Vehicle control device and vehicle control method

Abstract

In a first aspect of the vehicle control device and the vehicle control method of the present invention, the standby flow rate, which is the flow rate of an electric pump determined on the basis of a temperature relating to the temperature of a drive circuit for driving an electric motor, is set in advance before a vehicle accelerates. Due to the configuration described above, the power consumption of an electric pump for circulating a cooling medium in a circulation path connected to the drive circuit can be reduced while keeping the temperature rise accompanying the acceleration of the drive circuit for driving the electric motor capable of outputting power to the drive wheels within an allowable range.

Description

Vehicle control device and vehicle control method

[0001] The present invention relates to a vehicle control device and a vehicle control method.

[0002] The temperature adjustment device in Patent Document 1 has an electric water pump that circulates the coolant and a temperature sensor that detects the coolant temperature Tw in a circulation pipe that forms a circulation path together with the coolant flow paths formed in the motor and inverter installed in the electric vehicle, and when the coolant temperature Tw detected by the temperature sensor exceeds a predetermined temperature T0, a target flow rate is set so that the coolant circulates in a turbulent flow region, and when the coolant temperature Tw falls below the predetermined temperature T0, the target flow rate is set so that the coolant circulates in a laminar flow region, and the electric water pump is driven and controlled.

[0003] Japanese Patent Application Laid-Open No. 2005-224042

[0004] When a vehicle using an electric motor fully accelerates, the temperature of the inverter (inverter chip) that constitutes the motor's drive circuit rises rapidly. Therefore, if the flow rate of the electric pump that circulates the cooling medium is increased based on the temperature rise or acceleration detection, the response delay in the flow rate increase may be insufficient to prevent the temperature rise. Therefore, when the vehicle is stopped, where it is not known when the vehicle will fully accelerate, it is necessary to circulate the cooling medium at a high flow rate (e.g., maximum flow rate) in advance in preparation for full acceleration. However, the inventors of the present application discovered that if the temperature of the inverter chip is low before full acceleration, the maximum temperature (i.e., peak temperature) reached upon full acceleration will be lower, and circulating the cooling medium at a high flow rate appropriate for when the inverter chip temperature is high would waste the power consumed by the electric pump.

[0005] Therefore, an object of the present invention is to provide a vehicle control device and a vehicle control method that can reduce the power consumption of an electric pump that circulates a cooling medium while keeping the temperature rise in the drive circuit due to vehicle acceleration within an acceptable range.

[0006] In one aspect of the vehicle control device and vehicle control method according to the present invention, a standby flow rate, which is the flow rate of the electric pump calculated based on a temperature related to the temperature of a drive circuit that drives the electric motor, is set in advance before the vehicle accelerates.

[0007] According to the present invention, it is possible to reduce the power consumption of the electric pump that circulates the cooling medium while suppressing the temperature rise of the drive circuit that occurs during acceleration of the vehicle within an allowable range.

[0008] 1 is a diagram showing a cooling system for an electric drivetrain of a vehicle. FIG. 2 is a flowchart showing a first embodiment of standby flow rate control. FIG. 3 is a time chart showing temperature changes during full acceleration under low temperature conditions. FIG. 4 is a time chart showing temperature changes during full acceleration under low temperature conditions. FIG. 5 is a diagram showing the correlation between coolant temperature and standby flow rate. FIG. 6 is a time chart showing that the standby flow rate can be reduced when the temperature is low. FIG. 7 is a flowchart showing a second embodiment of standby flow rate control. FIG. 8 is a diagram showing the correlation between coolant temperature and output difference and standby flow rate. FIG. 9 is a time chart showing the difference in temperature rise due to output difference. FIG. 10 is a flowchart showing a third embodiment of standby flow rate control. FIG. 11 is a time chart showing changes in standby flow rate due to an obstacle. FIG. 12 is a flowchart showing a fourth embodiment of standby flow rate control. FIG. 13 is a diagram showing the correlation between the distance from the vehicle to an obstacle and a reduction correction coefficient. FIG. 14 is a flowchart showing a fifth embodiment of standby flow rate control. FIG. 15 is a flowchart showing a sixth embodiment of standby flow rate control. FIG. 16 is a flowchart showing a seventh embodiment of standby flow rate control. FIG. 17 is a flowchart showing an eighth embodiment of standby flow rate control. FIG. 18 is a flowchart showing an eighth embodiment of standby flow rate control. FIG. 19 is a flowchart showing an eighth embodiment of standby flow rate control. FIG. 20 is a flowchart showing an eighth embodiment of standby flow rate control. FIG. 21 is a flowchart showing an eighth embodiment of standby flow rate control. FIG. 22 is a flowchart showing an eighth embodiment of standby flow rate control. FIG. 23 is a flowchart showing an eighth embodiment of standby flow rate control. FIG. 24 is a flowchart showing an eighth embodiment of standby flow rate control. FIG. 25 is a flowchart showing an eighth embodiment of standby flow rate control. FIG. 26 is a flowchart showing an eighth embodiment of standby flow rate control. FIG. 27 is a flowchart showing an eight

[0009] Hereinafter, embodiments of a vehicle control device and a vehicle control method according to the present invention will be described with reference to the drawings. Fig. 1 is a configuration diagram showing an electric drivetrain 20 and a cooling system 30 for cooling the electric drivetrain 20, which are mounted on a vehicle 10. The electric drivetrain 20 includes a drive motor 21, which is an electric motor capable of outputting power to drive wheels 11, 11 of the vehicle 10, and an inverter 22 serving as a drive circuit for driving the drive motor 21. The vehicle 10 is either a hybrid vehicle that runs on multiple power sources, such as a combination of the drive motor 21 and an internal combustion engine, or an electric vehicle that runs on the power of the drive motor 21.

[0010] The cooling system 30 includes a cooling medium circulation path 31 connected to the electric drive system 20, an electric water pump 32 which is an electric pump for circulating cooling water as a cooling medium through the circulation path 31, temperature sensors 33A, 33B which detect the temperature of the cooling water flowing through the circulation path 31, a radiator 34 which cools the cooling water flowing through the circulation path 31, and a valve 35 which switches between a path that circulates the cooling water bypassing the radiator 34 and a path that circulates the cooling water via the radiator 34.

[0011] The control device 40 is an electronic control unit (ECU) equipped with a central processing unit (CPU) 41. The CPU 41 controls the electric drivetrain 20 and the cooling system 30 by executing programs stored in a storage device. In detail, the CPU 41 controls the electric water pump 32 and the valves 35 to control the cooling of the electric drivetrain 20, and also controls the power provided by the drive motor 21 to the drive wheels 11, 11 through control of the inverter 22.

[0012] The circulation path 31 of the cooling system 30 forms a circulation path for the coolant together with the flow paths provided in the inverter chips that make up the inverter 22. The coolant discharged by the electric water pump 32 cools the inverter chips and then flows into the radiator 34. The coolant cooled by the radiator 34 is then sucked into the electric water pump 32 and used again to cool the inverter chips.

[0013] The cooling system 30 can be a system that cools the inverter 22, the drive motor 21, and the battery that is the power source for the electric drive train 20. In other words, the circulation path 31 of the cooling system 30 can form a coolant circulation path together with the flow paths provided in the inverter 22, the battery, and the drive motor 21. In other words, the circulation path 31 of the cooling system 30 only needs to be connected to at least the inverter 22.

[0014] The circulation path 31 has a bypass path 31A that connects the upstream and downstream portions of the radiator 34. The valve 35 is provided at the portion where the bypass path 31A connects to the downstream portion of the radiator 34. The valve 35 opens and closes the circulation pipe in response to an electrical signal, thereby switching between circulating the coolant via the radiator 34 and circulating the coolant via the bypass path 31A, bypassing the radiator 34. The temperature sensor 33A detects the coolant temperature TW1 at the inlet of the inverter chip, and the temperature sensor 33B detects the coolant temperature TW2 at the outlet of the inverter chip.

[0015] The vehicle 10 also includes an automated driving system 50 that functions as an advanced driving assistant system (ADAS) or an autonomous driving system (ADS). The automated driving system 50 has an external environment information acquisition unit 51 that recognizes and acquires external environment information of the vehicle 10. The external environment information acquisition unit 51 recognizes and acquires external environment information such as information about the lane on which the vehicle 10 is traveling, information about obstacles ahead of the vehicle 10, and information about preceding vehicles, using a camera, radar, or even vehicle-to-vehicle communication. The external environment information acquisition unit 51 then outputs a signal indicating the acquired external environment information to the control device 40.

[0016] The vehicle 10 also includes a navigation device 60. The navigation device 60 includes a GPS (Global Positioning System) receiver that detects the position of the vehicle 10, a storage device that stores map information and road information, and a communication device that acquires the latest map information and road information from an external device. The navigation device 60 outputs a signal indicating the current position of the vehicle 10 on the map and information about its surroundings to the control device 40.

[0017] The vehicle 10 also includes an inclination angle sensor 70 that detects the inclination angle of the vehicle body relative to the horizontal plane (in other words, the road surface gradient). The inclination angle sensor 70 outputs a signal indicating the inclination angle to the control device 40.

[0018] The following describes in detail the control of the electric water pump 32 of the cooling system 30 by the CPU 41 of the control device 40 (in other words, the control method of the electric water pump 32 executed by the CPU 41). Before acceleration, the CPU 41 presets the flow rate of the electric water pump 32 to a standby flow rate in preparation for full acceleration of the vehicle 10 (in other words, a full load state of the drive motor 21).

[0019] Here, the CPU 41 executes a reduction correction process to reduce the standby flow rate from a default flow rate (in other words, a set value) that is set to, for example, the maximum flow rate of the electric water pump 32, in accordance with the temperature related to the temperature of the inverter 22. In other words, the CPU 41 sets in advance, before the vehicle 10 accelerates, the standby flow rate, which is the flow rate of the electric water pump 32 calculated in accordance with the temperature related to the temperature of the inverter 22.

[0020] 2 is a flowchart showing a first embodiment of standby flow rate control executed by the CPU 41. In the first embodiment, the CPU 41 executes processing to determine the standby flow rate in accordance with the temperature of the inverter 22 before acceleration of the vehicle 10. Note that in this embodiment, the control processes shown in the flowcharts are executed by interrupt processing at regular intervals.

[0021] In step S101, the CPU 41 detects a temperature related to the temperature of the inverter 22 (hereinafter also referred to as the inverter chip temperature). Here, the CPU 41 acquires the coolant temperature TW1 at the inlet of the inverter 22 detected by the temperature sensor 33A as a temperature detection unit as the temperature related to the inverter chip temperature.

[0022] The CPU 41 can acquire, as a temperature related to the inverter chip temperature, the coolant temperature TW2 at the outlet of the inverter 22 detected by the temperature sensor 33B serving as a temperature detection unit. Furthermore, if the inverter 22 includes a temperature sensor (in other words, a temperature detection unit) that detects the inverter chip temperature, the CPU 41 can acquire the detected value of the inverter chip temperature as a temperature related to the inverter chip temperature.

[0023] Furthermore, the CPU 41 can acquire, as a temperature equivalent to the inverter chip temperature, an estimated temperature of the inverter chip estimated from, for example, a detected value of the current flowing through the inverter 22. In this case, the functional unit that obtains the estimated temperature of the inverter chip from, for example, a detected value of the current flowing through the inverter 22 corresponds to the temperature detection unit.

[0024] In step S101, the CPU 41 detects the coolant temperature TW1 at the inlet of the inverter 22 as a temperature related to the inverter chip temperature, and then proceeds to step S102. In step S102, the CPU 41 sets the standby flow rate of the electric water pump 32 based on the coolant temperature TW1. Then, in the next step S103, the CPU 41 controls the flow rate of the electric water pump 32 to the standby flow rate.

[0025] The standby flow rate is a target discharge flow rate of the electric water pump 32 that is preset before the vehicle 10 accelerates in preparation for full acceleration of the vehicle 10. In other words, if control to increase the flow rate of the electric water pump 32 is performed based on the detection of acceleration, there is a possibility that the inverter chip temperature will exceed the allowable upper limit temperature due to a delay in the increase in the flow rate (in other words, the amount of circulating coolant). Therefore, the CPU 41 has a function to preset a flow rate that will prevent the inverter chip temperature from exceeding the allowable upper limit temperature even when the vehicle 10 is fully accelerated, and the flow rate that is set before the acceleration in preparation for this acceleration is called the standby flow rate.

[0026] Here, the CPU 41 variably sets the standby flow rate according to the coolant temperature TW1, which is a temperature corresponding to the temperature of the inverter 22, and sets the standby flow rate to be less than the default flow rate (for example, the maximum flow rate) the lower the coolant temperature TW1 is. This is because the lower the inverter chip temperature before acceleration, the lower the maximum temperature that the inverter chip temperature reaches as the vehicle 10 accelerates, and the greater the margin of the maximum temperature that can be reached relative to the allowable upper limit temperature.

[0027] 3 and 4 are time charts showing inverter chip temperature changes when the vehicle 10 is fully accelerated from a stopped state with the flow rate of the electric water pump 32 set to the maximum flow rate. Fig. 3 shows the temperature change when the inverter chip temperature (≈ coolant temperature TW1) in the stopped state before acceleration is T1 [°C]. Fig. 4 shows the temperature change when the inverter chip temperature (≈ coolant temperature TW1) in the stopped state before acceleration is T2 [°C], which is lower than T1 [°C].

[0028] In the example of Fig. 3, when the vehicle 10 is fully accelerated from a stopped state, the temperature of the inverter 22 rises to near the chip guaranteed temperature, which is the upper limit temperature allowed. On the other hand, in the example of Fig. 4, even when the vehicle 10 is fully accelerated from a stopped state, the inverter chip temperature does not rise to near the chip guaranteed temperature. In other words, if the difference between the upper limit temperature allowed of the inverter chip (in other words, the chip guaranteed temperature) and the maximum temperature reached by the inverter chip when the vehicle 10 is fully accelerated is defined as the temperature margin, the temperature margin in Fig. 4 is larger than the temperature margin in Fig. 3.

[0029] 4 , it is estimated that the inverter chip temperature will not exceed the upper limit temperature even if the electric water pump 32 is kept waiting for full acceleration with the flow rate reduced below the maximum flow rate. In other words, even if the inverter chip temperature is low when the vehicle is stopped before acceleration, keeping the electric water pump 32 waiting for full acceleration at the maximum flow rate would result in unnecessary work being done by the electric water pump 32. Therefore, the CPU 41 reduces the standby flow rate as the coolant temperature TW1, which is the temperature corresponding to the inverter chip temperature before acceleration, decreases, thereby preventing the electric water pump 32 from preparing for acceleration with an excessively high flow rate when the inverter chip temperature is low and reducing the power consumption of the electric water pump 32.

[0030] 5 is a diagram showing one aspect of the correlation between the coolant temperature TW1 before acceleration and the standby flow rate, with the vertical axis representing the standby flow rate [L / min] and the horizontal axis representing the coolant temperature TW1 [°C]. In Fig. 5, when the coolant temperature TW1 is lower than the temperature threshold value TW1th, the standby flow rate is reduced further from the maximum flow rate MAX as the coolant temperature TW1 decreases, and when the coolant temperature TW1 is higher than the temperature threshold value TW1th, the standby flow rate is set to the maximum flow rate MAX.

[0031] Here, the temperature threshold TW1th is the lower limit of the coolant temperature TW1 (inverter chip temperature) at which standby at the maximum flow rate is required, and the temperatures T1 and T2 in Figures 3 and 4 are T2 < TW1th and T1 ≥ TW1th. Therefore, under the temperature condition shown in Figure 3 (temperature before acceleration = T1), the maximum flow rate is set as the standby flow rate, and under the temperature condition shown in Figure 4 (temperature before acceleration = T2), a flow rate lower than the maximum flow rate is set as the standby flow rate.

[0032] 6 is a time chart illustrating an example of the inverter chip temperature rise during full acceleration of the vehicle 10 when the coolant temperature TW1 (inverter chip temperature) before acceleration is lower than the temperature threshold TW1th and the standby flow rate is set to a flow rate lower than the maximum flow rate. By setting the standby flow rate lower than the maximum flow rate, the inverter chip temperature rises more than when the standby flow rate is set to the maximum flow rate, but is prevented from exceeding the allowable upper limit temperature (i.e., the chip guaranteed temperature). In this way, by setting the standby flow rate according to the coolant temperature TW1 (inverter chip temperature) executed by the CPU 41, the inverter chip temperature rise during acceleration of the vehicle 10 can be kept within an allowable range while reducing the power consumption of the electric water pump 32 when the coolant temperature TW1 (inverter chip temperature) is lower than the temperature threshold TW1th.

[0033] 7 is a flowchart showing a second embodiment of standby flow rate control executed by the CPU 41. In the second embodiment, the CPU 41 executes a process of variably setting the standby flow rate based on the pre-acceleration coolant temperature TW1 (inverter chip temperature) and the pre-acceleration output of the inverter 22. In step S111, the CPU 41 detects the current output [kWh] of the inverter 22, and in step S112, detects, for example, the coolant temperature TW1 at the inlet of the inverter 22 as a temperature equivalent to the inverter chip temperature.

[0034] Next, in step S113, the CPU 41 sets the standby flow rate based on the coolant temperature TW1 and the output difference, which is the difference between the maximum output of the inverter 22 and the current output. Then, in the next step S114, the CPU 41 controls the flow rate of the electric water pump 32 to the standby flow rate.

[0035] 8 is a diagram illustrating the correlation between the coolant temperature TW1, the output difference, and the standby flow rate, with the vertical axis representing the standby flow rate [L / min] and the horizontal axis representing the output difference [kWh]. The correlation between the output difference and the standby flow rate for each coolant temperature TW1 is shown. The CPU 41 increases the standby flow rate as the output difference increases, and decreases the standby flow rate as the coolant temperature TW1 decreases. A large output difference indicates a low output of the inverter 22, and a small output difference indicates a high output of the inverter 22. Therefore, the CPU 41 decreases the standby flow rate as the output of the inverter 22 before acceleration increases.

[0036] This is because when the output difference is small, that is, when the increase in output when fully accelerated is small, the temperature rise due to full acceleration is expected to be smaller than when the output difference is large, that is, when the increase in output when fully accelerated is large. In other words, when the output difference is large, the amount of heat generated in the inverter chip when fully accelerated increases, and a larger flow rate is required as the standby flow rate, so the CPU 41 increases the standby flow rate compared to when the output difference is small.

[0037] Therefore, by setting the standby flow rate based on the coolant temperature TW1 and the output difference, the CPU 41 can reduce the standby flow rate as the output difference becomes smaller (in other words, as the output before acceleration becomes higher), even if the coolant temperature TW1 is at the same level, thereby further promoting reduction in power consumption of the electric water pump 32. Note that the state in which the output of the inverter 22 is high before acceleration includes a state in which the output of the inverter 22 is controlled to be high for driving the vehicle 10, as well as a state in which the output of the inverter 22 is controlled for heat generation, even though it is not an output for driving.

[0038] 9 is a time chart illustrating the difference in inverter chip temperature rise due to the output difference. In FIG. 9, the solid line shows the inverter output change when the inverter output is fully accelerated from 0 kWh, and the output difference OD2 at this time is at its maximum value. Also, in FIG. 9, the dotted line shows the inverter output change when the inverter output is fully accelerated from a state greater than 0 kWh, and the output difference OD1 at this time is smaller than the output difference OD2.

[0039] Full acceleration from an output of 0 kWh, that is, acceleration at the maximum output difference, is the condition under which the amount of heat generated by the inverter chip is the highest, and if the inverter chip temperature (coolant temperature TW1) before acceleration is the same, the maximum temperature reached will be higher than when the output difference is smaller than the maximum output difference. Therefore, if the output difference is smaller than the maximum output difference, the inverter chip temperature can be prevented from exceeding the allowable upper limit temperature (chip guaranteed temperature) even if the standby flow rate is set lower than when the maximum output difference is reached.

[0040] Therefore, even if the inverter chip temperature before acceleration is the same, the CPU 41 reduces the standby flow rate as the output difference becomes smaller (in other words, the higher the output before acceleration). Therefore, the second embodiment, in which the CPU 41 sets the standby flow rate based on the coolant temperature TW1 before acceleration and the output difference, can reduce the power consumption of the electric water pump 32 when the vehicle 10 accelerates from the partial throttle state, compared to the first embodiment, in which the standby flow rate is set based only on the coolant temperature TW1 before acceleration.

[0041] The standby flow rate setting in the first and second embodiments is adapted to prevent the inverter chip temperature from exceeding the allowable upper limit temperature even when the vehicle 10 is fully accelerated. Therefore, under conditions where the vehicle 10 is unlikely to be fully accelerated (or is unable to be fully accelerated), the inverter chip temperature can be prevented from exceeding the allowable upper limit temperature even if the standby flow rate is further reduced. The possibility of the vehicle 10 being fully accelerated is affected by the driving environment of the vehicle 10. For example, if an obstacle is present ahead of the vehicle 10, the possibility of the vehicle 10 being fully accelerated is reduced.

[0042] 10 is a flowchart showing a third embodiment of the standby flow rate control executed by the CPU 41. In the third embodiment, the CPU 41 executes a process of changing the standby flow rate based on the coolant temperature TW1 before acceleration, etc., in accordance with the recognition of the area ahead of the vehicle 10 and the presence or absence of an obstacle within the detection range.

[0043] In steps S121 to S123, the CPU 41 sets the standby flow rate based on the coolant temperature TW1 and the output difference, similar to steps S111 to S113 of the second embodiment. Note that the CPU 41 can set the standby flow rate based only on the coolant temperature TW1, similar to steps S101 and S102 of the first embodiment.

[0044] Next, the CPU 41 proceeds to step S124, where it determines whether or not there is an obstacle, such as another vehicle, a pedestrian, a safety device such as a road cone, or an object that has fallen onto the road, in the lane ahead of the vehicle 10 on which the vehicle 10 is traveling, in other words, whether or not an obstacle has been detected ahead of the vehicle 10. Here, the CPU 41 acquires information about the obstacle ahead of the vehicle 10 that has been recognized and acquired by the external environment information acquisition unit 51 using a camera, radar, or the like, and can determine whether or not there is an obstacle.

[0045] If an obstacle is present ahead of the vehicle 10 and the vehicle 10 is unlikely to be fully accelerated, the CPU 41 proceeds to step S125. In step S125, the CPU 41 corrects the standby flow rate set based on the coolant temperature TW1 and the output difference (or the standby flow rate set based on the coolant temperature TW1), i.e., the standby flow rate prepared for full acceleration, by decreasing it by a predetermined percentage, and sets the corrected result as the final standby flow rate. Thereafter, the CPU 41 proceeds to step S126, where it controls the flow rate of the electric water pump 32 to the standby flow rate reduced based on the information about the obstacle.

[0046] On the other hand, if there is no obstacle ahead of the vehicle 10 and there is a possibility that the vehicle 10 will be fully accelerated, the CPU 41 bypasses step S125 and proceeds to step S126, thereby setting the standby flow rate set based on the coolant temperature TW1 and the output difference (or the standby flow rate set based on the coolant temperature TW1), that is, the standby flow rate prepared for full acceleration, to its final value without reducing it.Then, in step S126, the CPU 41 controls the flow rate of the electric water pump 32 to the standby flow rate set based on the coolant temperature TW1 and the output difference (or the standby flow rate set based on the coolant temperature TW1).

[0047] 11 is a time chart showing how the standby flow rate is reduced when a preceding vehicle is present as an obstacle ahead of the vehicle 10. When the CPU 41 detects a preceding vehicle as an obstacle ahead of the vehicle 10 at time t1 in FIG. 11, it reduces the standby flow rate by a predetermined percentage from the flow rate before the obstacle was detected.

[0048] When an obstacle such as a preceding vehicle is present ahead of the vehicle 10, the vehicle 10 is less likely to be fully accelerated, and even if it is accelerated, the amount of heat generated by the inverter chip is kept lower than in the case of full acceleration. Therefore, when an obstacle such as a preceding vehicle is present ahead of the vehicle 10, the CPU 41 reduces the standby flow rate below the flow rate prepared for full acceleration, thereby further reducing the power consumption of the electric water pump 32.

[0049] In other words, the standby flow rate, which is set based on the coolant temperature TW1 and the output difference, is adapted so that the inverter chip temperature does not exceed the allowable upper limit temperature even when the vehicle 10 is fully accelerated. However, if the vehicle 10 is unable to fully accelerate due to an obstacle ahead, the standby flow rate can be further reduced to further reduce the power consumption of the electric water pump 32.

[0050] Incidentally, in the process of reducing the standby flow rate when an obstacle is present ahead of the vehicle 10, the CPU 41 can change the reduction correction rate according to the distance from the vehicle 10 to the obstacle ahead, and more specifically, the shorter the distance from the vehicle 10 to the obstacle ahead, the greater the reduction correction rate (in other words, the amount of reduction) of the standby flow rate can be. This is because the shorter the distance from the vehicle 10 to the obstacle ahead, the more difficult it is for the vehicle 10 to fully accelerate, and the less heat the inverter chip generates when accelerated.

[0051] 12 is a flowchart showing a fourth embodiment of the standby flow rate control executed by the CPU 41. In the fourth embodiment, the CPU 41 executes a process of changing the standby flow rate based on the coolant temperature TW1 before acceleration, etc., in accordance with the distance from the vehicle 10 to an obstacle ahead, which is information about the obstacle.

[0052] In steps S131 to S133, the CPU 41 sets the standby flow rate based on the coolant temperature TW1 and the output difference, similar to steps S111 to S113 of the second embodiment. Note that the CPU 41 can set the standby flow rate based only on the coolant temperature TW1, similar to steps S101 and S102 of the first embodiment.

[0053] Next, the CPU 41 proceeds to step S134 to determine whether or not an obstacle is present ahead of the vehicle 10. If an obstacle is present ahead of the vehicle 10, the CPU 41 proceeds to step S135 to set a reduction correction coefficient for the standby flow rate (0<reduction correction coefficient≦1.0) according to the distance from the vehicle 10 to the obstacle ahead. Next, the CPU 41 proceeds to step S136 to multiply the standby flow rate set in step S133 by the reduction correction coefficient to obtain the final standby flow rate.

[0054] Here, the shorter the distance from the vehicle 10 to the obstacle, the more the acceleration of the vehicle 10 is restricted, making it more difficult for the vehicle 10 to fully accelerate. Therefore, in step S135, the CPU 41 reduces the standby flow reduction correction coefficient as the distance from the vehicle 10 to the obstacle becomes shorter, thereby increasing the amount of reduction in the standby flow. In this way, by setting the standby flow reduction correction coefficient (0 < reduction correction coefficient ≦ 1.0) according to the distance from the vehicle 10 to the obstacle ahead, the CPU 41 can reduce the standby flow as much as possible when the distance is short and full acceleration is difficult, in response to the fact that the possibility of full acceleration varies depending on the distance, and can further reduce the power consumption of the electric water pump 32.

[0055] Fig. 13 is a diagram illustrating the correlation between the distance [m] from the vehicle 10 to an obstacle ahead and the reduction correction coefficient for the standby flow rate, with the vertical axis representing the reduction correction coefficient and the horizontal axis representing the distance from the vehicle 10 to the obstacle ahead. In one aspect shown in Fig. 13, when the distance from the vehicle 10 to the obstacle ahead is between 0 [m] and a predetermined distance, the reduction correction coefficient RQ maintains a value less than 1.0, and once the predetermined distance is exceeded, the reduction correction coefficient RQ is increased to 1.0, which means no reduction correction is performed.

[0056] After the CPU 41 reduces the standby flow rate in accordance with the distance from the vehicle 10 to the obstacle in step S136, the CPU 41 proceeds to step S137 and controls the flow rate of the electric water pump 32 to the standby flow rate. On the other hand, if there is no obstacle ahead of the vehicle 10, the CPU 41 bypasses steps S135 and S136 and proceeds to step S137. In other words, if there is no obstacle ahead of the vehicle 10, the CPU 41 does not reduce the standby flow rate based on the coolant temperature TW1 before acceleration, etc., but sets the standby flow rate as the final standby flow rate and controls the flow rate of the electric water pump 32.

[0057] The condition under which the possibility of the vehicle 10 fully accelerating is low is not limited to the presence of an obstacle ahead of the vehicle 10. For example, the possibility of the vehicle 10 fully accelerating also changes depending on the gradient of the road on which the vehicle 10 is traveling. Therefore, the CPU 41 can further reduce the power consumption of the electric water pump 32 by changing the standby flow rate in accordance with the gradient of the road on which the vehicle 10 is traveling.

[0058] In particular, when the road on which the vehicle 10 is traveling is downwardly inclined, the vehicle 10 is less likely to be fully accelerated than when the road is flat or upwardly inclined. Therefore, the CPU 41 can reduce the standby flow rate when the road on which the vehicle 10 is traveling is downwardly inclined. In other words, when the road on which the vehicle 10 is traveling is downwardly inclined, the CPU 41 can reduce the standby flow rate compared to when the road is flat or upwardly inclined.

[0059] 14 is a flowchart showing a fifth embodiment of the standby flow rate control executed by the CPU 41. In the fifth embodiment, the CPU 41 executes a process of changing the standby flow rate, which is based on the coolant temperature TW1 before acceleration, etc., in accordance with information about the gradient of the road on which the vehicle 10 is traveling.

[0060] In steps S141 to S143, the CPU 41 sets the standby flow rate based on the coolant temperature TW1 and the output difference, similar to steps S111 to S113 of the second embodiment. Note that the CPU 41 can set the standby flow rate based only on the coolant temperature TW1, similar to steps S101 and S102 of the first embodiment.

[0061] Next, the CPU 41 proceeds to step S144 and determines whether the road on which the vehicle 10 is traveling has a downhill gradient of a gradient equal to or greater than a predetermined gradient. Here, the CPU 41 acquires a signal indicating the inclination angle output by the inclination angle sensor 70 as information regarding the gradient of the road, and determines the gradient of the road on which the vehicle 10 is traveling. Note that if the map information of the navigation device 60 includes information regarding the gradient of the road, the CPU 41 can perform the gradient determination in step S144 based on the information regarding the gradient of the road as map information.

[0062] If the road on which the vehicle 10 is traveling has a downhill gradient of a predetermined gradient or greater, the CPU 41 proceeds to step S145. In step S145, the CPU 41 corrects, by a predetermined percentage, the standby flow rate set in step S143 based on the coolant temperature TW1 and the output difference (or the standby flow rate set based on the coolant temperature TW1), and sets the corrected result as the final standby flow rate. The CPU 41 then proceeds to step S146, where it controls the flow rate of the electric water pump 32 to the corrected standby flow rate.

[0063] On the other hand, if the CPU 41 determines that the road on which the vehicle 10 is traveling is not a downhill gradient of a predetermined gradient or greater, in other words, that the road is a substantially flat road or an uphill road, the CPU 41 bypasses step S145, which corrects the standby flow rate to decrease in accordance with the road gradient, and proceeds to step S146. Then, the CPU 41 controls the flow rate of the electric water pump 32 to the standby flow rate set based on the coolant temperature TW1 and the output difference (or the standby flow rate set based on the coolant temperature TW1).

[0064] In other words, when the road on which the vehicle 10 is traveling is flat or has an upward slope, the vehicle 10 is more likely to be fully accelerated than when the road is on a downward slope. Therefore, the CPU 41 does not reduce the standby flow rate on flat roads or on upward slopes, but reduces the standby flow rate when the road is on a downward slope, where full acceleration is less likely, thereby reducing the power consumption of the electric water pump 32 on downward slopes.

[0065] The CPU 41 can reduce the standby flow rate by a larger amount as the downhill gradient increases. The CPU 41 can also variably set the standby flow rate based on both the presence or absence of an obstacle (or the distance to the obstacle) and the gradient of the road on which the vehicle 10 is traveling. For example, the CPU 41 can select the larger of the amount of reduction based on the presence or absence of an obstacle (or the distance to the obstacle) and the amount of reduction based on the gradient of the road on which the vehicle 10 is traveling, and perform a reduction correction of the standby flow rate.

[0066] Incidentally, when a driver drives the vehicle 10, the tendency of the driver to accelerate varies, and even on the same road and in the same environment, depending on the driver, the vehicle 10 may or may not be fully accelerated. Therefore, the CPU 41 can acquire information regarding the driving characteristics of the driver of the vehicle 10 and reduce the standby flow rate in accordance with the information regarding the driving characteristics.

[0067] The information relating to the driver's driving characteristics is information indicating the acceleration tendency of each driver (in other words, the tendency to require acceleration force), or information indicating the driving characteristics of the vehicle 10 when a specific driver is driving. The CPU 41 can learn the acceleration tendency as a driving characteristic of the driver from, for example, the history of the accelerator pedal operation amount and operation speed, the selection history of the sports mode in an automatic transmission vehicle, the acceleration history of the vehicle 10, etc.

[0068] 15 is a flowchart showing a sixth embodiment of the standby flow rate control executed by the CPU 41. In the sixth embodiment, the CPU 41 acquires information relating to the acceleration tendency of each driver of the vehicle 10 as a driving characteristic of the driver, and executes a process of changing the standby flow rate in accordance with the acquired information relating to the acceleration tendency.

[0069] In steps S151 to S153, the CPU 41 sets the standby flow rate based on the coolant temperature TW1 and the output difference, similar to steps S111 to S113 of the second embodiment. Note that the CPU 41 can set the standby flow rate based only on the coolant temperature TW1, similar to steps S101 and S102 of the first embodiment.

[0070] Next, the CPU 41 proceeds to step S154 and determines whether the driving characteristics of the driver of the vehicle 10 tend to require strong acceleration force based on the learning results of the driving operation history up to that point, etc. The driving characteristics (more specifically, the driver's acceleration tendency) determined by the CPU 41 in step S154 may be based on the driver's average driving tendency, or may be based on the driver's past driving tendency on the road currently being traveled.

[0071] If the driver does not tend to require strong acceleration but tends to drive with gentle acceleration, that is, if the driver rarely accelerates at full speed, the CPU 41 proceeds to step S155. In step S155, the CPU 41 corrects the standby flow rate set based on the coolant temperature TW1 and the output difference (or the standby flow rate set based on the coolant temperature TW1) by a predetermined percentage, and sets the corrected result as the final standby flow rate. Thereafter, the CPU 41 proceeds to step S156 and controls the flow rate of the electric water pump 32 to the standby flow rate reduced based on the driving characteristics.

[0072] On the other hand, if the driver tends to request strong acceleration, there is a possibility that the vehicle 10 will be fully accelerated, so the CPU 41 bypasses step S155, which corrects the standby flow rate to decrease, and proceeds to step S156. Then, in step S156, the CPU 41 controls the flow rate of the electric water pump 32 to the standby flow rate set based on the coolant temperature TW1 and the output difference (or the standby flow rate set based on the coolant temperature TW1).

[0073] In the control process shown in the flowchart of Figure 15, the CPU 41 determines whether the driver tends to request strong acceleration force, but can distinguish between three or more types of acceleration force request tendencies and switch the standby flow rate reduction correction amount between multiple stages. The CPU 41 can also set the standby flow rate reduction amount based on at least one of the presence or absence of an obstacle (or the distance to the obstacle) and the gradient of the road on which the vehicle 10 is traveling, as well as the driver's driving characteristics. For example, when an obstacle is present ahead of the vehicle 10 or the road on which the vehicle 10 is traveling is downhill, the CPU 41 can reduce the standby flow rate even if the driver tends to request strong acceleration force, because the likelihood of full acceleration is reduced.

[0074] As described above, the likelihood that the vehicle 10 will be fully accelerated, in other words, the likelihood that the driver intends to fully accelerate, varies depending on the presence or absence of obstacles ahead of the vehicle 10 and the road gradient, and also on signal information such as traffic signals ahead of the vehicle 10 indicating permission to proceed or a stop, and the presence or absence of congestion ahead of the vehicle 10. Therefore, the CPU 41 predicts the driver's intention to accelerate based on external information and road information ahead of the vehicle 10, such as the presence or absence of obstacles, road gradient, traffic signals, and the presence or absence of congestion, and can reduce the standby flow rate when the driving environment does not indicate that the driver intends to accelerate. The external information and road information ahead of the vehicle 10 used to predict the driver's intention to accelerate can include information such as the curvature of the road, the presence or absence of snow on the road, the presence or absence of bumps in the road, and the legal speed limit.

[0075] 16 is a flowchart showing a seventh embodiment of standby flow rate control executed by the CPU 41. In the seventh embodiment, the CPU 41 predicts the driver's intention to accelerate based on external environment information ahead of the vehicle 10 and / or road information ahead of the vehicle 10, and executes processing to vary the standby flow rate in accordance with the prediction result.

[0076] In steps S161 to S163, the CPU 41 sets the standby flow rate based on the coolant temperature TW1 and the output difference, similar to steps S111 to S113 of the second embodiment. Note that the CPU 41 can set the standby flow rate based only on the coolant temperature TW1, similar to steps S101 and S102 of the first embodiment.

[0077] Next, the CPU 41 proceeds to step S164 and predicts the driver's intention to accelerate the vehicle 10 based on external environment information and / or road information ahead of the vehicle 10. Here, the CPU 41 acquires the external environment information and / or road information ahead of the vehicle 10 from the external environment information acquisition unit 51, the navigation device 60, the tilt angle sensor 70, etc. The CPU 41 can also acquire the external environment information and / or road information ahead of the vehicle 10 from another vehicle via vehicle-to-vehicle communication, and can also acquire the information from a cloud server external to the vehicle 10 via a wireless network.

[0078] The CPU 41 predicts that the driver is unlikely to intend to fully accelerate if at least one of the conditions that would prevent full acceleration of the vehicle 10 is met, such as the presence of an obstacle ahead of the vehicle 10, the road on which the vehicle 10 is traveling being on a downward slope, the traffic light ahead of the vehicle 10 instructing the vehicle 10 to stop (i.e., the traffic light ahead of the vehicle 10 is red), traffic congestion ahead of the vehicle 10, a sharp curve ahead, the vehicle 10 traveling on a snow-covered road or an uneven road, etc. On the other hand, if all of the conditions that prevent full acceleration as described above are not met, the CPU 41 predicts that the driver is likely to intend to fully accelerate.

[0079] After performing the process of predicting the driver's intention to accelerate in step S164, the CPU 41 proceeds to step S165 to determine whether or not it has predicted that the driver is likely to intend to fully accelerate. If the CPU 41 predicts that the driver is unlikely to intend to fully accelerate, it proceeds to step S166 to reduce the standby flow rate set based on the coolant temperature TW1 and the output difference (or the standby flow rate set based on the coolant temperature TW1) by a predetermined percentage, and sets the corrected result as the final standby flow rate.

[0080] In other words, when the CPU 41 predicts that the driver has no intention of accelerating, it reduces the standby flow rate. After that, the CPU 41 proceeds to step S167, and controls the flow rate of the electric water pump 32 to the standby flow rate that has been reduced.

[0081] On the other hand, if the CPU 41 predicts that the driver is likely to intend full acceleration, the CPU 41 bypasses step S166, which performs a decrease correction on the standby flow rate, and proceeds to step S167, where it controls the flow rate of the electric water pump 32 to the standby flow rate set based on the coolant temperature TW1 and the output difference (or the standby flow rate set based on the coolant temperature TW1). According to this control process, the CPU 41 can prevent the electric water pump 32 from performing unnecessary work when the driver is unlikely to intend full acceleration, thereby reducing the power consumption of the electric water pump 32.

[0082] In controlling the standby flow rate, the CPU 41 monitors the increase in inverter chip temperature due to acceleration, and if the peak temperature exceeds the set temperature, it can increase the flow rate. This makes it possible to suppress the standby flow rate while preventing the inverter chip temperature from rising excessively even if the actual temperature margin is smaller than expected.

[0083] 17 is a flowchart showing an eighth embodiment of the standby flow rate control executed by the CPU 41. In the eighth embodiment, the CPU 41 increases the standby flow rate when the peak temperature of the temperature rise caused by acceleration of the vehicle 10 exceeds a predetermined increase judgment temperature, and decreases the standby flow rate when the peak temperature of the temperature rise caused by acceleration of the vehicle 10 falls below a predetermined decrease judgment temperature (decrease judgment temperature<increase judgment temperature).

[0084] In step S171, the CPU 41 sets the standby flow rate in accordance with the control process exemplified in the first to seventh embodiments. Then, in step S172, the CPU 41 controls the flow rate of the electric water pump 32 to the standby flow rate.

[0085] Next, in step S173, the CPU 41 determines whether or not the vehicle 10 has accelerated, and if not, ends the current control process. On the other hand, if the CPU 41 determines in step S173 that the vehicle 10 has accelerated, the process proceeds to step S174, where the CPU 41 obtains and monitors temperature information to determine the peak temperature associated with acceleration. Then, in the next step S175, the CPU 41 determines whether or not the peak temperature associated with acceleration has exceeded an increase determination temperature (increase determination temperature≦allowable upper limit temperature), which is a threshold value for determining an increase in the standby flow rate.

[0086] If the peak temperature exceeds the increase determination temperature, the CPU 41 proceeds to step S176 and increases the standby flow rate by a predetermined percentage. This prevents the inverter chip temperature from rising excessively even if a disturbance occurs that causes the actual temperature margin to become smaller than the temperature margin estimated from the inverter chip temperature before acceleration.

[0087] On the other hand, if the CPU 41 determines in step S175 that the peak temperature is equal to or lower than the increase determination temperature, the CPU 41 proceeds to step S177 to determine whether the peak temperature associated with acceleration has fallen below a decrease determination temperature (decrease determination temperature<increase determination temperature≦allowable upper limit temperature), which is a threshold for determining whether to decrease the standby flow rate. If the peak temperature is below the decrease determination temperature, the CPU 41 proceeds to step S178 to decrease the standby flow rate by a predetermined percentage.

[0088] This prevents the electric water pump 32 from performing unnecessary work when a disturbance occurs that causes the actual temperature margin to be greater than the temperature margin estimated from the inverter chip temperature before acceleration. Also, if the peak temperature is equal to or lower than the amount increase determination temperature and equal to or higher than the amount decrease determination temperature (if the peak temperature is within the predetermined temperature range), the CPU 41 bypasses steps S176 and S178 and ends this routine, thereby maintaining the standby flow rate of the electric water pump 32 at the initial standby flow rate.

[0089] The CPU 41 can immediately apply the increase / decrease setting of the standby flow rate based on the peak temperature when it detects that the peak temperature exceeds the increase judgment temperature or when it detects that the peak temperature falls below the decrease judgment temperature. Furthermore, the CPU 41 can apply the increased / decreased standby flow rate from the next acceleration by setting the increased / decreased standby flow rate before the acceleration following the acceleration in which it is detected that the peak temperature has exceeded the increase judgment temperature or fallen below the decrease judgment temperature.

[0090] Furthermore, the CPU 41 can apply the standby flow rate increase / decrease setting at the earlier of the timing when it detects that the peak temperature is outside the predetermined temperature range and the next acceleration. The CPU 41 can also hold the standby flow rate increase / decrease setting for a period during acceleration when an increase / decrease request is determined based on the peak temperature, or until the vehicle 10 is keyed off (i.e., during the trip), or can hold the standby flow rate increase / decrease setting as a learning process until the next learning condition is met.

[0091] Since the CPU 41 sets the standby flow rate based on a temperature correlated with the inverter chip temperature, such as the cooling water temperature TW1, detected by a temperature detection unit such as a temperature sensor, if the temperature detection becomes abnormal due to a malfunction of the temperature detection unit, it will be impossible to set the standby flow rate according to the inverter chip temperature before acceleration. For this reason, it is preferable that the CPU 41 be configured to execute fail-safe processing in response to abnormal temperature detection.

[0092] 18 is a flowchart showing a ninth embodiment of standby flow rate control executed by the CPU 41. In the ninth embodiment, when the CPU 41 controls the standby flow rate based on the detected value of the temperature correlated with the inverter chip temperature, if an abnormality occurs in the temperature detection, the CPU 41 executes fail-safe processing.

[0093] In step S181, the CPU 41 determines whether an abnormality has occurred in the temperature detection of the inverter chip temperature by the temperature detection unit (temperature sensor). The CPU 41 determines that the temperature detection is in an abnormal state when an abnormality has been diagnosed in the temperature sensor or when an abnormality has been diagnosed in the AD converter for reading the output signal of the temperature sensor.

[0094] If the CPU 41 determines that there is no abnormality in the temperature detection by the temperature detection unit, the process proceeds to step S182, and executes control of the standby flow rate based on the temperature detected by the temperature detection unit in accordance with the control process exemplified in the first to eighth embodiments. On the other hand, if the CPU 41 determines that there is an abnormality in the temperature detection by the temperature detection unit, the process proceeds to step S183, and executes a predetermined fail-safe process.

[0095] As a fail-safe process in step S183, the CPU 41 uniformly sets the standby flow rate to the set flow rate for an abnormal state, for example. Here, the set flow rate for an abnormal state is the maximum flow rate of the electric water pump 32 or a flow rate close to the maximum flow rate. Note that the set flow rate for an abnormal state is adapted so as to sufficiently prevent the temperature of the inverter 22 from exceeding the allowable upper limit temperature upon full acceleration, even if the temperature of the inverter 22 before acceleration is relatively high.

[0096] Furthermore, the CPU 41 can execute, as the fail-safe processing in step S183, processing to limit the standby flow rate so that it does not become less than the lower limit flow rate. Furthermore, as the fail-safe processing in step S183, the CPU 41 can execute processing to limit the increase in the output of the drive motor 21, that is, processing to avoid full acceleration, thereby executing processing to reduce the amount of heat generated by the inverter chip due to acceleration. Here, the CPU 41 can execute the fail-safe processing for the standby flow rate and the fail-safe processing to limit the output of the drive motor 21 in parallel.

[0097] The CPU 41 can determine the end timing of the downward correction of the standby flow rate based on the rise in detected temperature and the passage of time, and can reset the standby flow rate, which is reduced from a default flow rate (for example, a maximum flow rate) based on the detected temperature, to the default flow rate as a set value. Figure 19 is a flowchart showing a tenth embodiment of standby flow rate control executed by the CPU 41. In the tenth embodiment, the CPU 41 determines the end timing of the downward correction of the standby flow rate based on the rise in temperature and the passage of time, and executes processing to reset the standby flow rate to the default flow rate.

[0098] In step S191, the CPU 41 executes the process of setting the standby flow rate by the control process exemplified in the first to ninth embodiments. Then, in the next step S192, the CPU 41 reduces the standby flow rate from the default flow rate, and then determines whether the coolant temperature TW1 has risen to or above a predetermined temperature (in other words, whether the temperature rise amount has exceeded a predetermined value) or whether the rate of rise of the coolant temperature TW1 has exceeded a predetermined value.

[0099] If the CPU 41 determines in step S192 that a predetermined temperature rise has occurred, the process proceeds to step S194, where the standby flow rate is reset to a default flow rate (for example, the maximum flow rate). On the other hand, if the CPU 41 determines in step S192 that a predetermined temperature rise has not occurred, the process proceeds to step S193, where the CPU 41 determines whether or not a predetermined time has elapsed since the standby flow rate was reduced from the default flow rate.

[0100] If the CPU 41 determines in step S193 that the elapsed time since the downward correction has reached a predetermined time, the CPU 41 proceeds to step S194 and resets the standby flow rate to the default flow rate. If the CPU 41 determines in step S193 that the elapsed time since the downward correction has not reached the predetermined time, the CPU 41 bypasses step S194 and ends the current control process, thereby continuing the process of setting the standby flow rate based on the coolant temperature TW1, etc.

[0101] Furthermore, the CPU 41 can reset the standby flow rate to a default flow rate based on a change in the driving environment of the vehicle 10. Fig. 20 is a flowchart showing an eleventh embodiment of the standby flow rate control executed by the CPU 41. In the eleventh embodiment, the CPU 41 executes processing to reset the standby flow rate to the default flow rate when a preceding vehicle is no longer present or is expected to no longer be present, after a state in which a preceding vehicle is present.

[0102] In step S201, the CPU 41 executes the standby flow rate setting process using the control process exemplified in the first to ninth embodiments. Then, in the next step S202, the CPU 41 determines whether the preceding vehicle has disappeared or is expected to disappear from a state in which the preceding vehicle was present. Here, in step S202, the CPU 41 can determine that the preceding vehicle has disappeared when the distance from the vehicle 10 to the preceding vehicle is greater than a certain value or when the preceding vehicle can no longer be recognized by forward recognition using a camera or the like.

[0103] Furthermore, in step S202, the CPU 41 can predict that the vehicle ahead of the vehicle 10 will no longer exist when the turn signal of the vehicle 10 or the preceding vehicle has been activated. Furthermore, in step S202, the CPU 41 can predict that the vehicle ahead of the vehicle 10 will no longer exist when the operation angle of the steering wheel of the vehicle 10 or the preceding vehicle has reached a certain value or more.

[0104] That is, the operation of the turn signal and steering operation of vehicle 10 causes vehicle 10 to predict that vehicle 10 will change lanes or turn right or left, thereby departing from a state in which vehicle 10 is following a leading vehicle, and that the leading vehicle will no longer be in front of vehicle 10. Conversely, the operation of the turn signal and steering operation of the leading vehicle causes vehicle 10 to predict that the leading vehicle will change lanes or turn right or left, thereby departing from a state in which vehicle 10 is traveling in front of vehicle 10, and that the leading vehicle will no longer be in front of vehicle 10.

[0105] If the CPU 41 determines in step S202 that a preceding vehicle has disappeared from the state where a preceding vehicle was present, the process proceeds to step S203. Also, if the CPU 41 predicts that a preceding vehicle will no longer exist from the state where a preceding vehicle was present, the process proceeds to step S203. Then, the CPU 41 resets the standby flow rate to the default flow rate in step S203. On the other hand, if a preceding vehicle continues to exist, the CPU 41 bypasses step S203 and ends the current control process, thereby continuing the process of setting the standby flow rate based on the coolant temperature TW1, etc.

[0106] According to this control process, when the preceding vehicle has restricted the acceleration behavior of the vehicle 10, the preceding vehicle is no longer there and the restriction on the acceleration behavior of the vehicle 10 is removed, increasing the possibility that the vehicle 10 will be fully accelerated, the standby flow rate is reset to the default flow rate. Therefore, even if the vehicle 10 is fully accelerated at the timing when the preceding vehicle has actually left, the temperature of the inverter 22 can be stably prevented from exceeding the allowable upper limit temperature.

[0107] The technical ideas described in the above embodiments can be used in appropriate combinations as long as no contradictions arise. Furthermore, although the contents of the present invention have been specifically described with reference to preferred embodiments, it is obvious that a person skilled in the art can adopt various modified embodiments based on the basic technical ideas and teachings of the present invention.

[0108] 10...vehicle, 20...electric drive system, 21...drive motor (electric motor), 22...inverter (drive circuit), 30...cooling system, 31...circulation path, 32...electric water pump (electric pump), 33A, 33B...temperature sensor (temperature detection unit), 34...radiator, 40...control device, 41...CPU

Claims

1. A vehicle control device mounted on a vehicle having an electric drive system including an electric motor capable of outputting power to drive wheels and a drive circuit that drives the electric motor, a circulation path connected to at least the drive circuit, an electric pump that circulates a cooling medium through the circulation path, and a temperature detection unit that detects a temperature related to the temperature of the drive circuit, and controls the electric pump, wherein a standby flow rate, which is the flow rate of the electric pump calculated in accordance with the temperature detected by the temperature detection unit, is set in advance before the vehicle accelerates.

2. A vehicle control device according to claim 1, wherein the standby flow rate is reduced as the output of the drive circuit before acceleration increases.

3. A vehicle control device according to claim 1, which acquires information relating to an obstacle ahead of the vehicle, and reduces the standby flow rate based on the information relating to the obstacle.

4. A vehicle control device according to claim 1, which acquires information relating to the gradient of a road on which the vehicle is traveling, and reduces the standby flow rate when the road on which the vehicle is traveling has a downward gradient.

5. A vehicle control device according to claim 1, which acquires information relating to the driving characteristics of a driver of the vehicle, and reduces the standby flow rate based on the driving characteristics.

6. A vehicle control device according to claim 1, which predicts whether or not the driver of the vehicle intends to accelerate, and reduces the standby flow rate when it is predicted that the driver does not intend to accelerate.

7. A vehicle control device according to claim 1, wherein the standby flow rate is increased when a peak temperature in the rise in the detected temperature caused by acceleration of the vehicle exceeds a predetermined temperature.

8. A vehicle control device according to claim 1, wherein the standby flow rate is reduced when a peak temperature in the rise in the detected temperature accompanying acceleration of the vehicle falls below a predetermined temperature.

9. A vehicle control device according to claim 1, wherein the standby flow rate is reset to a set value when the amount or rate of increase in the detected temperature due to acceleration of the vehicle exceeds a set value.

10. A vehicle control device according to claim 1, wherein the standby flow rate is reset to a set value when a state in which a preceding vehicle is present ahead of the vehicle changes to a state in which the preceding vehicle is not present ahead of the vehicle.

11. A vehicle control method executed by a control device mounted on a vehicle having an electric drive system including an electric motor capable of outputting power to drive wheels and a drive circuit that drives the electric motor, a circulation path connected to the electric drive system, an electric pump that circulates a cooling medium through the circulation path, and a temperature detection unit that detects a temperature related to the temperature of the drive circuit, the vehicle control method comprising: setting a standby flow rate, which is the flow rate of the electric pump calculated in accordance with the temperature detected by the temperature detection unit, in advance before accelerating the vehicle; and controlling the electric pump based on the standby flow rate.

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