JP7501441B2 - Motor cooling device and method for controlling the motor cooling device - Google Patents

Description

The present invention relates to a method for cooling an oil-cooled motor.

A conventional method for cooling motors, such as those used in vehicles, is to use an electric oil pump to circulate cooling oil stored in an oil pan inside the motor housing to cool parts such as the stator coil.

As shown in FIG. 1, a filter 3 is provided at the oil intake port 2 of the oil pan 1. The oil is cooled by an oil cooler 4 and cooling water.

In addition, the torque and rotation speed of the motor 6 are generally controlled using an inverter connected to the motor 6.

JP 2013-253674 A International Publication WO2015/122019 JP 2010-11546 A

However, in a motor cooling device that uses an electric oil pump 10 to cool an in-vehicle motor 6, the filter may become clogged due to contamination. In this case, the flow rate of the cooling oil decreases, causing the motor temperature to rise, which may lead to a malfunction of the motor 6 or a sudden stop of the vehicle due to overheating protection.

Patent Document 1 is disclosed as a prior art document for detecting filter clogging in an electric oil pump. However, Patent Document 1 does not disclose that this oil pump is used to cool the motor, or the protective action that is taken after filter clogging is detected.

Given the above, the challenge for motor cooling devices is to detect blockages in the cooling oil filter without using special sensors, thereby preventing motor failure or overheating.

The present invention has been devised in view of the above-mentioned problems in the related art, and one aspect thereof is a motor cooling device that cools a motor with cooling oil, and includes an electric oil pump that circulates the cooling oil through a cooling oil passage, a filter provided in the cooling oil passage, and a judgment unit that judges whether the filter is clogged, and the judgment unit measures the motor current, the coil temperature of the motor, and the outside air temperature or the oil temperature of the motor at multiple measurement points during normal operation, calculates motor losses based on the motor current, calculates a temperature difference by subtracting the outside air temperature or the oil temperature from the coil temperature, creates a data table of the motor losses and the temperature differences at multiple measurement points, measures the motor current, the coil temperature, and the outside air temperature or the oil temperature during actual operation, calculates the motor losses during actual operation based on the motor current during actual operation, and judges whether the motor losses during actual operation are clogged. The temperature difference estimate is derived using the torque loss and the data table, a temperature difference measurement value is calculated by subtracting the outside air temperature or the oil temperature during actual operation from the coil temperature during actual operation, and filter clogging is determined based on the temperature difference measurement value and the temperature difference estimate value, or the flow rate of the oil pump is temporarily reduced during actual operation, and the coil temperature before the reduction operation, the outside air temperature before the reduction operation or the oil temperature before the reduction operation, the coil temperature after the reduction operation, the outside air temperature after the reduction operation or the oil temperature after the reduction operation are measured, and filter clogging is determined based on a first temperature difference obtained by subtracting the coil temperature before the reduction operation from the outside air temperature before the reduction operation or the oil temperature before the reduction operation, and a second temperature difference obtained by subtracting the coil temperature after the reduction operation from the outside air temperature after the reduction operation or the oil temperature after the reduction operation.

In one embodiment, the motor is driven by an inverter, the inverter includes a control unit and a main circuit unit, the determination unit sets a torque limit value or a current limit value based on the measured temperature difference value and the estimated temperature difference value, or sets the torque limit value or the current limit value based on the first temperature difference and the second temperature difference, the control unit performs limit processing on the torque command value so that it does not exceed the torque limit value, or performs limit processing on the current command value so that it does not exceed the current limit value, generates a gate signal based on the torque command value after limit processing or the current command value after limit processing, and the main circuit unit controls the on/off of a switching element based on the gate signal.

In another aspect, a motor cooling device that cools a motor driven by an inverter with cooling oil includes an electric oil pump that circulates the cooling oil through a cooling oil passage, a filter provided in the cooling oil passage, and a judgment unit that judges whether the filter is clogged. The judgment unit measures the pump rotation speed and pump drive current at multiple measurement points during normal operation, creates a data table of the pump rotation speed and the pump drive current at multiple measurement points, measures the pump rotation speed and the pump drive current during actual operation, derives a pump drive current estimate based on the pump rotation speed during actual operation and the data table, and calculates a pump drive current estimate based on the pump rotation speed during actual operation and the data table. The inverter determines whether a filter is clogged based on a constant value and the pump drive current estimate, and sets a torque limit value or a current limit value based on the measured value of the pump drive current during actual operation and the pump drive current estimate. The inverter includes a control unit and a main circuit unit, the control unit performs limit processing on the torque command value so that it does not exceed the torque limit value, or performs limit processing on the current command value so that it does not exceed the current limit value, generates a gate signal based on the torque command value after limit processing or the current command value after limit processing, and the main circuit unit controls the on/off of a switching element based on the gate signal.

In one aspect, the determination unit outputs a reverse rotation command to reverse the oil pump if it determines that the filter is clogged.

According to the present invention, in a motor cooling device, it is possible to detect clogging of the cooling oil filter without using a special sensor, thereby preventing motor failure or overheating.

FIG. 2 is a diagram showing an example of the structure of a motor cooling device. FIG. 4 is a block diagram showing a control configuration for control when a filter is clogged in the embodiment. FIG. 4 is a block diagram showing a control configuration for filter clogging elimination control in the embodiment.

The following describes in detail an embodiment of the motor cooling device of the present invention with reference to Figures 1 to 3.

[Embodiment]
An example of a target motor cooling device is shown in Figure 1. The motor cooling device cools a motor driven by an inverter with cooling oil. As shown in Figure 1, a motor 6 equipped with a rotor 7 and a stator coil 8 is housed in a motor housing 5. An oil pan 1 is also provided in the motor housing 5, and a filter 3 is provided at an oil intake port 2 of the oil pan 1. The cooling oil is cooled by an oil cooler 4 and cooling water.

In FIG. 1, reference numeral 9 denotes a wall between the motor 6 and the oil pan 1, reference numeral 10 denotes an electric oil pump that circulates the cooling oil through the cooling oil passage, and reference numeral 11 denotes a cooling oil passage through which the cooling oil circulates.

The oil pump flow rate injected into the object to be cooled (stator coil 8) is controlled by the oil pump rotation speed. The oil pump rotation speed is controlled by a dedicated motor (a motor separate from the motor 6 of the object to be cooled) connected to the oil pump 10.

The following (A) to (C) show the methods for detecting filter blockage in the inverter's judgment section.

(A) Calculate the moving average loss of the motor 6 over a fixed period of time. From this motor loss, estimate the temperature difference, which is the deviation between the temperature Tc of the stator coil 8 (hereafter referred to as the coil temperature) and the outside air temperature (or oil temperature) Ta of the motor 6. Compare the estimated temperature difference with the measured temperature difference, and determine whether the filter is clogged based on the measured temperature difference relative to the estimated temperature difference.

Below, we explain how to estimate the temperature difference and how to determine if the filter is clogged.

(1) In a normal state where the filter is not clogged, the motor current I is measured at multiple measurement points, and the motor loss is calculated based on the measured values of the motor current I. Note that the method for calculating the motor loss uses conventional technology such as that described in Patent Document 2.

(2) The coil temperature Tc of the motor 6 and the outside air temperature (or oil temperature) Ta of the motor 6 at multiple measurement points are measured using a temperature sensor. The outside air temperature (or oil temperature) Ta is subtracted from the coil temperature Tc to calculate the temperature difference (= Tc - Ta). A data table of the motor losses at multiple measurement points and the above temperature difference (= Tc - Ta) is created. The data table is stored in the memory of the inverter's judgment unit. The above are the processing items under normal conditions when the filter is not clogged.

(3) When the device is in actual operation, the motor current I, the coil temperature Tc of the motor 6, and the outside air temperature (or oil temperature) Ta of the motor 6 are measured. The motor loss during actual operation is calculated based on the motor current I during actual operation, etc. The temperature difference measurement value is calculated by subtracting the outside air temperature (or oil temperature) Ta during actual operation from the coil temperature Tc during actual operation.

(4) The inverter control unit uses the motor loss during actual operation and the above data table to derive the estimated temperature difference (Tc-Ta). If the ratio of the "measured temperature difference (Tc-Ta)" to the "estimated temperature difference (Tc-Ta)" (the value obtained by dividing the "measured temperature difference" by the "estimated temperature difference") exceeds a predetermined value, it is determined that the filter is clogged.

(B) When the load is low and the temperature is low during actual operation of the device, the flow rate of the oil pump 10 is temporarily reduced. The coil temperature Tc1 before the reduction operation, the outside air temperature (or oil temperature) Ta1 before the reduction operation, the coil temperature Tc2 after the reduction operation, and the outside air temperature (or oil temperature) Ta2 after the reduction operation are measured. A first temperature difference ΔT1 (= Ta1 - Tc1) is calculated by subtracting the coil temperature Tc1 before the reduction operation from the outside air temperature (or oil temperature) Ta1 before the reduction operation. In addition, a second temperature difference ΔT2 (= Ta2 - Tc2) is calculated by subtracting the coil temperature Tc2 after the reduction operation from the outside air temperature (or oil temperature) Ta2 after the reduction operation.

The above temperature difference (Ta-Tc) is compared before and after the lowering operation. If the difference (ΔT1-ΔT2) between the first temperature difference ΔT1 (=Ta1-Tc1) before the lowering operation and the second temperature difference ΔT2 (=Ta2-Tc2) after the lowering operation is less than a predetermined value, it is determined that the cooling oil is not providing sufficient motor cooling effect, i.e., the filter is clogged.

(C) The pump drive current (current of the pump motor) estimated from the pump rotation speed is compared with the actual current flowing through the pump motor, and if the actual current is greater than the estimated current by a certain percentage or more, it is assumed that the filter is clogged.

Below, we explain how to estimate the pump drive current and how to determine if the filter is clogged.

(1) In a normal state with no clogged filters, measure the pump rotation speed Np and pump drive current Ip (current of the pump motor) at multiple measurement points. Create a data table of the pump rotation speed Np and pump drive current Ip at multiple measurement points.

(2) When the device is in actual operation, measure the pump rotation speed Np and pump drive current Ip.

(3) Derive an estimated pump drive current value based on the pump rotation speed Np during actual operation and a data table. If the ratio between the "measured pump drive current Ip during actual operation" and the "estimated pump drive current value" (the value obtained by dividing the "measured pump drive current Ip during actual operation" by the "estimated pump drive current value") exceeds a predetermined value, it is determined that the pump is in an overloaded state, i.e., that a clogged filter has occurred.

(D) If any or all of the above conditions (A) to (C) are met, it is determined that the filter is clogged, and in order to prevent a further increase in the temperature of the motor 6, either (E) filter clog control or (F) filter clog removal control is performed.

(E) Control when Filter is Clogged In the inverter 12 that controls the motor 6, torque suppression control is performed according to the degree of clogging.

Figure 2 shows the control configuration for (E) filter clogging control in this embodiment. As shown in Figure 2, the inverter 12 includes a main circuit unit 13, a control unit 14, and a determination unit 15.

The determination unit 15 of the inverter 12 inputs the motor current I, the motor coil temperature Tc, the motor's outside air temperature (or oil temperature) Ta, the pump rotation speed Np, and the pump drive current Ip, and determines whether the filter 3 is clogged by one of the methods (A) to (C).

If it is determined that there is clogging, in (A), the torque limit value Tlmt is set according to the ratio of the "measured temperature difference (Tc-Ta)" to the "estimated temperature difference (Tc-Ta)" (the value obtained by dividing the "measured temperature difference" by the "estimated temperature difference"). In (B), the torque limit value Tlmt is set according to the magnitude of (first temperature difference ΔT1 - second temperature difference ΔT2). In (C), the torque limit value Tlmt is set according to the ratio of the "measured pump drive current during actual operation" to the "estimated pump drive current" (the value obtained by dividing the "measured pump drive current during actual operation" by the "estimated pump drive current").

The control unit 14 performs limit processing on the torque command value Tref received from the higher-level system so that it does not exceed the torque limit value Tlmt, and generates a gate signal that turns on and off the switching element in the main circuit unit 13 based on the torque command value after limit processing. Note that the control unit 14 may use conventional technology such as that described in Patent Document 3.

The main circuit section 13 controls the on/off of each switching element based on the gate signal to pass the desired motor current I. This operation suppresses the torque and current of the motor 6, thereby suppressing the temperature rise of the stator coil 8.

In FIG. 2, the determination unit 15 sets a torque limit value Tlmt and outputs the torque limit value to the control unit 14. Instead of the torque limit value Tlmt, a current limit value Ilmt of the current command value calculated by the control unit 14 may be set, and limit processing may be performed on the current command value so that it does not exceed the current limit value Ilmt when the filter is clogged, and a gate signal may be generated based on the current command value after limit processing.

(F) Filter Clogging Removal Control The oil pump 10 is rotated in reverse for a certain period of time to return contaminants clogging the filter 3 to the oil pan 1, thereby causing the filter 3 to self-clean.

Figure 3 shows the control configuration of the filter clogging elimination control in this embodiment. The determination unit 15 of the inverter 12 detects the motor current I, the coil temperature Tc of the motor 6, the outside air temperature (or oil temperature) Ta of the motor, the pump rotation speed Np, and the pump drive current Ip, and determines whether the filter 3 is clogged by any of the methods (A) to (C). If it is determined that the filter 3 is clogged, a reverse rotation command is sent to the oil pump 10 for a certain period of time. This determination unit 15 may be provided outside the inverter 12. Also, the inverter 12 in Figure 3 may be replaced with a motor drive means other than an inverter.

In addition, in the present invention, the filter 3 may be installed at a location other than the oil intake port 2 of the oil pan 1, as long as the filter 3 is installed at any location in the cooling oil passage 11.

As described above, according to this embodiment, filter clogging of the oil pan 1 is detected and control is performed to suppress the subsequent rise in motor temperature. This eliminates the risk of insufficient cooling due to filter clogging, which can lead to motor 6 failure or overheating protection, etc., causing the vehicle to suddenly stop.

Although the present invention has been described in detail above only with respect to the specific examples, it will be clear to those skilled in the art that various modifications and alterations are possible within the scope of the technical concept of the present invention, and it goes without saying that such modifications and alterations fall within the scope of the claims.

Reference Signs List 1: Oil pump 2: Oil suction port 3: Filter 4: Oil cooler 5: Motor housing 6: Motor 7: Rotor 8: Stator coil 9: Wall 10: Oil pump 11: Oil passage 12: Inverter 13: Main circuit section 14: Control section 15: Determination section

Claims (6)

A motor cooling device that cools a motor with cooling oil,
an electric oil pump that circulates the cooling oil through the cooling oil passage;
A filter provided in the cooling oil passage;
A determination unit for determining whether a filter is clogged;
Equipped with
The determination unit is
under normal circumstances, a motor current, a coil temperature of the motor, and an outside air temperature or an oil temperature of the motor are measured at a plurality of measurement points, a motor loss is calculated based on the motor current, a temperature difference is calculated by subtracting the outside air temperature or the oil temperature from the coil temperature, a data table of the motor loss and the temperature difference at the plurality of measurement points is created, during actual operation, the motor current, the coil temperature, and the outside air temperature or the oil temperature are measured, the motor loss during actual operation is calculated based on the motor current during actual operation, an estimated temperature difference is derived using the motor loss during actual operation and the data table, a measured temperature difference value is calculated by subtracting the outside air temperature or the oil temperature during actual operation from the coil temperature during actual operation, and a filter clogging is determined based on the measured temperature difference and the estimated temperature difference value,
Alternatively, a motor cooling device characterized in that the flow rate of the oil pump is temporarily reduced during actual operation, and the coil temperature before the reduction operation, the outside air temperature before the reduction operation or the oil temperature before the reduction operation, the coil temperature after the reduction operation, the outside air temperature after the reduction operation or the oil temperature after the reduction operation are measured, and filter clogging is determined based on a first temperature difference obtained by subtracting the coil temperature before the reduction operation from the outside air temperature before the reduction operation or the oil temperature before the reduction operation, and a second temperature difference obtained by subtracting the coil temperature after the reduction operation from the outside air temperature after the reduction operation or the oil temperature after the reduction operation. The motor is driven by an inverter,
The inverter includes a control unit and a main circuit unit.
the determination unit sets a torque limit value or a current limit value based on the temperature difference measurement value and the temperature difference estimation value, or sets the torque limit value or the current limit value based on the first temperature difference and the second temperature difference;
the control unit performs limit processing on a torque command value so that the torque command value does not exceed the torque limit value, or performs limit processing on a current command value so that the current command value does not exceed the current limit value, and generates a gate signal based on the torque command value after limit processing or the current command value after limit processing;
2. The motor cooling device according to claim 1, wherein the main circuit portion controls the on/off of a switching element based on the gate signal. A motor cooling device that cools a motor driven by an inverter with cooling oil,
an electric oil pump that circulates the cooling oil through a cooling oil passage;
A filter provided in the cooling oil passage;
A determination unit for determining whether a filter is clogged;
Equipped with
The determination unit is
measuring a pump rotation speed and a pump drive current at a plurality of measurement points under normal conditions, creating a data table of the pump rotation speed and the pump drive current at the plurality of measurement points, measuring the pump rotation speed and the pump drive current under actual operation, deriving an estimated pump drive current value based on the pump rotation speed under actual operation and the data table, determining filter clogging based on the measured value of the pump drive current and the estimated value of the pump drive current under actual operation, and setting a torque limit value or a current limit value based on the measured value of the pump drive current and the estimated value of the pump drive current under actual operation;
The inverter includes a control unit and a main circuit unit.
the control unit performs limit processing on a torque command value so that the torque command value does not exceed the torque limit value, or performs limit processing on a current command value so that the current command value does not exceed the current limit value, and generates a gate signal based on the torque command value after limit processing or the current command value after limit processing;
The motor cooling device according to claim 1, wherein the main circuit portion controls the on/off of a switching element based on the gate signal. The motor cooling device according to any one of claims 1 to 3, characterized in that the determination unit outputs a reverse rotation command to reverse the oil pump if it determines that the filter is clogged. A control method for a motor cooling device that includes an electric oil pump that circulates cooling oil through a cooling oil passage, a filter provided in the cooling oil passage, and a determination unit that determines whether the filter is clogged, and that cools a motor with the cooling oil, comprising:
The determination unit is
under normal circumstances, a motor current, a coil temperature of the motor, and an outside air temperature or an oil temperature of the motor are measured at a plurality of measurement points, a motor loss is calculated based on the motor current, a temperature difference is calculated by subtracting the outside air temperature or the oil temperature from the coil temperature, a data table of the motor loss and the temperature difference at the plurality of measurement points is created, during actual operation, the motor current, the coil temperature, and the outside air temperature or the oil temperature are measured, the motor loss during actual operation is calculated based on the motor current during actual operation, an estimated temperature difference is derived using the motor loss during actual operation and the data table, a measured temperature difference value is calculated by subtracting the outside air temperature or the oil temperature during actual operation from the coil temperature during actual operation, and a filter clogging is determined based on the measured temperature difference and the estimated temperature difference value,
Alternatively, a control method for a motor cooling device, comprising: temporarily reducing the flow rate of the oil pump during actual operation; measuring the coil temperature before the reduction operation, the outside air temperature before the reduction operation or the oil temperature before the reduction operation, the coil temperature after the reduction operation, and the outside air temperature after the reduction operation or the oil temperature after the reduction operation; and determining whether a filter is clogged based on a first temperature difference obtained by subtracting the coil temperature before the reduction operation from the outside air temperature before the reduction operation or the oil temperature before the reduction operation, and a second temperature difference obtained by subtracting the coil temperature after the reduction operation from the outside air temperature after the reduction operation or the oil temperature after the reduction operation. A control method for a motor cooling device that includes an electric oil pump that circulates cooling oil through a cooling oil passage, a filter provided in the cooling oil passage, and a determination unit that determines whether the filter is clogged, and that cools a motor driven by an inverter with the cooling oil, comprising:
The determination unit is
measuring a pump rotation speed and a pump drive current at a plurality of measurement points under normal conditions, creating a data table of the pump rotation speed and the pump drive current at the plurality of measurement points, measuring the pump rotation speed and the pump drive current during actual operation, deriving an estimated pump drive current value based on the pump rotation speed during actual operation and the data table, determining filter clogging based on the measured value of the pump drive current and the estimated value of the pump drive current during actual operation, and setting a torque limit value or a current limit value based on the measured value of the pump drive current and the estimated value of the pump drive current during actual operation;
a control unit of the inverter performs limit processing on a torque command value so that the torque command value does not exceed the torque limit value, or performs limit processing on a current command value so that the current command value does not exceed the current limit value, and generates a gate signal based on the torque command value after limit processing or the current command value after limit processing;
A method for controlling a motor cooling device, comprising the steps of: a main circuit portion of the inverter controlling the on/off of a switching element based on the gate signal.

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