The present invention relates to a mechanical-electrical integrated electric drive system in which a rotary electric machine and a power conversion device for driving the rotary electric machine are integrated into one body.
Patent Document 1 describes an example of a power conversion device having a common mode noise reduction mechanism. The common mode noise (also called “common mode current”) is desired to be reduced since the common mode noise can cause malfunction to the power conversion device controlling the rotary electric machine. For example, the reduction of the common mode noise is desired in electric vehicles (traveling by using rotary torque generated by a rotary electric machine) and hybrid electric vehicles (traveling based on outputs of both an engine and a rotary electric machine) since the common mode noise exerts bad influence on the traveling performance of the vehicle. In consideration of the degree of freedom of the installation in vehicles, a mechanical-electrical integrated electric drive system formed by integrating the power conversion device and the rotary electric machine into one body is desirable.
However, in the invention described in Patent Document 1, a special noise reduction circuit is added to the power conversion device for the purpose of reducing the common mode current. The addition of the special noise reduction circuit leads to a cost rise and enlargement of the power conversion device. Further, the control of the power conversion device becomes complicated.
The invention of claim 1 provides a mechanical-electrical integrated electric drive system comprising: a rotary electric machine which includes a rotor, a stator having a stator core mounted with armature windings, and a housing holding the stator and having AC terminals of the armature windings arranged thereon; and a power conversion device which is fixed to the periphery of the housing and includes an inverter circuit and AC bus bars connecting the inverter circuit with the AC terminals. The mechanical-electrical integrated electric drive system comprises: a current-collecting member which is arranged in contact with the stator core to collect common mode current deriving from stray capacitance of the stator; and a connection wire which connects the current-collecting member to a virtual neutral point on the DC input side of the inverter circuit.
According to the present invention, the common mode current can be returned from the rotary electric machine's side to the virtual neutral point of the power conversion device inside the mechanical-electrical integrated electric drive system, by which the bad influence of the common mode current can be suppressed.
Referring now to the drawings, a description will be given in detail of a preferred embodiment of the present invention.
An engine EGN and a rotary electric machine 900 generate torque for the traveling of the vehicle. The rotary electric machine 900 has not only the function of generating the rotary torque but also a function of converting mechanical energy (applied to the rotary electric machine 900 from the outside) into electric power. The rotary electric machine 900 (implemented by a synchronous machine or an induction machine, for example) operates either as a motor or as a generator depending on the operation mode as mentioned above. In cases where the rotary electric machine 900 is installed in a vehicle, the rotary electric machine 900 is desirable to generate high power with a small size, and thus a permanent magnet-type synchronous motor employing neodymium magnets or the like is suitable as the rotary electric machine 900. The permanent magnet-type synchronous motors, in which the heating of the rotor is less than that in induction motors, are suitable for the use for vehicles also from this viewpoint.
The output torque of the engine EGN is transmitted to the rotary electric machine 900 via a power transfer mechanism TSM, while the rotary torque from the power transfer mechanism TSM or the rotary torque generated by the rotary electric machine 900 is transmitted to the wheels via a transmission TM and a differential gear DEF. In contrast, during the operation of regenerative braking, rotary torque is transmitted from the wheels to the rotary electric machine 900. The rotary electric machine 900 generates AC power according to the supplied rotary torque. The generated AC power is converted by a power conversion device 200 into DC power as will be explained below, and the DC power charges a high-voltage battery 136. The electric power stored in the battery 136 is reused as energy for the traveling of the vehicle.
The front bracket 908 and the rear bracket 910 are arranged at opposite ends of the housing 912 of the rotary electric machine 900 in its axial direction. A rotor shaft 920 protrudes from the center of the front bracket 908. The power conversion device 200 is fixed to the peripheral surface of the housing 912 (at a certain position in the radial direction) of the rotary electric machine 900.
A case 12 storing the circuit components of the power conversion device 200 is in a substantially cubic shape. A lid 8 is attached to the case 12 to cover the top opening of the case 12. The case 12 is fixed to the housing 912 of the rotary electric machine 900. The case 12 is made of electrically conductive material (metallic material such as die-cast aluminum in this embodiment). Communication of signals between the power conversion device 200 and an upper-level control device on the vehicle's side is performed via a connector 21.
A positive power supply terminal 509 and a negative power supply terminal 508 protrude from a hole 12j formed through the case 12 of the power conversion device 200. The DC electric power from the battery 136 is supplied to the power supply terminals 508 and 509. A channel for circulating a coolant is formed in the case 12. The coolant flows in through an inlet pipe 13 arranged on a side wall of the case 12 and is discharged through an outlet pipe 14. Electronic components (three-phase inverter circuit, etc.) inside the case 12 are cooled down by the coolant.
The outlet pipe 14 of the case 12 is connected via a junction member 14a to an inlet pipe 913 arranged on the housing 912 of the rotary electric machine 900. The coolant discharged from the outlet pipe 14 flows from the inlet pipe 913 of the housing 912 into a channel in the housing (channel 919 shown in
On the periphery of the center bracket 909, grooves are formed to surround the stator core 941. The center bracket 909 is stored in the housing 912. In this state, the channel 919 is formed by the grooves of the center bracket 909 and the inner circumferential surface of the housing 912. AC terminals 902U-902W are arranged to protrude from a surface 912e of the housing 912. Corresponding armature windings 945 of the stator 940 are connected to the AC terminals 902U-902W.
The housing 912 and the center bracket 909 are fixed to the front bracket 908 by using bolts or the like (unshown). The rear bracket 910 is fixed to the housing 912 by using bolts or the like (unshown). While the exterior parts of the rotary electric machine 900 are made up of four parts (the housing 912, the center bracket 909, the front bracket 908 and the rear bracket 910) in this embodiment, it is unnecessary to adhere to this configuration. For example, it is also possible to form the housing 912 and the center bracket 909 as one component. Similarly, there is no problem even if the front bracket 908, the housing 912 and the center bracket 909 are formed as one component. Incidentally, electrically conductive material is used as the material of the housing 912, the center bracket 909, the front bracket 908 and the rear bracket 910. In this embodiment, the material is assumed to be die-cast aluminum as a metallic material.
Further, in this embodiment, a plurality of conductor bars 950b extending in the axial direction of the stator core 941 and a conductor ring 950c extending one lap around the peripheral surface of the stator core 941 and connecting one ends of the conductor bars 950b together are arranged to be in contact with the periphery of the stator core 941.
The conductor bars 950b are arranged on the circumference of the stator core 941 at prescribed intervals in regard to the circumferential direction. In the rotary electric machine 900 having the structure shown in
As will be explained later, the conductor bars 950b are provided in order to collect the common mode current (common mode noise) flowing into the stator. The number of the conductor bars 950b may be one; however, the current-collecting effect increases with the increase in the number of the conductor bars 950b. The common mode current flowing into the conductor bars 950b flows into the conductor ring 950c and is thereafter returned to a virtual neutral point 510G on the input side of the inverter circuit via a connection wire 700. The virtual neutral point 510G is also called a “virtual ground point”.
The connection wire 700 is lead to the inside of the case 12 while penetrating the part where the housing 912 and the case 12 face each other. The connection wire 700 is not lead out to the outside of the casing of the electric drive system 1. In the part where the housing 912 and the case 12 face each other, a through hole is formed through the base part of the case 12 and the AC terminals 902U-902W project to the inside of the case 12.
Incidentally, the above structure in which one connection wire 700 is lead out from the rotary electric machine's side to the power conversion device's side is not necessarily essential. For example, similarly to the AC terminals 902U-902W arranged on the housing 912 for the connection between the armature windings 945 and AC bus bars 802U-802W, it is possible to provide the housing 912 with a terminal part extending from the inside of the housing 912 to the inside of the case 12 and connect a connection wire on the rotary electric machine's side with a connection wire on the power conversion device's side via the terminal part.
While the conductor bars 950b and the conductor ring 950c are fixed on the peripheral surface of the stator core 941 in this embodiment as members for collecting the common mode current, any type of structure may be employed as long as the structure has the function of the current-collecting member. For example, it is possible to apply thick plating on the entire peripheral surface of the stator core 941 and connect the connection wire 700 to the plated part. It is also possible to give the function of the current-collecting member to a part of the stator core 941 by replacing a part of the electromagnetic steel sheets of the stator core 941 with a conductor plate, for example. Aluminum, copper, etc. are usable as the material of the current-collecting member.
First, the circuitry of the power conversion device 200 will be explained by referring to
As shown in
Incidentally, it is possible in this embodiment to drive the vehicle (for the traveling) with the power of the rotary electric machine 900 alone, by operating the rotary electric machine 900 as a motor by use of the electric power of the battery 136. Further, in this embodiment, the battery 136 can be charged by operating the rotary electric machine 900 as a generator by use of the power of the engine EGN or the power from the wheels.
Although illustration is omitted in
The power conversion device 200 has the connector 21 for communication. Via the connector 21, the power conversion device 200 receives commands from the upper-level control device, transmits data representing status to the upper-level control device, and so forth. Based on the commands inputted through the connector 21, a control circuit 172 of the power conversion device 200 calculates control values for the rotary electric machine 900, calculates (determines) whether the rotary electric machine 900 should be operated as a motor or as a generator, generates a control pulse based on the result of the calculation, and supplies the generated control pulse to a driver circuit 174. According to the supplied control pulse, the driver circuit 174 generates drive pulses for controlling the inverter circuit 140.
Series circuits 150U-150W are formed by upper and lower arms. Here, IGBTs 328U-328W and diodes 156U-156W operate as the upper arm, and IGBTs 330U-330W and diodes 166U-166W operate as the lower arm. The inverter circuit 140 has the three series circuits 150 corresponding to the U-phase, V-phase and W-phase of the AC power to be outputted.
These three phases correspond to the three-phase armature windings (U-phase, V-phase, W-phase) of the rotary electric machine 900 in this embodiment. The upper/lower arm series circuit 150 for each of the three phases outputs AC current from an intermediate electrode 169 as the midpoint of the series circuit. The intermediate electrodes 169 are connected to the AC terminals 902U-902W of the rotary electric machine 900 via the AC terminals 320U-320W. As mentioned above, the AC terminals 320U-320W are connected to the AC terminals 902U-902W via the AC bus bars 802U-802W.
The collector electrode 153 of the upper arm IGBT 328 is electrically connected to positive capacitor terminals 506Y and 506X of capacitors 500Y (constituting a Y capacitor) and the smoothing capacitor 500X via a positive terminal 157. Meanwhile, the emitter electrode 154 of the lower arm IGBT 330 is electrically connected to negative capacitor terminals 504Y and 504X of the capacitors 500Y and 500X via a negative terminal 158. The connection wire 700, which is connected to the conductor ring 950c at one end (see
The capacitor 500X has the positive capacitor terminal 506X, the negative capacitor terminal 504X, the positive power supply terminal 509 and the negative power supply terminal 508. High-voltage DC power from the battery 136 is supplied to the positive and negative power supply terminals 509 and 508. Then, the high-voltage DC power is supplied from the positive and negative capacitor terminals 506X and 504X of the capacitor 500X to the inverter circuit 140.
On the other hand, the DC power obtained by the inverter circuit 140 by the conversion of the AC power is supplied to the capacitor 500X via the positive and negative capacitor terminals 506X and 504X, supplied from the positive and negative power supply terminals 509 and 508 to the battery 136 via the DC connectors (unshown), and stored in the battery 136.
The control circuit 172 includes a microcomputer for calculating the switching timing of the IGBTs 328 and the IGBTs 330. Information inputted to the microcomputer includes a target torque value which is required to be generated by the rotary electric machine 900, values of electric currents supplied from the series circuits 150 to the rotary electric machine 900, and the magnetic pole position of the rotor of the rotary electric machine 900.
The target torque value is a value based on a command signal supplied from the unshown upper-level control device. The electric current values are detected based on detection signals from a current sensor (unshown) installed in the power conversion device 200. The magnetic pole position is detected based on a detection signal from a rotary magnetic pole sensor (unshown) such as a resolver installed in the rotary electric machine 900.
The microcomputer in the control circuit 172 calculates d-axis and q-axis current command values for the rotary electric machine 900 based on the target torque value, calculates d-axis and q-axis voltage command values based on the differences between the calculated d-axis and q-axis current command values and detected d-axis and q-axis current values, and converts the calculated d-axis and q-axis voltage command values into U-phase, V-phase and W-phase voltage command values based on the detected magnetic pole position. Then, the microcomputer generates pulse-like modulation waves based on comparison between a carrier wave (triangular wave) and fundamental waves (sinusoidal waves) based on the U-phase, V-phase and W-phase voltage command values (hereinafter referred to as “PWM control”), and outputs the generated modulation waves to the driver circuit 174 as PWM (pulse-width modulation) signals.
According to the above control pulse, the driver circuit 174 supplies the drive pulses (for controlling the IGBTs 328 and 330 constituting the upper and lower arms of the three-phase series circuits 150) to the IGBTs 328 and 330 for the three phases. For driving the lower arm, the driver circuit 174 amplifies each PWM signal and outputs the amplified PWM signal to the gate electrode of each corresponding lower arm IGBT 330 as a drive signal. For driving the upper arm, the driver circuit 174 amplifies each PWM signal after shifting the reference electric potential level of the PWM signal to that of the upper arm, and outputs the amplified PWM signal to the gate electrode of each corresponding upper arm IGBT 328 as a drive signal. The IGBTs 328 and 330 perform the conduction/interruption operation according to the drive pulses from the driver circuit 174 and thereby convert the DC power supplied from the battery 136 into three-phase AC power. The three-phase AC power obtained by the conversion is supplied to the rotary electric machine 900.
In a conventional electric drive system in which the power conversion device 200 and the rotary electric machine 900 are provided separately, AC terminals 321U-321W of the power conversion device 200 are connected to the AC terminals 902U-902W of the rotary electric machine 900 generally via shield cables 820U-820W as shown in
In contrast, in the electric drive system of this embodiment, the power conversion device 200 and the rotary electric machine 900 are integrated into one body as shown in
A side face of the case 12 of the power conversion device 200 is provided with an inlet pipe 13 and an outlet pipe 14 for the cooling water (coolant). The three-phase inverter circuit 140 and nearby components are cooled down by the circulation of the coolant through a coolant channel (unshown) arranged in the power conversion device 200.
Next, the functions of the conductor bars 950b, the conductor ring 950c and the connection wire 700 shown in
V0=(Vu+Vv+Vw)/3 (1)
Assuming that the voltage of the battery 136 is Vdc and the intermediate electric potential of DC bus lines P and N (see
The phase voltages of the U-phase, V-phase and W-phase change as follows according to the ON/OFF operation of the upper arm IGBTs 328U-328W and the lower arm IGBTs 330U-330W of the inverter circuit 140:
When the PWM control is performed as described above, the switching pattern of the upper arm IGBTs 328U-328W and the lower arm IGBTs 330U-330W of the inverter circuit 140 includes the following eight modes:
The neutral point electric potential V0 in each of the above modes 0-7 is calculated by use of the above expression (1) as follows:
In PWM control, the modes are generally repeated like “7→6→1→0→1→6→7→6→1→0→1→2→7→2 1→0→1→2→7→ . . . ” along with the switching of the upper and lower arms. Accordingly, the neutral point voltage repeats an electric potential change by Vdc/3 like “Vdc/2, Vdc/6, −Vdc/6, −Vdc/2, −Vdc/6, Vdc/6→ . . . ”.
When the electric potential of the neutral point 946 changes as above, the stray capacitance 947 (stray capacitance between the stator core and the windings) repeats the charging and discharging. Therefore, the common mode current flows from the stator core 943 to the center bracket 909 which is in metallic contact with the stator 941. The common mode current flows further to the housing 912, the front bracket 908 and the rear bracket 910.
While stray capacitance 948 between the stator core 941 and the housing 912, the front bracket 908 and the rear bracket 910 is lower than the stray capacitance 947, the stray capacitance 948 is provided since the stator core 941, the center bracket 909, the housing 912, the front bracket 908 and the rear bracket 910 are fixed by means of surface contact such as shrink fitting and bolting.
Incidentally, in cases where the power conversion device 200 and the rotary electric machine 900 are provided separately as in
As indicated by the broken lines in
However, the countermeasure by use of the shield cables 820U-820W shown in
For example, in a configuration in which the shield cables 820U-820W in
In contrast, in this embodiment, the conductor bars 950b and the conductor ring 950c are arranged on the peripheral surface of the stator core 941 and the conductor ring 950c is connected to the virtual neutral point 510G of the power conversion device 200 by using the connection wire 700 as shown in
Since the conductor bars 950b are configured to be in electrical connection with the stator core 941, the common mode current entering the stator core 941 flows not into the shrink fitting surface between the stator core 941 and the center bracket 909 but into the conductor bars 950b and the conductor ring 950c as indicated by the arrows in
The common mode current flowing into the conductor bars 950b and the conductor ring 950c is lead by the connection wire 700 from the rotary electric machine 900's side to the power conversion device 200's side and flows into the virtual neutral point 510G via the capacitor 510Ya as shown in
While the stator core 941 is fit in the inner circumference of the center bracket 909 by means of shrink fitting and the center bracket 909 is fixed to the housing 912 in the above embodiment, the present invention is not to be restricted to stators 940 having such a configuration.
A stator 942 has a stator core 943 and three-phase armature windings 945. The peripheral surface of the stator core 943 is provided with a plurality of fixation parts 943X each having a through hole for a bolt. The stator core 943, stored in an inner circumferential part of a center bracket 909X, is fastened to the center bracket 909X by using bolts 960.
At least one conductor bar 950b extending in the axial direction of the stator core 943 is arranged on the peripheral surface of the stator core 943 to be in electrical connection with the stator core 943. Each conductor bar 950b is electrically connected to a conductor ring 950c which is arranged in the vicinity of an end of the stator core 943 in the axial direction. A connection wire 700 is connected to the conductor ring 950c. As explained above, the stator 942 in this example has a configuration equivalent to the above embodiment in regard to the collection of the common mode current.
In this configuration, a clearance is formed between the stator core 943 and the center bracket 909X, by which the common mode current flowing from the stator core 943 to the center bracket 909X's side can be reduced. Consequently, the common mode current can be collected more efficiently by using the conductor bars 950b and the conductor ring 950c.
With such a configuration, the fixing part (joint) between the case 12 of the power conversion device 200 and the housing 912 of the rotary electric machine 900 shown in
(a) As described above, the electric drive system 1 comprises: a rotary electric machine 900 which includes a rotor 930, a stator 940 having a stator core 941 mounting armature windings 945 thereon, and a housing 912 holding the stator 940 and having AC terminals 902U-902W of the armature windings 945 arranged thereon; and a power conversion device 200 which is fixed to the periphery of the housing 912 and includes an inverter circuit 140 and AC bus bars 802U-802W connecting the inverter circuit 140 with the AC terminals 902U-902W. The mechanical-electrical integrated electric drive system is configured to comprise: a conductor bar 950b and a conductor ring 950c as current-collecting members arranged in contact with the peripheral surface of the stator core 941 to collect common mode current deriving from stray capacitance of the stator 940; and a connection wire 700 which connects the conductor ring 950c to a virtual neutral point 510G on the DC input side of the inverter circuit 140.
Therefore, the common mode current flows into the conductor bar(s) 950b and then flows into the virtual neutral point 510G on the DC input side of the inverter circuit 140 via the conductor ring 950c and the connection wire 700 as shown in
(b) In the structure in which the metallic case 12 of the power conversion device 200 is fixed to the housing 912 of the rotary electric machine 900, the following configuration is desirable for preventing the bad influence of the common mode current on other devices: The connection wire 700 connected to the conductor ring 950c is lead from the inside of the housing 912 to the inside of the case 12 while penetrating a fixation surface where the housing 912 and the case 12 face each other (i.e., the surface 912e of the housing 912 shown in
(c) It is desirable to configure the housing 912 to include a first housing part 912a storing the stator core 941 and a second housing part 912b formed integrally with the first housing part 912a and storing the power conversion device 200. With such a configuration, the joint between the casing of the power conversion device 200 and the housing of the rotary electric machine is eliminated. This makes it easier to confine the common mode current in the metallic casing. Consequently, the radiated noise can be reduced.
The embodiments described above may be employed either individually or in combination since the effects of the embodiments can be achieved either individually or in a synergistic manner. The present invention is not to be restricted to the above embodiments; a variety of modifications, design changes, etc. to the embodiments are possible as long as the features of the present invention are not impaired.
Number | Date | Country | Kind |
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2011-259229 | Nov 2011 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP2012/078562 | 11/5/2012 | WO | 00 | 5/27/2014 |