JP2013225974A - Motor drive system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor drive system capable of efficiently utilizing regenerative energy of a motor.SOLUTION: A motor drive system includes first and second three-phase motors 16, 26 driven and controlled by first and second three-phase inverters 15, 25, respectively, while using a battery as a power supply. The motor drive system includes: a capacitor C disposed between a connection point of a set of switching elements of the first and second three-phase inverters 15, 25 and a ground potential side; first and second switches SW1, SW2 connected between the connection point and the capacitor C, respectively; and a control device 21. The control device 21 holds an on-state of the second switch SW2 during regeneration of the first three-phase motor 16, holds an off-state of the set of switching elements of the second three-phase inverter 25, and performs on-off control of the switching elements at a high potential side in at least one set of the switching elements of the other two sets of the switching elements.

Description

  The present invention relates to a motor drive system including a motor that is driven and controlled by a three-phase inverter using a battery as a power source.

  2. Description of the Related Art A motor drive system including a motor that is driven and controlled by a three-phase inverter using a battery as a power source is known, such as an electric vehicle and a hybrid vehicle. For example, this type of motor drive system is disclosed in Patent Document 1. This motor drive system is capable of charging a battery by receiving electric power from the outside. In this type of motor drive system, it is also known to charge a battery using regenerative energy of the motor.

JP 2011-211889 A

  However, depending on the state of the battery, the internal resistance may increase. In this case, there is a problem that the regenerative energy of the motor cannot be charged efficiently.

  Accordingly, an object of the present invention is to provide a motor drive system that can effectively use the regenerative energy of the motor.

  The motor drive system of the present invention is a motor drive system that includes first and second three-phase motors that are driven and controlled by first and second three-phase inverters using a battery as a power source. This motor drive system is provided between a connection point of a set of switching elements constituting one phase of the first three-phase inverter and the ground potential side, and one phase of the second three-phase inverter. And a capacitor disposed between the connection point of the set of switching elements and the ground potential side, and a first point connected between the connection point of the set of switching elements of the first three-phase inverter and the capacitor. 1 switch, a second switch connected between a connection point of a set of switching elements of the second three-phase inverter and a capacitor, and a switching element in the first and second three-phase inverters. And a control device that performs off-control. At the time of regeneration of the first three-phase motor, the control device holds the second switch in the on state, holds one set of switching elements of the second three-phase inverter in the off state, and switches the other two sets of switching The high-potential side switching element in at least one set of switching elements among the elements is controlled to be turned on / off, and when the second three-phase motor is regenerated, the first switch is kept on, and the first three-phase inverter One set of switching elements is held in the OFF state, and the high potential side switching elements in at least one set of the other two sets of switching elements are controlled to be turned on / off.

  According to this motor drive system, the regenerative energy of the first three-phase motor can be stored in the capacitor via the second three-phase inverter and the second switch. Regenerative energy can be stored in the capacitor via the first three-phase inverter and the first switch. Therefore, the regenerative energy of the motor can be used effectively.

When the first three-phase motor is driven after regeneration, the control device described above holds the second switch in the on state, holds a pair of switching elements in the second three-phase inverter in the off state, The low potential side switching element in at least one of the two sets of switching elements is controlled to be turned on / off, and when the second three-phase motor is driven after regeneration, the first switch is held in the on state, Holding one set of switching elements of the first three-phase inverter in an off state, and controlling on / off of a low potential side switching element in at least one set of the other two sets of switching elements;
The motor drive system according to claim 1.

  According to this, the regenerative energy stored in the capacitor can be effectively used for driving the first or second three-phase motor.

  According to the present invention, the regenerative energy of the motor can be effectively used in the two motor drive systems.

It is a figure which shows electrically the structure of the battery forklift which concerns on the 1st Embodiment of this invention. It is a figure which shows the equivalent circuit at the time of regeneration of the motor for driving | running | working in 1st Embodiment. It is a figure which shows the equivalent circuit at the time of the drive after regeneration of the motor for driving | running | working in 1st Embodiment. It is a figure which shows the equivalent circuit at the time of regeneration of the motor for cargo handling in 1st Embodiment. It is a figure which shows the equivalent circuit at the time of the drive after regeneration of the motor for cargo handling in 1st Embodiment. It is a figure which shows electrically the structure of the battery forklift which concerns on the 2nd Embodiment of this invention. It is a figure which shows the equivalent circuit at the time of regeneration of the motor for driving | running | working in 2nd Embodiment. It is a figure which shows the equivalent circuit at the time of the drive after regeneration of the motor for driving | running | working in 2nd Embodiment. It is a figure which shows the equivalent circuit at the time of regeneration of the motor for cargo handling in 2nd Embodiment. It is a figure which shows the equivalent circuit at the time of the drive after regeneration of the motor for cargo handling in 2nd Embodiment.

DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals.
[First Embodiment]

  FIG. 1 is an electrical diagram showing the configuration of the battery forklift according to the first embodiment of the present invention. The battery forklift according to the present embodiment includes, as a motor drive system, a travel motor and a cargo handling motor that are controlled by an inverter while using a battery as a power source.

  A three-phase AC motor is used for the traveling motor 16 and the cargo handling motor 26. In the three-phase AC motor, coils U, V, and W are delta-connected.

  The traveling inverter 15 is a three-phase inverter having six switching elements Q1 to Q6, and each switching element Q1 to Q6 is an IGBT (insulated gate bipolar transistor). The first switching element Q1 and the second switching element Q2, the third switching element Q3 and the fourth switching element Q4, the fifth switching element Q5 and the sixth switching element Q6 are respectively connected in series. The collectors of switching elements Q1, Q3, and Q5 are each connected to the plus terminal (high potential side) of battery 17, and the emitters of switching elements Q2, Q4, and Q6 are each connected to the minus terminal (low potential side) of battery 17. Yes. Between the collectors and emitters of the switching elements Q1 to Q6, a diode D is connected in antiparallel, that is, a state in which the cathode corresponds to the collector and the anode corresponds to the emitter.

  A connection point between the emitter of the switching element Q1 and the collector of the switching element Q2 is connected to a connection point between the coil U and the coil V of the traveling motor 16. A connection point between the emitter of the switching element Q3 and a collector of the switching element Q4 is connected to a connection point between the coil V and the coil W of the traveling motor 16. A connection point between the emitter of the switching element Q5 and the collector of the switching element Q6 is connected to a connection point between the coil U and the coil W of the traveling motor 16.

  The cargo handling inverter 25 is a three-phase inverter including six switching elements Q11 to Q16, and each switching element Q11 to Q16 is an IGBT (insulated gate bipolar transistor). The first switching element Q11 and the second switching element Q12, the third switching element Q13 and the fourth switching element Q14, the fifth switching element Q15 and the sixth switching element Q16 are respectively connected in series. The collectors of switching elements Q11, Q13, and Q15 are each connected to the plus terminal of battery 17, and the emitters of switching elements Q12, Q14, and Q16 are each connected to the minus terminal of battery 17. Between the collectors and emitters of the switching elements Q11 to Q16, a diode D is connected in antiparallel, that is, in a state where the cathode corresponds to the collector and the anode corresponds to the emitter.

  A connection point between the emitter of the switching element Q11 and the collector of the switching element Q12 is connected to a connection point between the coil U and the coil V of the cargo handling motor 26. A connection point between the emitter of the switching element Q13 and a collector of the switching element Q14 is connected to a connection point between the coil V and the coil W of the cargo handling motor 26. A connection point between the emitter of the switching element Q15 and a collector of the switching element Q16 is connected to a connection point between the coil U and the coil W of the cargo handling motor 26.

  The connection point between the emitter of the switching element Q1 and the collector of the switching element Q2 and the negative terminal (that is, the ground potential side) of the battery 17, and the connection point between the emitter of the switching element Q11 and the collector of the switching element Q12 And a negative terminal of the battery 17, a capacitor C is disposed. A switch SW1 is connected between the connection point between the switching element Q1 and the switching element Q2 and the capacitor C, and between the connection point between the switching element Q11 and the switching element Q12 and the capacitor C, A switch SW2 is connected.

  Gates as control terminals of the switching elements Q1 to Q6 and Q11 to Q16 are connected to the control device 21.

  FIG. 1 also shows a battery charging circuit that uses the coils of the traveling motor and the cargo handling motor and the switching elements of the inverter as components.

  The battery charging circuit includes a coil 13 that performs non-contact power acquisition using electromagnetic coupling, and a rectifier circuit 14. The rectifier circuit 14 forms a diode bridge using four diodes D1 to D4. The diodes D1 and D2 form a series circuit, and the connection point between the diodes D1 and D2 is connected to one terminal of the coil 13. The diodes D3 and D4 form a series circuit, and the connection point between the diodes D3 and D4 is connected to the other terminal of the coil 13. The series circuit of the diodes D1 and D2 and the series circuit of the diodes D3 and D4, that is, the rectifier circuit 14, are connected to the capacitor C in parallel.

  The control device 21 is connected to a current sensor 31 that detects a current flowing through the traveling motor 16 and a current sensor 32 that detects a current flowing through the cargo handling motor 26. The control device 21 includes a CPU and a memory (not shown), and the memory stores a control program necessary for driving the traveling motor 16 and the cargo handling motor 26. The memory stores a control program necessary for controlling each of the switching elements Q1 to Q6 and Q11 to Q16 when the battery 17 is charged in a state where the coil 13 performs power acquisition without contact. The memory stores a control program necessary for controlling the switching elements Q1 to Q6 and Q11 to Q16 when the traveling motor 16 and the cargo handling motor 26 are regenerated and driven after regeneration.

  The control device 21 keeps the switch SW2 in the on state and the first and second switching of the cargo handling inverter 25 when the cargo handling motor 26 is in the non-driven state during the regeneration of the traveling motor 16. The elements Q11, Q12, the fifth and sixth switching elements Q15, Q16, and the fourth switching element Q14 are held in the off state, and the third switching element (high potential side switching element) Q13 is controlled to be turned on / off. To do. On the other hand, at the time of regeneration of the cargo handling motor 26, the switch SW1 is held in the ON state, and the first and second switching elements Q1, Q2, the fifth and sixth switching elements Q5, Q6 of the traveling inverter 15 and The fourth switching element Q4 is held in the OFF state, and the third switching element (high potential side switching element) Q13 is controlled to be turned on / off.

  When the traveling motor 16 is driven (for example, when driving after regeneration, that is, when driving immediately after regeneration), the control device 21 is in a state where the cargo handling motor 26 is not driven and the capacitor C stores electric power. If the switch SW2 is kept on, the first and second switching elements Q11 and Q12, the fifth and sixth switching elements Q15 and Q16 of the cargo handling inverter 25, and the third The switching element Q13 is maintained in the OFF state, and the fourth switching element (low potential side switching element) Q14 is controlled to be turned on / off. On the other hand, when the cargo handling motor 26 is driven after regeneration, the switch SW1 is kept on, and the first and second switching elements Q1, Q2, and the fifth and sixth switching elements Q5, Q6 of the traveling inverter 15 are maintained. And the 3rd switching element Q3 is hold | maintained in an OFF state, and the 4th switching element (low electric potential side switching element) Q14 is controlled on / off.

  Next, the operation of the motor drive system configured as described above will be described.

  In the battery forklift, the switching elements Q <b> 1 to Q <b> 6 of the traveling inverter 15 are turned on / off by a command from the control device 21, whereby the DC power of the battery 17 is converted into AC power and supplied to the traveling motor 16. The traveling motor 16 is driven. Further, the switching elements Q11 to Q16 of the cargo handling inverter 25 are turned on / off by a command from the control device 21, whereby the DC power of the battery 17 is converted into AC power and supplied to the cargo handling motor 26. The motor 26 is driven.

  Next, when charging the battery 17, the coil 13 performs non-contact power acquisition using electromagnetic coupling, rectifies by the rectifier circuit 14, and is stabilized by the capacitor C. Then, the control device 21 holds the switches SW1 and SW2 in the on state, and turns off the switching elements Q1, Q2, Q5, Q6, Q11, Q12, Q15, and Q16 of the traveling inverter 15 and the cargo handling inverter 25. The third switching elements Q3 and Q13 and the fourth switching elements Q4 and Q14 are on / off controlled. That is, by turning ON / OFF the element for one phase in the inverter, the output of the coil 13 is boosted by using the inductance (coil) of the motor, and the current is supplied to the battery 17.

  Next, when the cargo handling motor 26 is in a non-driven state at the time of regeneration of the traveling motor 16, the control device 21 holds the switch SW2 in the on state and also controls the first and second of the cargo handling inverter 25. The second switching elements Q11 and Q12, the fifth and sixth switching elements Q15 and Q16, and the fourth switching element Q14 are held in the off state, and the third switching element Q13 is controlled to be turned on / off. That is, by turning ON / OFF the high potential side element in the element for one phase in the cargo handling inverter, the regenerative energy of the traveling motor 16 is used by using the inductance (coil) of the cargo handling motor 26 in the non-driven state. Is stored in the capacitor C.

  FIG. 2 shows an equivalent circuit during regeneration of the traveling motor 16. When the third switching element Q13 is in the ON state, a current flows as shown by a broken arrow in FIG. That is, a current flows through the path of the traveling inverter 15 → the third switching element Q13 → the coil V of the cargo handling motor 26 → the switch SW2 → the capacitor C → the traveling inverter 15 and the regenerative energy is accumulated in the capacitor C. On the other hand, when the third switching element Q13 is in the OFF state, a current path from the traveling inverter 15 to the capacitor C is not formed.

  Next, when the traveling motor 16 is driven (for example, after regeneration), when the cargo handling motor 26 is in a non-driven state and electric power is stored in the capacitor C, the control device 21 The switch SW2 is kept on, and the first and second switching elements Q11 and Q12, the fifth and sixth switching elements Q15 and Q16, and the third switching element Q13 of the cargo handling inverter 25 are turned off. The state is maintained, and the fourth switching element Q14 is controlled to be turned on / off. That is, the electric power stored in the capacitor C using the inductance (coil) of the unloading motor 26 by turning on / off the low-potential side element in the element for one phase in the cargo handling inverter. Is boosted and supplied to the traveling motor.

  FIG. 3 shows an equivalent circuit when the travel motor 16 is driven after regeneration. When the fourth switching element Q14 is in the ON state, a current flows as shown by a broken arrow in FIG. That is, current flows through a path of the capacitor C → the switch SW2 → the coil V of the cargo handling motor 26 → the fourth switching element Q14 → the capacitor C, and electromagnetic energy is accumulated in the coil V. Then, when the fourth switching element Q14 is turned off, a current flows through a path indicated by a two-dot chain line arrow in FIG. That is, the current flowing through the path of the capacitor C → the switch SW2 → the coil V of the cargo handling motor 26 → the diode D of the third switching element Q13 → the driving inverter 15 → the capacitor C, and the voltage stored in the capacitor C becomes the coil V A voltage obtained by adding a voltage due to the electromagnetic energy stored in is supplied to the traveling inverter 15.

  Further, when the traveling motor 16 is in a non-driven state during regeneration of the cargo handling motor 26, the control device 21 holds the switch SW1 in the on state, and the first and second of the traveling inverter 15 The switching elements Q1, Q2, the fifth and sixth switching elements Q5, Q6, and the fourth switching element Q4 are held in the off state, and the third switching element Q3 is controlled to be turned on / off. That is, the regenerative energy of the cargo handling motor 26 is obtained by using the inductance (coil) of the driving motor 16 in the non-driven state by turning on / off the high potential side element in the element for one phase in the driving inverter. Is stored in the capacitor C.

  FIG. 4 shows an equivalent circuit during regeneration of the cargo handling motor 26. When the third switching element Q3 is in the ON state, a current flows as shown by a broken arrow in FIG. That is, a current flows through the path of the cargo handling inverter 25 → the third switching element Q3 → the coil V of the traveling motor 16 → the switch SW1 → the capacitor C → the cargo handling inverter 25, and the regenerative energy is accumulated in the capacitor C. On the other hand, when the third switching element Q3 is in the OFF state, a current path from the cargo handling inverter 25 to the capacitor C is not formed.

  Next, when the cargo handling motor 26 is driven (for example, after driving after regeneration) and the cargo handling motor 26 is in a non-driven state and electric power is stored in the capacitor C, the control device 21 The switch SW1 is kept on, and the first and second switching elements Q1 and Q2, the fifth and sixth switching elements Q5 and Q6, and the third switching element Q3 of the traveling inverter 15 are turned off. The fourth switching element Q4 is on / off controlled while maintaining the state. That is, the electric power stored in the capacitor C using the inductance (coil) of the driving motor 16 in the non-driving state by turning ON / OFF the low potential side element in the element for one phase in the driving inverter. Is boosted and supplied to the traveling motor.

  FIG. 5 shows an equivalent circuit when the cargo handling motor 26 is driven after regeneration. When the fourth switching element Q4 is in the ON state, a current flows as shown by a dashed arrow in FIG. That is, current flows through the path of the capacitor C → the switch SW1 → the coil V of the traveling motor 16 → the fourth switching element Q4 → the capacitor C, and electromagnetic energy is accumulated in the coil V. And when the 4th switching element Q4 will be in an OFF state, it will become the electric current which flows through the path | route shown by the arrow of a dashed-two dotted line in FIG. That is, the current flowing in the path of the capacitor C → the switch SW1 → the coil V of the traveling motor 16 → the diode D of the third switching element Q3 → the cargo handling inverter 25 → the capacitor C, and the voltage stored in the capacitor C is changed to the coil V A voltage obtained by adding a voltage due to the electromagnetic energy stored in is supplied to the traveling inverter 15.

  According to the motor drive system of the first embodiment, the regenerative energy of the traveling motor 16 can be stored in the capacitor C via the cargo handling inverter 25 and the switch SW2, and the regenerative energy stored in the capacitor C is This can be used when the traveling motor 16 is driven. Similarly, the regenerative energy of the cargo handling motor 26 can be stored in the capacitor C via the traveling inverter 15 and the switch SW1, and the regenerative energy stored in the capacitor C can be used when the cargo handling motor 26 is driven. it can. Thus, the regenerative energy of the motor can be used effectively.

In the first embodiment, the battery charging circuit is configured to acquire power in a contactless manner using electromagnetic coupling. In such a form, a capacitor is required to stabilize high frequency components such as the carrier frequency. In the first embodiment, the capacitor C necessary in the battery charging circuit is used for accumulating regenerative energy of the motor, and no additional parts are required for effective use of the regenerative energy.
[Second Embodiment]

  FIG. 6 is a diagram electrically showing a configuration of a battery forklift according to the second embodiment of the present invention. The motor drive system in the battery forklift according to the second embodiment includes the first and second capacitors C1 and C2 instead of the capacitor C, and is different from the motor drive system in the battery forklift according to the first embodiment. Is different.

  The first capacitor C1 and the switch SW1 are connected in series, and this series circuit includes a connection point between the emitter of the switching element Q1 and the collector of the switching element Q2, and the negative terminal of the battery 17 (that is, the ground potential side). ) Is connected between. The second capacitor C2 and the switch SW2 are connected in series, and this series circuit is connected between the connection point between the emitter of the switching element Q11 and the collector of the switching element Q12 and the negative terminal of the battery 17. It is connected.

  Further, FIG. 6 shows a battery charging circuit that uses the coils of the traveling motor and the cargo handling motor and the switching elements of the inverter as components, and is different from the first embodiment.

  This battery charging circuit includes a Scott transformer 13 as a single-phase output transformer connected to a three-phase AC power source 11 (for example, a commercial 200V AC power source) via a switch 12. A rectifier circuit 14, a traveling inverter 15 and a traveling motor 16 are connected to one single-phase output 13A of the Scott transformer 13. A rectifier circuit 24, a cargo handling inverter 25, and a cargo handling motor 26 are connected to the other single-phase output 13B of the Scott transformer 13.

  The rectifier circuit 14 is constituted by a series circuit of two diodes D1 and D2, and is connected to a terminal 18a of one single-phase output 13A of the Scott transformer 13 at a connection point between the diodes D1 and D2. The plus side of the rectifier circuit 14 is connected to the plus terminal of the battery 17, and the minus side of the rectifier circuit 14 is connected to the minus terminal of the battery 17. A terminal 18b opposite to the terminal 18a to which the rectifier circuit 14 of one single-phase output 13A of the Scott transformer 13 is connected is connected to a connection point between the emitter of the switching element Q1 and the collector of the switching element Q2 via a wiring 20. Connected.

  The rectifier circuit 24 is composed of a series circuit of two diodes D3 and D4, and is connected to the terminal 19a of the other single-phase output 13B of the Scott transformer 13 at a connection point between the diodes D3 and D4. The plus side of the rectifier circuit 24 is connected to the plus terminal of the battery 17, and the minus side of the rectifier circuit 24 is connected to the minus terminal of the battery 17. Further, the terminal 19b opposite to the terminal 19a to which the rectifier circuit 24 of the other single-phase output 13B of the Scott transformer 13 is connected is connected to the connection point between the emitter of the switching element Q11 and the collector of the switching element Q12 via the wiring 20. Connected.

  Next, the operation of the motor drive system configured as described above will be described.

  The operation of driving the traveling motor 16 and the cargo handling motor 26 with the electric power of the battery 17 is the same as in the first embodiment.

  Next, when charging the battery 17, the state is maintained in which AC power is supplied from the three-phase AC power supply 11 to the Scott transformer 13. Specifically, after the plug of the charging cable of the three-phase AC power supply 11 is connected to the power outlet provided on the forklift, the switch 12 is held in the on state. Then, the control device 21 holds the switching elements Q1, Q2, Q5, Q6, Q11, Q12, Q15, Q16 of the traveling inverter 15 and the cargo handling inverter 25 in the off state, and the third switching elements Q3, Q13 and The fourth switching elements Q4 and Q14 are turned on / off. That is, by turning ON / OFF the element for one phase in the inverter, the output of the Scott transformer 13 is boosted using the inductance (coil) of the motor, and the current is supplied to the battery 17.

  Next, when the cargo handling motor 26 is in a non-driven state at the time of regeneration of the traveling motor 16, the control device 21 holds the switch SW2 in the on state and also controls the first and second of the cargo handling inverter 25. The second switching elements Q11 and Q12, the fifth and sixth switching elements Q15 and Q16, and the fourth switching element Q14 are held in the off state, and the third switching element Q13 is controlled to be turned on / off. That is, by turning ON / OFF the high potential side element in the element for one phase in the cargo handling inverter, the regenerative energy of the traveling motor 16 is used by using the inductance (coil) of the cargo handling motor 26 in the non-driven state. Is stored in the capacitor C2.

  FIG. 7 shows an equivalent circuit during regeneration of the traveling motor 16. When the third switching element Q13 is in the ON state, a current flows as shown by a broken arrow in FIG. That is, a current flows through a path of traveling inverter 15 → third switching element Q13 → coil V of cargo handling motor 26 → switch SW2 → capacitor C2 → traveling inverter 15, and regenerative energy is accumulated in the capacitor C2. On the other hand, when the third switching element Q13 is in the OFF state, a current path from the traveling inverter 15 to the capacitor C2 is not formed.

  Next, when the traveling motor 16 is driven (for example, after regeneration), when the cargo handling motor 26 is in a non-driven state and electric power is stored in the capacitor C, the control device 21 The switch SW2 is kept on, and the first and second switching elements Q11 and Q12, the fifth and sixth switching elements Q15 and Q16, and the third switching element Q13 of the cargo handling inverter 25 are turned off. The state is maintained, and the fourth switching element Q14 is controlled to be turned on / off. That is, the electric power stored in the capacitor C2 using the inductance (coil) of the unloading motor 26 by turning on / off the low potential side element in the element for one phase in the cargo handling inverter. Is boosted and supplied to the traveling motor.

  FIG. 8 shows an equivalent circuit when the travel motor 16 is driven after regeneration. When the fourth switching element Q14 is in the ON state, a current flows as shown by a broken arrow in FIG. That is, current flows through the path of the capacitor C 2 → the switch SW 2 → the coil V of the cargo handling motor 26 → the fourth switching element Q 14 → the capacitor C 2, and electromagnetic energy is accumulated in the coil V. And when the 4th switching element Q14 will be in an OFF state, it will become the electric current which flows through the path | route shown by the arrow of a dashed-two dotted line in FIG. That is, the current flows through the path of the capacitor C2, the switch SW2, the coil V of the cargo handling motor 26, the diode D of the third switching element Q13, the inverter 15 for traveling, and the capacitor C2, and the voltage stored in the capacitor C2 is changed to the coil V. A voltage obtained by adding a voltage due to the electromagnetic energy stored in is supplied to the traveling inverter 15.

  Further, when the traveling motor 16 is in a non-driven state during regeneration of the cargo handling motor 26, the control device 21 holds the switch SW1 in the on state, and the first and second of the traveling inverter 15 The switching elements Q1, Q2, the fifth and sixth switching elements Q5, Q6, and the fourth switching element Q4 are held in the off state, and the third switching element Q3 is controlled to be turned on / off. That is, the regenerative energy of the cargo handling motor 26 is obtained by using the inductance (coil) of the driving motor 16 in the non-driven state by turning on / off the high potential side element in the element for one phase in the driving inverter. Is stored in the capacitor C1.

  FIG. 9 shows an equivalent circuit during regeneration of the cargo handling motor 26. When the third switching element Q3 is in the ON state, a current flows as shown by a broken arrow in FIG. That is, current flows through the path of the cargo handling inverter 25 → the third switching element Q3 → the coil V of the traveling motor 16 → the switch SW1 → the capacitor C1 → the cargo handling inverter 25, and regenerative energy is accumulated in the capacitor C1. On the other hand, when the third switching element Q3 is in the OFF state, a current path from the cargo handling inverter 25 to the capacitor C1 is not formed.

  Next, when the cargo handling motor 26 is driven (for example, after driving after regeneration) and the cargo handling motor 26 is in a non-driven state and electric power is stored in the capacitor C, the control device 21 The switch SW1 is kept on, and the first and second switching elements Q1 and Q2, the fifth and sixth switching elements Q5 and Q6, and the third switching element Q3 of the traveling inverter 15 are turned off. The fourth switching element Q4 is on / off controlled while maintaining the state. That is, the electric power stored in the capacitor C1 using the inductance (coil) of the driving motor 16 in the non-driving state by turning ON / OFF the low potential side element in the element for one phase in the driving inverter. Is boosted and supplied to the traveling motor.

  FIG. 10 shows an equivalent circuit when the cargo handling motor 26 is driven after regeneration. When the fourth switching element Q4 is in the ON state, a current flows as shown by a broken arrow in FIG. That is, current flows through the path of the capacitor C 1 → the switch SW 1 → the coil V of the traveling motor 16 → the fourth switching element Q 4 → the capacitor C 1, and electromagnetic energy is accumulated in the coil V. And when the 4th switching element Q4 will be in an OFF state, it will become the electric current which flows through the path | route shown by the arrow of a dashed-two dotted line in FIG. That is, the current flows through the path of the capacitor C1, the switch SW1, the coil V of the traveling motor 16, the diode D of the third switching element Q3, the cargo handling inverter 25, and the capacitor C1, and the voltage stored in the capacitor C1 is changed to the coil V. A voltage obtained by adding a voltage due to the electromagnetic energy stored in is supplied to the traveling inverter 15.

  In the motor drive system of the second embodiment, the same advantages as those of the motor drive system of the first embodiment can be obtained.

  The present invention is not limited to the above-described embodiment, and various modifications can be made.

  At the time of regeneration, the high potential side switching element Q3 in the set of switching elements of the traveling inverter 15 and the high potential side switching element Q13 in the set of switching elements of the cargo handling inverter 25 are not controlled to be turned on / off. The elements Q3 and Q13 and the switching elements Q5 and Q15 may be alternately turned on / off. In this case, since the state where the current flows through the switching elements Q3 and Q13 and is regenerated and the state where the current flows through the switching elements Q5 and Q15 are alternately repeated, the heat generation of the switching elements can be dispersed, Since overheating of the inverter can be reduced, the charging current that can be supplied to the inverter can be increased.

  Similarly, when driving after regeneration, the low potential side switching element Q4 in the set of switching elements of the traveling inverter 15 and the low potential side switching element Q14 in the set of switching elements of the cargo handling inverter 25 are on / off controlled. Alternatively, the switching elements Q4 and Q14 and the switching elements Q6 and Q16 may be alternately turned on / off, respectively. In this case, since the state driven by the current flowing through the switching elements Q4 and Q14 and the state driven by the current flowing through the switching elements Q6 and Q16 are alternately repeated, the heat generation of the switching element can be dispersed, Since overheating of the inverter can be reduced, the charging current that can be supplied to the inverter can be increased.

  During regeneration, the set of switching elements Q1, Q2 of the traveling inverter 15 and the set of switching elements Q11, Q12 of the cargo handling inverter 25 are held in the off state, and the high potential side switching elements Q3, Q5 in the two sets of switching elements , Q13, Q15 may be on / off controlled. In this case, since current flows through the two switching elements while charging, the heat generated by the switching elements can be dispersed and the overheating of the inverter can be reduced, so that the charging current that can be supplied to the inverter can be increased.

  Similarly, a set of switching elements Q1 and Q2 of the traveling inverter 15 and a set of switching elements Q11 and Q12 of the cargo handling inverter 25 are held in an off state during driving after regeneration, and the low potential side in the two sets of switching elements The switching elements Q4, Q6, Q14, and Q16 may be on / off controlled. In this case, since current flows through the two switching elements while charging, the heat generated by the switching elements can be dispersed and the overheating of the inverter can be reduced, so that the charging current that can be supplied to the inverter can be increased.

  The vehicle is not limited to an electric vehicle that uses a battery as a power source, but may be applied to a hybrid vehicle that includes a travel motor that uses a battery as a power source in addition to a gasoline engine or a diesel engine.

  You may apply to the motor drive system provided with three sets of motors and inverters. For example, in the second embodiment, a single-phase three-output transformer is used as a three-phase transformer, and an inverter, a rectifier circuit, and a battery are connected to each single-phase output.

  The motor drive system only needs to have a three-phase motor that is driven and controlled by a three-phase inverter using a battery as a power source. The motor drive system may be used.

  A set of switching elements constituting one phase of a three-phase inverter connected via a wiring 20 to a terminal on the opposite side to the terminal to which the rectifier circuit is connected among the two terminals of the single-phase output of the transformer The connection point is not limited to the connection point of the switching elements Q1, Q2 for U phase and the switching elements Q11, Q12. For example, it may be a connection point between switching elements Q3 and Q4 for V phase and switching elements Q13 and Q14, or a connection point between switching elements Q5 and Q6 for W phase and switching elements Q15 and Q16.

  The connection of the coils U, V, and W of the traveling motor 16 and the cargo handling motor 26 is not limited to the delta connection, and may be a star connection.

  A power bipolar transistor or MOSFET may be used in place of the IGBT as a switching element used in the traveling inverter 15 and the cargo handling inverter 25. When MOSEFT is used, the MOSFET has a parasitic diode. Therefore, unlike the case of using an IGBT or bipolar transistor that does not have a parasitic diode as a switching element, it is not necessary to connect the diode D and the configuration is simplified. .

  The diodes constituting the rectifier circuits 14 and 24 are not limited to two, but three or more diodes may be connected in series.

  The charging method is not limited to the CC-CV-CC method (constant current-constant voltage-constant current method), but other charging methods such as CC-CV method (constant current-constant voltage method) and multi-stage constant current method. There may be.

  The battery is not limited to a liquid lead battery, and may be, for example, a sealed lead battery, a lithium ion battery, or a nickel metal hydride battery.

  DESCRIPTION OF SYMBOLS 13 ... Coil, 14 ... Rectifier circuit, 15 ... Traveling inverter (1st 3 phase inverter), 16 ... Traveling motor (1st 3 phase motor), 17 ... Battery, 21 ... Control apparatus, 25 ... For cargo handling Inverter (second three-phase inverter), 26 ... Motor for cargo handling (second three-phase inverter), 31, 32 ... Current sensor, C, C1, C2 ... Capacitor, D, D1, D2, D3, D4 ... Diode , Q1 to Q6, Q11 to Q16, a switching element, SW1, a first switch, SW2, a second switch.

Claims (2)

A motor drive system comprising first and second three-phase motors, each of which is driven and controlled by a first and second three-phase inverter using a battery as a power source,
One of the first three-phase inverters and one of the second three-phase inverters are connected between a connection point of a set of switching elements constituting one phase and the ground potential side. A capacitor disposed between the connection point of the pair of switching elements and the ground potential side;
A first switch connected between a connection point of the set of switching elements of the first three-phase inverter and the capacitor;
A second switch connected between a connection point of the set of switching elements of the second three-phase inverter and the capacitor;
A control device that performs on / off control of switching elements in the first and second three-phase inverters;
With
The control device includes:
During regeneration of the first three-phase motor, the second switch is held in an on state, the one set of switching elements of the second three-phase inverter is held in an off state, and the other two sets of switching On-off control of the high potential side switching element in at least one set of switching elements of the elements,
During regeneration of the second three-phase motor, the first switch is held in an on state, the one set of switching elements of the first three-phase inverter is held in an off state, and the other two sets of switching ON / OFF control of a high potential side switching element in at least one set of switching elements among the elements,
Motor drive system. The control device includes:
When the first three-phase motor is driven after regeneration, the second switch is held in an on state, the one set of switching elements of the second three-phase inverter is held in an off state, and the other two sets On-off control of the low potential side switching element in at least one set of the switching elements of
When the second three-phase motor is driven after regeneration, the first switch is held in an on state, the set of switching elements of the first three-phase inverter is held in an off state, and the other two sets On / off control of a low potential side switching element in at least one set of switching elements of
The motor drive system according to claim 1.

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