JP2017108568A - Motor control device, and drive control device for hybrid type vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To estimate a temperature of a magnet with accuracy, and thereby, to enable the minimum required usage of a motor to a requested power.SOLUTION: A motor control device is used for a hybrid type vehicle having an engine and a permanent magnet type motor. The motor control device comprises a rotation number sensor 8, a voltage detection sensor 9, and a motor controller 6 with a temperature calculation function and a current control function. The rotation number sensor 8 detects the rotation number of a motor 1. The voltage detection sensor 9 detects an induction voltage generated at the motor 1. The motor controller 6 estimates a temperature of a magnet of the motor 1 by using a predetermined operational expression on the basis of the rotation number of the rotation number sensor 8 and the induction voltage obtained by the voltage detection sensor 9. In addition, the motor controller 6 controls a current to be applied to the motor 1 depending on the estimated magnet temperature.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a drive control device, and more particularly to a drive control device for a hybrid vehicle having an engine and a permanent magnet motor. Moreover, it is related with the motor control apparatus used for this drive control apparatus.

  In a hybrid vehicle having an engine and a motor, a field pole is constituted by a permanent magnet as a drive motor. In this permanent magnet motor, heat is generated by supplying current to the stator, and the temperature of the magnet rises due to eddy current generated on the magnet surface. And when the temperature of a magnet becomes high temperature and magnetic flux load is large, it will be in the state which lost the magnetic force called permanent demagnetization in an instant.

  In order to avoid this fatal state of permanent demagnetization, it is generally necessary to use a material with high heat resistance called rare earth such as dysprosium and prepare a sufficient margin. However, rare earths are expensive, and it is not economically rational to prepare a large margin in preparation for a state of low occurrence. Furthermore, when a large amount of dysprosium is blended, there is a property that the residual magnetic flux decreases, resulting in a decrease in torque.

  Therefore, in order to cope with a rarely occurring high temperature state, it is conceivable to reduce the magnetic flux load at the high temperature, that is, to reduce the torque. For this purpose, it is necessary to accurately monitor the temperature of the magnet.

  However, since the magnet embedded in the rotor is rotating, it is difficult to directly measure the temperature of the magnet, and it is necessary to estimate the temperature of the magnet.

  Therefore, Patent Document 1 proposes a method of detecting the induced voltage of the motor and estimating the magnet temperature of the motor using the detection result and the characteristic equation.

JP 2007-6613 A

  The applied voltage V1 of the motor used in the temperature estimation method of Patent Document 1 (the applied voltage V1 of the motor under an arbitrary operation condition for performing temperature measurement) is obtained by the following equation.

V1 = Em + Id × Rt1 + Iq × jωL
Em: Induced voltage measured during operation at an arbitrary rotational speed N1 Id: Torque generation d-axis current Iq: q-axis current not contributing to torque generation Rt1: Winding resistance measurement value when magnet temperature is estimated jωL: Synchronous reactance

  However, the above formula includes the following three error factors depending on the current in addition to the induced voltage Em when no current is flowing.

(1) For example, it is necessary to obtain Id and Iq by calculation of a current measured by a current sensor in two phases of U phase and V phase.
(2) Since L (inductance) has a large current dependency, current correction is required.
(3) Since Rt1 has temperature dependency on the resistance of copper, temperature correction is required.

  As described above, there are many variables and constants used in the calculation and many error factors. Also, current sensors are generally more expensive and less accurate than voltage sensors. In addition, the decrease in magnetic force due to the temperature of the magnet is slight in the first place, and the temperature of the magnet cannot be accurately estimated unless the method is actually highly accurate.

  An object of the present invention is to be able to accurately estimate the temperature of a magnet so that a permanent magnet can be realized at low cost.

  (1) A motor control device according to the present invention is used in a hybrid vehicle having an engine and a permanent magnet motor. The motor control device includes a rotation speed detection unit, a voltage detection unit, a temperature calculation unit, and a current control unit. The rotation speed detection means detects the rotation speed of the motor. The voltage detection means detects an induced voltage generated in the motor. The temperature calculation means estimates the temperature of the magnet of the motor by a predetermined calculation formula based on the rotation speed obtained by the rotation speed detection means and the induced voltage obtained by the voltage detection means. The current control means controls the current flowing through the motor according to the calculation result of the temperature calculation means.

  Here, the induced voltage generated in the motor depends on the speed at which the magnetic flux generated by the magnet embedded in the rotor crosses the coil of the stator (that is, the rotational speed of the motor) and the flux linkage density. The interlinkage magnetic flux density is a magnetic flux generated by a permanent magnet. If the magnetic strength of the permanent magnet changes with temperature, the interlinkage magnetic flux density changes in proportion to it. If this principle is applied, the temperature can be estimated by detecting the induced voltage and the rotational speed.

  Therefore, in this apparatus, the rotational speed and induced voltage of the motor are detected, and the temperature of the magnet of the motor is estimated by a predetermined arithmetic expression based on the detection result. A current value that can flow through the motor to the maximum is extracted according to the estimated temperature of the magnet, and the motor is driven by this current value.

  Here, since the temperature of the magnet can be accurately estimated, the margin for permanent demagnetization can be reduced. As a result, it is possible to use an inexpensive permanent magnet having a rare earth compounding ratio with respect to the conventional permanent magnet, and it is possible to reduce the cost as compared with a conventionally mounted motor.

  (2) Preferably, the voltage detection means detects the induced voltage at a timing when an output stop command is issued to the motor (that is, PWM is stopped in the case of inverter driving).

  (3) Preferably, a voltage detection means measures the peak value of an induced voltage. In this case, it is not necessary to calculate the effective value, for example, compared to the case where the effective value of the induced voltage is detected, and the largest value is selected from many voltage measurement values in a certain angle range compared to the previous and subsequent values. It becomes work. Since the effective value calculation is not performed, the load on the CPU can be reduced.

  (4) Preferably, it further includes a rotational position detecting means for detecting the rotational position of the motor, and the voltage detecting means detects a peak voltage at a specific rotational position obtained by the rotational position detecting means.

  Here, since the measurement is performed at one angular position, the time required for voltage measurement is extremely short. Since the voltage can be measured in a short time even while the motor is driven, if it is wound up by the torsion spring element of the drive system, the torque is absorbed by the spring element because the torque is lost for a very short time, and the driver feels a shock. It can be expected that there is no effect.

  Here, “windup” and the operational effects of the present invention related thereto will be described.

  In a hybrid vehicle, a suspension as a torsion spring element such as a shaft or tire rubber or a larger torsion spring element exists from a drive motor to a tire grounding point. And there exists a property which a vehicle falls with respect to a top and bottom according to a driving force, and this brings about an effect equivalent to a torsion spring element. This phenomenon is called “windup” in the sense of winding up the torsion spring element.

  When a driving force is generated, these torsion spring elements are twisted, and the motor and the tire ground contact point are slightly out of phase. Conversely, when there is a phase difference, torque is generated.

  In the above situation, since the motor has a moment of inertia, even if the torque disappears for a moment, the phase difference between the motor and the tire ground contact point is not immediately resolved, and the wound torsion spring element is wound. Torque is generated until it returns. Utilizing this property, for a very short time, although the torque is reduced, the torque is not completely lost, so the driver is less likely to feel a shock.

  (5) Preferably, the motor is a permanent magnet motor for a hybrid electric vehicle used in combination with an engine. The voltage detecting means measures the induced voltage at the timing when the output stop command is issued to the motor during engine running or idling.

  (6) A drive control apparatus according to the present invention is a drive control apparatus for a hybrid vehicle having an engine and a permanent magnet motor, and includes a rotational speed detection means, a voltage detection means, a temperature calculation means, and a current control means. And an engine control unit. The rotation speed detection means detects the rotation speed of the motor. The voltage detection means detects an induced voltage generated in the motor. The temperature calculation means estimates the temperature of the magnet of the motor by a predetermined operator based on the rotation speed obtained by the rotation speed detection means and the induced voltage obtained by the voltage detection means. The current control means controls the current flowing to the motor according to the calculation result of the temperature calculation means, and if the magnet temperature estimated by the temperature calculation means is higher than a preset temperature, the vehicle with the subsequent motor When driving is requested, the current flowing to the motor is reduced from the current supply current. The engine control unit increases the engine output in accordance with the degree of reduction when the current control means reduces the current supplied to the motor.

  In the present invention as described above, the temperature of the magnet can be accurately estimated, and the minimum necessary motor for the required power can be used. Therefore, it is possible to reduce the cost of the motor and to reduce the size of the motor.

1 is a block diagram of a drive control system having a motor control device according to an embodiment of the present invention. The figure which shows an electric current value limiting value map.

[System configuration]
FIG. 1 is a block diagram of a drive control device for a hybrid vehicle including a motor control device according to an embodiment of the present invention. The drive control device shown in FIG. 1 is provided in a hybrid vehicle on which an engine (not shown) and a permanent magnet motor 1 (hereinafter simply referred to as “motor”) are mounted. The motor 1 is a so-called PM motor using a permanent magnet, and is a three-phase synchronous AC motor having three terminals of U phase, V phase and W phase. An inverter 2 as a motor driving unit is connected to the motor 1. The inverter 2 converts a direct current of the vehicle battery 3 into an alternating current. The inverter 2 changes the voltage, current, and frequency of the three-phase AC generated in the inverter 2 in order to control the torque and rotation speed (rotation speed) of the motor 1.

  The drive control device includes an engine control unit 5 that controls the engine, a motor control unit 6 that controls the inverter 2, and a hybrid control unit 7 that controls the engine control unit 5 and the motor control unit 6. . In addition, this apparatus includes a rotation speed sensor 8 that detects the number of rotations of the motor 1 and a voltage sensor 9 that detects a voltage between terminals of the motor 1.

  The motor control unit 6 receives an output signal from the rotation speed sensor 8 and an output signal from the voltage sensor 9. The motor control unit 6 receives a command from the hybrid control unit 7 and controls the inverter 2, whereby a necessary current is supplied to the motor 1. The motor 1 generates a required torque by the supplied current. Further, as will be described later, the motor control unit 6 controls the temperature calculation function for estimating the temperature of the magnet based on information from the sensors 8 and 9 and the current that flows to the motor 1 according to the estimated temperature. Current control function.

[Current control]
Hereinafter, the temperature calculation function and the current control function in the motor control unit 6 will be described. Here, the induced voltage generated in the motor 1 depends on the speed at which the magnetic flux generated by the magnet embedded in the rotor crosses the coil of the stator (that is, the rotational speed of the motor) and the linkage magnetic flux density.

Assuming that the induced voltage Em at idle, the armature flux linkage φ, and the rotational speed ω,
φ = Em / ω
There is a relationship.

  Since φ is a magnetic flux generated by a permanent magnet, if the magnetic strength of the permanent magnet changes with temperature, φ changes proportionally.

On the other hand, assuming that the magnet temperature T (° C.), the flux linkage φ0 at 0 ° C. and the rotational speed at that time are ω 0,
φ = aT + φ0
There is a relationship. Here, a is the flux linkage change Δφ / ΔT per 1K, and the unit is “Wb / K”. If this equation is transformed,
T = (φ−φ0) / a
And when I put it again as 1 / a = A,
T = A (φ−φ0) = A (Em / ω−Em0 / ω0) −−− (1)
It becomes.

  Therefore, Em is detected by the voltage sensor 9 and ω is detected by the rotational speed sensor 8. Further, if the material property A is examined in advance, Em0 and ω0 are measured, and Em and ω are measured when it is desired to estimate the temperature, the temperature T can be estimated by the above formula.

  Specifically, first, a torque 0 (zero) command is output from the hybrid control unit 7 to the motor control unit 6. In such a state, the induced voltage generated by the motor 1 can be detected by stopping the PWM drive for the motor 1 by the inverter 2. This induced voltage is detected by the voltage sensor 9. Since the induced voltage changes in a sine curve, its peak value is measured. And based on the detection result of the rotational speed sensor 8 and the voltage sensor 9, the motor magnet temperature Tmag is estimated using the following arithmetic expressions.

Tmag = A (Em-peak / ω-Em0-peak / ω0)
Em-peak: Peak value of the induced voltage

  In accordance with the estimated motor magnet temperature Tmag obtained as described above, a torque that can be commanded to the motor to the maximum is read from the map and extracted. Specifically, the current is limited using a map of maximum current = g (magnet temperature T, rotation speed ω) as shown in FIG. Then, when the vehicle is driven after the measurement, the motor is driven within the limit torque range.

  In such an embodiment, since the temperature of the magnet can be accurately estimated, a motor that does not have an excessive quality with respect to the required performance can be used. For this reason, compared with the conventionally mounted motor, a small motor can be used at low cost.

  Further, a torque 0 (zero) command is output from the hybrid control unit 7 to the motor control unit 6, thereby detecting the induced voltage at the timing when the PWM control stop command is issued from the motor control unit 6 to the inverter 2, and the magnet temperature Therefore, the fluctuation of the vehicle related to the present control can be eliminated. Furthermore, since the magnet temperature is estimated by detecting the peak value of the induced voltage, there is no need to calculate the effective value, for example, compared to the case where the effective value of the induced voltage is detected. From the measured voltage value, the largest value compared to the previous and next values is selected. Since the effective value calculation is not performed, the load on the CPU can be reduced.

[Other Embodiments]
The present invention is not limited to the above-described embodiments, and various changes or modifications can be made without departing from the scope of the present invention.

  (A) In the above embodiment, the method for measuring the peak value of the induced voltage is not particularly mentioned, but as shown by the two-dot chain line in FIG. 1, the rotational position sensor 10 that detects the rotational position of the motor 1 is provided. It is only necessary to measure the peak value of the induced voltage. That is, as described above, the induced voltage fluctuates in a sine curve, but if the rotational angle position of the motor is detected by the rotational position sensor 10, the timing at which the peak value of the induced voltage appears can be found. Therefore, the peak value of the induced voltage can be easily measured using the detection result of the rotational position sensor 10.

  (B) In equation (1), the motor magnet temperature is calculated using the peak value of the induced voltage, but the motor magnet temperature may be calculated using the effective value of the induced voltage.

  (C) When the estimated magnet temperature is higher than a preset temperature, the current flowing through the motor may be reduced from the current supply current up to the time when the vehicle is driven by the motor thereafter. In this case, it is preferable to increase the engine output according to the degree of reduction of the supply current. Thereby, it is possible to prevent the driving force from changing regardless of the magnet temperature.

DESCRIPTION OF SYMBOLS 1 Motor 2 Inverter 5 Engine control part 6 Motor control part 7 Hybrid control part 8 Rotational speed sensor 9 Voltage sensor 10 Rotational position sensor

Claims (6)

A motor control device for a permanent magnet motor,
Rotation speed detection means for detecting the rotation speed of the motor;
Voltage detecting means for detecting an induced voltage generated in the motor;
A temperature calculation means for estimating a temperature of the magnet of the motor by a predetermined operator based on the rotation speed obtained by the rotation speed detection means and the induced voltage obtained by the voltage detection means;
Current control means for controlling the current flowing through the motor according to the calculation result of the temperature calculation means;
A motor control device comprising:   The motor control device according to claim 1, wherein the voltage detection unit detects the induced voltage at a timing when an output stop command is issued to the motor.   The motor control device according to claim 1, wherein the voltage detection unit detects a peak value of the induced voltage. A rotation position detecting means for detecting a rotation position of the motor;
The voltage detection means detects a peak voltage at a specific rotation position obtained by the rotation position detection means;
The motor control device according to claim 3. The motor is a permanent magnet motor for a hybrid electric vehicle used in combination with an engine,
The motor control device according to claim 1, wherein the voltage detection unit measures the induced voltage at a timing when an output stop command is issued to the motor during engine running or idling. A drive control device for a hybrid vehicle having an engine and a permanent magnet motor,
Rotation speed detection means for detecting the rotation speed of the motor;
Voltage detecting means for detecting an induced voltage generated in the motor;
A temperature calculation means for estimating the temperature of the magnet of the motor by a predetermined calculation formula based on the rotation speed obtained by the rotation speed detection means and the induced voltage obtained by the voltage detection means;
The current flowing through the motor is controlled according to the calculation result of the temperature calculation means, and when the magnet temperature estimated by the temperature calculation means is higher than a preset temperature, the vehicle is subsequently driven by the motor. Current control means for reducing the current flowing to the motor when requested, from the supply current so far;
An engine control unit that increases engine output in accordance with the degree of reduction when the current control means reduces the supply current to the motor;
A drive control device for a hybrid vehicle comprising:

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