JP2002354888A - Permanent magnet motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a permanent magnet motor which enable use of a ferrite magnet under the extremely lower external air temperature environment. SOLUTION: When the warming-up is impossible because an external air temperature is low and temperature of ferrite magnet is lower than the available temperature, output of drive current of motor is limited to demagnetization limit of ferrite magnet or less. When the warming-up is possible, the motor is heated with a heater, a high-frequency current or the forcible circulation of the cooling water or oil. Moreover, when the external air temperature is low but temperature of ferrite magnet is not lower than the available temperature, a flowing path of the cooling water or oil is changed to the predetermined flowing path which is suitable for temperature maintaining of the ferrite magnet. When the operation is to be completed, circulation of the cooling water or oil in the higher temperature condition is stopped to store the cooling water or oil for maintaining the temperature thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a permanent magnet motor having a ferrite type permanent magnet.

[0002]

2. Description of the Related Art Generally, a high performance neody type permanent magnet is used for a permanent magnet motor. This neodymium-type permanent magnet is very expensive, occupies much of the cost of a permanent magnet motor, and causes the price to rise.

On the other hand, in recent years, the performance of low-priced ferrite-type permanent magnets (hereinafter referred to as "ferrite magnets") has been improved, and a magnetic force of a level required for a high-output motor can be generated. Is being commercialized.

[0004] The price of this ferrite magnet is very low, less than 1/10 of that of a neodymium type magnet.
When applied to a permanent magnet motor, there is an advantage that the price competitiveness is very high.

The characteristics of ferrite magnets are very compatible with reluctance motors currently being developed by our company, and there is an advantage that the output hardly drops even when used in place of neodymium-type permanent magnets.

[0006]

However, since the ferrite magnet has low resistance in an extremely low temperature environment of -20 ° C. or less, when an electric motor using a ferrite magnet is driven in an extremely low temperature environment, A ferrite magnet is demagnetized (magnetic force decreases) by a magnetic field generated by a drive current of the motor. Since the ferrite magnet does not return to the original magnetic force once it is demagnetized, the motor cannot output its original output thereafter, which may cause a failure.

[0007] The present invention has been made in view of the above, and an object of the present invention is to provide a permanent magnet motor capable of using a ferrite magnet without demagnetizing it even in an environment where the outside air temperature is extremely low. Is to do.

[0008]

According to a first aspect of the present invention, there is provided a permanent magnet motor having a mechanism for circulating a cooling medium through a predetermined flow path and a ferrite magnet. When the outside air temperature is lower than a predetermined value, determining means for determining whether the temperature of the ferrite magnet is lower than a usable temperature that does not cause demagnetization, and determining the ferrite magnet by the determining means. And a drive current limiting means for limiting the output of the drive current of the electric motor to be equal to or less than the demagnetization limit of the ferrite magnet when the temperature is determined to be equal to or lower than the usable temperature.

In the present invention, when the outside air temperature is low and the temperature of the ferrite magnet is lower than the usable temperature at which demagnetization does not occur, the output of the drive current of the motor becomes lower than the demagnetization limit of the ferrite magnet. With such a restriction, demagnetization of the ferrite magnet is prevented, so that the ferrite magnet can be used even in an environment where the outside air temperature is extremely low.

According to a second aspect of the present invention, there is provided the permanent magnet motor according to the first aspect, further comprising heating means for heating the electric motor when the determination means determines that the temperature of the ferrite magnet is lower than the usable temperature. It is characterized by.

In the present invention, when the outside air temperature is low and the temperature of the ferrite magnet is lower than the usable temperature, the motor is heated, so that the temperature of the ferrite magnet rises and demagnetization is prevented. The ferrite magnet can be used even in an environment where the outside air temperature is extremely low.

The present invention according to claim 3 provides the invention according to claim 1 or 2
In the permanent magnet motor described, when the temperature of the ferrite magnet is determined to be not lower than the usable temperature by the determination unit, a flow path of the cooling medium is provided in advance to a flow path suitable for keeping the temperature of the ferrite magnet. It is characterized by having a passage changing means for changing.

In the present invention, when the outside air temperature is low but the temperature of the ferrite magnet is not lower than the usable temperature, the flow path of the cooling medium is changed to a flow path suitable for keeping the temperature of the ferrite magnet provided in advance. By doing so, since the ferrite magnet is kept warm, demagnetization is prevented, and the ferrite magnet can be used even in an environment where the outside air temperature is extremely low. Note that the cooling medium refers to cooling water, oil, or the like.

The present invention described in claim 4 is the first to third aspects of the present invention.
In the permanent magnet electric motor according to any one of the above, when the temperature of the ferrite magnet is determined to be not lower than the usable temperature by the determination means, the circulation of the cooling medium is stopped at the end of the operation to store for keeping the temperature. It is characterized by having means.

In the present invention, when the outside air temperature is low but the temperature of the ferrite magnet is not lower than the usable temperature and the operation is terminated, the circulation of the cooling medium is stopped and stored for heat retention. Thus, the ferrite magnet is kept warm by the cooling medium, so that demagnetization is prevented, and the ferrite magnet can be used even in an environment where the outside air temperature is extremely low.

The present invention according to claim 5 provides the invention according to claims 1 to 4.
In the permanent magnet electric motor according to any one of the above, the driving current limiting means controls an output of a driving current of the electric motor in accordance with a temperature of the ferrite magnet.

The present invention described in claim 6 provides the invention according to claims 1 to 5
In the permanent magnet motor according to any one of the above, when the temperature of the cooling medium is equal to or less than a predetermined value, the heating means may include at least one of heating by a heater or heating by flowing a high-frequency current to a drive current circuit of the motor. Do one,
When the temperature of the cooling medium is not lower than the predetermined value, the heating is performed by circulating the cooling medium.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a configuration of a control device of a permanent magnet motor (hereinafter, appropriately referred to as “motor”) using a ferrite magnet according to one embodiment. The control device shown in the figure includes a rotating machine speed sensor 1 and an outside air temperature sensor 2.
A rotating machine temperature sensor 3, a magnet temperature calculating circuit 4, a motor control circuit 5, a heating control circuit 6, a cooling system control circuit 7, a cooling flow path driving circuit 8, a cooling water / oil driving circuit 9, And a configuration having:

The rotating machine speed sensor 1 detects the speed of the rotating machine provided in the electric motor and notifies the magnet temperature calculating circuit 4 and the electric motor control circuit 5 of the detected speed.

The outside air temperature sensor 2 detects the outside air temperature of the electric motor and notifies the magnet temperature calculation circuit 4 and the electric motor control circuit 5 of the detection.

The rotating machine temperature sensor 3 detects the temperature of the rotating machine and notifies the magnet temperature calculating circuit 4 and the motor control circuit 5 of the temperature.

The magnet temperature calculation circuit 4 performs a calculation for estimating the temperature of the ferrite magnet based on the speed of the rotating machine, the outside air temperature, and the temperature of the rotating machine, and notifies the motor control circuit 5 of the calculated value.

The motor control circuit 5 includes a rotating machine speed, an outside air temperature, a rotating machine temperature, a ferrite magnet temperature, an operation command,
Then, the operation mode of the electric motor is determined based on the detection result of a temperature sensor (not shown) for detecting the temperature of the cooling water / oil for cooling, and the operations of the heating control circuit 6 and the cooling system control circuit 7 are controlled. As will be described later, the operation modes are roughly classified into three types: a normal control mode, a heat retention control mode, and a low-temperature control mode.

In accordance with an instruction from the motor control circuit 5, the heating control circuit 6 controls the heating of the motor by the heater and the heating by supplying a high-frequency current to the drive current of the motor.

The cooling system control circuit 7 controls the operation of the cooling channel drive circuit 8 or the cooling water / oil drive circuit 9 in accordance with an instruction from the motor control circuit 5.

The cooling channel drive circuit 8 includes a cooling system control circuit 7
In accordance with the instruction from, control of the change valve for changing the flow path of the cooling water / oil to a flow path suitable for keeping the temperature of the ferrite magnet is performed.

The cooling water / oil drive circuit 9 controls the circulation, storage, discharge, etc. of the cooling water / oil in accordance with an instruction from the cooling system control circuit 7.

Next, an outline of processing of the permanent magnet motor by the control device having such a configuration will be described with reference to the flowchart of FIG.

In step S1, the motor control circuit 5 determines whether or not the outside air temperature detected by the outside air temperature sensor 2 during operation of the permanent magnet motor is lower than a predetermined value. If the outside air temperature is not lower than the predetermined value, it can be determined that there is no problem in the resistance of the ferrite magnet, so that the normal control mode is executed in step S2. In the normal control mode, the cooling water / oil drive circuit 9 causes cooling water or oil to flow through a predetermined flow path in the motor to cool the permanent magnet motor.

On the other hand, if the outside air temperature is equal to or lower than the predetermined value, the motor control circuit 5 determines in step S3 that the temperature of the ferrite magnet calculated by the magnet temperature calculation circuit 4 is demagnetized by the drive current at that time. It is determined whether the temperature is lower than the usable temperature (minimum temperature) that does not cause the generation. If the temperature of the ferrite magnet is not lower than the usable temperature,
In step S4, the heat retention control mode is executed. If the temperature of the ferrite magnet is equal to or lower than the usable temperature, step S5
To execute the low temperature control mode.

Next, the heat retention control mode executed in step 4 will be described with reference to the flowchart of FIG. In step S11, the motor control circuit 5 determines whether or not there is an operation command for the electric motor.
The process proceeds to step S12 to perform the cooling limit control. If there is no operation command, the process proceeds to step S13 to perform the heat retention control.

In the cooling limit control in step S12, the motor control circuit 5 controls the cooling water / oil drive circuit 9 so that the temperature of the ferrite magnet calculated by the magnet temperature calculation circuit 4 does not become lower than the usable temperature. Against cooling water
Limit the cooling of the motor by adjusting the speed and amount of oil circulation.

In the heat retention control when the process proceeds to step S13, in step S14, after the operation of the motor is completed, the motor control circuit 5 determines whether or not the outside air temperature is extremely low (for example, -20 ° C. or less). .

If the outside air temperature is not extremely low, in step S15, the cooling water / oil drive circuit 9 controls the cooling system control circuit 7
According to the instruction from the motor control circuit 5 via the controller, the circulation of the cooling water / oil is stopped while the temperature of the motor is still high. In step S16, the cooling water / oil in the high temperature state is stored in the electric motor and used for keeping the temperature of the ferrite magnet.

On the other hand, if the outside air temperature is extremely low, in step S17, the cooling passage drive circuit 8 sends the cooling water / oil according to the instruction from the motor control circuit 5 via the cooling system control circuit 7. An inversion valve that changes the flow path to a flow path suitable for keeping the temperature of the ferrite magnet prepared in advance is operated.

In step S18, the cooling water / oil drive circuit 9
Fills the motor with cooling water / oil through the changed flow path, and in step S19, the motor control circuit 5 determines whether or not the temperature of the cooling water / oil has dropped to near the freezing temperature. .

If the temperature of the cooling water / oil has not yet dropped to near the freezing temperature, the flow proceeds to step S20 where
The oil drive circuit 9 stops the flow of the cooling water / oil, stores it inside the motor, and uses it for keeping the ferrite magnet warm.

When the temperature of the cooling water / oil has decreased to near the freezing temperature, in step S21, the cooling water / oil driving circuit 9 discharges the cooling water / oil to the outside of the electric motor.

Next, the low-temperature control mode executed in step S5 will be described with reference to the flowchart of FIG.
In step S31, the motor control circuit 5 determines whether the warm-up operation is possible. The determination as to whether or not the warm-up operation is possible is made on the condition that there is a sufficient remaining amount of an energy source such as a battery. If the warm-up operation is possible, the process proceeds to step S32 to perform the warm-up control. If the warm-up operation is not possible, the process proceeds to step S33 to perform the output limit control.

In the output limiting control in step S33, since the temperature of the ferrite magnet at this time is lower than the usable temperature by the drive current at that time, the motor control circuit 5 controls the output of the drive current of the motor. Control for limiting the demagnetization limit of the ferrite magnet to be equal to or less than the demagnetization limit is performed on a drive current circuit (not shown). In this control, the output level of the drive current of the electric motor is determined by the type of ferrite magnet,
It is controlled so that it changes depending on the external temperature which fluctuates every moment.

In the warm-up control when proceeding to step S32, in step S34, the motor control circuit 5 determines whether the cooling water
It is determined whether the oil temperature is lower than a predetermined value.

If the temperature of the cooling water / oil is not lower than the predetermined value, the cooling water / oil driving circuit 9 determines the temperature in accordance with the instruction from the motor control circuit 5 through the cooling system control circuit 7 in step S35. The motor is heated by forcibly circulating the cooling water and oil in the high state inside the motor, and the temperature of the ferrite magnet is raised to be usable.

On the other hand, if the temperature of the cooling water / oil is equal to or lower than the predetermined value, in step S36, the cooling water / oil driving circuit 9
The cooling water and oil are discharged outside the motor, and in step S37,
The heating control circuit 6 controls the heating of the electric motor in accordance with an instruction from the electric motor control circuit 5 to raise the temperature of the ferrite magnet to make it usable.

In the heating control by the heating control circuit 5, a heater is provided in the electric motor to heat it, or a high-frequency current is supplied to a drive current circuit of the electric motor to heat the electric motor.

Therefore, according to the present embodiment, when the outside air temperature is low and the temperature of the ferrite magnet is lower than the usable temperature and the warm-up operation is not possible, the motor control circuit 5 drives the motor. By limiting the current output so that it is below the demagnetization limit of the ferrite magnet, the demagnetization of the ferrite magnet is prevented, so the ferrite magnet can be used even in an environment where the outside temperature is extremely low. it can.

According to this embodiment, when the outside air temperature is low and the temperature of the ferrite magnet is lower than the usable temperature and the warm-up operation is possible, the heater, the high-frequency current, or the forced circulation of the cooling water / oil is used. By heating the electric motor, the temperature of the ferrite magnet rises and demagnetization is prevented, so that the ferrite magnet can be used even in an environment where the outside air temperature is extremely low.

According to this embodiment, when the outside air temperature is low but the temperature of the ferrite magnet is not lower than the usable temperature,
The cooling flow path driving circuit 8 changes the flow path of the cooling water / oil to a flow path suitable for preserving the temperature of the ferrite magnet provided in advance, so that the ferrite magnet is kept warm and demagnetization is prevented. The ferrite magnet can be used even in an environment where the outside air temperature is extremely low.

According to the present embodiment, when the outside air temperature is low but the temperature of the ferrite magnet is not lower than the usable temperature and the operation is terminated, the circulation of cooling water and oil is stopped and stored for heat retention. By doing so, since the ferrite magnet is kept warm by the cooling water / oil at the high temperature, demagnetization is prevented, and the ferrite magnet can be used even in an environment where the outside air temperature is extremely low.

[0050]

As described above, according to the permanent magnet motor of the present invention, when the outside air temperature is low and the temperature of the ferrite magnet is lower than the usable temperature at which demagnetization does not occur, the driving current of the motor is reduced. By limiting the output of the ferrite magnet to below the demagnetization limit of the ferrite magnet, the demagnetization of the ferrite magnet is prevented, so that the ferrite magnet can be used even in an environment where the outside air temperature is extremely low. .

According to the present invention, when the outside air temperature is low and the temperature of the ferrite magnet is equal to or lower than the usable temperature, the motor is heated, thereby increasing the temperature of the ferrite magnet and preventing demagnetization. The ferrite magnet can be used even in an environment where the outside temperature is extremely low.

According to the present invention, when the outside air temperature is low but the temperature of the ferrite magnet is not lower than the usable temperature, the flow path of the cooling medium is changed to a flow path suitable for keeping the temperature of the ferrite magnet provided in advance. By doing so, the ferrite magnet is kept warm, so that demagnetization is prevented, and the ferrite magnet can be used even in an environment where the outside air temperature is extremely low.

According to the present invention, when the outside air temperature is low but the temperature of the ferrite magnet is not lower than the usable temperature and the operation is terminated, the circulation of the cooling medium is stopped and stored for heat retention. Thus, the ferrite magnet is kept warm by the cooling medium having a high temperature, so that demagnetization is prevented, and the ferrite magnet can be used even in an environment where the outside air temperature is extremely low.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a control device for a permanent magnet motor using a ferrite magnet according to an embodiment.

FIG. 2 is a flowchart showing an outline of processing of a permanent magnet motor by the control device.

FIG. 3 is a flowchart showing processing in a heat retention control mode.

FIG. 4 is a flowchart showing a process in a low-temperature control mode.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 rotating machine speed sensor 2 outside air temperature sensor 3 rotating machine temperature sensor 4 magnet temperature calculation circuit 5 motor control circuit 6 heating control circuit 7 cooling system control circuit 8 cooling channel drive circuit 9 cooling water / oil drive circuit

Claims (6)

[Claims] 1. A permanent magnet motor having a mechanism for circulating a cooling medium through a predetermined flow path and a ferrite magnet, wherein when the outside air temperature is lower than a predetermined value, the temperature of the ferrite magnet does not cause a demagnetization. Determining means for determining whether the temperature of the ferrite magnet is lower than the usable temperature.If the determining means determines that the temperature of the ferrite magnet is equal to or lower than the usable temperature, the output of the drive current of the motor is demagnetized by the ferrite magnet. And a drive current limiting means for limiting the current to be less than or equal to a limit. 2. The permanent magnet motor according to claim 1, further comprising heating means for heating the motor when the temperature of the ferrite magnet is determined to be lower than the usable temperature by the determination means. 3. When the determining means determines that the temperature of the ferrite magnet is not lower than the usable temperature, the flow path of the cooling medium is changed to a previously provided flow path suitable for keeping the temperature of the ferrite magnet. 3. The permanent magnet motor according to claim 1, further comprising a flow path changing unit. 4. When the determining means determines that the temperature of the ferrite magnet is not lower than a usable temperature,
The permanent magnet motor according to any one of claims 1 to 3, further comprising storage means for stopping circulation of the cooling medium at the end of the operation and storing the cooling medium for heat retention. 5. The permanent magnet motor according to claim 1, wherein the drive current limiting unit controls a drive current output of the motor according to a temperature of the ferrite magnet. 6. When the temperature of the cooling medium is equal to or lower than a predetermined value, the heating means performs at least one of heating by a heater and heating by supplying a high-frequency current to a drive current circuit of the electric motor. The permanent magnet electric motor according to any one of claims 1 to 5, wherein when the temperature is not lower than a predetermined value, heating is performed by circulating a cooling medium.