JP2011030355A - Electric drive unit and battery pack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric drive unit which increases a regeneration brake amount at low speed. <P>SOLUTION: In the electric drive unit which drives a motor M by using an inverter I with a secondary battery E as a power supply, the electric drive unit comprises a first switching element FET1 arranged between the inverter I and a positive electrode of the secondary battery E, a transformer T connected to wiring for connecting the first switching element FET1 and the inverter I at one ends of a primary winding n1 and a secondary winding n2, a second switching element FET2 connected between the other end of the primary winding n1 of the transformer T and a negative electrode of the secondary battery E, a diode D1 connected to a wiring for connecting the first switching element FET1 and the secondary battery E from the other end of the secondary winding n2 of the transformer T so that a current in a direction for charging the secondary battery flows, and a control circuit 22 which controls the first switching element FET1 and the second switching element FET2 so that a regeneration voltage from the inverter I is boosted. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electric drive device and a battery pack that drive a vehicle by a motor that uses a battery as a power source.

  2. Description of the Related Art Conventionally, there are known electric motorcycles and electric assist bicycles that use a secondary battery as a power source to drive a vehicle or assist driving force by a motor. In such electric motorcycles and electric assist bicycles, energy is effectively utilized by performing regenerative braking. At the time of this regenerative braking, the regenerative voltage from the motor is proportional to the number of revolutions of the motor. Therefore, at the time of regenerative braking at low speed, the regenerative voltage is lower than the battery voltage and cannot be stored in the secondary battery.

  In order to solve such a problem, Patent Document 1 discloses a technology in which a boost chopper circuit is configured by a switching element of an inverter and a winding of a motor, and a battery is charged by boosting a regenerative voltage from the motor. Yes.

  More specifically, Patent Document 1 discloses a motor control device that can control regenerative braking of an electric motor so as to obtain higher regenerative efficiency than before. This motor control device detects the rotational speed of an electric motor, an inverter that supplies electric power generated from the electric motor to a battery that is a power source of the electric motor, a control circuit that performs PWM (Pulse Wide Modulation) control on the inverter, and And a rotational speed / rotational position detection circuit. The control circuit limits the PWM duty to a value at a point where the regenerative power supplied to the battery reaches a peak or a value close to or below the PWM duty based on the output value of the rotation speed / rotation position detection circuit.

  In the regenerative braking by the step-up chopper circuit, when the rotation speed of the motor decreases and the step-up ratio increases, the charging time for the battery decreases, and the charging current and the motor current for the battery decrease (see FIG. (Refer FIG. 16 of patent document 1). Since the braking torque of the motor is proportional to the motor current, the braking torque becomes smaller as the motor is decelerated.

JP 2004-173444 A

SANYO TECHNICAL REVIEW Vol.35 No.1 pp106-123

  As described above, the regenerative braking by the boost chopper circuit has a problem that the regenerative braking force at low speed is small.

  The subject of this invention is providing the electric drive device and battery pack which can increase the amount of regenerative braking at low speed.

  In order to solve the above problems, an electric drive device according to the present invention is an electric drive device that drives a motor by an inverter using a secondary battery as a power source, and is provided between an inverter and one terminal of the secondary battery. One switching element, a transformer having one end of each of the primary winding and the secondary winding connected to the wiring connecting the first switching element and the inverter, the other end of the primary winding of the transformer, and the other end of the secondary battery. A current in the direction of charging the secondary battery flows from the second switching element connected between the terminals and the wiring connecting the first switching element and the secondary battery from the other end of the secondary winding of the transformer. It is characterized by comprising a connected diode and a control circuit for controlling the first switching element and the second switching element so as to boost the regenerative voltage from the inverter.

  The battery pack of the present invention includes a secondary battery, a first switching element provided between a connection terminal for connection to the inverter and one terminal of the secondary battery, a primary winding and a secondary winding. A transformer having one end of each line connected to a wiring connecting the first switching element and the connection terminal, and a second switching connected between the other end of the primary winding of the transformer and the other terminal of the secondary battery. A regenerative voltage from the inverter, and a diode connected so that a current in the direction of charging the secondary battery flows from the other end of the secondary winding of the transformer to the wiring connecting the first switching element and the secondary battery And a control circuit for controlling the first switching element and the second switching element so as to boost the voltage.

  According to the present invention, when the regenerative current is equal to or higher than a predetermined current, the second switching element, the transformer, the first switching element FET1, and the diode are connected to each other by turning on / off the second switching element. Therefore, it is possible to provide an electric drive device and a battery pack that can increase the amount of regenerative braking at a low speed.

It is a circuit diagram which shows the structure of the electric drive device which concerns on Example 1 of this invention. It is a figure for demonstrating operation | movement of the electric drive device which concerns on Example 1 of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a circuit diagram illustrating a configuration of an electric drive device according to a first embodiment of the present invention. In the following, a case where the electric drive device is applied to an electric assist bicycle will be described as an example.

  The electric drive device includes a drive unit 1 that is incorporated in a main body of the electric assist bicycle and drives the electric assist bicycle, and a battery pack 2 that is detachably attached to the electric assist bicycle and supplies power to the drive unit 1. And. The drive unit 1 and the battery pack 2 are connected by connection terminals 3a and 3b.

  The drive unit 1 includes an inverter I, a motor M, a torque sensor 11, a brake lever 12, a detection circuit 13, and a drive unit control circuit 14.

  The torque sensor 11 detects the torque generated when a person steps on the pedal, and sends it to the drive unit control circuit 14 as a torque signal. The brake lever 12 is used to brake the electrically assisted bicycle, and a brake signal indicating that the brake lever has been operated is sent to the drive unit control circuit 14. The detection circuit 13 detects the rotation speed and rotation position of the motor M, and sends it to the drive unit control circuit 14 as a detection signal.

  The drive unit control circuit 14 generates a control signal based on the torque signal from the torque sensor 11, the brake signal from the brake lever 12, and the detection signal from the detection circuit 13, and a plurality of switching elements Q <b> 1 to Q <b> 6 constituting the inverter I. Send to. The drive unit control circuit 14 transmits and receives signals necessary for control to and from the control circuit 22 of the battery pack 2.

  The inverter I operates in response to a control signal from the drive unit control circuit 14. That is, based on the torque signal from the torque sensor 11, the drive unit control circuit 14 determines whether or not the assist travel mode assists the travel of the electrically assisted bicycle, and if it is the assist travel mode, causes the inverter operation to be performed. Control signal is generated and sent to the inverter I. As a result, the inverter I converts the DC power supplied from the battery pack 2 via the connection terminals 3 a and 3 b into, for example, three-phase AC power and sends it to the motor M. The motor M is rotationally driven by AC power from the inverter I.

  On the other hand, based on the brake signal from the brake lever 12, the drive unit control circuit 14 determines whether or not it is a regenerative travel mode in which regenerative braking is performed, and if it is in the regenerative travel mode, a control for performing a boost chopper operation. A signal is generated and sent to inverter I. The motor M operates as a generator in the regenerative travel mode.

  In this case, the control signal from the drive unit control circuit 14 forms a boost chopper circuit by the switching element of the inverter I and the winding of the motor M, and the regenerative voltage from the motor M is boosted to connect the connection terminals 3a and 3b. Via the battery pack 2 is supplied.

  The battery pack 2 includes a secondary battery E, a first switching element FET1, a second switching element FET2, a first diode D1, a second diode D2, a transformer T, a current measuring instrument 21, and a control circuit 22. The first switching element FET1 and the second switching element FET2 are configured by field effect transistors (FETs). The first diode D1 corresponds to the “diode” of the present invention.

  The positive electrode (one terminal) of the secondary battery E is one terminal of an inverter I that drives the motor M via the first switching element FET1 for protecting the secondary battery E from overdischarge and the connection terminal 3a. It is connected to the.

  The negative electrode (the other terminal) of the secondary battery E is connected to the other terminal of the inverter I through the current measuring device 21 and the connection terminal 3b. One end of the primary winding n1 of the transformer T and one end of the secondary winding n2 are connected to the wiring connecting the first switching element FET1 and the connection terminal 3a to which the inverter I is connected. The primary winding n1 and the secondary winding n2 of the transformer T are connected to the wiring so that the polarities are reversed.

  The other end of the primary winding n1 of the transformer T is connected to the negative electrode of the secondary battery E via the first switching element FET2. The other end of the secondary winding n2 of the transformer T is connected to the positive electrode of the secondary battery E via the first diode D1. Further, one end of the winding n3 for collecting the exciting current of the transformer T in the secondary battery E is connected to the positive electrode of the secondary battery E through the second diode D2, and the other end is the negative electrode of the secondary battery E. It is connected to the.

  The voltage of the positive electrode of the secondary battery E, the current measured by the current measuring instrument 21, and the regenerative voltage appearing at the connection terminal 3 a are sent to the control circuit 22. The control circuit 22 generates a control signal based on the input voltage of the positive electrode of the secondary battery E, the current measured by the current measuring device 21 and the regenerative voltage appearing at the connection terminal 3a, and generates the first switching element FET1 and the second switching element FET1. This is sent to the switching element FET2. The control circuit 22 transmits and receives signals necessary for control to and from the drive unit control circuit 14 of the drive unit 1.

  In the electric drive device according to the first embodiment configured as described above, when the motor M is driven, that is, in the assist travel mode, as shown in “during motor drive” in FIG. 22 turns on the first switching element FET1 and turns off the second switching element FET2. As a result, DC power is supplied from the secondary battery E to the inverter I, and the inverter I performs an inverter operation, so that the motor M can be driven by the inverter I as in the prior art.

  Next, regenerative braking performed in the regenerative travel mode will be described. Since the regenerative braking force changes according to the regenerative current, a regenerative current Ir for obtaining a necessary regenerative braking amount is calculated. When the regenerative current Ir is small, regenerative braking is performed by causing the inverter I to operate as a boost chopper as in the prior art, and the secondary battery E is charged via the parasitic diode of the first switching element FET1.

  However, when the regenerative current Ir is large, braking is difficult by regenerative braking by the boost chopper operation of the inverter I. Therefore, the first switching element FET1 is turned off and the second switching element FET2 is turned on / off. A flyback booster circuit including the first switching element FET1, the transformer T, the second switching element FET2, the first diode D1, and the second diode D2 is caused to function.

  Therefore, when the regenerative current Ir is smaller than the predetermined switching current Is, the inverter I performs a boost chopper operation. When the regenerative current Ir is larger than the predetermined switching current Is, the fly Energy is regenerated in the secondary battery E by causing the buck type booster circuit to perform a boosting operation.

  The switching current Is varies depending on the ratio between the motor voltage generated by the motor M and the battery voltage. Therefore, the switching current Is is determined as a function of the ratio between the motor voltage and the battery voltage. Since the fluctuation of the battery voltage is small, the switching current Is can be determined as a function of the regenerative voltage. Further, since the motor voltage varies depending on the rotation speed of the motor M, the motor voltage may be determined as a function of the rotation speed of the motor M.

  When Ir ≧ Is, the control circuit 22 causes the second switching element FET2, the transformer T, the first switching element FET1, and the first diode by turning on / off the second switching element FET2 in accordance with the regenerative braking amount. D1 and the second diode D2 are caused to function as a forward type booster circuit.

At this time, the boost ratio from the regenerative voltage to the battery voltage is

It is represented by

  Here, n1 is the primary winding number of the transformer T, n2 is the secondary winding number, Ton is the ON time of the second switching element FET2, and Toff is the OFF time of the second switching element FET2.

  When the second switching element FET2 is turned on and the first switching element FET1 is turned off, a current flows through the path of one end of the inverter I → the primary winding n1 → the second switching element FET2 → the other end of the inverter I, Current flows through the path of one end of the inverter I → one end of the primary winding n1 → one end of the secondary winding n2 → secondary winding n2 → first diode D1 → secondary battery E → the other end of the inverter I. The next battery E is charged.

  That is, a voltage obtained by adding the boosted voltage of the secondary winding n2 to the regenerative voltage of the motor M is applied to the secondary battery E via the first diode D1, and the motor current flows to the second switching element FET2 and the second The secondary battery E is charged through the 1 diode D1.

  Further, when the second switching element FET2 is turned off and the first switching element FET1 is turned off, a current is passed through the path of one end of the winding n3 → the second diode D2 → the secondary battery E → the other end of the winding n3. Then, the secondary battery E is charged.

  Thus, according to the electric drive device according to the first embodiment, the Ton time for charging the secondary battery E when the rotation speed of the motor M decreases and the step-up ratio from the regenerative voltage to the secondary battery voltage increases. Therefore, the motor current is not reduced, and the motor current can be effectively used as the charging current of the secondary battery E.

  Note that the braking torque of the motor M is approximately proportional to the motor current and does not vary greatly with the rotational speed. Therefore, when the braking amount is constant, the motor current becomes substantially constant, and the step-up ratio increases due to deceleration. The charging current of the secondary battery E becomes small. This is because the kinetic energy is proportional to the square of the speed, so the regenerative energy is proportional to the speed when decelerating at a constant acceleration, and the regenerative current decreases according to the speed because the secondary battery voltage is substantially constant. caused by.

  In the electric drive device according to the first embodiment, the transformer T, the second switching element FET2, and the second diode D2 are in a state where the forward boost circuit is not functioning (the second switching element FET2 is kept off). In addition, no current flows through the first diode D1, and the DC power of the secondary battery E is supplied to the inverter I via the first switching element FET1, or the secondary battery E is generated by regenerative energy from the inverter I. Is configured to be charged.

  Note that the control torque of the motor M is approximately proportional to the motor current and does not vary greatly with the rotational speed. Therefore, when the braking amount is constant, the motor current is substantially constant, and the boost ratio is increased by deceleration. The charging current of the secondary battery E becomes small. This is because the kinetic energy is proportional to the square of the acceleration, so the regenerative energy is proportional to the speed when decelerating at a constant acceleration, and the regenerative current decreases according to the speed because the secondary battery voltage is substantially constant. Due to that.

  In braking on a downhill of an electrically assisted bicycle, the amount of braking is small because regenerative braking may be performed so that the speed does not increase. Further, since the motor speed is high, that is, the motor voltage is high, the step-up ratio from the motor voltage to the battery voltage is small. Therefore, generally, Ir <Is is satisfied, and the voltage can be boosted by the boosting chopper by the inverter I.

  On the other hand, when stopping an electrically assisted bicycle, a large braking amount is required, and Ir ≧ Is, and it is necessary to perform boosting by a forward boosting circuit, but generally the braking time when stopping is several seconds. Therefore, the operation time of the forward type booster circuit is short.

  Therefore, energization of the second switching element FET2, the transformer T, the first diode D1, and the second diode D2 is limited to regenerative braking at a low speed. Since such a state is a short time in normal use, the second switching element FET2, the transformer T, the first diode D1, and the second diode D2 can adopt elements rated for a short time. Therefore, as the first diode D1, one having a steady current capacity smaller than the steady current capacity of the first switching element FET1 can be used, so that an inexpensive battery pack 2 can be realized.

  Further, since the first switching element FET1 that constitutes a part of the forward type booster circuit functions as an overdischarge protection switch, a large-capacity diode element can be reduced.

  In the electric drive device according to the first embodiment, since the first switching element FET1, the transformer T, and the second switching element FET2 are built in the battery pack 2, in order to charge the secondary battery E, the battery pack 2 and the inverter I are disconnected, even if the connection terminals 3a and 3b of the battery pack 2 are accidentally short-circuited, the first switching element FET1 can cut off the short-circuit current.

  As described above, when the second switching element FET2 is built in the battery pack 2, in general, the control circuit 22 for controlling the second switching element FET2 is also built in the battery pack 2. At this time, since the amount of regenerative current is changed by the control of the second switching element FET2 and the braking amount of the motor M is changed, a braking signal indicating the braking amount is sent to the control circuit 22.

  The control circuit 22 performs control so that the input current value corresponds to the braking amount indicated by the received braking signal. This input current value is measured by a current measuring instrument 21 provided at a position where the current input to and output from the battery pack 2 can be measured.

  As described above, according to the electric drive device according to the first embodiment of the present invention, since the above-described control method is employed, regenerative braking corresponding to the required braking amount can be performed.

  The present invention can be used for an electric motorcycle or an electric assist bicycle driven by a motor using a battery as a power source.

DESCRIPTION OF SYMBOLS 1 ... Drive part, 2 ... Battery pack, 3a, 3b ... Connection terminal, 11 ... Torque sensor, 12 ... Brake lever, 13 ... Detection circuit, 14 ... Drive part control circuit, M ... Motor, I ... Inverter, 21 ... Current Measuring instrument, 22 ... control circuit, T ... transformer, n1 ... primary winding, n2 ... secondary winding, n3 ... winding, FET1 ... first switching element, FET2 ... second switching element, D1 ... first diode, D2 is a second diode, E is a secondary battery.

Claims (5)

In an electric drive device that drives a motor by an inverter using a secondary battery as a power source,
A first switching element provided between the inverter and one terminal of the secondary battery;
A transformer in which one end of each of the primary winding and the secondary winding is connected to a wiring connecting the first switching element and the inverter;
A second switching element connected between the other end of the primary winding of the transformer and the other terminal of the secondary battery;
A diode connected so that a current in a direction of charging the secondary battery flows from the other end of the secondary winding of the transformer to a wiring connecting the first switching element and the secondary battery;
A control circuit for controlling the first switching element and the second switching element to boost the regenerative voltage from the inverter;
An electric drive device comprising:   The electric drive device according to claim 1, wherein the control circuit turns off the first switching element during regenerative braking of the motor.   The electric drive device according to claim 1, wherein the control circuit performs on / off control of the second switching element according to a regenerative braking amount.   4. The electric drive device according to claim 1, wherein a steady current capacity of the diode is smaller than a steady current capacity of the first switching element. 5. A secondary battery,
A first switching element provided between a connection terminal for connecting to an inverter and one terminal of the secondary battery;
A transformer in which one end of each of the primary winding and the secondary winding is connected to a wiring connecting the first switching element and the connection terminal;
A second switching element connected between the other end of the primary winding of the transformer and the other terminal of the secondary battery;
A diode connected so that a current in a direction of charging the secondary battery flows from the other end of the secondary winding of the transformer to a wiring connecting the first switching element and the secondary battery;
A control circuit for controlling the first switching element and the second switching element to boost the regenerative voltage from the inverter;
A battery pack comprising:

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