JP2003319679A - Motor controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a booster circuit from being damaged if a high voltage is generated. <P>SOLUTION: The booster circuit U is provided on a current supply circuit provided between a motor drive and a battery. The booster circuit U includes a booster coil L, a transistor Q1, a transistor Q2, and a capacitor C2, and a Zener diode Z is connected in parallel with the transistor Q2. If a reverse voltage, which is higher than a predetermined voltage, is applied to the Zener diode Z on a drain side of the transistor Q2, this booster circuit passes the current from the Zener diode through the battery side. Another booster circuit connects only the Zener diode to the output of the booster coil L instead of the transistor Q2, so that the current is passed from the Zener diode through the battery side when the reverse voltage, which is higher than a predetermined voltage, is applied to the Zener diode Z on a cathode side of the Zener diode. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor control device for increasing the output voltage of a DC power supply by controlling a booster circuit in an electric power steering device for applying an assisting force by a motor to a steering system of an automobile or the like. Is.

[0002]

2. Description of the Related Art Conventionally, for example, the following are known as a motor control device for an electric power steering device.

A booster circuit is provided in a current supply circuit provided between a battery and a motor drive device that drives an electric motor based on a motor control signal output from a controller. The booster circuit includes a boosting coil connected to the output side of the battery, a first transistor connected to the output side of the boosting coil, and a second transistor connected to the output side of the boosting coil. , And a capacitor connected to the drain side of the second transistor. Based on the duty ratio drive signal output from the controller, the first transistor and the second transistor are alternately turned on and off to generate a high voltage on the drain side of the second transistor and increase the output voltage of the DC power supply. It is designed to let you.

Further, there is also known a controller in which a conventionally known bootstrap circuit is connected between the output side of the battery and the drain side of the first transistor. The bootstrap circuit includes a diode and a bootstrap capacitor, the capacitor is connected to the drain side of the first transistor, the anode side of the diode is connected to the output side of the battery, and the cathode side of the diode is bootstrapped. It is connected to a capacitor.

There is also known a controller in which a conventionally known charge pump is connected to the gate side of the second transistor. In this charge pump controller, the second transistor can be applied by the charge pump to be turned on / off even when the first transistor is all off during regeneration.

[0006]

In the bootstrap type controller, the second transistor cannot be turned on unless the first transistor is turned on because the bootstrap capacitor is not charged. Therefore, the regenerative current cannot be sufficiently absorbed in the battery, and the booster circuit may be damaged by the high voltage.

Further, as described above, in the control system in which the first transistor and the second transistor are alternately turned on and off based on the duty ratio drive signal, the PWM control output module is required separately from the motor drive device, and the control is performed. There is no choice but to raise the specifications to high specifications, which increases costs.

On the other hand, in the charge pump type controller,
Since it requires a circuit to drive the charge pump separately,
The control method becomes complicated. The main object of the present invention is to prevent the booster circuit from being damaged when a high voltage is generated in various booster type motor control devices used in various devices such as an electric power steering device.

[0009]

Means for Solving the Problems and Effects of the Invention Reference numerals of drawings (first embodiment shown in FIGS. 1-2 and 3 and second embodiment shown in FIGS. 1-2 and 4) of the following embodiments are designated by the same reference numerals. The present invention will be described by reference.

Invention of Claim 1 (corresponding to the first embodiment) A motor control device according to the present invention is configured as follows. Motor drive means (motor drive device 21) for driving the motor (electric motor 6) based on the motor control signal output from the control signal generation means (control device 17)
The booster circuit (U) is provided in the current supply circuit (25) provided between the DC power supply (battery 24) and the DC power supply. The booster circuit (U) is controlled based on the booster circuit control signal (duty ratio drive signals S1, S2) output from the booster circuit control means (control device 17) to increase the output voltage of the DC power supply (24). The booster circuit (U) of the current supply circuit (25) is connected to the booster coil (L) connected to the output side of the DC power supply (24) and the output side of the booster coil (L). A first switching element (transistor Q1) that is turned on / off based on the booster circuit control signal (S1) is connected to the output side of the booster coil (L) to be turned on / off based on the booster circuit control signal (S2). It has a second switching element (transistor Q2) and a capacitor (C2) connected to the output side of this second switching element (Q2).

A Zener diode (Z) is connected in parallel to the second switching element (Q2) between the input side and the output side of the second switching element (Q2). When a reverse voltage of a predetermined value or more is applied to the Zener diode (Z) on the output side of the second switching element (Q2), a current is supplied from the output side of the second switching element (Q2) to the Zener diode (Z ) To the input side of the second switching element (Q2). Therefore, the current on the output side of the second switching element (Q2) is absorbed by the DC power supply (24).

According to the present invention, the second switching element (Q
It is possible to prevent the booster circuit (U) from being damaged when a high voltage is generated on the output side of 2). * Invention of Claim 2 (corresponding to the second embodiment) A motor control device according to the present invention is configured as follows.

Motor drive means (motor drive device 21) for driving the motor (electric motor 6) based on the motor control signal output from the control signal generation means (control device 17)
The booster circuit (U) is provided in the current supply circuit (25) provided between the DC power supply (battery 24) and the DC power supply. The booster circuit (U) is controlled based on the booster circuit control signal (duty ratio drive signal S1) output from the booster circuit control means (control device 17) to increase the output voltage of the DC power supply (24). The booster circuit (U) of the current supply circuit (25) is
A step-up coil (L) connected to the output side of the DC power source (24), and a switching element connected to the output side of the step-up coil (L) and turned on / off based on the step-up circuit control signal (S1). (Transistor Q1), a backflow prevention element (Z) connected to the output side of the boosting coil (L), and a capacitor (C2) connected to the cathode side of the backflow prevention element (Z). I have it.

A Zener diode (Z) is used as the backflow prevention element. This Zener diode (Z)
When a reverse voltage of a predetermined value or more is applied to the Zener diode (Z) on the cathode side of the, the current is transferred from the cathode side of the Zener diode (Z) to the anode side of the Zener diode (Z) through the Zener diode (Z). I let it flow. Therefore, the current on the cathode side of the Zener diode (Z) is absorbed by the DC power supply (24).

In the present invention, the Zener diode (Z)
It is possible to prevent the booster circuit (U) from being damaged when a high voltage is generated on the cathode side of the. * Invention of Claim 3 (corresponding to the first and second embodiments) This invention is configured as follows on the premise of the invention of Claim 1 or Claim 2.

The motor (6) is mounted on the electric power steering device (M). The motor control signal is determined based on at least the steering torque (τ) of the steering wheel (1). In the present invention, claim 1
Alternatively, the effect of the invention of claim 2 can be exerted in the electric power steering device (M).

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION First Embodiment First, a motor control device according to a first embodiment of the present invention will be described with reference to FIGS.
And FIG. 3 will be described.

This motor control device is applied to the electric power steering device M shown in FIG. This electric power steering device M will be outlined. The steering shaft 2 connected to the steering wheel 1 is provided with a torsion bar 3. A torque sensor 4 is attached to the torsion bar 3. When the steering shaft 2 rotates and a force is applied to the torsion bar 3, the torsion bar 3 is twisted according to the force, and the torque sensor 4 detects a steering torque τ applied to the steering wheel 1 due to the twist. A speed reducer 5 is attached to the steering shaft 2. A gear 7 interlocking with the electric motor 6 is meshed with the speed reducer 5. The electric motor 6 is a brushless motor composed of a three-phase synchronous permanent magnet motor. A pinion 10 is attached to a pinion shaft 8 that interlocks with the speed reducer 5, and the pinion 10 is meshed with a rack 11, and the pinion 10 and the rack 11 constitute a pinion rack mechanism 9. Tie rods 12 are attached to both ends of the rack 11, and both tie rods 12 are attached.
A knuckle 13 is rotatably connected to the tip of the. A front wheel 14 is fixed to both knuckles 13. Both knuckles 13 are rotatably connected to a cross member 15. The rotation of the electric motor 6 is reduced by the speed reducer 5, transmitted to the pinion shaft 8, and further transmitted to the rack 11 of the pinion rack mechanism 9. By the movement of the rack 11, the directions of the front wheels 14 are changed via the tie rods 12 and the knuckles 13, and the traveling direction of the vehicle is changed. A vehicle speed sensor 16 is attached to both front wheels 14.

The torque sensor 4 outputs a voltage corresponding to the steering torque τ of the steering wheel 1. The vehicle speed sensor 16 outputs the vehicle speed V when the voltage is output as a pulse signal having a cycle corresponding to the rotational speeds of the front wheels 14. The control device 17 (control signal generating means) of the electric power steering device M includes a central processing unit (CPU) 18,
Read only memory (ROM) 19 and read and write only memory (RAM) 20 for temporarily storing data
It has and. A control program for causing the CPU 18 to perform arithmetic processing is stored in the ROM 19. The RAM 20 temporarily stores the calculation processing result and the like when the CPU 18 performs the calculation processing. This ROM1
9 stores a basic assist map (not shown). This basic assist map is for obtaining the basic assist current corresponding to the steering torque τ (turning torque T) and corresponding to the vehicle speed V. This basic assist map stores the basic assist current for the steering torque τ.

The motor drive device 21 (motor drive means) shown in FIG. 1 has FETs 22U and 23U as shown in FIG.
, A series circuit of FETs 22V and 23V, and F
It is configured by connecting a series circuit of ET22W, 23W in parallel. In each of the series circuits, a battery 24 (DC power source) mounted on the vehicle and the motor drive device 2 are installed.
1 and the booster circuit U of the current supply circuit 25 provided between
The output voltage boosted higher than the voltage of the battery 24 is applied as described later (described later). FET 22U, 23U
The connection point 26U between them is connected to the U-phase winding of the electric motor 6, the connection point 26V between the FETs 22V and 23V is connected to the V-phase winding of the electric motor 6, and the connection point 26W between the FETs 22W and 23W is an electric motor. 6 W-phase windings. The control device 17 has a well-known configuration for driving and controlling a three-phase synchronous permanent magnet motor, and includes FETs 22U, 23U, and FETs of the motor drive device 21 that is an inverter circuit.
Motor control signals (not shown) are output to 22V, 23V and FETs 22W, 23W, respectively. This motor control signal is obtained by calculating the assist current from the basic assist map based on the turning torque T calculated based on the steering torque τ and the vehicle speed V. The motor drive device 21 generates a three-phase exciting current corresponding to the motor control signal and supplies the exciting current to the electric motor 6 through the three-phase exciting current path.

<Details of Boosting Circuit U of Current Supply Circuit 25> As shown in FIG. 3A, this boosting circuit U includes a boosting coil L, a rectifying capacitor C1, a transistor Q1 (n-channel). -Type MOSFET consisting of a first switching element), a transistor Q2 (n-channel-type MOSFET consisting of a second switching element),
A boosting capacitor C2 is provided. The boosting coil L and the transistor Q2 are connected in series between a voltage application point P1 on the output side of the battery 24 and a voltage application point P2 on the supply side to the electric motor 6. The input side of the boosting coil L is connected to the voltage application point P1. In the transistor Q2, the source side is connected to the output side of the boosting coil L, the drain side is connected to the voltage application point P2, and the gate side is connected to the CPU 18 of the control device 17. The capacitor C1 is connected to the voltage application point P1 and the input side of the boosting coil L and is grounded. The capacitor C2 is connected to the voltage application point P2 and the drain side of the transistor Q2 and is grounded. In the transistor Q1, the drain side is connected to the output side of the boosting coil L and the source side of the transistor Q2, the source side is grounded, and the gate side is the CPU1 of the control device 17.
8 is connected. In order to detect the voltage at the voltage application point P2, the voltage application point P2 is connected to a voltage input port (not shown) of the CPU 18 of the control device 17 so that the output voltage VBPIG can be detected.

Particularly, in the present embodiment, the Zener diode Z is connected in parallel to the transistor Q2 between the source side (input side) and the drain side (output side) of the transistor Q2.

The transistors Q1 and Q2 are shown in FIG.
As shown in (b), the electric motor 6 is driven by the duty ratio drive signals S1 and S2 (booster circuit control signal) of the drive pattern sent from the control device 17 (booster circuit control means).
During power running and regeneration, the on / off drive is alternately performed as described below.

During power running of the electric motor 6, the transistors Q1 and Q2 in the booster circuit U perform a switching operation by duty control by the duty ratio drive signals S1 and S2. As a result, energy is repeatedly stored and released in the boosting coil L, and a high voltage is generated when the energy is released to the drain side of the transistor Q2. That is, when the transistor Q1 is turned on and the transistor Q2 is turned off, a current flows to the ground side via the transistor Q1. Next, when the transistor Q1 is turned off and the transistor Q2 is turned on, the current flowing through the boosting coil L is cut off, and the drain of the transistor Q2 which is on is operated so as to prevent the change of the magnetic flux due to the cutoff of this current. High voltage is generated on the side. With this repetition, a high voltage is repeatedly generated on the drain side of the transistor Q2, smoothed (charged) by the capacitor C2, and generated as the output voltage VBPIG at the voltage application point P2. At this time, the voltage boosted by the booster circuit U is related to the duty ratio α of the duty ratio drive signals S1 and S2 output from the control device 17. When the duty ratio α is large, the output voltage VBPIG is high, and when the duty ratio α is small, the output voltage VBPIG is low.

Next, when the electric motor 6 enters the regenerative state, the output voltage VBPIG rises, but since the transistor Q2 is turned on by duty control even during regenerative operation, the battery 24 is supplied to the battery 24 via the transistor Q2. Electric current flows and is absorbed. However, when a reverse voltage of a predetermined value or more is applied to the Zener diode Z on the output side of the transistor Q2, the Zener effect causes
A current flows from the output side of the transistor Q2 to the battery 24 side through the Zener diode Z. Therefore, the booster circuit U can be prevented from being damaged when a high voltage is generated on the drain side of the transistor Q2 by a simple control method that does not require a charge pump and its drive circuit.

[Second Embodiment] Next, a motor control device according to a second embodiment of the present invention will be described with reference to FIGS.

In the second embodiment, the booster circuit U of the current supply circuit 25 in the first embodiment is modified as follows. As shown in FIG. 4A, this booster circuit U
Includes a boosting coil L, a rectifying capacitor C1, a transistor Q1 (a switching element including an n-channel MOSFET), and a boosting capacitor C2. The transistor Q2 in the first embodiment is omitted, and instead, only the Zener diode Z (backflow prevention element) connected to the output side of the boosting coil L is adopted. The boosting coil L and the Zener diode Z are connected in series between a voltage application point P1 on the output side of the battery 24 and a voltage application point P2 on the supply side to the electric motor 6. In the Zener diode Z, the anode side is connected to the output side of the boosting coil L, and the cathode side is connected to the voltage application point P2. The drain side of the transistor Q1 is connected to the anode side of the Zener diode Z. The capacitor C2 is connected to the cathode side of the Zener diode Z.

The transistor Q1 of the electric motor 6 is driven by the duty ratio drive signal S1 (step-up circuit control signal) of the drive pattern sent from the controller 17 (step-up circuit control means) as shown in FIG. 4 (b). During power running and regenerative, on / off driving is performed alternately as described below.
The duty ratio drive signal S2 in the first embodiment is
(Boosting circuit control signal) is omitted due to the omission of the transistor Q2.

When the electric motor 6 is in the power running mode, the transistor Q1 in the booster circuit U causes the duty ratio drive signal S to rise.
The switching operation is performed by the duty control according to 1. As a result, energy is repeatedly stored and released in the boosting coil L, and when released to the cathode side of the Zener diode Z, a high voltage is generated, smoothed (charged) by the capacitor C2 and applied as the output voltage VBPIG. Point P2
Occurs in

Next, when the electric motor 6 enters the regenerative state, the output voltage VBPIG increases. However, when a reverse voltage of a predetermined value or more is applied to the cathode side of the Zener diode Z, a current flows from the cathode side of the Zener diode Z through the Zener diode Z due to the Zener effect.
It flows to the 4 side. Therefore, it is possible to prevent the booster circuit U from being damaged when a high voltage is generated on the cathode side of the Zener diode Z by a simple control method that does not require a charge pump and its drive circuit. Further, since the transistor Q2 is omitted, a simple PWM control by only the transistor Q1 is possible, which lowers the specification of the controller and leads to cost reduction.

[Brief description of drawings]

FIG. 1 is a principle view schematically showing an electric power steering device according to a first embodiment or a second embodiment.

FIG. 2 is a control block diagram of the device.

FIG. 3A is an electric circuit diagram showing a booster circuit of the electric power steering apparatus in the first embodiment,
(B) is a waveform diagram of a duty ratio drive signal for a transistor of the booster circuit.

FIG. 4A is an electric circuit diagram showing a booster circuit of the electric power steering apparatus in the second embodiment,
(B) is a waveform diagram of a duty ratio drive signal for a transistor of the booster circuit.

[Explanation of symbols]

M ... Electric power steering device, 1 ... Steering wheel, τ ... Steering torque, 6 ... Electric motor, 17 ... Control means (control signal generation means, booster circuit control means), 21 ...
Motor drive device (motor drive means), 24 ... Battery (DC power supply), 25 ... Current supply circuit, U ... Booster circuit, L
... boost coil, Q1 ... transistor (first switching element), S1 ... duty ratio drive signal (first boost circuit control signal), Q2 ... transistor (second switching element), S2 ... duty ratio drive signal (second boost) Circuit control signal), C2 ... Capacitor, Z ... Zener diode (backflow prevention element).

Claims (3)

[Claims] 1. A booster circuit is provided in a current supply circuit provided between a motor drive means for driving a motor based on a motor control signal output from a control signal generation means and a DC power supply.
In a motor control device that controls the booster circuit based on the booster circuit control signal output from the booster circuit control means to raise the output voltage of the DC power supply, the booster circuit of the current supply circuit is connected to the output side of the DC power supply. Connected boosting coil, a first switching element connected to the output side of the boosting coil and turned on / off based on the boosting circuit control signal, and the boosting circuit control connected to the output side of the boosting coil A second switching element that is turned on / off based on a signal and a capacitor connected to the output side of this second switching element are provided, and a zener diode is second-switched between the input side and the output side of this second switching element. It is connected in parallel to the element and the output side of this second switching element is more than the specified value in the opposite direction to this Zener diode. Motor control device is characterized in that the current when the voltage applied from the output side of the second switching element to flow through the Zener diode at the input side of the second switching element. 2. A step-up circuit is provided in a current supply circuit provided between the motor drive means for driving the motor based on the motor control signal output from the control signal generation means and the DC power supply.
In a motor controller that controls the booster circuit based on a booster circuit control signal output from the booster circuit control means to raise the voltage of a DC power supply, the booster circuit of the current supply circuit is connected to an output side of the DC power supply. A boosting coil, a switching element connected to the output side of the boosting coil and turned on / off based on the boosting circuit control signal, and a backflow prevention element connected to the output side of the boosting coil, The backflow prevention element is provided with a capacitor connected to the cathode side, and a Zener diode is adopted as the backflow prevention element. A reverse voltage of a predetermined value or more is applied to the Zener diode on the cathode side of the Zener diode. If the current flows from the cathode side of the Zener diode through the Zener diode, Motor control device being characterized in that to flow into de side. 3. The motor control according to claim 1, wherein the motor is installed in an electric power steering device, and the motor control signal is determined based on at least a steering torque of a steering wheel. apparatus.