Control device for electric unit

Abstract

To prevent overheating of a DCDC converter of an electric unit.SOLUTION: An electric unit 12 includes a first case part 40 which accommodates a motor 20 and a transaxle 22, a second case part 42 which accommodates a DCDC converter 26, and a case boundary part 46 being a boundary between the first case part 40 and the second case part 42. ATF is supplied to the motor 20 and the transaxle 22, and cooling water is supplied to the DCDC converter 26. A control device 14 acquires an error correction value from a time change amount of motor torque, estimates a temperature (case boundary temperature) of the case boundary part 46 from the ATF temperature, corrects the case boundary temperature by adding the error correction value to the case boundary temperature, estimates the DCDC converter temperature from the corrected case boundary temperature and the cooling water temperature, acquires an output limit value of the motor 20 from the DCDC converter temperature, and controls the motor 20 on the basis of the output limit value.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a control device for an electric unit, and more particularly to a control device for preventing overheating of a DCDC converter included in the electric unit.

Background Art

[0002] Conventionally, electric vehicles such as battery electric vehicles (BEV), fuel cell vehicles (FCEV), hybrid vehicles (HEV), and plug-in hybrid vehicles (PHEV) have been known. Some electric vehicles are equipped with an electric unit called an E-Axle. The electric unit includes a motor, a transaxle that transmits the power of the motor to the vehicle wheels, and an inverter that drives the motor, and is a drive unit that integrates them. Also known is an electric unit including a DCDC converter. The DCDC converter is a boost converter that boosts the power supplied from the battery and outputs it to the inverter.

[0003] Patent Document 1 discloses a power conversion system including a converter configured to boost a voltage by operating at a set carrier frequency, and a control device that executes protection control of the converter. The control device estimates the temperature rise amount of the converter according to at least one of the voltage ratio before and after boosting of the converter and the carrier frequency, and the detected value of the current flowing through the converter, and when the integrated value of the temperature rise amount reaches a threshold value, executes control for suppressing the current flowing through the converter.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The electric unit includes a first case portion that houses a motor and a transaxle, a second case portion that houses a DCDC converter, and a case boundary portion that forms a boundary between the first case portion and the second case portion. In the electric unit, ATF (Automatic Transmission Fluid) as cooling oil is supplied to the motor and the transaxle, and cooling water is supplied to the inverter and the DCDC converter.

[0006] The temperature of the DCDC converter is affected by heat dissipation by the cooling water, heat generation by the DCDC converter itself, and heat reception from the case boundary portion heated by the motor or the like. In particular, when the case boundary portion is at a high temperature, the temperature of the DCDC converter is greatly affected by the temperature of the case boundary portion. In this case, the temperature of the DCDC converter is likely to rise, and there is a risk of exceeding its heat-resistant temperature.

[0007] Therefore, it is desired to more accurately estimate the temperature of the case boundary portion, more accurately obtain the temperature of the DCDC converter, and when the temperature of the DCDC converter is high, control that can protect the DCDC converter by limiting the motor output.

[0008] An object of the present invention is to prevent overheating of the DCDC converter in the electric unit.

Means for Solving the Problems

[0009] The control device for an electric unit according to the present invention includes a motor, a transaxle that transmits the power of the motor to the vehicle wheels, an inverter that drives the motor, and a DCDC converter that boosts the power supplied from a battery and outputs it to the inverter, and is a control device in an electric unit in which these are integrated. The electric unit includes a first case portion in which the motor and the transaxle are housed, a second case portion in which the DCDC converter is housed, and a case boundary portion that is the boundary between the first case portion and the second case portion. In the electric unit, ATF is supplied to the motor and the transaxle, and cooling water is supplied to the inverter and the DCDC converter. The electric unit includes an ATF temperature sensor that detects the ATF temperature, which is the temperature of the ATF, and a water temperature sensor that detects the cooling water temperature, which is the temperature of the cooling water. In the storage device of the control device, a correlation formula showing the relationship between the ATF temperature and the case boundary temperature, which is the temperature of the case boundary portion, an error correction function showing the relationship between the time change amount of the motor torque of the motor and the error correction value, the heat dissipation amount of the DCDC converter according to the cooling water temperature, the heat generation amount of the DCDC converter itself, and a converter temperature estimation function for estimating the temperature of the DCDC converter in consideration of the heat reception amount of the DCDC converter according to the case boundary temperature, and a motor output limit map showing the relationship between the temperature of the DCDC converter and the output limit value of the motor are stored in advance. The control device acquires the time change amount of the motor torque in a past fixed time, acquires the error correction value corresponding to the time change amount of the motor torque using the error correction function, estimates the case boundary temperature corresponding to the ATF temperature using the correlation formula, corrects the case boundary temperature by adding the error correction value to the case boundary temperature, estimates the temperature of the DCDC converter corresponding to the corrected case boundary temperature and the cooling water temperature using the converter temperature estimation function, acquires the output limit value of the motor corresponding to the temperature of the DCDC converter using the motor output limit map, and controls at least one of the inverter and the DCDC converter based on the output limit value.

Effect of the Invention

[0010] According to the present invention, since there is no temperature sensor at the case boundary portion, first, the ATF temperature is acquired by the ATF temperature sensor, and the temperature of the case boundary portion (case boundary temperature) is estimated from the ATF temperature using a correlation formula. However, if the fluctuation of the motor torque is large, the correlation between the ATF temperature and the case boundary temperature is broken, and the estimation accuracy of the case boundary temperature decreases. Therefore, in the present invention, an error correction value corresponding to the amount of change in the motor torque over time is acquired, and the case boundary temperature obtained by the correlation formula is corrected by the error correction value. Therefore, the case boundary temperature can be estimated more accurately. The temperature of the DCDC converter can be obtained more accurately, and the motor output can be limited according to the temperature of the DCDC converter to prevent overheating of the DCDC converter.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments described herein. The same reference numerals are given to the same elements in all the drawings, and redundant explanations are omitted.

[0013] FIG. 1 is a schematic configuration diagram of the electric unit 12. The electric unit 12 is mounted on an electric vehicle. The electric unit 12 includes a motor 20, a transaxle 22 that transmits the power of the motor 20 to the vehicle wheels, an inverter 24 that drives the motor 20, and a DCDC converter 26 that boosts the electric power supplied from a battery (not shown) and outputs it to the inverter 24, and they are integrated.

[0014] The motor 20 is a motor generator, also referred to as MG. In the embodiment described herein, the electric unit 12 has only one motor 20 (MG1), but the electric unit 12 may be configured to have a plurality of motors 20.

[0015] The electric unit 12 includes a case 38. The case 38 includes a first case portion 40 that houses the motor 20 and the transaxle 22, and a second case portion 42 that houses the DCDC converter 26. The electric unit 12 includes a case boundary portion 46 that forms the boundary between the first case portion 40 and the second case portion 42.

[0016] In the electric unit 12, ATF is supplied to the motor 20 and the transaxle 22. The ATF is an oil that cools and lubricates the motor 20 and the transaxle 22. The ATF circulates through a circulation circuit (not shown) including a pump and an oil cooler. The electric unit 12 includes an ATF temperature sensor 34. The ATF temperature sensor 34 detects the temperature of the ATF (referred to as the ATF temperature) in, for example, an oil sump provided at the lower part of the first case portion 40.

[0017] In the electric unit 12, cooling water is supplied to the inverter 24 and the DCDC converter 26. The cooling water is supplied to the cooling water passage 30 and cools the inverter 24 and the DCDC converter 26 through the cooling water passage 30. The cooling water circulates through a circulation circuit (not shown) including a pump and a radiator. The electric unit 12 includes a water temperature sensor 32. The water temperature sensor 32 detects the temperature of the cooling water (referred to as the cooling water temperature) supplied to the DCDC converter 26, for example.

[0018] The control device 14 is an ECU that controls the electric unit 12. The control device 14 may be a part of the electric unit 12 or may be located at a position separated from the electric unit 12. The control device 14 includes a CPU, a RAM, a ROM, a flash memory, an input / output interface, etc. The control device 14 may be configured to include a microcomputer. The control device 14 includes a storage device 15 composed of a flash memory or the like. Detection values of the ATF temperature sensor 34 and the water temperature sensor 32 are input to the control device 14.

[0019] In the storage device 15 of the control device 14, a correlation formula (see FIG. 2(A)) showing the relationship between the ATF temperature and the temperature of the case boundary portion 46 (referred to as the case boundary temperature), an error correction function (see FIG. 2(B)), a converter temperature estimation function (formula (1) described later), and a motor output limit map (FIG. 2(C)) are stored in advance.

[0020] FIG. 2(A) is a diagram schematically showing the correlation between the ATF temperature T ATF and the case boundary temperature T case . When the ATF temperature T ATF increases, the case boundary temperature T case also increases. The correlation formula between the ATF temperature T ATF and the case boundary temperature T case is created using experiments, analysis data, etc. at the design stage of the electric unit 12.

[0021] As described later, the control device 14 determines the case boundary temperature T case corresponding to the ATF temperature T ATFIt is estimated using the correlation formula (Fig. 2(A)). However, if there are large fluctuations in the motor torque or the like, the correlation between the ATF temperature and the case boundary temperature will break down, and the estimation accuracy of the case boundary temperature will decrease. Therefore, in this embodiment, an error correction function (Fig. 2(B)) is used to obtain an error correction value corresponding to the amount of change in the motor torque over time, and the case boundary temperature obtained by the correlation formula is corrected by the error correction value. That is, since the correlation formula produces errors due to sudden heat generation and changes in the amount of heat dissipation of external disturbance factors, an error correction value is obtained from a function (error correction function) of the amount of change over time ΔXi / Δt such as the motor torque and the water pump rotation speed (described later), and this is used to correct the case boundary temperature T case is corrected.

[0022] Fig. 2(B) is a diagram illustrating an error correction function (a function representing an error correction term ε (error correction value)). The error correction function in this figure shows the relationship between the amount of change over time (ΔMG1 torque / Δt) of the motor torque of the motor 20 and the error correction term ε. The error correction term ε indicates the error between the value obtained by the correlation formula (Fig. 2(A)) and the actual value. The error correction function is created using experiments, analysis data, etc. at the design stage of the electric unit 12.

[0023] The converter temperature estimation function is a polynomial for estimating the temperature T dcdc of the DCDC converter 26. The converter temperature estimation function is a function that takes into account the heat dissipation amount of the DCDC converter 26 according to the cooling water temperature, the heat reception amount of the DCDC converter 26 according to the case boundary temperature (the temperature of the case boundary portion 46), and the heat generation amount of the DCDC converter itself. The following formula (1) is an example of the converter temperature estimation function.

[0024] T dcdc = const.A × cooling water temperature T LLC + const.B × case boundary temperature T case + const.C ···(1)

[0025] The converter temperature estimation function is created using experiments, analysis data, etc. at the design stage of the electric unit 12.

[0026] Figure 3(C) is a diagram illustrating a motor output limit map. The motor output limit map shows the relationship between the temperature T of the DCDC converter 26 dcdc and the motor output limit value. In Figure 3(C), it shows that when the motor output limit value is less than 1, the output of the motor 20 is restricted. The motor output limit map is set so that the temperature T of the DCDC converter 26 dcdc does not exceed its heat-resistant temperature. The motor output limit map is created using experiments, analysis data, etc. at the design stage of the electric unit 12.

[0027] Figure 3 is a flowchart showing the overheat prevention control of the DCDC converter 26. The figure shows the control when the electric unit 12 is used in a vehicle. The control flow in Figure 3 is executed at a predetermined cycle. In steps S14 to S18 in Figure 3, it is described that an error correction value (error correction term) is calculated from a plurality of factors including the water pump rotation speed, but here, the case where only the motor torque is used as a factor will be described.

[0028] In step S10, the control device 14 acquires the cooling water temperature T from the water temperature sensor 32 LLC In step S12, the control device 14 acquires the ATF temperature T from the ATF temperature sensor 34 ATF

[0029] In steps S14 and S16, the control device 14 acquires the amount of change over time of the torque command value (motor torque) of the motor 20 over a past fixed time. In step S18, the control device 14 acquires an error correction value (error correction term ε) corresponding to the amount of change over time of the motor torque using an error correction function (see Figure 2(B)).

[0030] In step S20, the control device 14 estimates the case boundary temperature (temperature of the case boundary part 46 (peripheral parts)) corresponding to the ATF temperature using a correlation formula (see Figure 2(A)), and adds the error correction value (calculated in S18) to the case boundary temperature to correct the case boundary temperature.

[0031] Next, in step S22, the control device 14 determines the temperature T of the DCDC converter 26 corresponding to the corrected case boundary temperature (obtained in S20) and the cooling water temperature (obtained in S10). dcdc This temperature T is estimated using the converter temperature estimation function (see the above formula (1)).

[0032] Next, in steps S24 to S28, the control device 14 uses a motor output limit map (see Fig. 2(C)) to obtain the output limit value of the motor 20 corresponding to the temperature T dcdc (calculated in S22), and controls the motor 20 based on this output limit value.

[0033] Specifically, in step S24, the control device 14 checks whether the temperature T dcdc of the DCDC converter 26 is higher than the threshold value T th1 . If step S24 is No (when T dcdc is less than or equal to the threshold value T th1 ), the control device 14 ends the processing for this cycle.

[0034] On the other hand, if step S24 is Yes (when T dcdc is higher than the threshold value T th1 ), in step S26, the control device 14 uses a motor output limit map (see Fig. 2(C)) to obtain the output limit value of the motor 20 corresponding to the temperature T dcdc (calculated in S22). Then, in step S28, the control device 14 controls at least one of the inverter 24 and the DCDC converter 26 based on this output limit value to limit the output of the motor 20.

[0035] According to the embodiments described above, since there is no temperature sensor at the case boundary portion 46, first, the ATF temperature is acquired by the ATF temperature sensor 34, and the temperature of the case boundary portion 46 (case boundary temperature) is estimated from the ATF temperature using the correlation formula. However, if the motor torque fluctuation of the motor 20 is large, the correlation between the ATF temperature and the case boundary temperature is broken, and the estimation accuracy of the case boundary temperature decreases. Therefore, in this embodiment, an error correction value (error correction term ε) corresponding to the amount of change in motor torque over time is acquired, and the case boundary temperature obtained by the correlation formula is corrected by the error correction value. Therefore, the case boundary temperature can be estimated more accurately. The temperature T dcdc of the DCDC converter can be obtained more accurately, and the output of the motor 20 can be limited according to the temperature T dcdc of the DCDC converter 26 to prevent overheating of the DCDC converter 26.

[0036] For components whose temperature is dominated by the amount of heat transfer from surrounding components (such as the case boundary portion 46) (in this embodiment, the DCDC converter 26), the temperature cannot be sufficiently lowered only by limiting its own heat generation amount, and there is a risk of component damage. When the surrounding components of itself are at a high temperature, it receives heat from the surrounding components or cannot sufficiently dissipate the heat amount from itself, so its own temperature rises. This is because the temperature of the surrounding components themselves cannot be lowered only by limiting the heat generation amount of itself. However, according to the embodiments described above, the temperature of the surrounding components can be lowered to prevent its own overheating. It is possible to protect components that cannot prevent heat resistance exceeding only by limiting their own heat generation amount. It is possible to achieve both component protection and power performance without additional sensors.

[0037] Note that factors affecting the error correction value (error correction term ε) can also be considered other than motor torque. FIG. 4(A) is a diagram showing the breakdown of the correlation according to the amount of change in the torque of MG2 over time, FIG. 4(B) is a diagram showing the breakdown of the correlation according to the amount of change in the torque of MG1 over time, and FIG. 4(C) is a diagram showing the breakdown of the correlation according to the amount of change in the engine room temperature over time.

[0038] Therefore, an error correction value (error correction term ε) may be calculated in consideration of a plurality of disturbance factors ΔXi (motor torque (MG1, MG2, ···), engine room temperature, etc.). Note that this is shown in S14 to S18 of FIG. 3. The engine room temperature depends on the water pump rotation speed that contributes to the heat dissipation amount of the radiator. Therefore, an error correction value (error correction term ε) corresponding to the amount of change over time of the water pump rotation speed may be calculated.

[0039] Note that the error correction function (function representing the error correction term ε), f(ΔXi / Δt), may be generated using, for example, multivariate regression, multi-dimensional grid, or neural network.

Explanation of Signs

[0040] 12 Electric unit, 14 Control device, 15 Storage device, 20 Motor, 22 Transaxle, 24 Inverter, 26 DCDC converter, 30 Cooling water passage, 32 Water temperature sensor, 34 ATF temperature sensor, 38 Case, 40 First case part, 42 Second case part, 46 Case boundary part (case interface).

Claims

【Claim 1】 A motor, A transaxle that transmits the power of the motor to the vehicle wheels, An inverter that drives the motor, A DC-DC converter that boosts the power supplied from the battery and outputs it to the inverter, and a control device in an electric unit that integrates them, The electric unit, A first case part that houses the motor and the transaxle, A second case part that houses the DC-DC converter, A case boundary part that is the boundary between the first case part and the second case part, In the electric unit, ATF is supplied to the motor and the transaxle, and cooling water is supplied to the inverter and the DC-DC converter, The electric unit includes an ATF temperature sensor that detects the ATF temperature, which is the temperature of the ATF, and a water temperature sensor that detects the cooling water temperature, which is the temperature of the cooling water, In the storage device of the control device, A correlation formula showing the relationship between the ATF temperature and the case boundary temperature, which is the temperature of the case boundary part, An error correction function showing the relationship between the time change amount of the motor torque of the motor and the error correction value, A converter temperature estimation function for estimating the temperature of the DC-DC converter, taking into account the heat dissipation amount of the DC-DC converter according to the cooling water temperature, the heat generation amount of the DC-DC converter itself, and the heat reception amount of the DC-DC converter according to the case boundary temperature, A motor output limit map showing the relationship between the temperature of the DC-DC converter and the output limit value of the motor are stored in advance, The control device, Obtains the time change amount of the motor torque over a past fixed time, Obtains the error correction value corresponding to the time change amount of the motor torque using the error correction function, Estimates the case boundary temperature corresponding to the ATF temperature using the correlation formula, adds the error correction value to the case boundary temperature to correct the case boundary temperature, Estimates the temperature of the DC-DC converter corresponding to the corrected case boundary temperature and the cooling water temperature using the converter temperature estimation function, Obtains the output limit value of the motor corresponding to the temperature of the DC-DC converter using the motor output limit map, and controls at least one of the inverter and the DC-DC converter based on the output limit value, A control device for an electric unit, characterized by the above.

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