JP2015096015A - Electrical rear-wheel-drive-power regulation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for sufficiently regulating the number of revolutions of a cooling fan for air-cooling an electrical rear-wheel-drive-power regulation device for regulating drive power applied to rear wheels of a four-wheel drive vehicle.SOLUTION: A current detector detecting a carrying current for carrying a current to a motor regulating drive power applied to rear wheels from an inverter, and an integration unit integrating current values detected within previous predetermined time are prepared. The number of revolutions of a cooling fan is determined according to a rule that the number of revolution becomes higher as temperature detected by a temperature detector is higher, and the number of revolutions becomes lower as the integration current value integrated by the integration unit is smaller. In summer in which a calorific value is small, the cooling fan is prevented from unnecessary rotation due to reduction in the number of revolutions.

Description

  In the present specification, an electric device that adjusts the driving force applied to the rear wheels of a four-wheel drive vehicle (hereinafter referred to as an electric rear wheel driving force adjusting device) is disclosed. In particular, an electric rear wheel driving force adjustment device that rotates a cooling fan to cool the air is disclosed.

When the driving force applied to the rear wheels of the four-wheel drive vehicle is adjusted, slipping can be prevented and driving stability can be improved. Therefore, an electric device has been developed that adjusts the driving force applied to the rear wheel by connecting a motor to the drive shaft of the rear wheel and energizing the motor from an inverter.
Since the electric rear wheel driving force adjusting device generates heat when it operates, it needs to be air-cooled. The electric rear wheel driving force adjusting device referred to in the present specification is a device for adjusting the driving force applied to the rear wheel, and means an electric device that needs to be air-cooled during operation, such as an inverter alone, a motor alone, or A combination of an inverter and a motor. In other words, the technology disclosed in this specification can be applied to a cooling fan that cools an inverter, and can also be applied to a cooling fan that cools both an inverter and a motor.

  Patent Document 1 discloses a technique for water-cooling an inverter that energizes a motor that drives an electric vehicle. In the technique of Patent Document 1, the amount of cooling water is increased as the temperature of the inverter is higher, and the amount of cooling water is increased as the temperature increase rate of the inverter is higher. According to the technology that adjusts the cooling water amount depending only on the temperature of the inverter, the inverter may overheat due to a response delay. In the technique of Patent Document 1, since the amount of cooling water is adjusted in consideration of not only the temperature but also the rate of temperature increase, the inverter can be prevented from overheating.

JP-A-10-210790

  In the technique of Patent Document 1, the amount of cooling water is determined in consideration of not only the temperature of the inverter but also the rate of temperature increase. When applied to the air cooling technique, the rotational speed of the cooling fan is determined in consideration of not only the temperature but also the rate of temperature increase. However, even if the rotational speed of the cooling fan is determined in consideration of not only the temperature but also the rate of temperature increase, there is a problem in the case of the electric rear wheel driving force adjusting device.

  In the case of an electric rear wheel driving force adjusting device that cools by air, the heat capacity of the heat transfer path from the heat generating part to the air cooling part is large, so the temperature increase rate starts to increase from the timing when the heat generation amount per unit time increases. The time difference between timings is large. Further, there is a large time difference from the timing at which the number of rotations of the cooling fan is increased to the timing at which the cooling amount at the heat generating portion starts to increase. For this reason, in the technique of adjusting the rotation speed of the cooling fan using the temperature increase rate as an index, the response delay is not eliminated. In order to prevent the electric rear wheel driving force adjusting device from overheating even if there is a response delay, the rotational speed of the cooling fan must be determined in anticipation of the response delay.

The electric rear wheel driving force adjusting device is a device that prevents the occurrence of slip and enhances running stability, and operates frequently during running on snowy roads, but its operating frequency decreases in summer. It has the characteristics that the duration of heat generation is long while driving on snowy roads and the duration of heat generation is short in summer.
In the technology that determines the rotation speed of the cooling fan based on the temperature of the electric rear wheel driving force adjustment device and the rate of temperature rise, the electric rear wheel driving force adjustment device does not overheat even under long heat generation conditions. There must be. When air-cooling the electric rear wheel drive force adjustment device, due to the above-mentioned problem of response delay, it is necessary to set the rotation speed in anticipation of the response delay and a reasonable rotation speed even under the condition of long heat generation duration. Don't be.

  The relationship between the "cooling fan speed and the temperature and temperature rise rate of the electric rear wheel drive force adjustment device" that can meet the above needs was created. It turns out that the problem of rotating unnecessarily or rotating at an unnecessary high speed occurs. For example, in order to prevent overheating during running on a snowy road having a long heat generation duration, it may be necessary to start rotation of the cooling fan when the electric rear wheel driving force adjusting device is heated to about 30 ° C. is there. Even when a technique for increasing the number of revolutions as the temperature increase rate increases is used, the temperature at the start of rotation of the cooling fan cannot be increased so much due to the problem of the response delay. For example, even when using a technology that increases the number of revolutions as the temperature rise rate increases, if the temperature at the start of the cooling fan rotation is not set to about 35 ° C, it will prevent overheating while running on a snowy road with a long heat generation duration There are things you can't do. In this case, in summer, there is a problem that the cooling fan is rotated even though the electric rear wheel driving force adjusting device is not operating. Alternatively, there is a problem that the cooling fan is rotated at a speed higher than that required when the heat generation duration is short. If the cooling fan is rotated unnecessarily or at an unnecessary high speed, the life of the cooling fan is unnecessarily reduced.

  The present specification provides a technique for adjusting the number of rotations of a cooling fan for air-cooling an electric rear wheel driving force adjusting device without excess or deficiency.

  The electric device disclosed in the present specification adjusts the driving force applied to the rear wheels of the four-wheel drive vehicle to improve traveling stability. The electric device detects a current flowing in the electric device, a current detector that integrates current values detected within a predetermined time immediately before the current detector, and detects a temperature of the electric device. A temperature detection unit, a cooling fan that air-cools the electric device, and a control unit that controls the number of rotations of the cooling fan are provided. The control unit controls the number of rotations of the cooling fan according to a rule that increases the number of rotations as the temperature detected by the temperature detection unit is higher, and decreases the number of rotations as the integrated current value integrated by the integration unit decreases.

  The integrated current value integrated by the integrating unit is proportional to the integrated heat generation amount within a predetermined time. According to the above apparatus, the rotational speed is determined according to a rule that “the higher the temperature, the higher the speed and the lower the integrated heat generation amount, the lower the speed”. According to this method, the above-mentioned problem of response delay is reduced. The necessity of determining the rotational speed in anticipation of the response delay is reduced, and the rotational speed can be brought close to the truly required rotational speed. For this reason, it is possible to prevent overheating while running on a snowy road having a long heat generation duration, and to prevent the cooling fan from rotating unnecessarily in the summer when the heat generation duration is short.

  Details of the technology disclosed in this specification and further improvements will be described in detail in the detailed description and examples.

The figure which shows the structure of the electrically driven rear-wheel drive force adjustment apparatus of an Example. The figure which shows the relationship between the temperature of an electrically driven rear-wheel drive force adjustment apparatus, and the rotation speed of a cooling fan. The figure which shows the relationship between the temperature of an electrically driven rear-wheel drive force adjustment apparatus, and the rotation speed of a cooling fan. The cooling fan control procedure figure. The figure which shows the relationship between the temperature of an electrically driven rear-wheel drive force adjustment apparatus, and a season.

The main features of the embodiments described below are listed below. The technical elements described below are independent technical elements and exhibit technical usefulness alone or in various combinations, and are limited to the combinations described in the claims at the time of filing. It is not a thing.
(Characteristic 1) The inverter that energizes the motor that adjusts the driving force applied to the rear wheels is cooled.
(Characteristic 2) The number of revolutions is determined in consideration of the cooling air temperature in addition to the temperature and the integrated current value.
(Characteristic 3) The number of revolutions is determined in consideration of the temperature rise rate in addition to the temperature and the integrated current value.
(Characteristic 4) The rule for increasing the rotational speed as the temperature is higher and lowering the rotational speed as the integrated current value is smaller is a rule for correcting the rotational speed in consideration of the cooling air temperature and / or the temperature increase rate. included. That is, the rule that the rotational speed is increased as the temperature is higher and the rotational speed is decreased as the integrated current value is smaller is to determine the rotational speed by taking at least the temperature and the integrated current value into account. Do not exclude the addition.

  FIG. 1 shows a configuration of an electric rear wheel driving force adjusting device according to an embodiment. Reference numeral 2 is an in-vehicle battery, and reference numeral 14 is a motor. The motor 14 is for adjusting the driving force applied to the rear wheel 16 of the four-wheel drive vehicle, and the rear wheel 16 is connected to the drive shaft. Reference numeral 4 is an inverter that converts a DC voltage supplied from the in-vehicle battery 2 into a three-phase AC and energizes the motor 14. The inverter 4 is provided with a current detection unit 6 that detects a current flowing through the inverter 4, a cooling fan 8 that air-cools the inverter 4, and a temperature detection unit 10 that detects the temperature of the case of the inverter 4. Reference numeral 18 is a device for controlling the inverter 4 (referred to as an inverter ECU or an inverter control device), which controls on / off of a plurality of switching elements incorporated in the inverter 4 and controls the rotation speed of the cooling fan 8. Control. The current detection unit 6, the cooling fan 8, and the temperature detection unit 10 are connected to the inverter control device 18. The inverter control device 18 is also connected to a cooling air temperature detector 12 that detects the temperature of the air blown by the cooling fan 8. The inverter is placed in the trunk room behind the vehicle. Conventionally, it is arranged in a space that accommodates a spare tire.

  The inverter control device 18 inputs the energization current detected by the current detection unit 6 at a constant cycle, and calculates the integrated current value by summing the predetermined number of energization current detection values input immediately before. This process is equivalent to obtaining a value obtained by integrating the energization current value over the predetermined time immediately before.

FIG. 2 shows the relationship between the inverter temperature (detected by the temperature detection unit 10), the integrated current value, and the rotational speed of the cooling fan 8 built in the inverter control device 18.
A graph C1 in FIG. 2A shows the relationship between the temperature and the rotation speed when the integrated current value is within the reference range. The relationship is set such that the higher the temperature, the higher the rotational speed. Graph C2 in FIG. 2 (1) shows the relationship between the temperature and the rotation speed when the integrated current value is equal to or greater than the reference range. Compared to the graph C1, the rotational speed is increased even at the same temperature. Graph C3 in FIG. 2 (1) shows the relationship between the temperature and the rotation speed when the integrated current value is below the reference range. Compared to the graph C1, the rotational speed is lowered even at the same temperature. (1) of FIG. 2 shows an example in which the number of rotations is increased as the temperature detected by the temperature detection unit 10 is higher, and the number of rotations is decreased as the integrated current value integrated by the integration unit is smaller.

The graph C1 in FIG. 2 (2) is equal to the graph C1 in FIG. 2 (1). Graph C4 in FIG. 2 (2) shows the relationship between the temperature and the rotational speed when the integrated current value is equal to or greater than the reference range. Compared to the graph C1, the rotational speed is increased even at the same temperature. Further, the temperature at which the cooling fan starts to rotate is low. Graph C5 in FIG. 2 (2) shows the relationship between the temperature and the rotation speed when the integrated current value is below the reference range. Compared to the graph C1, the rotational speed is lowered even at the same temperature. Further, the temperature at which the cooling fan starts to rotate is high. FIG. 2 (2) also shows an example in which the rotational speed is increased as the temperature detected by the temperature detection unit 10 is higher, and the rotational speed is decreased as the integrated current value integrated by the integrating unit is smaller.
Actually, the relationship of (1) and (2) in FIG. 2 may be used together. That is, as shown in FIG. 2 (1), the smaller the integrated current value, the lower the rate of increase of the rotational speed with respect to the temperature rise, and as shown in FIG. 2 (2), the smaller the integrated current value, the cooling fan. The temperature at the start of rotation may be increased.

FIG. 3 shows the relationship between the temperature and the number of revolutions employed in the example. A graph C6 indicated by a solid line shows the relationship between the temperature and the rotational speed when the integrated current value is within the reference range (20 to 40 A). If the case temperature of the inverter 4 is 10 ° C. or less, the rotational speed is zero. In the range of 70 ° C., the number of revolutions is low, and when it is 70 ° C. or more, the number of revolutions is high. Graph C7 shows the relationship between the temperature and the number of revolutions when the integrated current value is not less than the reference range (40 A or more), and the number of revolutions is zero if it is −10 ° C. or less. If the speed is low and 10 ° C. or higher, the rotation speed is high speed. As indicated by the upward arrow, the rotational speed is increased if the integrated current value is high even at the same temperature. Graph C8 shows the relationship between the temperature and the rotational speed when the integrated current value is below the reference range (20A or lower). The rotational speed is zero when the temperature is 40 ° C. or lower, and the rotational speed is low when the temperature is 40 ° C. or higher. As indicated by the downward arrow, if the integrated current value is small even at the same temperature, the rotational speed is lowered. This also follows the rule that the rotational speed is increased as the temperature detected by the temperature detection unit 10 is higher, and the rotational speed is decreased as the integrated current value integrated by the integrating unit is smaller.
As illustrated in FIG. 3, the relationship between the temperature and the rotational speed and the relationship between the integrated current value and the rotational speed may be a relationship that determines the rotational speed according to the temperature range or the range of the integrated current value.

  FIG. 4 shows a control procedure of the cooling fan 8. In step S2, the magnitude of the energization current detected by the current detection unit 6 is input. In step S4, an integrated current value within a predetermined time (T time) immediately before is calculated. In this embodiment, step S2 is repeatedly executed at a constant cycle. Therefore, if the immediately preceding predetermined number of detection values are summed, the integrated current value within the immediately preceding predetermined time can be calculated. In step S6, one graph is selected from the graphs C6, C7, and C8 in FIG. 3 based on the integrated current value. In step S8, the rotational speed of the cooling fan 8 is determined based on the selected graph and the case temperature of the inverter 4.

  At the time of implementation, after the rotational speed is determined based on the temperature and the integrated current value, processing for correcting the rotational speed based on the temperature of the cooling air may be added as shown in step S10. In addition to the cooling air temperature, the rotational speed may be corrected in consideration of the temperature increase rate. What is necessary is to determine the rotational speed based on the temperature and the integrated current value, and then the rotational speed may be corrected in consideration of the cooling air temperature and the temperature increase rate. The technology of this specification does not exclude adding factors other than temperature and integrated current value. In step S12, the cooling fan 8 is rotated at the rotational speed determined by the inverter control device 18 (control unit).

The vertical axis | shaft of FIG. 5 has shown temperature. Graph B1 shows the initial temperature in winter of the electric rear wheel driving force adjusting device. The initial temperature in winter is low. The electric rear wheel driving force adjusting device is frequently operated when running on a snowy road and has a long continuous heat generation time. Graph B2 shows the temperature generated when the electric rear wheel driving force adjusting device is not air-cooled, and shows that the electric rear wheel driving force adjusting device is overheated to an allowable temperature or higher. Graph B3 shows the temperature generated when the cooling fan is rotated when the temperature rises to T1, and is suppressed to an allowable temperature.
Graph B4 shows the initial temperature in summer of the electric rear wheel driving force adjusting device. If the rotation start temperature of the cooling fan in the summer is T1, the cooling fan will be rotated in the summer even though the electric rear wheel driving force adjusting device is not operating. The electric rear wheel driving force adjusting device operates less frequently in summer and has a shorter continuous heat generation time. Graph B5 shows the temperature that occurs when the electric rear wheel driving force adjusting device is not air-cooled, and shows that the electric rear wheel driving force adjusting device is overheated to an allowable temperature or higher. It still fits at a lower temperature than graph B2. Graph B6 indicates the temperature that is generated when the cooling fan is rotated when the temperature rises to T2, and is suppressed to an allowable temperature. Since the graph B5 is stored at a lower temperature than the graph B2, overheating can be prevented even when T2> T1.

When the number of rotations is determined according to a rule that increases the number of rotations as the temperature detected by the temperature detection unit 10 is higher and the number of rotations decreases as the integrated current value integrated by the integration unit decreases, the rotation start temperature of the cooling fan is determined. It is possible to set T1 in winter and T2 in summer. In the above example, the cooling fan can be prevented from rotating unnecessarily while preventing overheating. In the above example, the inverter is applied to a cooling fan that air-cools. It can also be applied to a cooling fan that cools both the inverter and motor.

As mentioned above, although the Example of the technique which this specification discloses was described in detail, these are only illustrations and do not limit a claim. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.
The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology illustrated in the present specification or the drawings achieves a plurality of objects at the same time, and has technical utility by achieving one of the objects.

2: Vehicle battery 4: Inverter 6: Current detection unit 8: Cooling fan 10: Temperature detection unit 12: Cooling air temperature detection unit 14: Motor 16: Rear wheel 18: Inverter control device (inverter ECU, control unit)

Claims (1)

An electric device that adjusts the driving force applied to the rear wheels of a four-wheel drive vehicle,
A current detection unit for detecting an energization current of the electric device;
An integration unit for integrating the current values detected within the predetermined time immediately before by the current detection unit;
A temperature detector for detecting the temperature of the electric device;
A cooling fan for air-cooling the electric device;
A control unit for controlling the number of rotations of the cooling fan,
According to the rule that the controller increases the rotational speed as the temperature detected by the temperature detector is higher, and decreases the rotational speed as the integrated current value integrated by the integrating unit decreases, the rotational speed of the cooling fan An electric rear wheel driving force adjusting device characterized by controlling the motor.

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