Patent Application
20130127280
The present invention relates to an electric rotating machine and an electric vehicle using the electric rotating machine.
Some electric rotating machines are such that magnetic poles of a rotor are formed by permanent magnets. In these electric rotating machines, the magnetic flux of a d-axis generated by the permanent magnets is constant. Therefore, substantially constant magnetic flux intersects the stator windings regardless of rotational speed. Thus, the back-EMF induced in a stator is increased as rotational speed increases. On the other hand, the voltage of a power source to supply an AC current to the stator windings is substantially constant regardless of the rotational speed of the electric rotating machine. Thus, if the rotational speed of the electric rotating machine is increased to increase the back-EMF induced in the stator windings as described above, a difference in voltage between the power voltage and the interphase voltage of the stator windings is reduced, so that it becomes impossible to supply the current required for the stator windings. Consequently, if the electric rotating machine is increased in rotational speed, it becomes difficult for required rotary torque to be generated.
The back-EMF along with the increased rotational speed of the electric rotating machine is suppressed to a low level as much as possible. This makes it easy to supply the required current to the stator windings. Thus, torque generated during high-speed rotation can be more increased. One of solutions to suppress the back-EMF to a low level as much as possible is to reduce the magnetic flux of the d-axis intersecting the stator windings. The amount of the magnetic flux of the d-axis intersecting the stator windings is suppressed, the magnetic flux of the d-axis being generated by the permanent magnets forming the magnetic pole during the high-speed operation of the electric rotating machine. For this purpose, a current supplied to the stator windings is controlled to generate in the stator windings the magnetic flux with a polarity opposite to that of the magnetic flux of the d-axis generated by the permanent magnets (the field weakening control).
Patent Document 1 discloses the technology in which the magnetic flux of a d-axis is irreversibly demagnetized by field weakening control to reduce the linkage magnetic flux of stator windings.
If a large field weakening current is used, the current of a d-axis unrelated directly to the rotary torque of a motor is increased, which lowers efficiency. Thus, there is a problem with the lowered efficiency of the electric rotating machine in a high-speed operation state.
It is an object of the present invention to provide an electric rotating machine that can improve its efficiency in a high-speed operation state. In addition, it is another object of the invention to improve the efficiency of an electric vehicle in a high-speed operation state by the use of the electric rotating machine of the present invention.
The characteristic recited in claim 1 is as below.
An electric rotating machine includes a stator and a rotor. The stator has a stator core with slots and stator windings. The rotor includes a rotor core and a plurality of first permanent magnets and of second permanent magnets. The rotor core is provided with laminated electromagnetic steel sheets and formed with a plurality of magnetic poles arranged in a circumferential direction. The plurality of first and second permanent magnets form the plurality of corresponding magnetic poles. The first permanent magnet and the second permanent magnet for forming each of the magnetic poles of the rotor are different from each other in recoil permeability.
The characteristic recited in claim 2 is that in the configuration recited in the above claim 1, the second permanent magnet is disposed so that a magnetization easy axis of the second permanent magnet forming each magnetic pole of the rotor is disposed along magnetic flux of a d-axis made by the first permanent magnet.
The characteristic recited in claim 3 is as below. In the electric rotating machine recited in claim 1 or 2, the rotor core of the electric rotating machine is formed with a magnetic insertion hole adapted to receive permanent magnets for forming each magnetic pole, and the first permanent magnet and the second permanent magnet are received and held in the magnet insertion hole.
The characteristic recited in claim 4 is as below. In the electric rotating machine recited in any one of claims 1 to 3, the first permanent magnet has a coercivity property higher than that of the second permanent magnet, and the second permanent magnet has recoil permeability higher than that of the first permanent magnet.
The characteristic recited in claim 5 is as below. In the electric rotating machine recited in claim 4, the first permanent magnet is a neodymium magnet or a ferrite magnet and the second permanent magnet is an AlNiCo magnet.
The characteristic recited in claim 6 is as below. In the electric rotating machine recited in any one of claims 1 to 3, the rotor has auxiliary magnetic poles each formed between magnetic poles adjacent to each other among a plurality of magnetic poles formed along the circumferential direction, and a magnetic circuit is formed through which magnetic flux of a q-axis generated by the stator windings passes via the auxiliary magnetic pole.
The characteristic recited in claim 7 is as below. In the electric rotating machine recited in claim 6, the rotor has the magnet insertion holes formed along the circumferential direction so as to correspond to the associate magnetic poles. The magnet insertion holes are each adapted to receive the first permanent magnet and the second permanent magnet forming a corresponding one of the magnetic poles arranged in the circumferential direction. The magnet insertion hole is shaped to have a circumferential length greater than a radial length. The magnetic insertion hole is shaped such that a side located on the outer circumferential side of the rotor has a length greater than a side located on a central side of the rotor. The first permanent magnet and the second permanent magnet are fixedly received in each of the magnet insertion holes in a laminated state in a radial direction of the rotor. The first permanent magnet and the second permanent magnet are magnetized along the radial direction of the rotor in such a manner as to have respective magnetic polarities alternately reversed for each magnetic pole. Magnetic air gaps are provided inside each of the magnet insertion holes at both circumferential ends of at least a permanent magnet located on an outer circumferential side of the first and second permanent magnets.
The characteristic recited in claim 8 is as below. In the electric rotating machine recited in claim 7, a magnetic pole piece portion is formed in the rotor core between the outer circumferential side of the magnet insertion hole for each magnetic pole and the outer circumference of the rotor core, and a magnetic circuit is formed in which the magnetic flux of the d-axis generated by the first and second permanent magnets passes through the magnetic pole piece portion and the stator core and intersects the stator windings.
The characteristic recited in claim 9 is as below. In the electric rotating machine recited in claim 6, at least two sets of the first permanent magnets and the second permanent magnets for forming each magnetic pole are installed in the rotor so as to correspond to each of the magnetic poles arranged in the circumferential direction, and a first magnet insertion hole adapted to receive one set of the first and second permanent magnets of the two sets and a second magnet insertion hole adapted to receive the other set of the first and second permanent magnets are formed so as to correspond to each of the magnetic poles. The first magnet insertion hole and the second magnet insertion hole provided so as to correspond to each of the magnetic poles are formed in a state where an outer circumferential side thereof is more open than a central side thereof, i.e., where ends of the first and second magnet insertion holes on the outer circumferential side of the rotor are more spaced from each other than ends thereof on the central side of the rotor. The first permanent magnet and the second permanent magnet are fixedly received in each of the first magnet insertion hole and the second magnet insertion hole in a stacked state.
The characteristic recited in claim 10 is as below. In the electric rotating machine recited in claim 9, a magnetic air gap is formed at the outer circumferential-side end portion of each of the first magnet insertion hole and the second magnet insertion hole.
The characteristic recited in claim 11 is as below. In the electric rotating machine recited in claim 10, a magnetic pole piece portion is formed in the stator core on the outer circumferential side of the first magnet insertion hole and the second magnet insertion hole, and a magnetic circuit is formed in which the magnetic flux of the d-axis generated by the first and second permanent magnets passes through the magnetic pole piece portion and the stator core and intersects the stator windings.
The characteristic recited in claim 12 is as below. In the electric rotating machine recited in any one of claims 8 to 11, an auxiliary magnetic pole is formed between the magnetic poles adjacent to each other, and a bridge portion connecting the magnetic pole piece portion with the auxiliary magnetic pole portion adjacent thereto is formed on the outer circumferential side of the magnetic air gap, the bridge portion reducing leakage magnetic flux from the magnetic piece portion to the auxiliary magnetic pole.
The characteristic recited in claim 13 is as below. In an electric vehicle including the electric rotating machine recited in any one of claims 1 to 12, the electric vehicle includes a control circuit for controlling the electric rotating machine and the control circuit operates the first and second permanent magnets within a range of reversible demagnetization.
The characteristic recited in claim 14 is as below. In the electric vehicle recited in claim 13, in a first operating range where rotational speed of the electric rotating machine is higher than a predetermined rotational speed, the control circuit controls an AC current to be supplied to the stator windings so as to generate magnetic flux in a direction of reducing magnetic flux of a d-axis generated by the permanent magnets, and the magnetic flux generated by the stator windings acts as magnetic flux with a polarity opposite to that of the second permanent magnet forming the magnetic pole of the rotor.
The present invention has an effect of enabling an improvement in the efficiency of the electric rotating machine in the high-speed operating state. The electric vehicle including the electric rotating machine can improve the efficiency thereof in the high-speed operating state.
Embodiments describe below not only the contents in the columns of the above “Problem to be Solved by the Invention” and “Effect of the Invention” but also solutions to various problems to put productions to practical use. Their specific details will be described in the following embodiments.
A first embodiment of the present invention will be described with reference to
The electric rotating machine 1 has a magnetic pole position detector PS for detecting the position of the magnetic pole of the rotor 3. The magnetic pole position detector PS is composed of e.g. a resolver. Further, the electric rotating machine 1 has a rotational speed detector E for detecting the rotational speed of the rotor 3. In this embodiment, the rotational speed detector E is an encoder. The encoder is disposed on the side of the rotor 3 and produces pulses in synchronization with the rotation of the shaft 8. The encoder can determine the rotational speed by counting the number of the pulses. The electric rotating machine 1 detects the position of the magnet on the basis of the signal of the magnetic pole detector PS and the rotational speed on the basis of the output signal of the rotational speed detector E. A control unit, not shown, supplies to the stator windings 5 an alternating current for generating the target torque of the electric rotating machine 1. In this way, the current to be supplied to the stator windings 5 is controlled by the control unit, thereby controlling the output torque of the electric rotating machine.
The permanent magnets 400 include first permanent magnets 401 (shown in
The rotor 3 includes the rotor core 7 composed of electromagnetic steel sheets laminated in the direction along the rotational axis, and the first permanent magnets 401 and the second permanent magnets 402 installed in the rotor core 7 to form magnetic poles. In the embodiment with
In
In the embodiment illustrated in
The first permanent magnet 401 with low recoil permeability and the second permanent magnet 402 with high recoil permeability are received and secured in each of the magnet insertion holes 6 in such a laminated state as to have the same magnetizing direction and polarities in the same direction with each other. In addition, they are magnetized to have polarities opposite to those of the first permanent magnet 401 and the second permanent magnet 402 that form an adjacent magnet pole as described above.
The magnet insertion holes 6 of the rotor core 7 are each formed by punching using a press machine, for example. The rotor core 7 formed of the electromagnetic steel sheets laminated in the direction along the rotational axis is secured to the shaft 8 for rotation therewith.
The rotor core 7 of the rotor 3 forms, over the whole circumference, auxiliary magnetic pole portions 33 each of which is located between magnetic poles adjacent each other in the circumferential direction. The auxiliary magnetic pole portion 33 is adapted to pass therethrough magnetic flux φq of a q-axis generated by the stator. The rotor core 7 of the rotor 3 is partially illustrated in
Reluctance torque is generated based on a difference between the magnetic resistance of the magnetic flux φd of the q-axis passing through the auxiliary magnetic pole portion 33 and the magnetic resistance of the magnetic circuit having the permanent magnets through which the magnetic flux φd of the d-axis passes. The circumferential width of the auxiliary magnetic pole portion 33 is made wide in the present embodiment as illustrated in
In
The magnetic air gap 35 and the magnetic air gap 41 have the functions described below. The magnetic air gap 35 has a side extending in the circumferential direction along the outer circumference of the rotor. Since the magnetic air gap 35 is shaped to extend in the circumferential direction, a bridge portion 39 is formed between the magnetic pole piece portion 34 and the auxiliary magnetic pole portion 33 which are formed by the rotor core on the stator side of the permanent magnets. The bridge portion 39 functions to reduce leakage magnetic flux leaking from the magnetic pole piece portion 34 via the bridge portion 39 to the auxiliary magnetic portion 33. The bridge portion 39 between the magnetic pole piece portion 34 and the auxiliary magnetic pole portion 33 can be formed into the shape extending in the circumferential direction by the circumferentially extending shape of the magnetic air gap 35. The shape of the bridge portion is thinned in the radial direction and lengthened in the circumferential direction. For example, this can make small the value of the magnetic flux content that causes magnetic saturation. With the bridge portion shaped described above, the magnetic resistance of the bridge portion 39 can be increased. Consequently, the amount of the magnetic flux passing through the bridge portion can be reduced, which produces an effect of reducing the leakage magnetic flux. In addition, concentration of centrifugal force on the stator side corner of the magnet insertion hole 6 can be alleviated, which leads to an improvement in mechanical reliability.
Further, if the boundary portion between the auxiliary magnetic pole 33 and the permanent magnet drastically varies in magnetic flux density, torque ripple is likely to occur. However, the magnetic air gaps 35 are provided at the stator-side end portions of the sets of the permanent magnets composed of the first permanent magnets 401 and the second permanent magnets 402 arranged in the V-shape as in the present embodiment. Therefore, the drastic variation in the magnetic flux density can be reduced at the boundary portion between the auxiliary magnetic pole 33 and the permanent magnet. This leads to an effect of reducing the torque triple.
In the present embodiment, the two types of the permanent magnets different from each other in recoil permeability are inserted into the magnet insertion hole 6. The permanent magnets are each arranged so that the magnetization easy axis thereof may extend in the direction along the magnetic circuit of the magnetic flux φd. Incidentally, the magnetization easy axis of the permanent magnet means a direction where the magnet is easily magnetized. The first permanent magnet 401 and the second permanent magnet 402 shown in
The two or more types of the permanent magnets different from each other in recoil permeability are inserted into and secured in the magnetic insertion hole 6 in the present embodiment. Therefore, the volume that accounts for a portion of the rotor in order to hold the magnets can be reduced, leading to the downsizing of the rotor. The configuration of the present embodiment easily improves the mechanical strength of the rotor compared with the case where two types of permanent magnets different from each other in recoil permeability are disposed at respective different positions. Further, the insertion work for the two types of permanent magnets is easy. In the case of the configuration of the present embodiment, the materials for the first permanent magnet 401 and the second permanent magnet 402 that are not magnetized are inserted into and held in a common magnet insertion hole 6. In this way, the materials for the two types of permanent magnets are inserted and thereafter magnetizing work can be done at one time. Therefore, the magnetizing work facilitates.
A description is given of the permanent magnets different from each other in recoil permeability to be inserted into and held in the magnet insertion hole 6.
The above recoil permeability means a rate at which the magnetization of a permanent magnet decreases when a magnetic field is applied thereto in a direction opposite to the magnetization. This means that the greater the recoil permeability, the more the magnetic flux of the permanent magnet is easily to decrease. In the magnetic property of these permanent magnets, the magnetic field may be applied thereto in the direction opposite to the magnetization direction of the permanent magnet. In such a case, if the oppositely-oriented magnetic field is stopped in the range where the recoil permeability keeps the linearity, the magnetization of the permanent magnet is restored to its original state. However, the oppositely-oriented magnetic field having such intensity as to reach the range where the recoil permeability does not keep the linearity may be applied thereto. In such a case, even if the oppositely-oriented magnetic field is stopped, the magnetization of the permanent magnet is not restored to the original state. In these phenomena, the former restoring state is called the reversible demagnetization and the latter not-restoring state is called the irreversible demagnetization. The range where recoil permeability keeps the above linearity is not limited to the range where recoil permeability keeps the complete linearity but includes also a range where the recoil permeability has near-linearity. The magnetic field in the direction opposite to that of the magnetization can be applied by allowing a negative current (hereinafter, called the field weakening current) to flow to the d-axis if a pole-central axis is the d-axis. This field weakening current is a method used to hold and suppress at a constant level back-EMF which increases in proportion to rotational speed during the high-speed operation of the electric rotating machine.
According to the first embodiment described above, the permanent magnet with high recoil permeability is inserted into the magnet insertion hole. This reduces the magnetic flux generated by the permanent magnet with high recoil permeability if the field weakening current is allowed to flow during high-speed operation. The reduction of the magnetic flux φd of the d-axis is increased compared with the conventional field weakening current. Consequently, the linkage flux due to the magnetic flux φd of the d-axis is reduced. This suppresses an increase in back-EMF along with the increased rotational speed, which can improve the limit of the high-speed rotation that can be used by the electric rotating machine. In addition, since the field weakening current can be reduced compared with the high-speed operation of the conventional electric rotating machine, the efficiency of the electric rotating machine during the high-speed operation is improved.
Furthermore, the permanent magnet with low recoil permeability and the permanent magnet with high recoil permeability are disposed in the same magnet insertion hole. The permanent magnet with low recoil permeability has large coercivity; therefore, it can assist the permanent magnet with high recoil permeability, so that the magnetic field applied to the permanent magnet with high recoil permeability is reduced. Thus, it becomes hard for the permanent magnet with high recoil permeability to be irreversibly demagnetized.
These results show the following: The angular difference in the magnetization easy axis direction between the permanent magnet with high recoil permeability and the permanent magnet with low recoil permeability is set at θ=0. In other words, the magnetization easy axis direction of the permanent magnet with high recoil permeability is made parallel to that of the permanent magnet with low recoil permeability. This allows the permanent magnet with high recoil permeability to have a small operating point. Thus, it is harder for the permanent magnet with high recoil permeability to be irreversibly demagnetized. Consequently, a magnetization circuit for re-magnetization is unnecessary. Thus, the number of component parts as a system can be reduced. Incidentally, the permanent magnet with high recoil permeability is disposed at a position where its average radius is smaller than that of the permanent magnet with low recoil permeability. However, their positions may be reversed.
The configuration of an electric rotating machine system of the present embodiment is next described with reference to
The electric rotating machine 1 using the permanent magnets has the configuration described earlier or a configuration described later. The DC power source 51 may be composed of, for example, an AC power source and a converter section for converting the AC power from the AC power source to DC power. Alternatively, the DC power source 51 may be a lithium ion secondary battery or a nickel ion secondary battery mounted on a vehicle. The control unit is an inverter device, which receives DC power from the DC power source 51, converts the DC power to AC power and supplies the AC power to the stator windings 5 of the electric rotating machine 1. The inverter device includes a power system inverter circuit 53 (a power conversion circuit) electrically connected between the DC power source 51 and the stator windings 5, and a control circuit 130 for controlling the operation of the inverter circuit 53.
The inverter circuit 53 has a bridge circuit composed of switching semiconductor devices, e.g., MOS-FET (metal-oxide semiconductor field-effect transistors), or IGBT (insulated-gate bipolar transistors). The inverter circuit 53 converts the DC power from a smoothing capacitor module into AC power, or converts the AC power generated by the electric rotating machine into DC power. The bridge circuit mentioned above is configured such that high potential side switches, low potential side switches and series circuits, which are called arms, are electrically connected to one another in parallel in the number equal to that of the phases of the electric rotating machine 1. In the present embodiment where three-phase AC power is generated, the bridge circuit has three sets of the arms. The high potential side switch of each arm has a terminal electrically connected to the positive terminal of the DC power source 51. In addition, the low potential side switch has a terminal electrically connected to the negative terminal of the DC power source 51. A connecting point between an upper switching semiconductor device and a lower switching semiconductor device of each arm is electrically connected to the stator windings 5 of the electric rotating machine 1 so that phase voltage may be supplied from the connecting point to the stator windings 5.
A phase current supplied from the inverter circuit 53 to the stator windings 5 is measured by a current detector 52 installed on a bus bar for each phase to supply AC power to the electric rotating machine. The current detector 52 is e.g. a current transformer. The control circuit 130 operates to control the switching action of the switching semiconductor devices of the inverter circuit 53 to provide target torque on the basis of input information including torque commands and braking commands. The input information includes, for example, a current command signal Is, i.e., torque demanded for the electric rotating machine 1, and a magnetic pole position θ of the rotor 3 of the electric rotating machine 1. The current command signal Is, i.e., demanded torque, is obtained by being calculated in the control circuit 130 on the basis of a command sent from an upper controller in response to demand such as an accelerator operation amount demanded by a driver in the case of a vehicle. The magnetic pole position θ is detection information obtained from the output of the magnetic pole position detector PS.
A speed control circuit 58 calculates a speed difference ωe from a speed command ωs and actual speed ωf and exercises PI control on the speed difference ωe and outputs the current command Is, i.e., torque command and a rotational angle θ1 of the rotor 3. The speed command ωs is created based on the demand command of the upper controller. The actual speed ωf is real speed which is obtained from the positional information θ1 from the encoder via an F/V converter 61 that is adapted to convert a frequency to voltage. The above PI control is a generally used control system which uses a proportional term P multiplying a deviation value by a proportional constant and an integral term I.
A phase shift circuit 54 phase-shifts and outputs a rotation-synchronized pulse generated by the rotational speed detector E, i.e., the position information θ of the rotor 3 in response to the command of the rotational angle θ1 from the speed control circuit 58. The phase shift is designed to move forward, for example, the resultant vector of armature magnetomotive force created by the current flowing in the stator windings 5, by an electric angle of 90 degrees or more with respect to the direction of the magnetic flux or field made by the permanent magnet 400.
A sine/cosine wave generating circuit 59 generates sine wave output resulting from phase-shifting the back-EMF of each winding of the stator windings 5 on the basis of the magnetic pole position of the permanent magnet 400 of the rotor 3 detected by the magnetic pole position detector PS and the phase-shifted position information θ of the rotor from the phase shift circuit 54. Incidentally, a phase-shift amount includes also a value of zero.
A 2-phase to 3-phase converter circuit 56 outputs current commands Isu, Isv, Isw of each phase in response to a current command IS from the speed control circuit 58 and the output of the sine/cosine wave generating circuit 59. The phases have respective individual current control systems 55a, 55b, 55c. The current control systems 55a, 55b, 55c send respective signals corresponding to the current commands Isu, Isv, Isw and current detection signals Ifu, Ifv, Ifw from the current detector 52 to the inverter circuit 53 for controlling the switching action of the switching semiconductor devices. In this way, each phase current of three-phase alternating current is controlled. In this case, the current of the combined phase is controlled perpendicularly to field magnetic flux or controlled to the phase-shifted position. Thus, the property equal to that of a DC machine can be provided without a commutator.
The signals outputted from the current control systems 55a, 55b, 55c of the respective phases of the AC current are each sent to a corresponding one of the control terminals of the switching semiconductor devices constituting the arms of the phases. In this way, each of the switching semiconductors performs switching action, which is on-off operation, so that the DC power supplied from the DC power source 51 via the smoothing capacitor module is converted into AC power. The AC power is supplied to the corresponding phase windings of the stator windings 5.
The inverter device of the first embodiment constantly forms a current (a phase current flowing in each phase winding) flowing in the stator windings 5 so that the resultant vector of the armature magnetomotive force flowing in the stator windings 5 may be perpendicular to or phase-shifted with respect to the direction of the magnetic flux or field made by the permanent magnet 400. In this way, the electric rotating machine system can provide the property equal to that of the DC machine by the use of the commutatorless, i.e., brushless electric rotating machine 1. Incidentally, the field weakening current is used to exercise control to constantly form a current (a phase current flowing in each phase winding) flowing in the stator windings 5 so that the resultant vector of the armature magnetomotive force made by the current flowing in the stator windings 5 may move forward by 90 degrees (an electric angle) or more with respect to the direction of the magnetic flux or field made by the permanent magnet 400.
The electric rotating machine system of the first embodiment controls the current (the phase current flowing in each phase winding) flowing in the stator windings 5 on the basis of the magnetic pole position of the rotor 3 so that the resultant vector of the armature magnetomotive force made by the current flowing in the stator windings 5 may be perpendicular to the direction of the magnetic flux or field made by the permanent magnet 400. Thus, the electric rotating machine 1 can continuously output the maximum torque. When the field weakening control is necessary, it is needed only to control the current (the phase current flowing in each phase winding) flowing in the stator windings 5 on the basis of the magnetic pole position of the rotor 3 so that the resultant vector of the armature magnetomotive force made by the current flowing in the stator windings 5 may move forward by 90 degrees (electric angle) or more with respect to the direction of the magnetic flux or field made by the permanent magnet 400.
A description is next given of magnetization determination and magnetization method encountered when the second permanent magnet 402 with high recoil permeability is operated in the range of irreversible demagnetization. The electric rotating machine 1 is further equipped with a magnetic flux detector 60, which outputs flux content. A magnetization determining circuit 61 receives a value representing the flux content and the actual speed of outputted by the F/V converter 62 and determines whether or not re-magnetization is necessary. If the magnetic flux based on the field weakening current is applied to the permanent magnet 400, a strong magnetic flux that exceeds the range of reversible demagnetization may be applied to the permanent magnet. In such a case, the permanent magnet, particularly, the second permanent magnet may be likely to be demagnetized. If the permanent magnet is irreversibly magnetized as mentioned above, then the flux content generated by the permanent magnet is reduced. Therefore, the permanent magnet needs to be re-magnetized. If it is determined that the re-magnetization of the permanent magnet is needed, the magnetization determination circuit 61 issues a magnetization command to the phase shift circuit 54.
A description is next given of a method for magnetizing the second permanent magnet 402 when the magnetization determination circuit 61 issues the magnetization command to the phase shift circuit 54. It goes without saying that a special magnetization circuit may be used for magnetization. However, a certain level of re-magnetization is possible by the use of the above-mentioned control circuit 130 without use of the special magnetization circuit.
A second embodiment of the present invention is next described with reference to
In the second embodiment depicted in
According to the second embodiment, the permanent magnet with high recoil permeability is received in the magnet insertion hole 6. This produces the same function and effect as those of the first embodiment. That is to say, if a field weakening current is allowed to flow during high-speed operation, linkage flux caused by the permanent magnet with high recoil permeability is reduced. Therefore, an increase in back-EMF is suppressed, which can increase the maximum rotational speed. Further, the permanent magnet with low recoil permeability and the permanent magnet with high recoil permeability are arranged in the same magnet insertion hole. A magnetic field applied to both the permanent magnets can be shared by them; therefore, it becomes hard for the permanent magnets to be irreversibly demagnetized. Thus, a magnetization circuit for re-magnetization becomes unnecessary, which can reduce the number of component parts as a system.
A third embodiment of the present invention is next described with reference to
According to the third embodiment, the permanent magnet with high recoil permeability is received in the magnet insertion hole. With this, if a field weakening current is allowed to flow during high-speed operation, linkage flux caused by the permanent magnet with high recoil permeability is reduced. Therefore, an increase in back-EMF is suppressed, which can increase the maximum rotational speed. Further, the permanent magnet with low recoil permeability and the permanent magnet with high recoil permeability are arranged in the same magnet insertion hole. A magnetic field applied to both the permanent magnets can be shared by them; therefore, it becomes hard for the permanent magnets to be irreversibly demagnetized. Thus, a magnetization circuit for re-magnetization becomes unnecessary, which can reduce the number of component parts as a system. The permanent magnets are disposed on the outside in the outside-diameter direction of the rotor. The magnetization easy axis directions of the permanent magnets are oriented in such three directions as to coincident with or intersect the d-axis. In this way, the magnetic flux density made by the rotor can be approximated to a sine wave, so that torque pulsation and electromagnetic noise can be reduced.
A fourth embodiment of the present invention is next described with reference to
According to the fourth embodiment, the permanent magnet with high recoil permeability is inserted into the magnet insertion hole. With this, if a field weakening current is allowed to flow during high-speed operation, the interlinkage flux caused by the permanent magnet with high recoil permeability is reduced. Thus, the maximum rotational speed can be increased. Further, the permanent magnet with low recoil permeability and the permanent magnet with high recoil permeability are disposed in the same magnet insertion hole. A magnetic field applied to both the permanent magnets can be shared by them. Therefore, it becomes hard for the permanent magnets to be irreversibly demagnetized. Thus, a magnetization circuit for re-magnetization becomes unnecessary, which can reduce the number of component parts as a system.
Further, two layers of the magnet insertion holes shaped in a V-shape are provided; therefore, reluctance torque is increased, which makes it possible to downsize the electric rotating machine.
A fifth embodiment of the present invention is next described with reference to
The fifth embodiment is different from the first embodiment in that a permanent magnet with high recoil permeability and a permanent magnet with low recoil permeability are disposed in respective different magnet insertion holes. Further, the permanent magnet with high recoil permeability is disposed near the center of a pole. If all poles or at least one pole is configured as above, the effect is naturally produced. Further, although a rectangular parallelepipedic permanent magnet is used for explanation in the fifth embodiment, also a circular or semicircular permanent magnet produces the same effect. Here, the permanent magnet with high recoil permeability is disposed at a position where its average radius is smaller than that of the permanent magnet with low recoil permeability. However, even if their positions are reversed, the same effect can be produced.
According to the fifth embodiment, the permanent magnet with high recoil permeability is inserted into the magnet insertion hole. With this, if a field weakening current is allowed to flow during high-speed operation, the interlinkage flux caused by the permanent magnet with high recoil permeability is reduced to suppress an increase in back-EMF. Thus, the maximum rotational speed can be increased. Further, the permanent magnet with high recoil permeability is disposed near the center of a pole; therefore, it becomes hard for an oppositely-oriented magnetic field to be applied thereto. Thus, it becomes hard for the permanent magnet with high recoil permeability to be irreversibly demagnetized. Further, the permanent magnet with high recoil permeability and the permanent magnet with low recoil permeability are disposed in the respective different magnet insertion holes and therefore they have an iron bridge portion therebetween. A demagnetization field coefficient with respect to the magnetization easy axis direction of each of the permanent magnets is reduced. Thus, it becomes hard for the permanent magnet to be irreversibly demagnetized.
The magnet insertion hole is shared by the first and second permanent magnets, which are arranged in the stacked manner in the first embodiment. However, the first and second permanent magnets may be arranged in a row. In this case, the magnet flux of a d-axis is composed of the magnetic flux generated by the first and second permanent magnets. In addition, the first and second permanent magnets 401, 402 are arranged so that their magnetization easy axis directions may extend in the direction along the magnetic flux of the d-axis.
A sixth embodiment of the present invention is described with reference to
The sixth embodiment is different from the second embodiment described with reference to
According to the sixth embodiment described above, the permanent magnet with high recoil permeability is inserted into the magnet insertion hole. With this, if a field weakening current is allowed to flow during high-speed operation, the interlinkage flux caused by the permanent magnet with high recoil permeability is reduced to suppress an increase in back-EMF. Thus, the maximum rotational speed can be increased. Further, the permanent magnet with high recoil permeability is disposed near the center of a pole; therefore, it becomes hard for an oppositely-oriented magnetic field to be applied thereto. Thus, it becomes hard for the permanent magnet with high recoil permeability to be irreversibly demagnetized. Further, the permanent magnet with high recoil permeability and the permanent magnet with low recoil permeability are disposed in the respective different magnet insertion holes and therefore they have an iron bridge portion therebetween. A demagnetization field coefficient with respect to the magnetization easy axis direction of each of the permanent magnets is reduced. Thus, it becomes hard for the permanent magnet to be irreversibly demagnetized.
A seventh embodiment of the present invention will be described with reference to
The seventh embodiment is different from the seventh embodiment in that a permanent magnet with high recoil permeability and a permanent magnet with low recoil permeability are disposed in respective different magnet insertion holes. If all poles or at least one pole is configured as above, the effect is naturally produced. Further, although a rectangular parallelepipedic permanent magnet is used for explanation in the seventh embodiment, also a circular or semicircular permanent magnet produces the same effect. Here, the permanent magnet with high recoil permeability is disposed at a position where its average radius is smaller than that of the permanent magnet with low recoil permeability. However, even if their positions are reversed, the same effect can be produced.
According to the seventh embodiment described above, the permanent magnet with high recoil permeability is inserted into the magnet insertion hole. With this, if a field weakening current is allowed to flow during high-speed operation, the interlinkage flux caused by the permanent magnet with high recoil permeability is reduced to suppress an increase in back-EMF. Thus, the maximum rotational speed can be increased. Further, two layers of the magnet insertion holes each shaped in a V-shape are provided; therefore, reluctance torque is increased, which makes it possible to downsize the electric rotating machine.
An eighth embodiment of the present invention will be described with reference to
The eighth embodiment is different from the sixth embodiment shown in
According to the eighth embodiment described above, the permanent magnet with high recoil permeability is inserted into the magnet insertion hole. With this, if a field weakening current is allowed to flow during high-speed operation, the interlinkage flux caused by the permanent magnet with high recoil permeability is reduced to suppress an increase in back-EMF. Thus, the maximum rotational speed can be increased.
Further, two layers of the magnet insertion holes are formed; therefore, reluctance torque is increased, which makes it possible to downsize the electric rotating machine.
A ninth embodiment of the present invention is described with reference to
A feature is here to use the two or more types of permanent magnets different from each other in recoil permeability in the direction along the rotational axis. If all poles or at least one pole is configured as above, the effect is naturally produced. Although a rectangular parallelepipedic permanent magnet is used for explanation in the ninth embodiment, also a circular or semicircular permanent magnet produces the same effect. Here, the permanent magnet with high recoil permeability is disposed at a position where its average radius is smaller than that of the permanent magnet with low recoil permeability. However, even if their positions are reversed, the same effect can be produced.
According to the ninth embodiment described above, a permanent magnet with high recoil permeability is inserted into a magnet insertion hole. With this, if a field weakening current is allowed to flow during high-speed operation, the interlinkage flux caused by the permanent magnet with high recoil permeability is reduced to suppress an increase in back-EMF. Thus, the maximum rotational speed can be increased. The internal-rotation type electric rotating machines are described above; however, the present invention can be applied also to external-rotation type electric rotating machines. Additionally, the present invention can be applied also to both distributed-winding electric rotating machines and concentrated-winding electric rotating machines.
A tenth embodiment is next described with reference to
A body 100 of the electric vehicle is supported by four wheels 110, 112, 114, 116. This electric vehicle is of front-wheel drive. An electric rotating machine 1 which develops running torque or braking torque is mechanically connected to a front axle 154. Rotary torque developed by the electric rotating machine 1 is transmitted by a mechanical transmission mechanism. The electric rotating machine 1 is driven by the three-phase AC power generated by the control unit 130 and the inverter circuit 53 which are described with
The DC power source 51 composed of a high-voltage battery such as a lithium secondary battery is installed as a power source for the control unit 130. The DC power from the DC power source 51 is converted into AC power by the switching action of the inverter circuit 53 based on the control of the control unit 130. The AC power is supplied to the electric rotating machine 1. The wheels 110, 114 are driven by the rotary torque of the electric rotating machine 1, so that the vehicle travels.
When a driver puts on brake, the control unit 130 reverses the phase of the AC power with respect to the magnetic pole of the rotor, the AC power being generated by the inverter circuit. This allows the electric rotating machine to operate as a generator, thereby performing regenerative braking operation. The electric rotating machine 1 develops the rotary torque in the direction of suppressing running to generate a braking force against the running of the vehicle 100. At this time, the kinetic energy of the vehicle is converted into electric energy, with which the DC power source 51 is charged.
Incidentally, the tenth embodiment describes the electric rotating machine as being used to drive the wheels of the electric vehicle. However, the electric rotating machine can be used as a driving apparatus for electrically-driven vehicles and for electrically-driven construction machines, and as the other driving apparatus. Incidentally, if the electric rotating machine according to the present embodiment is applied to an electrically-driven vehicle, particularly, to an electric vehicle, the maximum rotational speed can be increased, whereby the high-power electric vehicle can be provided.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2010/004844 | 7/30/2010 | WO | 00 | 1/28/2013 |
