Patent Application
20140183985
The present invention relates to a rotating electric machine such as electric motors and generators and relates in particular to a rotating electric machine that suppresses insulation defects in the stator coil ends.
In recent years, rotating electric machines are being utilized in hybrid vehicles and electric vehicles by methods such as driving vehicle tires by way of electric motors or utilizing these electric motors as generators to charge a lithium cell by utilizing the drive inertia when an automobile decelerates.
There are also of course demands for a high output from these types of rotating electric machines; however, this high output causes new problems causing phenomena such as an increase in the vibration applied to the stator coil of the rotating electric machine or causes the stator coil to emit a large amount of heat.
In a specific example of a problem caused by heat emission, when a high temperature heat cycle is applied in particular to the stator coil of hybrid vehicles by repeated forward movement and stopping, a phenomenon occurs in which insulation defects tend to easily occur in the welded coupling section between the coil end of the stator coil and the other adjacent coil end.
In order to make an electrical coupling to the coil end of the other adjacent coil, the insulation coating (such as enamel sheath) on the coil end of the stator coil must be removed to expose the coil conductor section and each of the conductors coupled together by welding.
Methods proposed in the related art for removing the insulation coating on the coil ends include a method for removing the insulation coating by pressing a rotating brush up against the insulation coating such as disclosed in patent document 1, and a method for removing the insulation coating by immersing the insulation coating in organic solvent such as disclosed in patent document 2.
As described above, the insulation coating of the coil end is removed in order to couple the adjacent coil ends in the vicinity of the welded section on the coil ends of the stator coil.
During repetitive heat cycles in a state where a high temperature is reached from large heat emissions due to electrical current flow in the stator coil caused by the high output, or a state where the electrical current flow is cut off and the stator coil cools down from the high temperature; a large peeling force occurs due to heat at the boundary between the coil conductor and the insulation coating on the coil end and the insulation coating peels, consequently causing insulation defects to easily occur due to the insulation breaking down because of this peeling. This (peeling) phenomenon occurs each time the heat cycle repeats so a basic solution is required.
In the method disclosed in patent document 3, a varnish is applied to suppress deterioration of the insulation coating of the stator coil housed within a slot in the stator core caused by cutting oil or other factors. An incidental usage is that letting varnish soak into the coil end section of the stator coil creates an effect where the peeling phenomenon of the insulation coating on the boundary between the coil conductor and the insulation coating on the coil end can likely be suppressed to a certain extent due to the adhesive force of the varnish.
However, in this peeling suppression effect, a side effect that promotes the peeling phenomenon was found to occur when a high temperature heat cycle is applied to the stator coil. The reason is described in detail among the problems.
In either case, a high temperature heat cycle applied to the stator coil causes a large peeling force to occur and the insulation coating is peels due to heat at the boundary between the coil conductor and the insulation coating on the coil end so that this peeling consequently causes a breakdown in the insulation that makes insulation defects easily occur.
Patent literature 1: Japanese Unexamined Patent Application Publication No. Heil0 (1998)-14182
Patent literature 2: Japanese Unexamined Patent Application Publication No. 2011-14510
Patent literature 3: Japanese Unexamined Utility Model Application Publication No. Hei5 (1993)-039178
As described above, the method such as described in patent document 3 for covering the insulation coating with varnish was proposed as a method to generally protect the insulation coating of the coil from peeling and damage.
However, in addition to the peeling phenomenon due to repeated high temperature heat cycles, a side effect was found to likely occur, in which the epoxy type thermosetting resin utilized as the varnish, itself emits gas during high temperatures from 180° C. to 200° C. or more and after cooling later on, the volume of the varnish shrinks to promote a peeling phenomenon of the insulation coating due to the heat contraction of the varnish itself.
Therefore, not much can be expected from the peeling suppression effect on the insulation coating rendered by the varnish at high temperatures as implemented in the example of the related art for the phenomenon of large heat emissions from the stator coil accompanying a high output.
However, the use of the varnish is effective versus mechanical vibration and so cannot be excluded from the present invention. In other words, even varnish can be used if effective in preventing peeling.
Results from an analysis made by the present inventors, revealed that in the removal methods in patent document 1 and patent document 2, the tip section whose insulation coating was removed is in a state nearly perpendicular to the coil conductor surface.
When a heat cycle is then applied, the coil conductor and insulation coating each have their own unique expansion coefficient and so the expansion and contraction of the coil conductor and insulation coating are different from each other. However, when the removed section of the insulation coating is in a perpendicular state, the cross sectional area of the removed section of the insulation coating is approximately equal to the cross sectional area of a normal insulation coating, and the expansion force and the contraction force that accompanies the expansion and contraction becomes large in proportion to the cross sectional area.
The removed section of the insulation coating is therefore a perpendicular shape so that the cross sectional area at that section is a maximum and a large expansion force and contraction force are generated. A large gap therefore occurs relative to the coil conductor which consequently causes peeling. Moreover, the contraction force of the varnish applied here promotes the peeling phenomenon even further.
An object of the present invention is therefore to provide a rotating electric machine that prevents peeling of the insulation coating on the coil end due to the heat cycle.
A feature of the present invention is that the tip of the insulation coating is formed in a sloped surface so that the thickness of the insulation coating on the coil end is a shape having a slope that gradually becomes thinner towards the welded coupling section of the conductor.
Forming the thickness of tip of the insulation coating so that the slope becomes thinner, prevents the peeling that occurs in the insulation coating due to heat contraction in the period from high temperature heat emission in the coil until cooling.
An embodiment of the present invention is hereafter described in detail while referring to the accompanying drawings. The rotating electric machine is first of all described while referring to
In
A flow passage member 22 is formed in the inner side of a housing 1. The stator 4 is clamped to the inner side of this flow passage member 22 by shrink-fitting, etc. The flange at the left end shown in the drawing for the flow passage member 22 is enclosed and fastened between the housing 1 and the cover 2. A flow passage 24 is formed between the flow passage member 22 and the housing 1.
The coolant for cooling the rotating electric machine is drained from the drain outlet 34 of housing 1 after being filled into the flow passage 24 from the fill inlet 32 formed in the housing 1.
As shown in the cross sectional view in
Twenty-four slots 411 are formed on the stator core 412 on which the stator coil 413 is inserted. The stator core 412 is formed into an annular shape containing inner circumferential slots formed by blanking or etching processing a single electromagnetic steel sheet with a thickness for example of 0.05 to 0.35 mm; a laminated steel plate is formed by stacking approximately several hundred of the formed electromagnetic steel sheets; and the plurality of slots 411 positioned radially at equidistant intervals are formed along the inner circumference.
Returning to
Among the bearings 7a, 7b, the bearing 7a on the cover 2 side is clamped to the cover 2 by a clamp plate not shown in the drawings, and the bearing 7b is clamped to a cavity section installed at the bottom of the housing 1.
A pulley 12 is mounted by way of the nut 11 on the left end of the shaft 6. A sleeve 9 and a spacer 10 are mounted between the pulley 12 and the bearing 7a of the shaft 6.
The outer circumference of the sleeve 9 and the inner circumference of the pulley 12 form a roughly cone shape and the pulley 12 and shaft 6 are firmly secured into one piece by the tightening force of the nut 11 and are capable of rotating as one integrated piece
When used as an electric motor, the rotor 5 is driven to rotate relative to the stator 4 and the rotational force of the shaft 6 is output externally by the pulley 12, when used as a generator, the rotational force from the pulley 12 is input to the shaft 6 and electricity is generated by the stator coil.
As shown in
The rotor core 513 is comprised of magnetic material, and shorting rings 512 are each respectively mounted on both axial ends of the rotor core 513 to electrically short each conductor bar 511.
The perspective view in
The rotor core 513 is formed the same as the stator core 412 by blanking or etching processing an electromagnetic steel sheet with a thickness of 0.05 to 0.35 mm, and stacking approximately several hundreds of the formed electromagnetic steel sheets to forma laminated steel plate.
As shown in
Each of the conductor bars 511 and the shorting rings 512 are formed from aluminum or aluminum alloy, and integrated into one piece with the rotor core 513 by die casting.
The shorting rings 512 mounted on both ends of the rotor core 513 are mounted so as to protrude from the rotor core 513.
Though not shown in
One stator coil 413 is inserted into a pair of slots enclosing a specified number of slots.
A coil end (called coil end from hereon) 414 is formed on both end surfaces of the stator core 412 by the stator coil 413 protruding externally from each slot.
A straight section is formed by the stator coil 413 extending in a linear shape on the coil end 414 in the vicinity of outlet section of each slot. An insulation film is wound between the stator core 412 and the stator coil 413.
Vibration occurs in the stator coil 413 housed in the stator core 412, the stator core 412, and the insulation film due to rotational vibration of the rotor 5 separated by a gap and mounted to allow rotation.
In order to prevent this vibration of the stator core 412 and the stator coil 413 and to prevent electrical breakdown of the insulation due to damage caused during insertion of the stator coil 413 into the stator core 412, a varnish comprised of epoxy synthetic resin is soaked into the stator core 412.
A varnish comprised of epoxy synthetic resin covers the insulation coating surface of the coil to protect the insulation coating between each of the conductor wiring for the coil end 414 and the stator coil 413.
In the rotating electric machine as described above, insulation defects between the insulation coating and the conductor of the coil end 414 and method of the present invention for solving the problem are described.
The stator coil 413 is overall comprised of a conductor 416 and an insulation coating 415 of enamel material of polyamide-imide or polyester-imide covering this conductor 416.
The insulation coating 415 in the vicinity of the coil end 414 of the stator coil 413 of the related art is then removed to expose the conductor 416. This exposed conductor 416 is coupled by welding to conductor 416 of the adjacent coil end inserted in another slot of the stator core 414.
However, in the above described methods for removing the insulation coating 415 by utilizing a rotating brush or organic solvent as shown in patent document 1 and patent document 2, the slope on the tip of the stripped surface 417 of the insulation coating 415 was found to become a perpendicular shape of approximately 90 degrees relative to the surface of the conductor 416 as in the cross section shown in
When a heat cycle is then applied, the conductor 416 and the insulation coating 415 each have their own unique expansion coefficients and so will have respectively different expansion and contraction.
When the stripped surface 417 of insulation coating 415 is a perpendicular shape, the cross sectional area of the stripped surface 417 of insulation coating 415 is approximately the same as the cross sectional area of a normal insulation coating 415, and the expansion force and contraction force that accompanies expansion and contraction becomes large in proportion to the cross sectional area.
The stripped surface 417 of the insulation coating is a perpendicular shape relative to the conductor 416 so that the cross sectional area at the stripped surface 417 becomes a maximum, and a large expansion force and contraction force are generated in axial direction or in perpendicular direction, or in both directions of the conductor on this section.
A large gap therefore occurs between the conductor 416 and the stripped surface 417 of the insulation coating so that the peeling phenomenon occurs.
Moreover, at the tip section of the stripped surface 417 of the insulation coating 415, a phenomenon was found to occur that further peels the insulation coating 415 from the conductor 416 due to generation of a force that promotes peeling at the boundary of the insulation coating 415 and the conductor 416, caused by the heat contraction force generated in the varnish that covers the insulation coating 415 when the temperature drops from a high environmental temperature.
Therefore, as described above, when the stator coil emits heat due to the high output from the rotating electric machine causing a high temperature, a large peeling force occurs due to heat at the boundary of the coil conductor 416 and the insulation coating 415 of the coil end 414, and the insulation coating consequently peels from the conductor 416 so that insulation defects tend to easily occur.
Whereupon, the present invention proposes a technology that is capable of preventing the phenomenon of peeling of the insulation coating 415 from the conductor 416 due to the heat cycle.
In the first embodiment of the present invention, a sloped surface 418 is formed on the insulation coating so that the thickness of the tip of the insulation coating 415 on the coil end 414 becomes a shape having a slope that is gradually thinner towards the welded coupling section where the conductor 416 is welded.
The structure of the coil end 414 of the first embodiment is hereafter described in detail.
The stator coil 413 is a rectangular lead (a so-called rectangular wire), and the coil end 414 is a conductor on which an insulation coating 415 is formed and the conductor 416 whose the insulation coating 415 is removed, that forms the welded coupling section.
Here, the conductor 416 is formed as a conductor whose cross section is rectangular with no change in shape including the section where the insulation coating 415 is formed, and the insulation coating 415 is formed uniformly over this conductor.
The tip of the insulation coating 415 is formed with a sloped surface 418 having a slope angle A relative to the surface of the conductor 416 so that the thickness of just the insulation coating 415 gradually becomes thinner towards the tip side of the coil end 414. For example, when the conductor 416 is a rectangular copper wire, a sloped surface 418 having a slope angle θ is formed so that the thickness of the tips at the four points on the insulation coating 415 contacting each surface (four surfaces) of the conductor 416 gradually becomes thinner.
Here, the sloped surface 418 is formed in a linear shape but a curve shape may be utilized and a small number of irregularities may be present under actual circumstances. What is required is that the tip thickness of the insulation coating 415 of the coil end 414 is a shape whose slope becomes gradually thinner towards the welded coupling section where the conductor 416 is welded, and need only be capable of suppressing the peel load of the insulation coating 415 described later on to a specified value.
A sloped surface 418 is in this way formed having a slope angle θ so that the thickness of the stripped surface of the insulation coating 415 becomes gradually thinner. The expansion force and the contraction force due to the heat cycle generated in this section is proportional to the cross sectional area and so becomes gradually smaller as this cross sectional area decreases. The expansion force and the contraction force at the end point of the sloped surface 418 therefore become considerably smaller. Therefore, the peeling between the conductor 461 and the sloped surface 418 of the insulation coating 415 can be prevented.
The sloped surface 418 formed as described above is capable of preventing peeling even if a contraction force from the varnish is applied, because of the basically strong coupling of the sloped surface 418 of insulation coating 415.
Here, the sloped surface 418 at the tip of the insulation coating 415 and the slope angle θ of the surface of the conductor 416 must preferably be set to a value so that the peeling force generated at the boundary of the insulation coating 415 and conductor 416 when the stator coil 413 is transitioning from a high temperature to a cooling temperature (or the reverse) does not exceed the peel load on the insulation coating 415.
As shown in
The vertical axis in
One type is a coil (characteristic A) covered with a polyamide-imide layer on the conductor periphery; one type is a coil (characteristic B) covered with a plural layers of polyimide and polyamide-imide on the conductor periphery; and one type is a coil (characteristic C) covered with a polyimide layer on the conductor periphery.
As shown in
A peeling width of 1.5 mm was set in a state where it has returned to an ambient temperature of 20° C. after being heated to 180° C. in the heat cycle, and peeling then performed, and the load at this time measured with a force gauge. Consequently, the fatigue limit value that peels the insulation coating 415 was approximately a maximum of 0.16 N.
Returning to
In the second embodiment of the present invention, the sloped surface 419 is formed on the surface of the insulation coating 415 and the conductor 416 so as to be a shape for which the thickness of the tip of the insulation coating 415 of coil end 414 forms a slope that becomes gradually thinner towards the welded coupling section by welding.
The structure of the coil end 414 of the second embodiment is hereafter described in detail.
In contrast to the first embodiment, where the tip surface of just the insulation coating 415 forms a slope, in the second embodiment an insulation coating side sloped surface 420 is formed on the tip surface of the insulation coating 415, and a conductor side sloped surface 421 is formed on the inner side from the conductor main surface of the conductor 416 followed by this insulation coating side sloped surface 420, to together form a sloped surface 419.
In this embodiment also, the four surfaces of the rectangular copper wire are structured so that a slope is formed as the surface of the conductor 416 and the tip of the insulation coating 415 on the four locations, on the surface of the conductor 416 and the insulation
Also, as shown in
Further, compared to the first embodiment, the second embodiment can be expected to render the effect of a method that easily forms the continuous sloped surface 419 on the surfaces of the insulation coating 415 and the conductor 416.
Namely in contrast to the first embodiment that required a precision technology in a forming process that removed just the insulation coating 415 since the sloped surface 418 was formed only on the insulation coating 415; in the second embodiment, a continuous sloped surface 419 is formed over the surfaces of the insulation coating 415 and the conductor 416 so that a boundary can be formed between the insulation coating 415 and the conductor 416 without a clear division, and the second embodiment can be expected to render the effect of not requiring a precision technology in a forming process that was needed in the first embodiment.
The effect can also be anticipated that the insulation film mounted in the slot beforehand can be mounted in the stator without damage since the coil tip is a fine shape compared to the first embodiment.
In this embodiment also, the sloped surface 419 need not be a strictly linear shape, and more specifically may have a shape in which the thickness of the tip of the insulation coating 415 of the coil end 414 becomes gradually thinner towards the welded coupling section where the conductor 416 is welded, and is satisfactory provided that the peel load of the insulation coating 415 is suppressed to within a specified value.
The method for forming the coil end including the sloped surface 419 of the second embodiment is described next.
In
This space 424 forms the exposed conductor 416 from the insulation coating 415 of the stator coil, and the sloped angle section 425 forms the sloped surface 419 shown in
When mounting the stator coil covered with insulation coating at the bottom in the metallic press mold 426, the metallic press mold 423 stamps the conductor 416 and insulation coating 415 at a specified downward pressing force into the specified shape (here, the shape shown in
In the third embodiment of the present invention, a sloped surface 422 is formed on the surface of the insulation coating 415 and conductor 416 so as to be a shape having a slope in which the thickness of the tip of the insulation coating 415 of the coil end 414 becomes gradually thinner towards the welded coupling section formed by welding the same as in the second embodiment.
Here, the point differing from the second embodiment is that an arc shaped sloped surface is formed over the conductor 416.
In this embodiment also, the fatigue limit value after heating to 180° C. in the heat cycle as described in
The present embodiment can also be expected to render the effect of a method that easily forms having the continuous sloped surface 422 on the surfaces of the insulation coating 415 and the conductor 416.
The same effect as in the second embodiment can also be anticipated in this embodiment or namely that the insulation coating mounted in the slot beforehand can be mounted in the stator without damage since the coil tip is a fine shape compared to the first embodiment.
The method for forming the coil end including the sloped surface 422 in the third embodiment is described next.
In
This space 427 forms the exposed conductor 416 from the insulation coating 415 of the coil the same as shown in
When actually mounting the stator coil covered with insulation coating at the bottom in the metallic press mold 426, the metallic press mold 426 stamps the conductor 416 and the insulation coating 415 at a specified downward pressing force into the specified shape (here, the shape shown in
The method for forming the first embodiment was omitted but a sloped surface can be formed on the insulation coating 415 in the same way as in the first embodiment if a metal mold such as for stamping a sloped surface on insulation coating 415 is fabricated.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2011-155855 | Jul 2011 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2012/064870 | 6/11/2012 | WO | 00 | 1/6/2014 |
