Rotary electric machine

A rotary electric machine includes a stator, a rotor, and a field coil; the rotor includes a first magnetic pole having a first annular portion and a plurality of claw portions and a second magnetic pole having a second annular portion and a plurality of projection portions; in the rotor, the claw portions and the projection portions are circumferentially alternately positioned, and the first magnetic pole and the second magnetic pole are maintained in a non-contact state by providing a radial gap, a circumferential gap, and an axial gap between the first magnetic pole and the second magnetic pole; and the gap arrangement member has an axial positioning portion that is axially locked with respect to at least one of the first magnetic pole and the second magnetic pole, and axially positions the first magnetic pole and the second magnetic pole.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a brushless wound field type rotary electric machine.

2. Description of the Related Art

As a related art, JP 3445492 B2 discloses a brushless wound field type rotary electric machine in which a stator is disposed radially outside a rotor and magnetic flux is supplied from a field coil that is stationary with respect to the rotor, and thus eliminating a brush that is necessary to magnetize the rotor.

JP 2010-516558 A discloses a structure in which an engine and a rotary electric machine are connected so that the rotary electric machine functioning as an electric motor at the time of engine startup and functioning as a generator during traveling is disposed on the outer circumference of a power transmission device.

By combining JP 3445492 B2 with JP 2010-516558 A, the three members of a stator, a rotor, and a field coil are disposed on positions coaxial with a rotation axis and of different diameters in a narrow space on the outer circumferential side of a power transmission device. Therefore, a severe restriction is imposed on the volume of a rotary electric machine, the degree of freedom of design is restricted, and the output performance of the rotary electric machine is limited.

A brushless wound field type rotary electric machine in which a first magnetic pole and a second magnetic pole are positioned while being maintained in a non-contact state with a simple configuration in a rotor of a rotary electric machine, thereby increasing the degree of freedom of design and improving the output performance is desired.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to provide a brushless wound field type rotary electric machine in which a first magnetic pole and a second magnetic pole are positioned while being maintained in a non-contact state with a simple configuration.

In order to solve the above problem, a rotary electric machine according to one aspect of this invention includes:

a stator having a stator winding that generates a rotating magnetic field by an alternating current;

a rotor that is rotatably held about a rotation axis with respect to the stator; and

a field coil that excites the rotor by a direct current, wherein:

the rotor includes

a first magnetic pole that has a first annular portion and a plurality of claw portions extending in an axial direction of the rotation axis from the first annular portion, and

a second magnetic pole that has a second annular portion and a plurality of projection portions radially projecting on an outer circumferential surface of the second annular portion;

in the rotor,

the claw portions of the first magnetic pole and the projection portions of the second magnetic pole are circumferentially alternately positioned, and

the first magnetic pole and the second magnetic pole are maintained in a non-contact state by providing a radial gap, a circumferential gap, and an axial gap between the first magnetic pole and the second magnetic pole;

the rotor further includes a gap arrangement member of a non-magnetic material arranged in the radial gap or the circumferential gap; and

the gap arrangement member has an axial positioning portion that is axially locked with respect to at least one of the first magnetic pole and the second magnetic pole, and axially positions the first magnetic pole and the second magnetic pole.

According to the present invention, radial positioning or circumferential positioning of the first magnetic pole and the second magnetic pole is performed by the gap arrangement member of the non-magnetic material arranged in the radial gap or the circumferential gap, and axial positioning is performed by the axial positioning portion of the gap arrangement member. Accordingly, by the gap arrangement member providing the plurality of functions, the structure in which the first magnetic pole and the second magnetic pole are positioned while being maintained in a non-contact state radially or circumferentially and axially can be simply and easily achieved.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments of a rotary electric machine1according to the present invention will be described with reference to the drawings.

First, an overall configuration of the rotary electric machine1will be described with reference toFIG. 1.

As shown inFIG. 1, the rotary electric machine1is a brushless wound field type rotary electric machine1disposed between an engine8and a transmission9of a vehicle along a rotation axis10and positioned between a power transmission device4and a case5including the power transmission device4. The rotary electric machine1includes at least a rotor2, a stator3, and a field coil7. The power transmission device4is disposed in a power transmission path from an output shaft of the engine8to the transmission9, and is, for example, a torque converter, a friction type clutch, a fluid coupling, or the like.

The stator3is a cylindrical member that is fixedly held in the case5in a non-rotatable manner. The stator3includes, for example, a stator core in which electromagnetic steel plates are laminated, a plurality of slots formed in the stator core, and a plurality of stator windings14mounted in the slots. The stator3includes the stator winding14therein, and generates a rotating magnetic field by an alternating current flowing through the stator winding14.

The rotor2is connected to a synchronous rotary member rotating synchronously with the output shaft of the engine8, and a central axis of the output shaft of the engine8is the rotation axis10. Therefore, the output shaft of the engine8and the rotation axis10of the rotor2of the rotary electric machine1have the same central axis.

The rotor2is fixedly disposed on an outer shell (synchronous rotary member) of the power transmission device4. An outer circumferential surface of the rotor2faces an inner circumferential surface of the stator3, and an end face of the rotor2on the transmission9side faces an end face of the field coil7on the engine8side. Thus, the rotor2is rotatably held with respect to the stator3and the field coil7about the rotation axis10. As will be described later, the rotor2has a first magnetic pole21and a second magnetic pole22.

The field coil7is shifted to the transmission9side with respect to the rotor2along the rotation axis10, disposed side by side along the rotation axis10with respect to the rotor2, and is fixedly held on the case5on the transmission9side. The field coil7is provided inside a field core6(illustrated inFIG. 11), and excites magnetic flux by a direct current. It should be noted that the field coil7can also be shifted to the engine8side with respect to the rotor2along the rotation axis10and disposed side by side with respect to the rotor2via a second air gap12.

A first air gap11is formed between the rotor2and the stator3, and delivers magnetic flux between the rotor2and the stator3via the first air gap11. The first air gap11is a gap formed between the inner circumferential surface of the stator3and the outer circumferential surface of the rotor2and extends axially along the rotation axis10.

The second air gap12is formed between the rotor2and the field core6, and delivers magnetic flux between the rotor2and the field coil7via the second air gap12. The second air gap12is a gap formed between the end portion on the transmission9side in the axial direction of the rotation axis10of the rotor2and the end portion on the engine8side of the field core6.

In this way, the field coil7is disposed side by side in the axial direction of the rotation axis10with respect to the rotor2via the second air gap12. According to this configuration, since the field coil7is arranged being axially shifted with respect to the rotor2, an increase in the radial thickness of the field coil7allows magnetic flux of the field coil7to be increased and the degree of freedom of design to be increased.

In the rotary electric machine1having the configuration described above, magnetic flux by the field coil7is generated when the field coil7is energized. Magnetic flux by the field coil7is configured to return from the field core6to the field core6via the second air gap12, the first magnetic pole21of the rotor2, the first air gap11, the stator3, the first air gap11, the second magnetic pole22of the rotor2, and the second air gap12. At this time, for example, if the direct current is applied to the field coil7, magnetic flux by the field coil7is generated, and the first magnetic pole21and the second magnetic pole22are magnetized into, for example, the N pole and the S pole, respectively.

A case where the rotary electric machine1is caused to function as an electric motor (starter motor) at the time of starting the engine8will be described. Based on a start command of the engine8, an unillustrated inverter is driven to flow a three-phase alternating current through the stator3to magnetize the stator3, and flow the direct current through the field coil7. When the direct current flows through the field coil7, the first magnetic pole21and the second magnetic pole22of the rotor2are excited. As a result, the rotor2starts to rotate with respect to the stator3, and an electromotive force having an induced voltage is generated in the stator3.

After that, the induced voltage increases in response to a rotational speed of the rotor2. When the rotational speed reaches a rotational speed of the initial explosion lower than the idling rotational speed corresponding to the idling of the engine8and the start of the engine8is completed, the driving of the inverter is stopped, and thereafter, transition is made automatically to a power generation mode, i.e., a case where the rotary electric machine1is caused to function as a generator (alternator), so as to hold a predetermined induced voltage (required voltage).

In this power generation mode, when the field coil7continues to be excited, the excitation current is adjusted so that the induced voltage becomes constant at a predetermined induced voltage. The excitation current is adjusted so that the magnetizing force of the rotor2decreases as the rotational speed increases, thereby making the induced voltage constant. When the field coil7is not excited, the advance angle of the three-phase alternating current is adjusted by the inverter so that the induced voltage becomes constant at a predetermined induced voltage. It may also be adjusted by combining the above two methods. By controlling in this manner, when the rotor2rotates, the rotary electric machine1functions as a generator.

As a result, when the engine8and the rotary electric machine1are connected together, the rotary electric machine1can function as an electric motor (starter motor) at the time of starting the engine and can function as a generator (alternator) during traveling.

First Embodiment

Next, the configuration of the rotor2of the rotary electric machine1according to the first embodiment will be described in detail with reference toFIG. 2toFIG. 8.

As shown inFIG. 2, the rotor2is a claw pole type, and includes the first magnetic pole21, the second magnetic pole22, and a magnetic pole holding member23.

The first magnetic pole21has a first annular portion21aand a plurality of claw portions21b, and is composed of, for example, a soft magnetic material such as iron. The claw portion21bextends in the axial direction of the rotation axis10from the first annular portion21a. The claw portion21bhas, for example, a rectangular thin plate shape. The claw portions21bare disposed at regular intervals, e.g., at equal intervals, in the circumferential direction, and the axial lengths of the claw portions21bare all the same. The outer circumferential surface of each of the claw portions21bextends on the same circumference as the outer circumferential surface of the first annular portion21a. The claw portion21bis configured to be in a non-contact state with respect to the second magnetic pole22and to have a radial gap16in the radial direction when the first magnetic pole21and the second magnetic pole22are combined.

As shown inFIG. 6, each of the claw portions21bextends to an end edge of the engine8side of the first annular portion21a, thereby forming a first tip end locking portion21c. The first tip end locking portion21cis a stepped portion formed by notching the outer circumferential end edge of the claw portion21b. The outer circumferential surface of each of the first tip end locking portions21cis positioned on the same circumference about the central axis of the rotation axis10.

The second magnetic pole22has a second annular portion22aand a plurality of projection portions22b, and is composed of, for example, a soft magnetic material such as iron. The second annular portion22ahas the radial gap16with respect to the first annular portion21aand the claw portion21b, and is disposed so as to partially overlap with the claw portion21bas viewed from the radial direction. The projection portion22bprotrudes radially outwards from the outer circumferential surface of the second annular portion22a. The projection portions22bare disposed with a circumferential gap17in the circumferential direction with respect to the claw portions21b. The projection portion22bhas, for example, a rectangular plate shape. The projection portions22bare also disposed at regular intervals, e.g., at equal intervals, in the circumferential direction, and the radial heights of the projection portions22bare all the same. The axial lengths of the projection portions22bare all the same and are shorter than the axial lengths of the claw portions21b. The outer circumferential surface of each of the projection portions22bis positioned on the same outer circumference as the outer circumferential surface of each of the claw portions21babout the central axis of the rotation axis10.

As shown inFIG. 2,FIG. 3, andFIG. 6, an engagement recess portion38is formed in the radial gap16of one axial side (for example, the side opposite to the magnetic pole holding member23or the side of the transmission9) of the first annular portion21aand the second annular portion22a. The engagement recess portion38is composed of a first engagement recess portion38aand a second engagement recess portion38b. The first engagement recess portion38ais a recess portion formed by notching the radial inside of the first annular portion21a. The second engagement recess portion38bis a recess portion formed by notching the radial outside of the second annular portion22a.

As shown inFIG. 2,FIG. 3, andFIG. 6, a plurality of permanent magnets27are disposed at positions corresponding to the respective claw portions21bof the first magnetic pole21. Specifically, the permanent magnet27is disposed in the radial gap16formed in the same circumferential position as the claw portion21bof the first magnetic pole21and between the inner circumferential surface of the claw portion21band the outer circumferential surface of the second annular portion22a. According to this disposition, magnetic flux by the permanent magnet27is formed between the claw portion21bof the first magnetic pole21and the projection portion22bof the second magnetic pole22. The permanent magnet27has, for example, a rectangular plate shape.

The permanent magnet27is a magnet made mainly from neodymium or a magnet made mainly from ferrite. Specifically, various types of permanent magnets such as an SmCo magnet, an AlNiCo magnet, or a neodymium bonded magnet can be used as the permanent magnet27. The permanent magnet27can be disposed on the entire radial gap16at the claw portion21bor a part thereof.

According to this configuration, the output performance of the rotary electric machine1can be improved by using magnetic flux by the permanent magnet27in addition to magnetic flux by the field coil7. Further, by sandwiching and holding the permanent magnet27between the claw portion21band the second annular portion22a, the strength of the permanent magnet27with respect to a centrifugal force acting at the time of rotation can be reinforced, deformation of the permanent magnet27due to the centrifugal force can be prevented, and the centrifugal strength at the time of high rotation can be improved.

In the assembled rotor2, each of the claw portions21bof the first magnetic pole21is disposed in an intermediate portion of the circumferential gap17between the adjacent projection portions22b. Due to this, the claw portion21band the projection portion22bare circumferentially alternately positioned.

In the assembled rotor2, as shown inFIG. 2andFIG. 6, a gap for maintaining a non-contact state is formed between the first magnetic pole21and the second magnetic pole22. That is, there is the radial gap16in the radial direction between the first annular portion21aand the second annular portion22a, there is the circumferential gap17in the circumferential direction between the claw portion21band the projection portion22b, and there is an axial gap18in the axial direction between the first annular portion21aand the projection portion22b. Due to these gaps16,17, and18, the first magnetic pole21and the second magnetic pole22can maintain a non-contact state in the radial direction, the circumferential direction, and the axial direction, respectively.

The rotor2further includes the magnetic pole holding member23for fixing while maintaining the non-contact state. As shown inFIG. 3, the magnetic pole holding member23is an annular member, and has a base portion23a, a locking portion23b, an opening portion26, and an overhanging portion28. The magnetic pole holding member23is composed of a non-magnetic material such as aluminum or austenitic stainless steel. The locking portion23bprotrudes to one axial side (for example, the transmission9side) at the end portion on the outer circumferential side of the base portion23a, and is locked with respect to the first tip end locking portion21cof the claw portion21b. Because of this locking structure, the claw portion21bsupported in a cantilever manner with respect to the first annular portion21aof the first magnetic pole21is radially held by the magnetic pole holding member23, and it is hence possible to resist the centrifugal force acting at the time of rotation.

The opening portion26is formed on the base portion23aof the magnetic pole holding member23. The opening portion26is an opening penetrating the base portion23ain the thickness direction. As shown inFIG. 2, the opening portions26are disposed at regular intervals, e.g., at equal intervals, in the circumferential direction, and have pairs of one opening portion26aand the other opening portion26b. The one opening portion26aand the other opening portion26bare formed symmetrically in the circumferential direction across the projection portion22b. The opening portion26is used to provide a snap-fit coupling by an engagement claw portion34described later.

As shown inFIG. 7, the one opening portion26ahas one introduction hole26cand one engagement hole26d. The one introduction hole26cis formed radially inward, and has a circumferential length and a radial width larger than those of the one engagement hole26d. The one engagement hole26dis formed radially outward and is formed circumferentially near the projection portion22b. The one introduction hole26cis a hole for introducing therethrough a one engagement claw portion34aof an intervention member30described later. The one engagement hole26dis a hole for receiving therethrough a one leg portion33aof the intervention member30described later and engaging the one engagement claw portion34ato an engaged surface23e.

Similarly, the other opening portion26bhas the other introduction hole26eand the other engagement hole26f. The other introduction hole26eis formed radially inward, and has a circumferential length and a radial width larger than those of the other engagement hole26f. The other engagement hole26fis formed radially outward and is formed circumferentially near the projection portion22b. The other introduction hole26eis a hole for introducing therethrough the other engagement claw portion34bof the intervention member30described later. The other engagement hole26fis a hole for receiving therethrough the other leg portion33bof the intervention member30to be described later and engaging the other engagement claw portion34bto the engaged surface23e.

The magnetic pole holding member23has the plurality of overhanging portions28arranged in the circumferential gap17. The overhanging portion28extends towards one axial side (for example, the transmission9side) from the base portion23a. The shape and the dimension of the overhanging portion28is configured so as to fill the circumferential gap17.

The overhanging portion28of the magnetic pole holding member23is disposed in the circumferential gap17so as to fill the circumferential gap17, so that a circumferential phase shift between the first magnetic pole21and the second magnetic pole22is resolved, and hence torque is reliably transmitted between the first magnetic pole21and the second magnetic pole22.

As shown inFIG. 2,FIG. 3, andFIG. 6, in the rotor2, the intervention member30is arranged in the radial gap16. The intervention member30serves as a gap arrangement member arranged in the radial gap16and is composed of a non-magnetic material such as aluminum, austenitic stainless steel, or a resin material.

As shown inFIG. 8, the intervention member30has an annular base portion31, an engagement protrusion portion32, a plurality of leg portions33, and the plurality of engagement claw portions34. The annular base portion31has an annular shape. The engagement protrusion portion32is formed at an end portion on one axial side (for example, the side opposite to the magnetic pole holding member23or the side of the transmission9) of the annular base portion31, and protrudes in the radial direction. The engagement protrusion portion32includes a first engagement protrusion portion32aprotruding radially outward and a second engagement protrusion portion32bprotruding radially inward. The engagement protrusion portion32of the intervention member30is configured to engage with the engagement recess portion38of the radial gap16. That is, the first engagement protrusion portion32aand the second engagement protrusion portion32bare configured to engage with the first engagement recess portion38aand the second engagement recess portion38b, respectively.

The leg portion33extends from the annular base portion31towards the other axial side (for example, the side of the magnetic pole holding member23or the side of the engine8) in the radial gap16. The leg portions33are disposed at regular intervals, e.g., at equal intervals, in the circumferential direction, and are constituted by pairs of the one leg portion33aand the other leg portion33b. The leg portion33is elastically deformable to provide a snap-fit coupling.

The engagement claw portion34is formed at an end portion on the other axial side (for example, the side of the magnetic pole holding member23or the side of the engine8) of the leg portion33, and has a hook shape protruding towards the projection portion22bin the circumferential direction. The engagement claw portion34includes the one engagement claw portion34aformed in the one leg portion33aand the other engagement claw portion34bformed in the other leg portion33b. The one leg portion33aand the one engagement claw portion34aand the other leg portion33band the other engagement claw portion34bare provided so as to be circumferentially symmetrical across the projection portion22b. The engagement claw portion34of the intervention member30is configured to axially engage with the opening portion26of the magnetic pole holding member23. That is, the one engagement claw portion34aand the other engagement claw portion34bare configured to axially engage with the one engagement hole26dand the other engagement hole26fand the engaged surface23e, respectively.

On one axial side (for example, the side opposite to the magnetic pole holding member23or the side of the transmission9) of the intervention member30, the annular base portion31is sandwiched in the radial gap16between the first annular portion21aand the second annular portion22aso that the engagement protrusion portion32is axially engaged with the engagement recess portion38of the radial gap16. According to this configuration, on one axial side of the intervention member30, axial positioning and fixing are performed by engagement of the engagement protrusion portion32with respect to the engagement recess portion38, and hence the engagement protrusion portion32serves as an axial positioning portion.

The one engagement claw portion34aand the other engagement claw portion34bare introduced into the one introduction hole26cand the other introduction hole26e, respectively. Thereafter, by elastically deforming the one leg portion33aand the other leg portion33bradially outwardly, the one engagement claw portion34aand the other engagement claw portion34bengage with the one engagement hole26dand the other engagement hole26f, respectively, and engage with the engaged surface23e. Accordingly, by fitting the engagement claw portion34to the one engagement hole26dand the other engagement hole26fof the opening portion26, the intervention member30is fixed to the magnetic pole holding member23by a snap-fit coupling. According to this configuration, since axial positioning is performed by the axial engagement at the other axial side of the one engagement claw portion34aand the other engagement claw portion34b, the one engagement claw portion34aand the other engagement claw portion34bserve as axial positioning portions. Axial positioning can be simply and easily achieved by the engagement protrusion portion32engaging with the engagement recess portion38and the engagement claw portion34engaging with the engaged surface23e. Further, the snap-fit coupling allows the intervention member30to be easily and reliably fixed to the magnetic pole holding member23.

In this manner, the intervention member30is provided with the engagement protrusion portion32on one axial side and the engagement claw portion34on the other axial side, and hence axial positioning of the first magnetic pole and the second magnetic pole can be simply and easily performed.

The first magnetic pole21and the second magnetic pole22are radially held in a non-contact state via the annular base portion31of the intervention member30arranged in the radial gap16. Since the annular base portion31of the intervention member30, the first annular portion21aof the first magnetic pole21, and the second annular portion22aof the second magnetic pole22have the same central axis (i.e., they are coaxial), radial positioning (so-called centering) of the first magnetic pole and the second magnetic pole can be simply and easily performed.

In the rotor2of the rotary electric machine1according to this invention, it is possible to simply and easily perform radial positioning (so-called centering) of the first magnetic pole21and the second magnetic pole22by the intervention member30arranged in the radial gap16, and axial positioning is performed by the axial positioning portion of the intervention member30, that is, the engagement protrusion portion32and the engagement claw portion34. Accordingly, by the intervention member30providing the plurality of functions, the structure in which the first magnetic pole21and the second magnetic pole22are positioned while being maintained in a non-contact state radially and axially can be simply and easily achieved.

Variation of First Embodiment

A variation of the rotary electric machine1according to the first embodiment will be described with reference toFIG. 9.FIG. 9is a perspective view of the rotor2of the rotary electric machine1according to the variation, as cut vertically along the rotation axis10. In the variation shown inFIG. 9, in comparison with the rotor2shown inFIG. 2, the engagement claw portion34of the intervention member30is engaged with the engaged surface22eof the projection portion22b.

As well as the embodiment shown inFIG. 2, the intervention member30shown inFIG. 9is arranged in the radial gap16, and includes the annular base portion31, the engagement protrusion portion32, the leg portions33(the one leg portion33aand the other leg portion33b), and the engagement claw portions34(the one engagement claw portion34aand the other engagement claw portion34b). The projection portion22bhas the engaged surface22eon the other axial side (for example, the side facing the magnetic pole holding member23or the side of the engine8).

The engagement protrusion portion32radially protruding is formed at the end portion on one axial side (for example, the side opposite to the magnetic pole holding member23or the side of the transmission9) of the annular base portion31. The engagement protrusion portion32is configured to axially engage with the engagement recess portion38of the radial gap16. The engagement protrusion portion32serves as the axial positioning portion.

At the other axial end (for example, the side of the magnetic pole holding member23or the side of the engine8) of the leg portion33, the engagement claw portions34(the one engagement claw portion34aand the other engagement claw portion34b) having a hook shape protruding towards the projection portion22bin the circumferential direction are formed. The leg portions33(the one leg portion33aand the other leg portion33b) circumferentially and elastically deform towards the projection portion22b, so that the engagement claw portions34(the one engagement claw portion34aand the other engagement claw portion34b) are configured to axially engage with the engaged surface22eof the projection portion22b. The engagement claw portion34of the intervention member30is fixed to the projection portion22bby a snap-fit coupling. In this way, the one engagement claw portion34aand the other engagement claw portion34bserve as axial positioning portions. Accordingly, axial positioning can be simply and easily achieved by the engagement protrusion portion32engaging with the engagement recess portion38and the engagement claw portion34engaging with the engaged surface22e.

In the rotor2of the rotary electric machine1according to this variation, it is possible to simply and easily perform radial positioning (so-called centering) of the first magnetic pole21and the second magnetic pole22by the intervention member30arranged in the radial gap16, and axial positioning is performed by the axial positioning portion of the intervention member30, that is, the engagement protrusion portion32and the engagement claw portion34. Accordingly, by the intervention member30providing the plurality of functions, the structure in which the first magnetic pole21and the second magnetic pole22are positioned while being maintained in a non-contact state radially and axially can be simply and easily achieved.

In the rotor2of the rotary electric machine1according to the variation, the plurality of permanent magnets27are axially locked by a magnet locking portion22dof the second magnetic pole22. That is, the magnet locking portion22dradially and outwardly protrudes at the end portion on the other axial side (for example, the side of the magnetic pole holding member23or the side of the engine8) of the second annular portion22aof the second magnetic pole22. The radial gap16at the end portion on the other axial side is narrowed in the radial direction by the magnet locking portion22d. Due to this, it is possible to axially fix the permanent magnet27arranged in the radial gap16.

Another Variation of First Embodiment

Another variation of the rotary electric machine1according to the first embodiment will be described with reference toFIG. 10.FIG. 10is a perspective view of the rotor2of the rotary electric machine1according to another variation, as cut vertically along the rotation axis10. In another variation shown inFIG. 10, in comparison with the rotor2shown inFIG. 2, the engagement claw portion34of the intervention member30is engaged with both the claw portion21bof the first magnetic pole21and the permanent magnet27on the other axial side (for example, the side facing the magnetic pole holding member23or on the side of the engine8). It is to be noted that the engagement claw portion34of the intervention member30does not necessarily need to engage with both the claw portion21bof the first magnetic pole21and the permanent magnet27, and it may engage with only the permanent magnet27, for example.

The intervention member30shown inFIG. 10, arranged in the radial gap16, has the annular base portion31, the engagement protrusion portion32, the leg portions33(the one leg portion33aand the other leg portion33b), and the engagement claw portions34(the one engagement claw portion34aand the other engagement claw portion34b). The one engagement claw portion34aand the other engagement claw portion34bhave a hook shape extending to the opposite side of the projection portion22bin the circumferential direction.

The claw portion21bhas the engaged surface21eon the other axial side. The permanent magnet27also has an engaged surface27eon the other axial side. The engaged surface21eand the engaged surface27eare configured to be flush with each other when the permanent magnet27is arranged in the radial gap16.

The leg portions33(the one leg portion33aand the other leg portion33b) circumferentially and elastically deform towards the opposite side of the projection portion22b, so that the engagement claw portions34(the one engagement claw portion34aand the other engagement claw portion34b) axially engage with both the engaged surface21eof the claw portion21band the engaged surface27eof the permanent magnet27. As a result, the intervention member30is fixed to the claw portion21band the permanent magnet27by a snap-fit coupling. Since the engagement claw portion34serves as the axial positioning portion, axial positioning can be simply and easily achieved by the engagement protrusion portion32engaging with the engagement recess portion38and the engagement claw portion34engaging with both the claw portion21band the permanent magnet27. The engagement claw portion34can axially fix the permanent magnet27arranged in the radial gap16.

Second Embodiment

Next, the configuration of the rotor2of the rotary electric machine1according to the second embodiment will be described in detail with reference toFIG. 11toFIG. 16.

As shown inFIG. 11andFIG. 12, the rotor2is a claw pole type, and includes the first magnetic pole21, the second magnetic pole22, and a magnetic pole holding member23.

The first magnetic pole21has a first annular portion21aand a plurality of claw portions21b, and is composed of, for example, a soft magnetic material such as iron. The claw portion21bextends in the axial direction of the rotation axis10from the first annular portion21a. The claw portion21bhas, for example, a rectangular thin plate shape. The claw portions21bare disposed at regular intervals, e.g., at equal intervals, in the circumferential direction, and the axial lengths of the claw portions21bare all the same. The outer circumferential surface of each of the claw portions21bextends on the same circumference as the outer circumferential surface of the first annular portion21a. The claw portion21bis configured to be in a non-contact state with respect to the second magnetic pole22and to have the radial gap16in the radial direction when the first magnetic pole21and the second magnetic pole22are combined.

Each of the claw portions21bextends to the end edge of the engine8side of the first annular portion21a, thereby forming the first tip end locking portion21c. The first tip end locking portion21cis a stepped portion formed by notching the outer circumferential end edge of the claw portion21b. The outer circumferential surface of each of the first tip end locking portions21cis positioned on the same circumference about the axial center of the rotation axis10.

The second magnetic pole22has a second annular portion22aand a plurality of projection portions22b, and is composed of, for example, a soft magnetic material such as iron. The second annular portion22ais disposed so as to partially overlap with the claw portion21bas viewed from the radial direction through the radial gap16inside the claw portion21b. The projection portion22bradially protrudes on the outer circumferential surface of the second annular portion22a. The projection portions22bare disposed with the circumferential gap17in the circumferential direction with respect to the claw portions21b. The projection portion22bhas, for example, a rectangular plate shape. The projection portions22bare also disposed at regular intervals, e.g., at equal intervals, in the circumferential direction, and the radial heights of the projection portions22bare all the same. The axial lengths of the projection portions22bare all the same and are shorter than the axial lengths of the claw portions21b.

The outer circumferential surface of each of the projection portions22bis positioned on the same outer circumference with respect to the outer circumferential surface of each of the claw portions21babout the axial center of the rotation axis10. Each of the projection portions22bextends to an end edge of the engine8side of the second annular portion22a, thereby forming a second tip end locking portion122c. The second tip end locking portion122cis a stepped portion formed by notching the outer circumferential end edge of the projection portion22b. The outer circumferential surface of each of the second tip end locking portions122cis positioned on the same circumference with respect to the outer circumferential surface of each of the first tip end locking portions21cabout the axial center of the rotation axis10. Accordingly, the outer circumferential surface of each of the first tip end locking portions21cand the outer circumferential surface of each of the second tip end locking portions122care positioned on the same circumference about the axial center of the rotation axis10. According to this configuration, since the outer circumferential surface of the first tip end locking portion21cand the outer circumferential surface of each of the second tip end locking portions122care positioned on the same outer circumference, it is easy to fit the first tip end locking portion21cand each of the second tip end locking portions122cwith a fitting portion123a, which will be described later, of the magnetic pole holding member23.

The surface on the side facing the projection portion22bof each of the claw portions21bis provided with an engagement projection portion121d. The engagement projection portion121dcircumferentially protrudes towards the projection portion22b. The engagement projection portion121dhas a rectangular shape in plan view as shown inFIG. 13, and has a rectangular shape as seen from the axial direction as shown inFIG. 15. The outer circumferential surface of the engagement projection portion121dis positioned on the same circumference as the outer circumferential surface of the first tip end locking portion21cof the claw portion21b. The engagement projection portion121dof the claw portion21bengages with an axial engagement portion132of a spacer member130.

As shown inFIG. 11,FIG. 12,FIG. 14, andFIG. 15, the plurality of permanent magnets27are disposed in positions corresponding to the respective claw portions21bof the first magnetic pole21. Specifically, the permanent magnet27is disposed in the radial gap16in the same circumferential position as the claw portion21bof the first magnetic pole21and between the inner circumferential surface of the claw portion21band the outer circumferential surface of the second annular portion22a. According to this disposition, magnetic flux by the permanent magnet27is formed between the claw portion21bof the first magnetic pole21and the projection portion22bof the second magnetic pole22. The permanent magnet27has, for example, a rectangular plate shape.

The permanent magnet27is a magnet made mainly from neodymium or a magnet made mainly from ferrite. Specifically, various types of permanent magnets such as an SmCo magnet, an AlNiCo magnet, or a neodymium bonded magnet can be used as the permanent magnet27. The permanent magnet27can be disposed on the entire radial gap16at the claw portion21bor a part thereof.

According to this configuration, the output performance of the rotary electric machine1can be improved by using magnetic flux by the permanent magnet27in addition to magnetic flux by the field coil7. Further, by sandwiching and holding the permanent magnet27with the claw portion21band the second annular portion22a, the strength of the permanent magnet27with respect to the centrifugal force can be reinforced, deformation of the permanent magnet27due to the centrifugal force can be prevented, and the centrifugal strength at the time of high rotation can be improved.

The rotor2is assembled as follows. By axially moving the first magnetic pole21with respect to the second magnetic pole22, each of the claw portions21bof the first magnetic pole21is inserted in the intermediate portion of the circumferential gap17between the adjacent projection portions22b. Thereby, the claw portion21band the projection portion22bare assembled in a state of being circumferentially alternately disposed. It is configured that in the assembled state, the outer circumferential surface of each of the first tip end locking portions21cand the outer circumferential surface of each of the second tip end locking portions122care positioned on the same circumference about the axial center of the rotation axis10.

In the assembled state, as shown inFIG. 14, a gap for maintaining a non-contact state is formed between the first magnetic pole21and the second magnetic pole22. That is, there is the radial gap16in the radial direction between the claw portion21band the second annular portion22a, there is the circumferential gap17in the circumferential direction between the claw portion21band the projection portion22b, and there is the axial gap18in the axial direction between the first annular portion21aand the projection portion22b. Therefore, the first magnetic pole21and the second magnetic pole22maintain a non-contact state in the radial direction, the circumferential direction, and the axial direction.

The rotor2further includes the magnetic pole holding member23for fixing while maintaining the non-contact state. As shown inFIG. 13, the magnetic pole holding member23is an annular member, and has the fitting portion123aat an end portion on the outer circumferential side. The magnetic pole holding member23is composed of a non-magnetic material such as aluminum or austenitic stainless steel. The fitting portion123aprotrudes on the transmission9side, for example, and is fitted with the first tip end locking portion21cof the claw portion21bof the first magnetic pole21and the second tip end locking portion122cof the projection portion22bof the second magnetic pole22. With this fitting structure, the first magnetic pole21and the second magnetic pole22are fixedly held with respect to the radial direction by the magnetic pole holding member23. Further, the magnetic pole holding member23has a through hole (not illustrated) for bolting by a bolt138described later.

As shown inFIG. 16, the spacer member130is composed of a pair of rectangular parallelepiped members that are a one spacer member130aand an other spacer member130b. The one spacer member130aand the other spacer member130bare configured to be circumferentially symmetrical. Hereinafter, the one spacer member130aand the other spacer member130bare simply referred to as the spacer member130.

The spacer member130has an axially extending screw bore131and the axial engagement portion132. The spacer member130serves as a gap arrangement member arranged in the circumferential gap17and is composed of a non-magnetic material such as aluminum or austenitic stainless steel. The axial engagement portion132is provided on the side facing the claw portion21bof the first magnetic pole21. The axial engagement portion132has an engagement end portion133and an engagement recess portion134and is formed by partially notching a corner portion facing both the claw portion21band the magnetic pole holding member23.

The engagement end portion133and the engagement recess portion134are axially aligned. The engagement end portion133is, for example, a plate-like portion positioned on the transmission9side, and axially engages with the engagement projection portion121dof the claw portion21b. The engagement recess portion134is, for example, a recess portion positioned on the engine8side, and receives the engagement projection portion121dof the claw portion21b.

As shown inFIG. 13andFIG. 14, the spacer member130is disposed between the claw portion21bof the first magnetic pole21and the projection portion22bof the second magnetic pole22so as to fill the circumferential gap17. At this time, the surface on the side facing the projection portion22bof the spacer member130abuts against the projection portion22b, and the surface on the side facing the claw portion21bof the engagement end portion133of the spacer member130abuts against the claw portion21b, and hence the circumferential gap17is substantially filled with the spacer member130. The engagement recess portion134of the spacer member130receives the engagement projection portion121dof the claw portion21band the engagement end portion133abuts against the surface (the surface of the transmission9side, for instance) of the side not facing the magnetic pole holding member23of the claw portion21b, so that the axial engagement portion132axially engages with the engagement projection portion121d.

In the rotor2of the rotary electric machine1according to the present invention, the spacer member130is fixedly held with respect to the radial direction by being fitted with the magnetic pole holding member23in a state of being disposed between the claw portion21bof the first magnetic pole21and the projection portion22bof the second magnetic pole22so as to fill the circumferential gap17. That is, the magnetic pole holding member23is axially mounted with respect to the first magnetic pole21and the second magnetic pole22in a state where the spacer member130is disposed between the claw portion21band the projection portion22b. At this time, the fitting portion123aof the magnetic pole holding member23is fitted with the first tip end locking portion21cof the claw portion21bof the first magnetic pole21and the second tip end locking portion122cof the projection portion22bof the second magnetic pole22.

Then, by screwing a screw portion of the bolt138into the screw bore131of the spacer member130, the spacer member130is fixed (i.e., bolted) to the magnetic pole holding member23with the bolt138. This bolting allows the spacer member130to be easily and reliably fixed to the magnetic pole holding member23. When the spacer member130is bolted to the magnetic pole holding member23, the engagement end portion133of the spacer member130is drawn towards the magnetic pole holding member23side and axially engaged with the engagement projection portion121dof the claw portion21b, and hence the first magnetic pole21is axially held and fixed to the magnetic pole holding member23. Further, the second magnetic pole22can be fixed to the magnetic pole holding member23by an arbitrary fixing method described later.

The spacer member130is disposed between the claw portion21bof the first magnetic pole21and the projection portion22bof the second magnetic pole22so as to fill the circumferential gap17, thereby circumferentially holding the first magnetic pole21and the second magnetic pole22. As a result, the circumferential phase shift between the first magnetic pole21and the second magnetic pole22is resolved, and thus torque is reliably transmitted between the first magnetic pole21and the second magnetic pole22.

According to the above configuration, in addition that the first magnetic pole21and the second magnetic pole22are radially held by the magnetic pole holding member23, the torque is circumferentially reliably transmitted between the first magnetic pole21and the second magnetic pole22by the spacer member130filling the circumferential gap17, and the spacer member130is axially engaged with the claw portion21bof the first magnetic pole21, thereby axial holding the first magnetic pole21. Accordingly, by the spacer member130providing the plurality of functions, the structure in which the first magnetic pole21and the second magnetic pole22are fixed to the magnetic pole holding member23while being maintained in a non-contact state radially, circumferentially, and axially can be easily achieved.

A variation of the second embodiment will be described with reference toFIG. 17.FIG. 17is a perspective view of the rotor2according to a variation of the second embodiment, as cut vertically along the rotation axis10. In the variation shown inFIG. 17, in comparison with the rotary electric machine1shown inFIG. 12, the bolt138for fixing the second magnetic pole22to the magnetic pole holding member23is provided.

An unillustrated screw bore is formed in the second magnetic pole22, and a through hole corresponding to the screw bore is formed in the magnetic pole holding member23. While the screw bore of the second magnetic pole22is formed in the second annular portion22aon the radial inside of each of the projection portions22bas shown inFIG. 17for example, it is not limited to this position.

By screwing the screw portion of the bolt138into the screw bore of the second magnetic pole22, the second magnetic pole22is fixed (i.e., bolted) to the magnetic pole holding member23with the bolt138. This bolting allows the second magnetic pole22to be easily and reliably fixed to the magnetic pole holding member23. Accordingly, the first magnetic pole21and the second magnetic pole22can be easily and reliably fixed to the magnetic pole holding member23.

While the specific embodiments of the present invention have been described, the present invention is not limited to the embodiments described above and various variations can be made within the scope of the present invention.

In the first embodiment, the permanent magnet27is disposed in the radial gap16corresponding to the claw portion21b. However, the radial gap16may be left void without disposing the permanent magnet27in the radial gap16.

In the first embodiment, the example of fixing by the snap-fit coupling has been presented as a fixing method of the intervention member30to the magnetic pole holding member23and the projection portion22b. However, welding or brazing of the engagement claw portion34to the engaged surfaces22eand23e, rivet caulking of the engagement claw portion34to the opening portion26, or the like can also be used. According to this fixing method, the first magnetic pole21and the second magnetic pole22can be easily and reliably fixed to the magnetic pole holding member23.

In the second embodiment, the permanent magnet27is disposed in the radial gap16in the claw portion21bof the first magnetic pole21. However, the radial gap16may be left void without disposing the permanent magnet27in the radial gap16in the claw portion21b.

In the second embodiment, the example of bolting with the bolt138has been presented as a fixing method of the first magnetic pole21and the second magnetic pole22to the magnetic pole holding member23. However, welding, rivet caulking, brazing, or the like can also be used. According to this fixing method, the first magnetic pole21and the second magnetic pole22can be easily and reliably fixed to the magnetic pole holding member23.

InFIG. 1showing the schematic configuration of the rotary electric machine1, the position of the stator3and the position of the field coil7may be interchanged, thereby providing a configuration in which the field coil7is disposed radially outside the rotor2and the stator3is disposed by being axially shifted with respect to the rotor2. In this case, the first air gap11is formed between the rotor2and the stator3, on the other hand, the second air gap12is formed between the rotor2and the field coil7.

In the above embodiment, the rotor2is fixed to the outer shell (synchronous rotary member) of the power transmission device4. In a case where the power transmission device4is a torque converter, for example, the outer shell (synchronous rotary member) of the power transmission device4is a front cover of the torque converter or a drive plate connected to the engine8side. Examples of the synchronous rotary member having a similar function include a clutch cover of a friction type clutch, a flywheel connected to the engine8side of the friction type clutch, an outer shell of a fluid coupling, and a drive plate connected to the engine8side of the fluid coupling.

In the above embodiments, as an example, the rotary electric machine1is disposed between the engine8and the transmission9along the rotation axis10. However, the rotary electric machine1may be replaced with an alternator, connected to the output shaft of the engine8, disposed between the engine8and the transmission9, disposed between the transmission9and a drive shaft, or mounted to the drive shaft itself.

The rotary electric machine1of this invention is not limited to use for vehicles but can also be used for widely-used generators and electric motors.

This invention and the embodiments are summarized as follows.

A rotary electric machine1according to one aspect of this invention includes:

a stator3having a stator winding14that generates a rotating magnetic field by an alternating current;

a rotor2that is rotatably held about a rotation axis10with respect to the stator3; and

a field coil7that excites the rotor2by a direct current, wherein:

the rotor2includes

a first magnetic pole21that has a first annular portion21aand a plurality of claw portions21bextending in an axial direction of the rotation axis10from the first annular portion21a, and

a second magnetic pole22that has a second annular portion22aand a plurality of projection portions22bradially projecting on an outer circumferential surface of the second annular portion22a;

in the rotor2,

the claw portions21bof the first magnetic pole21and the projection portions22bof the second magnetic pole22are circumferentially alternately positioned, and

the first magnetic pole21and the second magnetic pole22are maintained in a non-contact state by providing a radial gap16, a circumferential gap17, and an axial gap18between the first magnetic pole21and the second magnetic pole22;

the rotor2further includes a gap arrangement member30;130of a non-magnetic material arranged in the radial gap16or the circumferential gap17; and

the gap arrangement member30;130has an axial positioning portion32,34;132that is axially locked with respect to at least one of the first magnetic pole21and the second magnetic pole22, and axially positions the first magnetic pole21and the second magnetic pole22.

According to the above configuration, radial positioning or circumferential positioning of the first magnetic pole21and the second magnetic pole22is performed by the gap arrangement member30;130of the non-magnetic material arranged in the radial gap16or the circumferential gap17, and axial positioning is performed by the axial positioning portion32,34;132of the gap arrangement member30;130. Accordingly, by the gap arrangement member30;130providing the plurality of functions, the structure in which the first magnetic pole21and the second magnetic pole22are positioned while being maintained in a non-contact state radially or circumferentially and axially can be simply and easily achieved.

Further, in the rotary electric machine1of one embodiment, the gap arrangement member30is arranged in the radial gap16, and performs radial positioning of the first magnetic pole21and the second magnetic pole22.

According to the above embodiment, by the gap arrangement member30providing the plurality of functions, the structure in which the first magnetic pole21and the second magnetic pole22are positioned while being maintained in a non-contact state radially and axially can be simply and easily achieved.

Further, in the rotary electric machine1of one embodiment,

the rotor2further includes the magnetic pole holding member23of the non-magnetic material that radially holds the claw portion21bof the first magnetic pole21.

According to the above embodiment, the claw portion21bof the first magnetic pole21is radially held by the magnetic pole holding member23, and it is hence possible to resist the centrifugal force acting at the time of rotation.

Further, in the rotary electric machine1of one embodiment,

the magnetic pole holding member23includes the overhanging portion28arranged in the circumferential gap17.

According to the above embodiment, the circumferential phase shift between the first magnetic pole21and the second magnetic pole22is resolved by the overhanging portion28, and thus torque is reliably transmitted between the first magnetic pole21and the second magnetic pole22.

Further, in the rotary electric machine1of one embodiment,

the rotor2has the engagement recess portion38on the one axial side and the engaged surface22eon the other axial side,

the gap arrangement member30has the engagement protrusion portion32that engages with the engagement recess portion38on the one axial side and the engagement claw portion34that engages with the engaged surface22eon the other axial side, and

the engagement protrusion portion32and the engagement claw portion34serve as the axial positioning portions.

According to the above embodiment, axial positioning can be simply and easily achieved by the engagement protrusion portion32engaging with the engagement recess portion38and the engagement claw portion34engaging with the engaged surface22eof the rotor2.

Further, in the rotary electric machine1of one embodiment,

the rotor2has the engagement recess portion38on the one axial side and the magnetic pole holding member23has the engaged surface23eon the other axial side,

the gap arrangement member30has the engagement protrusion portion32that engages with the engagement recess portion38on the one axial side and the engagement claw portion34that engages with the engaged surface23eon the other axial side, and

the engagement protrusion portion32and the engagement claw portion34serve as the axial positioning portions.

According to the above embodiment, axial positioning can be simply and easily achieved by the engagement protrusion portion32engaging with the engagement recess portion38and the engagement claw portion34engaging with the engaged surface23eof the magnetic pole holding member23.

Further, in the rotary electric machine1of one embodiment,

the field coil7is disposed side by side in the axial direction of the rotation axis10with respect to the rotor2.

According to the above embodiment, an increase in the radial thickness of the field coil7allows magnetic flux of the field coil7to be increased and the degree of freedom of design to be increased.

Further, the rotary electric machine1of one embodiment, further includes

the permanent magnet27in the radial gap16in the same circumferential position as the claw portion21bof the first magnetic pole21and between the inner circumferential surface of the claw portion21band the outer circumferential surface of the second annular portion22a.

According to the above embodiment, the output performance of the rotary electric machine1can be improved by using magnetic flux by the permanent magnet27in addition to magnetic flux by the field coil7.

Further, in the rotary electric machine1of one embodiment,

the gap arrangement member130is arranged in the circumferential gap17, and performs circumferential positioning of the first magnetic pole21and the second magnetic pole22.

According to the above embodiment, by the gap arrangement member130providing the plurality of functions, the structure in which the first magnetic pole21and the second magnetic pole22are positioned while being maintained in a non-contact state circumferentially and axially can be simply and easily achieved.

Further, in the rotary electric machine1of one embodiment,

the rotor2further includes the magnetic pole holding member23of the non-magnetic material that radially holds the first magnetic pole21and the second magnetic pole22.

According to the above embodiment, the first magnetic pole21and the second magnetic pole22are radially held by the magnetic pole holding member23, and it is hence possible to resist the centrifugal force acting at the time of rotation.

Further, in the rotary electric machine1of one embodiment,

the gap arrangement member130is fixed to the magnetic pole holding member23in a state where the axial positioning portion132is engaged with the claw portion21b.

According to the above embodiment, the first magnetic pole21and the second magnetic pole22are fixed while being maintained in a non-contact state radially, circumferentially, and axially.

Further, in the rotary electric machine1of one embodiment,

the claw portion21bhas the engagement projection portion121dcircumferentially protruding on the side facing the projection portion22b,

the gap arrangement member130has the axial engagement portion132axially engaging with respect to the engagement projection portion121don the side not facing the magnetic pole holding member23, and

the axial engagement portion132of the gap arrangement member130engages with the engagement projection portion121dof the claw portion21b.

According to the above embodiment, since the axial engagement portion132of the gap arrangement member130engages with the engagement projection portion121dof the claw portion21b, axial engagement can be easily achieved.

Further, in the rotary electric machine1of one embodiment,

the claw portion21bof the first magnetic pole21has the first tip end locking portion21cat the end edge on the magnetic pole holding member23side,

the projection portion22bof the second magnetic pole22has the second tip end locking portion122cat the end edge on the magnetic pole holding member23side, and

the magnetic pole holding member23has the fitting portion123afitted to the first tip end locking portion21cand the second tip end locking portion122con the outer circumferential side.

According to the above embodiment, the first magnetic pole21and the second magnetic pole22are fixedly held with respect to the radial direction by the magnetic pole holding member23.

Further, in the rotary electric machine1of one embodiment,

the outer circumferential surface of the first tip end locking portion21cand the outer circumferential surface of the second tip end locking portion122care positioned on the same circumference about the axial center of the rotation axis10.

According to the above embodiment, it is easy to fit the first tip end locking portion21cand each of the second tip end locking portions122cwith the fitting portion123aof the magnetic pole holding member23.

Further, in the rotary electric machine1of one embodiment,

fixing of the gap arrangement member130to the magnetic pole holding member23is bolting, welding, rivet caulking, or brazing.

According to the above embodiment, the gap arrangement member130can be easily and reliably fixed to the magnetic pole holding member23.

Further, in the rotary electric machine1of one embodiment,

the field coil7is disposed side by side in the axial direction of the rotation axis10with respect to the rotor2.

According to the above embodiment, an increase in the radial thickness of the field coil7allows magnetic flux of the field coil7to be increased and the degree of freedom of design to be increased.

Further, the rotary electric machine1of one embodiment, further includes

the permanent magnet27in the radial gap16in the same circumferential position as the claw portion21bof the first magnetic pole21and between the inner circumferential surface of the claw portion21band the outer circumferential surface of the second annular portion22a.

According to the above embodiment, the output performance of the rotary electric machine1can be improved by using magnetic flux by the permanent magnet27in addition to magnetic flux by the field coil7.