizing the first magnetic pole21and the second magnetic pole22, for example, to N pole and S pole, respectively.

A description will be given of a configuration where such a rotary electrical machine10serves as a starter to perform a start function. In accordance with a command to start the engine8, an inverter (not shown) is driven to cause a three-phase alternating current flow through the stator3to magnetize the stator3and to cause a current flow through the field coil2. Causing the current flow through the field coil2excites the first magnetic pole21and the second magnetic pole22of the rotor1. As a result, the rotor1starts to rotate relative to the stator3, and an electromotive force having an induced voltage is generated in the stator3.

Thereafter, the induced voltage increases according to a rotation speed of the rotor1, and when the rotation speed reaches an initial explosion rotation speed lower than an idling speed corresponding to idling of the engine8, the driving of the inverter is stopped, and the rotary electrical machine10automatically shifts to a power generation mode, in other words, a mode where the rotary electrical machine10serves as a dynamo to perform a power generating function, so as to hold a predetermined induced voltage (required voltage).

In the power generation mode, when the field coil2continues to excite, an excitation current is adjusted to make the induced voltage constant at a predetermined induced voltage. When the excitation current is adjusted, the excitation current is first adjusted to make a magnetizing force of the field coil2constant. This is an intention of making the field coil2function just like a permanent magnet. As described above, when the rotor1rotates in a state as if a permanent magnet is disposed, the rotary electrical machine10functions as a dynamo.

As a result, connecting the engine8and the rotary electrical machine10allows the engine to start and allows the rotary electrical machine10to function as a generator (dynamo) during traveling.

According to the third embodiment, in the brushless field winding type rotary electrical machine10disposed on the outer circumference of the automobile starting apparatus4, the second air gap212between the field coil2and the rotor1is formed to be inclined relative to the rotational axis7. Specifically, employed is a structure in which the first magnetic pole21of the rotor1is an annular member having a large number of the claw portions21b, the second magnetic pole22is an annular member having a large number of the protrusions22b, and the first and second magnetic poles21,22are alternately arranged in the circumferential direction and held by the magnetic pole holding member23made of a nonmagnetic material. Such a configuration can exhibit the following effects.

First, as shown in (b) ofFIG. 14as a combination example of conventional JP 3445492 B2 and JP 2010-516558 T that is a comparative example to the third embodiment, when the rotary electrical machine110is disposed outside the starting apparatus104in the radial direction, and three members of the stator103, the rotor101, and the field coil102are arranged in a space between the case105and the starting apparatus104from the outside to the inside in the radial direction, the more the number of turns of the field coil102increases to increase the magnetic flux of the field coil102, the more the thickness in the radial direction increases, which makes it unable to put the three members into the space and accordingly fails to increase the magnetic flux.

On the other hand, in the third embodiment, as shown in (a) ofFIG. 14, employed is a configuration in which the field coil2is shifted in the axial direction of the rotational axis7to be in parallel to the stator3and the rotor1. This configuration causes only the two members of the stator3and the rotor1to be present outside the starting apparatus4in the radial direction, which eliminates the need for a space for disposing the field coil2outside the starting apparatus4in the radial direction. Accordingly, it is possible to reduce the radial dimension of the outside of the starting apparatus4by at least the space for disposing the field coil2or increase the thickness of the stator3or the rotor1by the space for disposing the field coil2for effective use of the space for disposing the field coil2. Further, since the field coil2is disposed at a position shifted in the axial direction relative to the stator3and the rotor1, it is possible to increase the thickness of the field coil2in the radial direction to increase the magnetic flux of the field coil2without considering the space for the stator3and the rotor1. This makes it possible to increase the degree of freedom in designing.

Further, as shown in (b) ofFIG. 14, when the stator103, the rotor101, and the field coil102are arranged from the outside to the inside in the radial direction, it is required that a dimension of an interval between the rotor101and the field coil102to be designed in consideration of the change in thickness caused by expansion due to the centrifugal force applied to the rotor101and be generally designed larger than a required dimension.

On the other hand, as shown in (a) ofFIG. 14, the field coil2is shifted in the axial direction relative to the stator3and the rotor1to form as the second air gap212an interval inclining from the axial direction between the field coil2and the rotor1, which makes it possible to increase the efficiency of the rotary electrical machine10and reduce the axial force as described above.

Further, in the radial arrangement as shown in (b) ofFIG. 14, concentricity (position adjustment of concentric positions) between the rotor101on a rotating side and the field coil102on a stationary side is strictly adjusted; however, as shown in (a) ofFIG. 14, when the field coil102is shifted in the axial direction, there is no need to adjust the concentricity between the rotor1on the rotating side and the field coil2on the stationary side as strict as the configuration in (b) ofFIG. 14.

Further, in the configuration in (a) ofFIG. 14, allowing the field coil2to be disposed in either a space in the engine or a space adjacent to the transmission of the rotor1in the axial direction makes it possible to use the space effectively.

Further, the rotor1of the rotary electrical machine10is connected to the starting apparatus4that is a synchronous rotating member synchronously rotating with an output shaft (rotational shaft)7of the engine8, and the rotary electrical machine10is disposed so that the center axis of the output shaft of the engine8is aligned with a rotation axis of the rotor1, which makes it possible to surely transmit a rotational driving force of the rotary electrical machine10to the engine8even in a cold state and surely start the engine8in the cold state.

Therefore, according to the third embodiment, in a narrow space on an inner circumferential side of the case5and an outer circumferential side of the starting apparatus4, one of the stator3and the field coil2other than the rotor1is disposed. Such a disposition only requires two members to be arranged on diameters that are coaxial with the rotational axis7but different from each other, and thus allows an increase in the degree of freedom in designing and an increase in the output performance of the rotary electrical machine10. Furthermore, the second air gap212has the inclined portion212bthat is an interval inclined from the axial direction of the rotational axis7on one end surface of the rotor1in the axial direction of the rotational axis7, which makes it possible to increase the efficiency of rotary electrical machine10and reduce the axial force.

Fourth Embodiment

As shown inFIGS. 15 to 17, a fourth embodiment of the present invention can have a structure in which a permanent magnet27is disposed inside the rotor1in the configuration of the third embodiment.

More specifically, the permanent magnet27having, for example, a rectangular plate shape is provided at the same circumferential position as each of the claw portions21bof the first magnetic pole21, on an inner diameter side of each of the claw portions21bof the first magnetic pole21and on an outer diameter side of the second annular portion22aof the second magnetic pole22, and is sandwiched between an inner circumferential surface of each of the claw portions21band the outer circumferential surface of the second annular portion22a. This arrangement causes, as shown inFIG. 16, a magnet magnetic flux28of the permanent magnet27to be formed between each of the claw portions21bof the first magnetic pole21and the protrusions22bof the second magnetic pole22.

The permanent magnet27is a magnet primarily made of neodymium or a magnet primarily made of ferrite. Specifically, as the permanent magnet27, various kinds of permanent magnets such as a SmCo magnet, an AlNiCo magnet, a neodymium bonded magnet, and the like can be used. The permanent magnet27is disposed entirely or partially an inner surface of each of the claw portions21b.

Such a configuration makes it possible to increase output performance by using the magnet magnetic flux28of the permanent magnet27in addition to a magnetic flux generated in the rotor1by the field coil2. Further, holding the permanent magnet27with the claw portions21bmakes it possible to increase strength of the permanent magnet27against a centrifugal force, which can prevent the permanent magnet27from deforming due to the centrifugal force and thus increase centrifugal strength during high speed rotation.

By appropriately combining arbitrary embodiments or modifications of the above various embodiments or modifications, respective effects can be produced. Additionally, combination between embodiments, combination between working examples, or combination between an embodiment(s) and a working example(s) is possible, and combination between characteristics in different embodiments or working examples is possible as well.

INDUSTRIAL APPLICABILITY

The rotary electrical machine according to the aspect of the present invention allows an increase in the degree of freedom in designing and an increase in the output performance, and is suitable for a power transmitting apparatus including a rotary electrical machine that integrally has a power generating function and an engine start function of an alternator and a starter motor of a vehicle.

REFERENCE SIGNS LIST

1. rotor2. field coil3. stator4. starting apparatus5. case6. field core7. rotational axis8. engine9. transmission10. brushless field winding type rotary electrical machine11. first air gap12. second air gap14. AC coil15. field coil magnetic flux16. radial interval17. circumferential interval19. axial interval21. first magnetic pole21a. first annular portion21b. claw portion21c. first leading end locking portion22. second magnetic pole22a. second annular portion22b. protrusion22c. second leading end locking portion22d. inserting portion23. magnetic pole holding member23a. fitting portion27. permanent magnet28. magnetic flux of permanent magnet89. region where field coil is disposed on a side adjacent to engine of stator91,92. bar graph212. second air gap212a,212c. perpendicular portion212b. inclined portionα. inclination angle