JPH10210790A - Overheat protector for power converter, inverter controller and inverter cooler for electric automobile having that function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent overheat of an element the switching element of an inverter is in high temperature state and the temperature of the element rises abruptly due to full opening of accelerator. SOLUTION: An inverter ECU9 determines a torque (torque command) to be outputted from a motor 5 based on the opening A% of accelerator. The torque command is then regulated based on the temperature of a semiconductor element in an inverter 3 and the time variation rate thereof. A control signal corresponding to a regulated torque command is then generated. According to the control signal, the inverter 3 supplies a motor 5 with a current 5. When the temperature of the semiconductor element is high and the time variation rate thereof is also high, the torque command is reduced correspondingly. When the output torque is reduced, heat generation from the semiconductor element is also reduced and overheating of the element is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power converter overheat protection device for preventing overheating of a power converter such as an inverter, and more particularly to a device for preventing overheating by suppressing heat generation and cooling of a power converter.

[0002]

2. Description of the Related Art Conventionally, a power converter such as an inverter is used to convert power from a power supply and supply the converted power to a load device. Generally, a power converter converts power by switching operation of a plurality of semiconductor elements. If the semiconductor element is overheated due to heat generated by internal loss of the semiconductor element, the element may be destroyed. Therefore, techniques for preventing overheating of a semiconductor element have been conventionally proposed. Here, a device for protecting an inverter mounted on an electric vehicle will be described. This inverter is
The current from the battery is converted and supplied to the motor for driving the vehicle.

In order to prevent overheating of the inverter, there are a method of cooling the inverter and a method of suppressing heat generation of the semiconductor element itself. The cooling device used in the former method has, for example, a water pump that sends cooling water as a cooling medium to a water jacket of the inverter, and the inverter is cooled by circulating the cooling water in the jacket.

[0004] In the motor driving device described in Japanese Patent Application Laid-Open No. 7-67389, a temperature switch is provided on a radiator of an inverter. This motor drive device stops the motor when detecting that the inverter has reached a predetermined temperature. Thus, overheating exceeding the predetermined temperature is prevented.

[0005] Further, there has been proposed an inverter control device that suppresses heat generation of the inverter by adjusting the output torque of the motor. If the motor output torque is large,
The heat value of the semiconductor element at that time is large, and the heat value of the semiconductor element is small if the output torque is small. Therefore, the control device of this conventional example suppresses heat generation of the semiconductor element by adjusting output torque when the temperature of the semiconductor element (hereinafter, referred to as element temperature) increases as described below.

This conventional inverter control device detects an accelerator operation by a driver and detects an element temperature. Usually, a required value (torque command) of the output torque of the motor is determined according to the accelerator operation, and a drive signal corresponding to the required value is output to the inverter. The inverter performs a switching operation in accordance with the drive signal, and the motor generates an output torque indicated by the required value in response to the switching operation.

In this conventional inverter control device, as shown in FIG. 10, the element temperature is reduced to a limit start temperature T1.
When this is the case, the required value of the output torque is corrected downward. For example, if the element temperature is Ta, the torque command is multiplied by the limiting rate a. Then, a drive signal corresponding to the corrected torque command is output to the inverter. If the inverter is controlled so that the output torque of the motor decreases, the amount of heat generated by the semiconductor element decreases accordingly. Therefore, overheating of the semiconductor element can be prevented by the above control.

As shown in FIG. 10, in this conventional control device, an element breakdown temperature Td at which a semiconductor element is destroyed.
At a lower zero output temperature T2, the torque command limit rate α
Is set to 0. Therefore, when the temperature reaches zero output temperature T2, the output torque is reduced to zero. When the semiconductor element reaches the stop temperature Ts (T2 <Ts <Td), the inverter
Stop by itself to prevent overheating.

[0009]

In the prior art, for example, overheating of the inverter is prevented by stopping the motor when the temperature of the inverter reaches a predetermined temperature. However, when the temperature of the inverter is rapidly rising, the temperature does not stop immediately after the motor is stopped, and the temperature of the inverter may exceed the predetermined temperature.

Further, in the inverter control device using the output limiting ratio shown in FIG. 10, it is assumed that the element temperature is around T2 and the driver fully opens the accelerator. At this time, the torque command increases in accordance with the full opening of the accelerator, and the element temperature rises rapidly. Then, even when the output torque is reduced to 0 when the element temperature reaches the temperature T2, the temperature rise does not stop immediately. Therefore, the element temperature may exceed the temperature T2, which may cause overheating of the element.

If the zero output temperature T2 in FIG. 10 is set low, overheating can be prevented even when the element temperature rises rapidly as described above. This is because there is a margin from when the element temperature exceeds T2 to when the element is overheated. However, in this case, the output restriction line in FIG. 10 is set downward. Therefore, even when the element temperature does not rise rapidly, the output is excessively limited, which is not preferable.

In the prior art, when an abnormally high current flows through the inverter, such as when a short circuit occurs in the motor winding, the element temperature rises rapidly. Then, the element temperature easily exceeds the zero output temperature T2 and reaches the element breakdown temperature Td.

As described above, in the prior art, overheating is prevented by adjusting the temperature based on the temperature of the inverter as a criterion. However, there is a problem that the element may be overheated when the element temperature rises rapidly. This problem occurs not only in inverters but also in other power converters, and also occurs not only in electric vehicle power converters.

The present invention has been made to solve the above problems. An object of the present invention is to provide an overheat protection device that can reliably prevent overheating of a semiconductor element of a power converter even when the temperature of the semiconductor element rises sharply. Another object of the present invention is to provide an inverter control device and an inverter cooling device for an electric vehicle having the above functions.

[0015]

[Means for Solving the Problems]

(1) An overheat protection device for a power converter according to the present invention is a device that protects a power converter that converts power from a power supply and supplies the load to a load device from overheating during use. Based on the temperature detection means to be detected and the temperature detection result,
A temperature change rate calculating means for obtaining a time change rate of the converter temperature, a temperature adjustment amount is determined according to the detected converter temperature value and the time change rate, and the temperature of the power converter is adjusted according to the determined temperature adjustment amount. And a converter temperature adjusting means for preventing overheating of the power converter due to a rapid rise in temperature by adjusting the temperature based on the rate of change of the converter temperature with time.

Here, the power source is, for example, a battery or a capacitor, the load device is, for example, a motor or a generator, and the power converter is, for example, an inverter or a chopper. Also,
The temperature detecting means may directly detect the temperature of the semiconductor element, or may obtain the parameter indicating the temperature of the semiconductor element by detecting the temperature of other parts of the power converter.

Further, the temperature adjustment by the converter temperature adjusting means is realized by suppressing the heat generation of the converter itself or by changing the cooling amount of the converter. The former heat suppression is, for example,
This is realized by limiting the output of the motor as the load device. As the output torque is restricted, the heat value of the semiconductor element decreases. Further, the latter change in the cooling amount is realized, for example, by controlling a cooling device provided in the power converter. The cooling amount changes by adjusting the flow amount of the cooling medium sent to the power converter by the cooling device.

According to the present invention, the amount of temperature adjustment is determined according to the time change rate in addition to the converter temperature. The time change rate indicates whether the temperature of the converter has risen rapidly.
Then, the temperature of the power converter is adjusted according to the determined temperature adjustment amount. Therefore, according to the present invention, even when the converter temperature rises sharply from a high state, overheating of the converter can be prevented by adjusting the temperature in accordance with the time rate of change of the converter temperature.

According to the present invention, the temperature adjustment amount can be appropriately set based on the converter temperature and its time rate of change. That is, aggressive temperature adjustment is performed when the converter temperature rises sharply, and temperature adjustment is not performed as much as possible in other cases. As a result, it is possible to reliably prevent overheating when the converter temperature suddenly rises while minimizing the limitation of the motor output for suppressing heat generation.

Incidentally, an example of a method of determining the temperature adjustment amount is as follows. (A) When the converter temperature is high and the time change rate is large, the temperature adjustment amount is increased, and (b) The converter temperature is high. If the rate of time change is small, the amount of temperature adjustment is reduced. (C) If the converter temperature is low, the amount of temperature adjustment is reduced even if the rate of time change is high.

(2) The inverter control device for an electric vehicle according to the present invention is a control device for controlling an inverter for supplying a current to the motor to generate an output torque corresponding to an accelerator operation to the motor. Command value determining means for determining a torque command value based on an accelerator operation of the inverter, temperature detecting means for detecting a semiconductor element temperature of the inverter, temperature change rate detecting means for obtaining a time change rate of the semiconductor element temperature, and a semiconductor element temperature And a command value adjusting means for adjusting the torque command value based on the time rate of change, and a control means for generating a control signal to the inverter in accordance with the adjusted torque command value adjusted by the command value adjusting means, By adjusting the output torque in accordance with the rate of change of the element temperature with time, overheating due to a rapid rise in temperature of the semiconductor element is prevented.

Here, the temperature detecting means may directly detect the temperature of the semiconductor element. Further, a parameter (not limited to the temperature) indicating the element temperature outside the inverter or outside the inverter may be detected, and the element temperature may be determined based on the detected parameter.

The temperature change rate detecting means may calculate the time change rate of the element temperature based on the detection result by the temperature detecting means, or may calculate the time change rate based on other detected values. Further, the time change rate may be obtained by estimation. As a specific example, based on the accelerator operation amount, when the accelerator operation amount is large, it is determined that the time change rate of the element temperature is large. Further, the determination may be made based on a plurality of conditions such as an accelerator operation and a vehicle speed.

In this configuration, the torque command value is adjusted according to the time change rate in addition to the element temperature detection value. When the rate of change with time is large, the element temperature has risen sharply. Therefore, the torque command value is adjusted to be small, and a control signal according to the adjusted torque command value is output to the inverter. Since the inverter operates according to this drive signal,
As the output torque of the motor decreases, the element temperature of the inverter also decreases.

According to this aspect, for example, when the element temperature is high and rises sharply, the torque command is largely adjusted to prevent the element from overheating. If the temperature does not rise rapidly even when the element temperature is high, the torque command is not adjusted as greatly as when the temperature rises. In this way, it is possible to reliably prevent overheating of the element while performing torque adjustment according to the necessity.

(3) An inverter cooling device for an electric vehicle according to the present invention is a device for cooling an inverter that supplies electric current to a motor, and a cooling pump for sending a cooling medium to a cooling medium passage provided in the inverter. A temperature detecting means for detecting a semiconductor element temperature of the inverter; a temperature change rate detecting means for detecting a time change rate of the semiconductor element temperature; and determining a flow rate of the cooling medium based on the semiconductor element temperature and the time change rate. And a pump control means for controlling the cooling pump in accordance with the determined flow rate, and by adjusting the flow rate of the cooling medium according to the time change rate of the semiconductor element temperature, the overheating accompanying the rapid rise in the temperature of the semiconductor element is suppressed. prevent. Also in this case, the temperature detecting means and the temperature change rate detecting means can have the various configurations described above.

According to this aspect, the flow rate of the cooling medium is determined based on the detected element temperature value and its time rate of change.
When the rate of change with time is large, the element temperature has risen sharply. Therefore, the flow rate of the cooling medium is determined to be large, and the cooling pump is driven according to the flow rate.

According to this aspect, for example, when the element temperature is high and rises rapidly, the flow rate of the cooling medium is increased to prevent the element from overheating. If the temperature does not rise rapidly even when the element temperature is high, the flow rate of the cooling medium is not increased as much as at the time of the rapid rise. In this way, it is possible to reliably prevent element overheating while suppressing the energy consumption of the cooling device by setting the flow rate of the cooling medium according to the necessity.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention (hereinafter, referred to as embodiments) will be described below with reference to the drawings.

[Embodiment 1] In Embodiment 1, a temperature control function characteristic of the present invention is provided in an inverter control device for controlling an inverter. FIG. 1 is a block diagram showing a drive system of an electric vehicle provided with the inverter control device of the present embodiment.

An inverter 3 is connected to a battery 1 as a power supply device.
Are connected, and the motor 3 for driving the vehicle is connected to the inverter 3. The output shaft of the motor 5 is connected to the wheels 7 via a rotating shaft and a differential gear device.

The inverter 3 is provided with a plurality of switching elements. The switching element is a semiconductor element such as an IGBT, a bipolar transistor, a thyristor, and a MOS-FET. Inverter 3 is an inverter EC
It is controlled by U9. And the inverter EC
The plurality of switching elements perform a switching operation according to the drive signal input from U9. By this switching operation, the direct current supplied from the battery 1 is converted into an alternating current and supplied to the motor 5.

The inverter ECU 9 is provided with the accelerator pedal 1
When the driver depresses the accelerator pedal 11, the amount of depression is detected. The depression amount is expressed using the accelerator opening A% as follows. That is, 100% is set when the accelerator is fully opened. Then, the ratio of the accelerator pedal depression amount at that time to the pedal depression amount when the accelerator pedal is fully opened, expressed in%, is referred to as an accelerator opening degree A%.

The inverter ECU 9 is connected to a temperature sensor 13 provided in the case of the inverter 3. Based on the input from the temperature sensor 13, the inverter ECU 9 obtains the switching element temperature INV-T. Here, the temperature sensor 13 may be configured to directly detect the element temperature INV-T. Further, the temperature sensor 13 may detect the temperature of a certain portion that changes according to the element temperature, and the inverter ECU 9 may obtain the element temperature INV-T from this temperature. Furthermore, the following control may be performed by processing the temperature of the above-described certain part in the same manner as the actual element temperature INV-T.

Further, the inverter ECU 9 obtains the amount of change in the element temperature per unit time based on the element temperature INV-T, and sets this as the temperature change rate ΔT / Δt. At this time, the inverter ECU 9 uses a built-in timer device to determine how much the element temperature INV-T has changed during the unit time.

Next, the operation of the inverter control device according to the present embodiment will be described. The inverter ECU 9 calculates the torque to be output by the motor from the accelerator opening A% according to FIG. 2, and sets the obtained torque as the torque command T *. Then, the torque command T * is adjusted using the two types of limiting rates shown in FIG. 3, that is, the first limiting rate α and the second limiting rate β. Here, the torque command T * multiplied by the first limit rate α and the second limit rate β is used as the adjusted torque command T *.

On the left side of FIG. 3, a limit line m for defining the first limit rate α is shown. The first limiting rate α is determined based on the element temperature INV-T. Element temperature INV-
When T is equal to or lower than the limit start temperature T1, the first limit rate α is 10
0%. Therefore, the torque command T * is not changed depending on the first limit rate α. Then, the element temperature INV-T
Is higher than the limit start temperature T1, the first limit rate α corresponding to the element temperature INV-T at that time is applied to the torque command T *. The element temperature INV-T is zero output temperature T
When it reaches 2 or more, the first limit rate α becomes 0, and the torque command T * also becomes 0.

On the right side of FIG. 3, a limit line n for defining the second limit rate β is shown. The second limit rate β is determined based on the temperature change rate ΔT / Δt. This second limiting ratio β is used when the element temperature INV-T is equal to or higher than the above-described limiting start temperature T1. When the temperature change rate ΔT / Δt is equal to or less than the first reference value δ1, the second limit rate β is 100%.
Therefore, the torque command T * is not changed depending on the second limit rate β. When the temperature change rate ΔT / Δt becomes higher than the first reference value δ1, the change rate ΔT / Δ at that time is used.
The second limit rate β corresponding to t is applied to the torque command T *. When the temperature change rate ΔT / Δt reaches or exceeds the second reference value δ2, the second limit rate β becomes zero, and the torque command T * also becomes zero.

FIG. 4 is a flowchart showing a process for adjusting the torque command T * using the above-mentioned first limit rate α and second limit rate β. The inverter ECU 9 compares the temperature change rate ΔT / Δt with the third reference value δ3 (S1
0), if the rate of change ΔT / Δt is larger, the inverter output is set to 0 (shutdown) (S12). The third reference value δ3 is set assuming a temperature change rate when an abnormally high current flows through the switching element. Therefore, the third reference value δ3 is set to a value much larger than the second reference value δ2. In step S10, it is detected that the element temperature INV-T is increasing at an abnormal speed due to, for example, occurrence of a short circuit in the motor winding.

If the temperature change rate ΔT / Δt is equal to or less than the third reference value δ3, the device temperature INV-T is compared with the limit start temperature T1 (S14). Then, if the element temperature INV-T is lower, the process returns to the start. At this time, the torque command T * obtained from the accelerator opening A% is used as the final command value as it is, and adjustment using the limiting rate is not performed.

On the other hand, at step S14, INV-T> T
If it is 1, the first limiting rate α is determined from the element temperature INV-T according to the limiting line m on the left side of FIG. 3 (S16), and further, the temperature change rate ΔT /
The second restriction rate β is determined from Δt (S18). And
The torque limit T * obtained from the accelerator opening A% is multiplied by the first limit rate α and the second limit rate β, and the result is set as the final torque command T * (S20).

In the inverter ECU 9, a drive signal to be supplied to the inverter 3 is generated in the following manner based on the torque command T * obtained according to the above flowchart. That is, the motor current corresponding to the torque command T * is obtained, and this is supplied to the current control unit as the current command I *. The current control unit, based on the current command I *,
A voltage command indicating a PWM threshold value in a subsequent PWM control unit is generated. The PWM control unit compares the voltage command with a carrier having a predetermined waveform to perform pulse width modulation (P
WM) is generated. This switching signal is supplied to the inverter 3 as a drive signal.

The plurality of switching elements of the inverter 3 switch according to a switching signal. As a result, the DC current supplied from the battery 1 is converted to AC and supplied to the motor 5. Here, the voltage command is generated according to the current command, and the switching signal is generated according to the voltage command. Therefore, inverter 3
As a result, an AC current corresponding to the current command is supplied to the motor 5, and the output torque of the motor 5 becomes a value corresponding to the torque command T *.

The operation of the inverter control device according to this embodiment has been described above. During normal operation, the temperature of the switching element does not rise, and the element temperature INV-T is lower than the limit start temperature T1. Therefore, the first limit rate α and the second limit rate β
No adjustment of the torque command is performed.

It is assumed that the element temperature INV-T rises, exceeds the limit start temperature T1, and reaches Tb (FIG. 3) close to the zero output temperature T2. Further, since the accelerator is in the half-open state, the temperature change rate ΔT / Δt is not so high, and δb (<δ1)
(FIG. 3). At this time, as shown in FIG.
The first limiting rate corresponding to the temperature Tb is αa, and the second limiting rate corresponding to the temperature change rate δb is 100%. Therefore, αb is added to the torque command determined from the accelerator opening A%.
And a value obtained by multiplying by 1 is the final torque command T *. Then, a drive signal corresponding to the final torque command T * is supplied to the inverter 3. Thus, the amount of heat generated by the switching elements in the inverter 3 is reduced. This is because if the output torque is limited, the amount of heat generated by the switching element is reduced accordingly.

The element temperature INV-T is the above Tb,
In addition, since the accelerator is fully open, the temperature change rate ΔT /
It is assumed that Δt is large and δc (δ1 <δc <δ2) (FIG. 3). At this time, the second restriction rate becomes βc as shown in FIG. Therefore, a value obtained by multiplying the torque command determined from the accelerator opening A% by αb and βc is set as the final torque command T *. Therefore, in this case, the torque limitation is performed to a greater extent than in the case described above.

As described above, in this embodiment, the element temperature I
Even when NV-T is high, attention is paid to the fact that the required degree of element temperature adjustment is different depending on the time change rate ΔT / Δt, and the torque is limited according to the necessity. In other words, if the time change rate is small even if the element temperature is high, the element temperature does not rise sharply, and an appropriate torque limit corresponding to this is performed. If the element temperature is high and the time rate of change is large, the torque is further limited so that the element does not overheat due to a rapid rise in temperature. Therefore, according to the present embodiment,
Element overheating can be reliably prevented while limiting the torque to the minimum necessary. In particular, even when the element temperature rises sharply due to an accelerator full-open operation or the like while the element temperature is high, overheating of the switching element is reliably prevented.

Referring to FIG. 6, it will be described that the minimum output restriction is efficiently performed as described above. FIG.
A limit line m (equivalent to FIG. 3) defining the first limit rate,
This is shown in comparison with a conventional restriction line (equivalent to FIG. 10). Both limit lines are lines when applied to the same type of vehicle drive system. In the present embodiment, the zero output temperature T2 is set higher than before, and the limit line m is set higher than before. When the element temperature does not rise rapidly, this setting can sufficiently prevent the element from overheating. Therefore, in the present embodiment, when the temperature change rate is not large, the output torque can be made higher than before (the shaded portion in FIG. 6), and when the temperature change rate is large, the output torque can be increased by using the second limit rate β. And the overheating of the element is reliably prevented.

In this embodiment, the temperature change rate ΔT /
When Δt exceeds the third reference value δ3, the inverter output is set to 0 (shut down). For example, when an abnormally high current flows through the switching element due to the occurrence of a short circuit in the motor winding, the element temperature rises abnormally fast. At this time, as in the prior art, the element temperature becomes zero output temperature T2.
If the torque command T * is reduced to 0 after the temperature has reached, the element temperature may overshoot and reach an overheated region. On the other hand, in the above control, the inverter output is set to 0 when the temperature change rate ΔT / Δt exceeds the third reference value δ3, so that overheating of the element is prevented.

In the present embodiment, the torque command T * is adjusted based on the element temperature INV-T and the temperature change rate ΔT / Δt. On the other hand, other control values may be adjusted. That is, instead of the torque command T *, the current command I
*, A voltage command, or a switching signal may be adjusted. Further, the torque command T * is adjusted based on the element temperature INV-T, and the temperature change rate ΔT / Δ
It is also conceivable to adjust the voltage command based on t.

As a modification of the present embodiment, a map as shown in FIG. 5 may be provided. In this map, the output limiting rate γ is determined in association with the element temperature INV-T and the temperature change rate ΔT / Δt. That is, the output limiting ratio γ on the map corresponds to the product of the first limiting ratio α and the second limiting ratio β. First, as described above, the inverter ECU 9 performs steps S10 to S10 in the flowchart of FIG.
After executing S14, the output limiting ratio γ is obtained from the map of FIG. 5, and the torque command is corrected using this limiting ratio γ. Then, a drive signal corresponding to the corrected torque command is output to the inverter.

[Embodiment 2] In Embodiment 2, a temperature adjusting function characteristic of the present invention is provided in an inverter cooling device for cooling an inverter. FIG. 7 is a block diagram showing a drive system of an electric vehicle provided with the inverter cooling device of the present embodiment. 7, the same components as those in FIG. 1 are denoted by the same reference numerals. In the following:
A description of the same parts as those in the first embodiment will be appropriately omitted.

As in the first embodiment, an inverter 3 is connected to a battery 1 serving as a power supply device, and a motor 5 for driving a vehicle is connected to the inverter 3. The output shaft of the motor 5 is connected to the wheels 7 via a rotating shaft and a differential gear device.

The inverter 3 is provided with a plurality of switching elements. Inverter 3 is an inverter EC
It is controlled by U20. Inverter ECU 20
Is connected to the accelerator pedal 11 as in the first embodiment, and detects the accelerator opening A%. Then, according to FIG. 2 described above, the torque command T * is calculated from the accelerator opening A%.
Ask for. A voltage command is generated based on the torque command T *, and a pulse width modulated (PWM) switching signal is generated by comparing the voltage command with a carrier having a predetermined waveform. This switching signal is supplied to the inverter 3 as a drive signal. The plurality of switching elements of the inverter 3 switch according to a switching signal. As a result, the DC current supplied from the battery 1 is converted to AC and supplied to the motor 5. In this manner, the output torque of the motor 5 is controlled by the torque command T *.
Is obtained.

The inverter 3 is provided with a water jacket through which cooling water flows. A water pump 22 for sending cooling water to the water jacket is attached to the inverter 3. Heat generated in the switching elements and other parts is transmitted to the cooling water in the water jacket. When the water pump 22 is driven, the cooling water circulates in the jacket and through a radiator (not shown). Thus, the inverter is cooled.

The water pump 22 has a pump motor, and is driven by the rotational force of the pump motor. The pump motor is controlled by the inverter ECU 20. The inverter ECU 20 determines the operating voltage P of the pump motor, and supplies a voltage instruction signal corresponding to the operating voltage P to the pump motor. The pump motor is
In accordance with the voltage instruction signal, driving is performed at the operating voltage P indicated by the signal.

The rotation speed of the pump motor changes according to the operating voltage P. The flow rate of the cooling water changes according to the rotation speed of the pump motor. Therefore, the inverter E
The CU 20 controls the pump motor to
The flow rate of cooling water can be adjusted.

Further, as in the first embodiment, the inverter ECU 20 is connected to the temperature sensor 13 provided in the case of the inverter 3 and detects the element temperature INV-T. Further, the inverter ECU 20 determines the element temperature I
Temperature change rate (temporal change rate of element temperature) Δ based on NV-T
Find T / Δt.

Next, the operation of the inverter cooling device according to the present embodiment will be described. FIG. 8 is a flowchart showing a process performed by the inverter ECU 20 for controlling the pump motor of the water pump 22. After the start of traveling, the element temperature INV-T is detected every predetermined time (S30),
The temperature change rate ΔT / Δt is obtained (S32). Then, based on the element temperature INV-T and the temperature change rate ΔT / Δt, the operating voltage P of the pump motor is determined using the map of FIG. 9 (S34).

In FIG. 9, the horizontal axis represents the device temperature INV-T.
The vertical axis represents the temperature change rate ΔT / Δt. And
The operating voltage P of the pump motor is defined for each area divided by a straight line descending to the right on the map. As shown, when the element temperature is low and the temperature change rate is small, the operating voltage P = 0. This is because when the element temperature and the temperature change rate are in this range, it is unnecessary to cool the inverter by circulating the cooling water. Then, as the element temperature increases and the temperature change rate increases, the setting of the operating voltage is changed to P0, P1, P2, P3, P4,.
Here, P0 <P1 <P2 <P3 <P4... Therefore, even at the same rate of temperature change, the operating voltage P increases as the element temperature increases. Further, even at the same element temperature, the operating voltage P increases as the temperature change rate increases.

The inverter ECU 20 generates a voltage instruction signal corresponding to the determined operating voltage P and outputs it to the pump motor (S36). The pump motor is driven to rotate at the operating voltage P indicated by the voltage instruction signal. Accordingly, the pump motor rotates at a rotation speed corresponding to the operating voltage P determined according to the map of FIG. 9, and the cooling water having a flow rate corresponding to the rotation speed circulates through the water jacket and the radiator.
When the operating voltage P = 0, the water pump stops. Then, inverter ECU 20 determines in step S3
Returning to 0, the same control is repeated.

The operation of the inverter cooling device according to the present embodiment has been described above. When the temperature of the switching element has not risen and the temperature change rate ΔT / Δt is low, element overheating does not occur even if the cooling water does not circulate. Therefore, the pump motor is stopped, and power consumption is saved.

When the element temperature INV-T increases, cooling by circulating cooling water is required. At this time, the element temperature I
The higher the NV-T, the more it is necessary to release more heat by increasing the flow rate of the cooling water. Therefore, in the present embodiment, the operating voltage P is set higher as the element temperature INV-T is higher. Also, as the temperature change rate ΔT / Δt is larger, the element temperature rises sharply, and the possibility that the element temperature enters an overheating region is high. As described in the first embodiment, the temperature change rate increases when, for example, the accelerator is fully opened.
Therefore, the larger the temperature change rate ΔT / Δt, the higher the operating voltage P is set. This increases the flow rate of the cooling water and allows more heat to escape to the cooling water.

As described above, in the present embodiment, the element temperature I
Even when the NV-T is high, attention is paid to the fact that the required degree of element temperature adjustment is different depending on the time change rate ΔT / Δt, and cooling is performed according to this necessity. That is,
If the time change rate is small even if the element temperature is high, the element temperature does not rise sharply, and accordingly, appropriate cooling is performed. If the element temperature is high and the time rate of change is large, the flow rate of the cooling water is increased so that the element is not overheated due to a rapid rise in temperature. Therefore, according to the present embodiment, it is possible to reliably prevent element overheating while reducing energy consumption by minimizing the operating voltage of the pump motor. In particular, even when the element temperature rises rapidly due to an accelerator full open operation or the like in a state where the element temperature is high, overheating of the element is reliably prevented.

In the present embodiment, the present invention is applied to a device for cooling an inverter for supplying current from a battery to a motor. On the other hand, the present invention is similarly applicable to an inverter that converts a current generated by a generator and supplies the converted current to a battery.

In the first embodiment, the output torque of the motor is limited, and in the second embodiment, the flow rate of the cooling water is adjusted. Needless to say, both configurations of Embodiment 1 and Embodiment 2 may be provided in the drive system of the electric vehicle to prevent overheating of the semiconductor element. As an example, the overheating prevention by the pump motor control of the second embodiment is performed by using the element temperature INV−
Performed when T is relatively low. Then, the overheating prevention by the torque adjustment of the first embodiment is performed on the high temperature side. With this configuration, the overheating prevention by the cooling device is executed with priority,
The torque adjustment is performed when the cooling device alone is not sufficient. Therefore, it is possible to avoid torque limitation as much as possible.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a drive system of an electric vehicle including an inverter control device according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a relationship between an accelerator opening and a torque command.

FIG. 3 is an explanatory diagram showing a limit line that defines a limit rate for adjusting a torque command.

FIG. 4 is a flowchart showing a torque command adjustment process using the limiting ratio of FIG. 3;

FIG. 5 is an explanatory diagram showing a map for obtaining an output limiting ratio for adjusting a torque command in a modification of the first embodiment.

FIG. 6 is an explanatory diagram showing a comparison between a limit line that defines a first limit rate according to the first embodiment and a conventional limit line.

FIG. 7 is a block diagram illustrating a configuration of a drive system of an electric vehicle including the inverter cooling device according to the second embodiment.

FIG. 8 is a flowchart illustrating an operation of the inverter cooling device according to the second embodiment.

FIG. 9 is an explanatory diagram showing a map for determining an operating voltage of a pump motor of the cooling device.

FIG. 10 is an explanatory diagram showing an output limiting ratio used for adjusting a motor output torque in the related art.

[Explanation of symbols]

1 battery, 3 inverters, 5 motors, 7 wheels, 9, 20 inverter ECU, 11 accelerator pedal, 13 temperature sensor, 22 water pump.

Claims (5)

[Claims] An overheat protection device for a power converter that protects a power converter that converts power from a power supply and supplies the load to a load device from overheating during use, wherein a temperature detection that detects a temperature of the power converter. Means, a temperature change rate calculating means for obtaining a time change rate of the converter temperature based on the temperature detection result, and a temperature adjustment amount determined according to the converter temperature detected value and the time change rate, and the determined temperature adjustment Converter temperature adjusting means for adjusting the temperature of the power converter in accordance with the amount of power, wherein overheating of the power converter due to a rapid rise in temperature is prevented by temperature adjustment based on the rate of change of the converter temperature over time. Overheat protection device for power converter. 2. The control device according to claim 1, wherein the load device is a motor, and the converter temperature adjustment means controls a power conversion of a power converter to adjust an output torque of the motor. An overheat protection device for a power converter, wherein the converter temperature is adjusted by adjusting output torque. 3. The apparatus according to claim 1, wherein the converter temperature adjustment means is provided in a cooling device that cools the power converter by flowing a cooling medium, and the adjustment of the converter temperature is performed by controlling the cooling medium. An overheat protection device for a power converter, which is performed by changing a flow amount. 4. An inverter control device for an electric vehicle that controls an inverter that supplies a current to a motor and generates an output torque in accordance with an accelerator operation to the motor, wherein a torque command value is determined based on a driver's accelerator operation. Command value determining means for determining; a temperature detecting means for detecting a semiconductor element temperature of the inverter; a temperature change rate detecting means for obtaining a time change rate of the semiconductor element temperature; and the torque based on the semiconductor element temperature and its time change rate. Command value adjusting means for adjusting the command value, and control means for generating a control signal to the inverter in accordance with the adjusted torque command value adjusted by the command value adjusting means, and An inverter control device for an electric vehicle, wherein overheating due to a rapid rise in temperature of a semiconductor element is prevented by adjusting output torque. . 5. An inverter cooling device for an electric vehicle for cooling an inverter that supplies a current to a motor, comprising: a cooling pump for sending a cooling medium to a cooling medium passage provided in the inverter; and detecting a temperature of a semiconductor element of the inverter. Temperature detecting means, a temperature change rate detecting means for detecting a time rate of change of the semiconductor element temperature, and a flow rate of the cooling medium is determined based on the semiconductor element temperature and the time rate of change thereof. An electric vehicle, comprising: pump control means for controlling a cooling pump; andadjusting a flow rate of a cooling medium according to a time change rate of the temperature of the semiconductor element to prevent overheating due to a rapid rise in temperature of the semiconductor element. Inverter cooling device.