Rotating electric machine

Abstract

Rotating electric machine (100) with: a pathogen section (40) which has pathogen windings (41, 42), and a switching device (50) for switching the excitation windings (41, 42) between a series connection state in which the excitation windings (41, 42) are connected in series with each other and have the same winding direction and the same current conduction direction, and a parallel connection state in which the excitation windings (41, 42) are connected in parallel with each other and have the same winding direction and the same current conduction direction, wherein the switching device (50) comprises: a first switch (55) for connecting first ends of the excitation windings (41, 42) together, a second switch (56) for connecting second ends of the excitation windings (41, 42) together, and a third switch (57) for connecting the excitation windings (41, 42) in series with a power supply (30), wherein the switching device (50) is configured to switch the excitation windings (41, 42) into the series connection state by switching off the first and second switches and switching on the third switch, and to switch the excitation windings (41, 42) into the parallel connection state by switching on the first and second switches and switching off the third switch.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention

[0001] The present invention relates to a rotating electrical machine having a rotor on which excitation windings are wound. 2. Description of the state of the art

[0002] DE 10 2006 058 179 A1 discloses a high-pressure cleaning device with an electric motor and a pump driven by the electric motor. The electric motor has an excitation section with an excitation winding, wherein the excitation windings can be switched between a series connection state and a parallel connection state.

[0003] JP 2012 - 223 073 A describes a rotating electrical machine with a temperature sensor for enabling a change in the duty cycle of switching elements provided in its field circuit (field current circuit) to suppress an excitation current (field current) supplied to its field winding when it is detected that the temperature of the rotating electrical machine has increased excessively during regenerative power generation.

[0004] In the above-described rotating electric machine, since a control circuit is required to perform duty control of the switching elements of the excitation circuit, its arrangement is complicated and the manufacturing cost is high. SUMMARY

[0005] It is a task to solve this problem.

[0006] This object is achieved by a rotating electrical machine as defined in claim 1.

[0007] An advantageous embodiment is specified in the dependent patent claim.

[0008] According to the embodiment, there is provided a rotating electric machine having a rotor on which an excitation section is wound with a plurality of excitation windings, the rotating electric machine being capable of changing the value of a current flowing through the excitation section with a simpler arrangement.

[0009] Other advantages and features of the invention will become apparent from the following description with reference to the drawings and the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The attached drawings show: Fig. 1 is a diagram showing the overall arrangement of a rotating electrical machine according to an embodiment of the invention, Fig. 2 an equivalent circuit diagram of a circuit consisting of an excitation winding and a switch circuit of the rotating electrical machine, and Fig. 3 is a timing diagram for describing an example of a control of the rotating electrical machine. PREFERRED EMBODIMENTS OF THE INVENTION

[0011] Fig. 1 is a diagram illustrating the circuit arrangement of a rotating electric machine 100 according to an embodiment of the invention. According to this embodiment, the rotating electric machine 100 is mounted on a vehicle as an ISG (Integrated Starter Generator). The rotating electric machine 100 functions as a starter motor, operating with electric power supplied from a battery 200 installed in the vehicle to start the vehicle's engine. After the engine is started, the rotating electric machine 100 functions as an alternator, generating electric power to charge the battery 200. The battery 200 is a lead-acid battery whose terminal voltage is approximately 12 V.

[0012] The rotating electric machine 100 includes an inverter 10, a stator 20, an excitation circuit (field circuit) 30, a rotor 40, and a switching circuit 50. The inverter 10, the excitation circuit 30, and the switching circuit 50 are housed in a space provided within the casing of the rotating electric machine 100. That is, the rotating electric machine 100 comprises an electromechanical integrated assembly in which its mechanical components, including the stator 20 and the rotor 40, and its electronic components, including the inverter 10, the excitation circuit 30, and the switching circuit 50, are housed in the common casing.

[0013] The inverter 10 includes a series connection of an upper U-phase branch switching element Sup and a lower U-phase branch switching element Sun, a series connection of an upper V-phase branch switching element Svp and a lower V-phase branch switching element Svn, and a series connection of an upper W-phase branch switching element Swp and a lower W-phase branch switching element Swn. These switching elements may be MOSFETs.

[0014] The stator 20 has a U-phase winding 20u, a V-phase winding 22v and a W-phase winding 22w arranged at intervals of 120 degrees in the mechanical angle.

[0015] The wiring connection of the U-phase of the rotating electric machine 100 is explained in detail below. The source of the upper U-phase arm switching element Sup and the drain of the lower U-phase arm switching element Sun are connected to each other. A first end of the U-phase winding 22u is connected to the node of these switching elements. A second end of the U-phase winding 22u is connected to a neutral point 24. The drain of the upper U-phase arm switching element Sup is connected to the positive terminal of the battery 200. The source of the lower U-phase arm switching element Sun is connected to the negative terminal of the battery 200. Since the wiring connections of the V-phase and the W-phase are similar to that of the U-phase, their explanation is omitted.

[0016] The upper U-phase branch switching element Sup, the lower U-phase branch switching element Sun, the upper V-phase branch switching element Svp, the lower V-phase branch switching element Svn, the upper W-phase branch switching element Swp and the lower W-phase branch switching element Swn are respectively connected in reverse parallel to an upper U-phase branch diode Dup, a lower U-phase branch diode Dun, an upper V-phase branch diode Dvp, a lower V-phase branch diode Dvn, an upper W-phase branch diode Dwp and a lower W-phase branch diode Dwn.

[0017] The excitation circuit 30 includes a series connection of an upper excitation arm switching element Sfp and a lower excitation arm switching element Sfn. The source of the upper excitation arm switching element Sfp and the drain of the lower excitation arm switching element Sfn are connected to each other. The drain of the upper excitation arm switching element Sfp is connected to the positive terminal of the battery 200. The source of the lower excitation arm switching element Sfn is connected to the negative terminal of the battery 200. The excitation circuit 30 serves as a power supply (power source) for supplying electric power to the rotor 40.

[0018] The switching elements Sup, Sun, Svp, Svn, Swp, and Swn of the inverter 10 and the switching elements Sfp and Sfn of the excitation circuit 30 are controlled by on / off control signals sent from a control unit (not shown). The rotor 40 has a first excitation winding (field winding) 41 and a second excitation winding (field winding) 42. The rotor 40 functions as an excitation section (field section) when current is supplied to the first excitation winding 41 and the second excitation winding 42. A first end of the first excitation winding 41 is connected to a first connecting part 51 of the switch circuit 50 through a first brush 61. A second end of the first excitation winding 41 is connected to a connecting part 52 of the switch circuit 50 through a second brush 62. A first end of the second excitation winding 42 is connected to a third connecting part 53 of the switch circuit 50 through a third brush 63.A second end of the second excitation winding 42 is connected to a fourth connecting part 54 of the switch circuit 50 through a fourth brush 64. The first excitation winding 41 and the second excitation winding 42 are the same in terms of winding direction.

[0019] The first connecting part 51 and the third connecting part 53 are connected to each other by a first switch 55 formed from a MOSFET. The second connecting part 52 and the fourth connecting part 54 are connected to each other by a second switch 56 formed from a MOSFET. Furthermore, the second connecting part 52 and the third connecting part 53 are connected to each other by a third switch 57 formed from a MOSFET.

[0020] The first connection part 51 of the switch circuit 50 is connected to a connection part between the source of the upper excitation branch switching element Sfp and the drain of the lower excitation branch switching element Sfn of the excitation circuit 30. The fourth connection part 54 of the switch circuit 50 is connected to the negative terminal of the battery 200.

[0021] Fig. 2 shows an equivalent circuit diagram of a circuit consisting of the rotor 40 and the switch circuit 50. In Fig. 2, the first to fourth brushes 61 to 64 connecting the rotor 40 to the switch circuit 50 are omitted for illustration.

[0022] The first end of the first excitation winding 41 is connected to the first connecting part 51, and the second end of the first excitation winding 41 is connected to the second connecting part 52. The first end of the second excitation winding 42 is connected to the third connecting part 53, and the second end of the second excitation winding 42 is connected to the fourth connecting part 54. As described above, the first connecting part 51 and the third connecting part 53 are connected to each other by the first switch 55, the second connecting part 52 and the fourth connecting part 54 are connected to each other by the second switch 56, and the second connecting part 52 and the third connecting part 53 are connected to each other by the third switch 57.

[0023] Since the first excitation winding 41 and the second excitation winding 42 have the same winding direction, the first excitation winding 41 and the second excitation winding 42 can be brought into a parallel connection state (parallel connection state) in which they have the same winding direction and the same current conducting direction by turning on the first switch 55 and the second switch 56 and turning off the third switch 57. On the other hand, the first excitation winding 41 and the second excitation winding 42 can be brought into a series connection state (series connection state) in which they have the same winding direction and the same current conducting direction by turning on the third switch 57 and turning off the first switch 55 and the second switch 56.That is, the switching circuit 50 performs control to switch the first excitation winding 41 and the second excitation winding 42 between the series connection state in which they have the same winding direction and the same current conducting direction and the parallel connection state in which they have the same winding direction and the same current conducting direction.

[0024] According to this embodiment, the first excitation winding 41 and the second excitation winding 42 have the same cross-section and the same number of turns N. Accordingly, the first excitation winding 41 and the second excitation winding 42 have the same length and the same resistance R. Therefore, when the first excitation winding 41 and the second excitation winding 42 are connected in series with each other, their combined resistance is 2R, and when the first excitation winding 41 and the second excitation winding 42 are connected in parallel with each other, their combined resistance is R / 2.

[0025] Accordingly, when the voltage applied or generated in the series or parallel connection of the first excitation winding 41 and the second excitation winding 42 is V, the value of a current flowing through the first excitation winding 41 and the value of a current flowing through the second excitation winding 42 are both equal to V / 2R when connected in series with each other, and are both equal to V / R when connected in parallel with each other.

[0026] The product of the current value and the number of turns when the first excitation winding 41 and the second excitation winding 42 are connected in parallel is twice as large as when they are connected in series. Accordingly, by connecting the first excitation winding 41 and the second excitation winding 42 in parallel to generate a larger magnetomotive force, the rotating electric machine 100 can be used as a motor.

[0027] In contrast, the current flowing through the first excitation winding 41 and the second excitation winding 42 when connected in series is half that when connected in parallel. Accordingly, by connecting the first excitation winding 41 and the second excitation winding 42 in series, aging deterioration of the first to fourth brushes can be reduced, although the magnetomotive force and electromotive force become smaller.

[0028] Switching between the series connection state and the parallel connection state of the first excitation winding 41 and the second excitation winding 42 by the switch circuit 50 is performed according to the control state of the vehicle. Specifically, the first excitation winding 41 and the second excitation winding 42 are connected in series to allow a large current to flow in cases where a larger torque is required. The cases where a larger torque is required include the case where the rotating electric machine 100 is made to function as a starter motor and the case where the rotating electric machine 100 is used to generate assist torque. In contrast, in the case where the rotating electric machine 100 is made to function as an alternator (generator, alternator), it is not necessary to conduct a large current.Accordingly, in such a case, the first excitation winding 41 and the second excitation winding 42 are connected in series with each other.

[0029] Fig. 3 shows a timing chart explaining an example of the control of the rotating electric machine 100.

[0030] In this example, when the vehicle driver turns on the ignition switch at time t1, the first switch 55 and the second switch 56 are turned on (closed), while the third switch 57 remains off (open). As a result, the first excitation winding 41 and the second excitation winding 42 are connected in series with each other. Thereafter, when the vehicle driver performs an operation to start the engine at time t2, the engine is started. In this example, it is assumed that the vehicle with the rotating electric machine 100 is provided with a starter motor that generates a torque greater than the torque generated by the rotating electric machine 100, and that the engine is started by this starter motor at time t2.This is because, since the torque required for cold starting of the engine is greater than the torque required for warm starting of the engine, there is a concern that the engine cannot be cold started by the rotating electric machine 100 due to insufficient torque even if electric power is supplied to the rotating electric machine 100 with the first excitation winding 41 and the second excitation winding 42 connected in parallel to each other.

[0031] When the vehicle driver presses the accelerator pedal at time t3 after starting the engine, the vehicle begins to accelerate and transitions to constant speed travel at time t4. Thereafter, when the vehicle begins to decelerate at time t5, the rotating electric machine begins to function as an alternator, resulting in the battery 200 being charged by the electromotive force occurring in the series connection of the first excitation winding 41 and the second excitation winding 42.

[0032] When the vehicle speed decreases to almost zero and it is determined that the vehicle has stopped at time t6, the engine is automatically stopped by the idle stop function. At this time, the switch circuit 50 turns on the first switch 55 and the second switch 56 and turns off the third switch 57 to connect the first excitation winding 41 and the second excitation winding 42 in parallel to prepare for the engine to restart.

[0033] For example, when the vehicle driver requests a restart in the engine at time t7 by operating the accelerator pedal while the engine is stopped by the idle stop function, the engine is restarted by using the rotating electric machine 100 as a motor.

[0034] Thereafter, if it is confirmed at time t8 that the engine has been restarted, regenerative power recovery becomes possible while the vehicle is traveling. Accordingly, the switch circuit 50 turns off the first switch 55 and the second switch 56 and turns on the third switch 57 to connect the first excitation coil 41 and the second excitation coil 42 in series to prepare for regenerative power generation.

[0035] In the example of Fig.3 causes the rotating electric machine 100 to function as a motor to restart the engine, however, the rotating electric machine 100 may be caused to function as a motor to accelerate the vehicle. In this case, the first excitation winding 41 and the second excitation winding 42 are kept connected in parallel after confirming that the engine has been restarted, and are connected in series when an end of the vehicle's acceleration is detected or a start of the vehicle's deceleration is detected.

[0036] In this case, switching of the first excitation winding 41 and the second excitation winding 42 from the parallel connection state to the series connection state is triggered when it is confirmed that the engine has been restarted. However, this may be triggered when the vehicle starts accelerating at time t9.

[0037] The embodiment described above provides the following advantages.

[0038] The first excitation winding 41 and the second excitation winding 42 are switched between the series connection state and the parallel connection state by the switching circuit 50. Accordingly, the value of a current flowing through the first excitation winding 41 and the second excitation winding 42 can be easily changed.

[0039] The first field winding 41 and the second field winding 42 are placed in the parallel connection state to increase the current flowing therethrough only when the rotating electric machine 100 is required to generate a large torque, and are placed in the series connection state to decrease the current flowing therethrough only when the rotating electric machine is required to generate a small torque. Accordingly, it is possible to suppress temporal deterioration of the first to fourth brushes 61 to 64. Modifications

[0040] According to the above-described embodiment, the rotating electric machine 100 is of the electromechanical integrated type. However, the rotating electric machine 100 does not have to be of the electromechanical integrated type. In this case, although the inverter 10, the excitation circuit 30, and the switching circuit 50, which are electronic components, are arranged outside the casing of the rotating electric machine 100, the rotating electric machine 100 may be configured to include the inverter 10, the excitation circuit 30, and the switching circuit 50.

[0041] According to the above-described embodiment, the vehicle is provided with a starter motor for cold-starting the engine. However, if the rotating electric machine 100 can generate sufficient torque for cold-starting the engine, such a starter motor may optionally be omitted. In this case, when the vehicle driver turns on the ignition switch, the first switch 55 and the second switch 56 are turned on, and the third switch 57 is turned off to place the first excitation coil 41 and the second excitation coil 42 in the parallel connection state.

[0042] According to the above-described embodiment, the first excitation winding 41 and the second excitation winding 42 are the same in diameter and length. However, they may be different from each other in diameter or length.

[0043] According to the above-described embodiment, the rotor 40 has two windings (the first and second excitation windings 41 and 42). However, the rotor 40 may have three or more excitation windings. In this case, the first ends of these excitation windings are connected to each other by the first switch, the second ends of these excitation windings are connected to each other by the second switch, and the third switch is provided in each of the passages (connections) that connect these excitation windings in series with the excitation circuit 30.

[0044] According to the above-described embodiment, the rotating electric machine 100 is mounted on a vehicle. However, the rotating electric machine 100 may be mounted on an object other than a vehicle. In this case, switching between the series connection state and the parallel connection state is performed according to the torque required by that object or a control state of the object.

[0045] According to the above-described embodiment, the rotor 40 and the switching circuit 50 are connected to each other through the first to fourth brushes 61 to 64. However, if the rotating electric machine 100 is of a brushless type, these brushes may be replaced with switching elements.

[0046] According to the above-described embodiment, the rotating electric machine is a three-phase motor. However, the rotating electric machine 100 may be an AC motor other than a three-phase motor or a DC motor.

[0047] According to the above-described embodiment, the first excitation winding 41 and the second excitation winding 42 are wound on the rotor 40 and used as an excitation section. However, they may be wound on the stator 20 to be used as an excitation section.

[0048] The switches used in the above-described embodiment are formed from MOSFETs. However, they do not necessarily have to be formed from MOSFETs. According to the above-described embodiment, the battery 200 is a lead-acid battery whose terminal voltage is approximately 12 V. However, a high-energy-density battery, such as a lithium-ion battery, may be used as the battery 200.

Claims

[1] Rotating electrical machine (100) with: an excitation section (40) having excitation windings (41, 42), and a switching device (50) for switching the excitation windings (41, 42) between a series connection state in which the excitation windings (41, 42) are connected in series with one another and have the same winding direction and the same current conducting direction, and a parallel connection state in which the excitation windings (41, 42) are connected in parallel with one another and have the same winding direction and the same current conducting direction, wherein the switching device (50) comprises: a first switch (55) for connecting first ends of the excitation windings (41, 42) to each other, a second switch (56) for connecting two ends of the excitation windings (41, 42) to each other, and a third switch (57) for connecting the excitation windings (41, 42) in series with a power supply (30), wherein the switching device (50) is configured to switch the excitation windings (41, 42) into the series connection state by turning off the first and second switches and turning on the third switch, and to switch the excitation windings (41, 42) into the parallel connection state by turning on the first and second switches and turning off the third switch. [2] The rotating electric machine (100) according to claim 1, wherein the rotating electric machine (100) functions as a motor for starting an engine of a vehicle on which the rotating electric machine (100) is mounted, and functions as an alternator for generating regenerative power while the vehicle is running, and the switching means (50) switches the excitation windings (41, 42) to the series connection state for starting the engine and switches the excitation windings (41, 42) to the parallel connection state for generating regenerative power.

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