Refrigerant flow amount controlling device of cooling system for inverter of driving motor of motorcar and oil

Abstract

To ensure sufficient cooling effect even when causing unbalance in loads on right and left wheels in a cooling system 1 where refrigerant flow passages 2pL 2pR for cooling invertors with respect to the right and left wheels and motor oil in a motorcar where the right and left wheels are respectively provided with driving motors and invertors 4L, 4R are connected to a radiator 6 and a pump 3 pressure-sending the refrigerant in parallel.SOLUTION: A refrigerant flow amount controlling device 10 of a cooling system of a motorcar provided with a driving motor and an invertor to each of right and left wheels acquires refrigerant temperatures in refrigerant flow passages with respect to the right and left wheels, estimates a refrigerant flow amount in the refrigerant flow passages on the basis of the refrigerant temperature with respect to a wheel having the lower one of the refrigerant temperatures in the refrigerant flow passages with respect to the right and left wheels, and increases a refrigerant pressure-sending amount of a pump so that the refrigerant flow amount in the refrigerant flow passage with respect to the wheel having the lower refrigerant temperature reaches the refrigerant flow amount of the refrigerant flow passage when the loads on the driving motors of the right and left wheels are substantially equal to each other.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a cooling system for the periphery of a drive motor of an electric vehicle, and more specifically, to a refrigerant flow control device for a cooling system configured such that a drive motor and an inverter are provided for each of the left and right wheels, and refrigerant flow paths for cooling the left and right inverters and motor oil are connected in parallel to a pump and a radiator. [Background technology]

[0002] In electric vehicles and other motor-driven vehicles, various cooling systems have been proposed as means for cooling inverters that control the current supplied to drive motors, motor oil, etc., in which a coolant such as cooling water is circulated between the periphery of the inverter and a radiator, and heat absorbed by the inverter is released by the radiator. For example, Patent Document 1 discloses an attempt to estimate the power loss occurring in a drive circuit such as an inverter, determine the supply amount of the coolant based on the estimated power loss, and achieve both thermal protection of the load drive circuit and power saving of the cooling device. Patent Document 2 proposes a configuration in which a coolant flow path passing around the drive circuit is divided into multiple branch paths arranged in parallel, the flow rate of the liquid medium flowing through each of the multiple branch paths is detected, and the cause of an abnormality occurring in the cooling system is identified based on the state of the pump, the coolant temperature, etc. when an imbalance in the flow rates between the branch paths is detected. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2008-253098 [Patent Document 2] International Publication No. 2012 / 144031 Summary of the Invention [Problem to be solved by the invention]

[0004] In a vehicle (such as a racing car) in which the left and right wheels are each provided with a drive motor and an inverter for the drive motor, a coolant flow path for cooling the inverter and the motor oil is provided for each of the left and right wheels, and the coolant flow paths for the left and right wheels are configured to be connected in parallel to a radiator that dissipates heat from the coolant and a pump that pumps the coolant (see FIG. 1). In the case of a cooling system configured as described above, when the load balance of the left and right motors differs, the flow rates of the left and right coolant flow paths become unbalanced, and the cooling effect may decrease. More specifically, for example, while a vehicle V is traveling on an S-shaped curve 100 as shown in FIG. 2, if the load on the right side increases first and only the inverter temperature on the right side increases, the viscosity of the coolant on the right side decreases, and as a result, the flow rate of the coolant on the right side increases while the flow rate of the coolant on the left side decreases. In this state, when the load on the left side increases next time and the inverter temperature on the left side increases, the flow rate on the left side decreases, and a situation occurs in which a sufficient cooling effect cannot be obtained, which may cause a decrease in the power performance of the vehicle. In order to avoid such a situation, in a cooling system in which the refrigerant flow paths of the inverters for the left and right wheels, etc. are connected in parallel as described above, it is preferable to control the refrigerant flow rate appropriately according to the load on the left and right wheels so that a sufficient cooling effect can be obtained.

[0005] Thus, the main object of the present invention is to ensure a sufficient cooling effect even if an imbalance occurs in the load on the left and right wheels in a cooling system for an electric vehicle in which each of the left and right wheels is provided with a drive motor and an inverter therefor, and the refrigerant flow paths of the inverters, etc. of the left and right wheels are connected in parallel. [Means for solving the problem]

[0006] According to the present invention, the above problem is solved by providing a refrigerant flow rate control device for a cooling system in which a refrigerant flow path for cooling inverters and motor oil for left and right wheels of an electric vehicle, each of which is provided with a drive motor and an inverter therefor, is connected in parallel to a radiator and a pump that pumps the refrigerant, a refrigerant temperature acquisition means for acquiring refrigerant temperatures in the refrigerant flow paths for the left and right wheels; a refrigerant flow rate estimating means for estimating a refrigerant flow rate in the refrigerant flow path based on a refrigerant temperature of a wheel that has a lower refrigerant temperature in the refrigerant flow path for the left and right wheels; a pump pressure-feed amount control means for increasing a pressure-feed amount of the refrigerant from the pump so that a refrigerant flow rate in the refrigerant flow path for the wheel having a lower refrigerant temperature reaches a refrigerant flow rate in the refrigerant flow path when the loads on the drive motors for the left and right wheels are substantially equal; This is achieved by an apparatus comprising:

[0007] In the above configuration, the cooling system to be controlled by the device of the present invention is a system for cooling inverters and motor oil for the left and right wheels of an electric vehicle in which each of the left and right wheels is provided with a drive motor and an inverter therefor, as described above, and the coolant flow paths for cooling the inverters for the left and right wheels are connected in parallel to a common radiator and a pump for pumping the coolant. The coolant may typically be water that may contain antifreeze or the like. The "coolant temperature acquisition means" may be a means for detecting or estimating the refrigerant temperature of each of the left and right refrigerant flow paths using any method. For example, if a refrigerant temperature sensor is provided downstream of each of the left and right refrigerant flow paths, the means may be such a temperature sensor, or since the refrigerant temperature of each of the left and right refrigerant flow paths corresponds to the output of the drive motor for the left and right wheels, it may be estimated from the torque and rotation speed (output) of the left and right wheels (in this case, a map indicating the correspondence between the output and the water temperature prepared in advance may be used). Regarding the "coolant flow rate estimation means", since the refrigerant flow rates in the respective refrigerant flow paths for the left and right wheels are functions of the refrigerant temperatures in the respective refrigerant flow paths, the refrigerant flow rate in the refrigerant flow path for the wheel with the lower refrigerant temperature in the refrigerant flow path for the left and right wheels may be estimated by any method based on the refrigerant temperature in the corresponding refrigerant flow path. Typically, a map (which gives the refrigerant flow rate with the refrigerant temperature in the refrigerant flow path as a variable) created using a relationship between the refrigerant temperature in the refrigerant flow path and the refrigerant flow rate in the refrigerant flow path for each pump pumping amount, which has been previously investigated through experiments or the like, may be used. Regarding the "pump pumping amount control means", "the refrigerant flow rate in the refrigerant flow path when the loads of the drive motors for the left and right wheels are substantially equal" refers to a flow rate when the refrigerant flow rates in the refrigerant flow paths for the left and right wheels are substantially equal when the outputs of the drive motors for the left and right wheels are substantially equal when the vehicle is traveling in a straight line. This flow rate is determined according to the amount of refrigerant pumped by the pump, i.e., the output of the pump, and the amount of refrigerant pumped by the pump is usually determined based on the total output of the drive motors for the left and right wheels, or the refrigerant temperature (from the pump to the point where it branches into the refrigerant flow paths for the left and right wheels) so as to obtain a sufficient cooling effect.However, when the outputs (loads) of the drive motors for the left and right wheels are different, as described above, the refrigerant flow rate in the refrigerant flow passage on the side with the lower output is reduced, and the output of the pump is increased (more than normal) to compensate for the reduction. Specifically, the increase in the amount of refrigerant pumped out by the pump may be controlled using a map that provides an increase in pump output to compensate for the difference (reduction) obtained by subtracting the refrigerant flow rate in the refrigerant flow passage for the wheel with the lower refrigerant temperature from the refrigerant flow rate in the refrigerant flow passage when the loads of the drive motors for the left and right wheels are substantially equal, which map has been prepared in advance through experiments or the like.

[0008] In the above configuration, when the loads of the drive motors of the left and right wheels are different, the refrigerant flow rate in the refrigerant flow path for the wheel with the smaller load is reduced compared to when the loads of the drive motors of the left and right wheels are equal, and therefore the pump output is increased to compensate for this reduction. With this configuration, even when the loads of the drive motors of the left and right wheels are different, a shortage of refrigerant flow rate in either of the refrigerant flow paths for the left and right wheels is avoided.

[0009] In the embodiment, in the above-mentioned device of the present invention, first, the output of the pump may be basically controlled so that the refrigerant is at a flow rate that can sufficiently cool the inverter and the motor oil in response to the temperature of the refrigerant pumped from the pump. In such a control process, when the loads of the drive motors for the left and right wheels are different, the pump output is increased from a value determined in response to the temperature of the refrigerant pumped from the pump so as to compensate for the reduction in the refrigerant flow rate in the refrigerant flow path for the wheel with the smaller load. In order to achieve this control, more specifically, when the loads of the drive motors for the left and right wheels are different, the refrigerant temperatures of the refrigerant flow paths for the left and right wheels are estimated based on the loads, the refrigerant flow rates of the refrigerant flow paths are estimated from the estimated refrigerant temperatures, and for the wheel with the lower refrigerant temperature, the reduction in the refrigerant flow rate at that time relative to the flow rate that should flow when the loads of the drive motors for the left and right wheels are equal is calculated, and the pump output may be increased to compensate for the calculated reduction. Effect of the Invention

[0010] Thus, with the device of the present invention, in a cooling system for an electric vehicle in which each of the left and right wheels is provided with a drive motor and an inverter therefor, and the refrigerant flow paths of the inverters etc. for the left and right wheels are connected in parallel, even if an imbalance in the load on the left and right wheels occurs, a sufficient refrigerant flow rate is ensured in both of the refrigerant flow paths of the left and right wheels, and a sufficient cooling effect is obtained. This guarantees the cooling effect of the system and improves the power performance of the vehicle or the reliability of the cooling system.

[0011] Other objects and advantages of the present invention will become apparent from the following description of preferred embodiments of the invention. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram of one embodiment of a cooling system for an electric vehicle to which the device of the present embodiment is applied. [Diagram 2] FIG. 2 is a diagram showing an example of a driving pattern of a vehicle when the refrigerant flow rate is adjusted by the device of this embodiment. [Diagram 3] FIG. 3 is a flowchart showing the operation of the device of this embodiment. [Explanation of symbols]

[0013] 1...Cooling system, 2s...Refrigerant flow path (common), 2pL...Refrigerant flow path (left wheel), 2pR...Refrigerant flow path (right wheel), 3...Pump, 4L, R...Left and right inverters, 5L, R...Motor oil system, 6...Radiator, 7...Temperature sensor, 10...Flow control device, V...Vehicle BEST MODE FOR CARRYING OUT THEINVENTION

[0014] The present invention will now be described in detail with reference to some preferred embodiments thereof with reference to the accompanying drawings, in which like reference numerals indicate like parts.

[0015] Cooling System Configuration The cooling system of an electric vehicle to which the refrigerant flow control device of this embodiment is applied is a system for cooling inverters and motor oil for left and right wheels of an electric vehicle such as a racing car, in which left and right wheels are each provided with a drive motor and an inverter for the drive motor. In this cooling system, as shown in Fig. 1, a refrigerant flow path 2s from one pump 3 that pumps the refrigerant is branched into two flow paths 2pL and 2pR corresponding to the left and right wheels, and each of the flow paths passes through the inverters 4L and 4R of the left and right wheels and the motor oil systems 5L and 5R, and then merges again, passes through the radiator 6, and returns to the pump 3. In this configuration, the refrigerant (dotted arrow) is pumped from the pump 3, absorbs heat in the inverters 4L and 4R and the motor oil systems 5L and 5R, and releases the heat in the radiator 6, thereby cooling the inverters 4L and 4R and the motor oil systems 5L and 5R. The refrigerant may be water that may contain antifreeze or the like. In addition, the pumping amount (output) of the pump 3 is basically increased or decreased by the flow control device 10 (when the loads of the drive motors of the left and right wheels are substantially equal) according to the temperature sensor 7 provided in the coolant flow path 2s or the branched coolant flow paths 2pL, 2pR so that the coolant flow rate in the coolant flow paths 2pL, 2pR is an amount that can sufficiently cool the inverters 4L, 4R and the motor oil systems 5L, 5R. As will be described in more detail later, the loads (outputs) of the drive motors of the left and right wheels are input to the flow control device 10, and the flow control device 10 may be used for the coolant flow control according to this embodiment, which is executed when the loads of the drive motors of the left and right wheels are different. The flow control device 10 may be realized by an operation according to a program by a computer device of any type. ["The loads of the drive motors of the left and right wheels are substantially equal" refers to the case where the loads of the drive motors of the left and right wheels are equal within the margin of error.]

[0016] Cooling system status when the loads on the left and right wheel drive motors are different As explained in the "Summary of the Invention" section, in the case of a cooling system having a configuration in which the refrigerant flow paths 2pL and 2pR for the left and right wheels are connected in parallel to the refrigerant flow path 2s passing through the radiator 6 and the pump 3 as shown in Fig. 1, when the loads of the left and right drive motors are substantially equal, the refrigerant flows through the left and right refrigerant flow paths 2pL and 2pR at approximately the same flow rate, but when the loads of the left and right drive motors are different, the heat generation amount on the side with the larger load increases, so the viscosity of the refrigerant decreases, and the flow rate of the refrigerant flow path on the side with the larger load increases accordingly, while the flow rate of the refrigerant flow path on the side with the smaller load decreases. In this state, if the load on the side with the smaller load remains small, the heat generation amount does not increase, but when the load on the side with the smaller load increases and the heat generation amount increases, the refrigerant flow rate decreases, so there is a possibility that sufficient cooling effect cannot be obtained. Specifically, as shown in FIG. 2, when a vehicle V passes through an S-shaped curve 100, at the first curve (II), the load on the right side increases, causing a decrease in the refrigerant flow rate on the left side. When the load on the left side increases at the following curve (III), the increase in the refrigerant flow rate on the left side, which had been decreasing, is delayed, which may result in an insufficient cooling effect.

[0017] In this embodiment, as described above, when the loads of the left and right drive motors are different, the refrigerant flow rate of the side with the smaller load is reduced compared to when the loads of the left and right drive motors are substantially equal, and in order to avoid a reduction in the cooling effect of the side with the smaller load, when the loads of the left and right drive motors are different, the pump pumping amount of the refrigerant is increased to compensate for the reduction in the refrigerant flow rate of the side with the smaller load compared to when the loads of the left and right drive motors are substantially equal, thereby allowing the refrigerant to flow at a sufficient flow rate even on the side with the smaller load, thereby achieving a sufficient cooling effect. For this purpose, in this embodiment, when the loads of the left and right drive motors are different, the refrigerant temperatures of the left and right wheels are obtained, and the reduction in the refrigerant flow rate is calculated for at least the side with the lower refrigerant temperature (the side with the smaller load) compared to when the loads of the left and right drive motors are substantially equal, and the pump pumping amount of the refrigerant is increased compared to when the loads of the left and right drive motors are substantially equal so that the reduction in ...

[0018] Refrigerant flow control device operation In one aspect, the refrigerant flow control device according to the present embodiment may be operated as shown in FIG. 3. Referring to the figure, first, the magnitude of the load (output) of each drive motor of the left and right wheels is acquired (step 1). Information on the magnitude of the load of the drive motor may be acquired from a control device (not shown) of each drive motor. Here, when the loads of the drive motors of the left and right wheels are substantially equal (step 2), the pump output is controlled based on the refrigerant temperature (step 3). Specifically, the refrigerant temperature from when it is pumped out from the pump until it enters the inverters of the left and right wheels may be referenced, but is not limited to this, and the temperature of any part of the refrigerant flow path may be referenced. In addition, since the refrigerant temperature is related to the magnitude of the load of the drive motor, it may be estimated from the magnitude of the load of the drive motor. The pump output value may be determined by referring to the refrigerant temperature using a map that gives a pump output value to a refrigerant temperature prepared in advance through experiments or the like. The pump output value here is set to a refrigerant flow rate that provides a sufficient cooling effect corresponding to the refrigerant temperature at that time.

[0019] In step 2, if the loads on the drive motors of the left and right wheels are not substantially equal, the refrigerant temperatures of the refrigerant flow paths for the left and right wheels may be acquired in any manner (step 4). As one manner, the refrigerant temperature is related to the magnitude of the load on the drive motor as described above, and therefore may be estimated from the magnitude of the load on the drive motor for each of the left and right wheels. Alternatively, if temperature sensors are provided for each of the left and right wheels to detect the refrigerant temperatures downstream of the inverters 4L, 4R and motor oil systems 5L, 5R, the temperature sensor values ​​may be used as the refrigerant temperatures for the left and right wheels.

[0020] Thereafter, for at least the side with the lower refrigerant temperature, a flow rate in the refrigerant flow path (refrigerant flow rate (low side)) is estimated based on the refrigerant temperature (step 5) (the flow rate in the refrigerant flow path on the side with the higher refrigerant temperature may also be estimated). In this regard, since the flow rate in the refrigerant flow path also depends on the pump pumping volume, the refrigerant flow rate (low side) estimated here may be determined based on the refrigerant temperature for each pump pumping volume. Specifically, the relationship between the refrigerant temperature and the refrigerant flow rate may be investigated in advance through experiments or the like for each pump pumping volume, and a map that gives the refrigerant flow rate for the refrigerant temperature may be prepared, and the refrigerant flow rate (low side) at the refrigerant temperature may be estimated using such a map. In addition, in calculating the refrigerant flow rate (low side), first, a distribution ratio of the refrigerant flow rates for the left and right wheels may be calculated from the refrigerant temperatures for the left and right wheels, and the refrigerant flow rate (low side) may be determined from the distribution ratio.

[0021] Next, the flow rate of the refrigerant flow path (refrigerant flow rate (uniform)) is determined on the assumption that the loads of the drive motors of the left and right wheels are substantially uniform (step 6). Here, the refrigerant flow rate (uniform) may be the refrigerant flow rate when the refrigerant flows uniformly through the refrigerant flow paths 2pL and 2pR of the left and right wheels when the pump output corresponding to the refrigerant temperature from when it is pumped out from the pump until it enters the inverters of the left and right wheels is determined as in step 3, and the pump is operated at that pump output. This refrigerant flow rate (uniform) is a flow rate that provides a sufficient cooling effect in response to the loads of the drive motors of the left and right wheels. In other words, the refrigerant flow rate (uniform) is set so that a sufficient cooling effect can be obtained if the flow rate in each refrigerant flow path reaches the refrigerant flow rate (uniform). Specifically, the refrigerant flow rate (uniform) may be estimated using a map that is prepared in advance through experiments or the like and that provides the refrigerant flow rate (uniform) using the refrigerant temperature from when it is pumped out from the pump until it enters the inverters of the left and right wheels as a variable.

[0022] Thereafter, the reduction amount of the refrigerant flow rate in the refrigerant flow path on the lower refrigerant temperature side is calculated by refrigerant flow rate (uniform) - refrigerant flow rate (low side) (step 7), and the pump output is increased to compensate for this reduction amount so that the flow rate in the refrigerant flow path on the lower refrigerant temperature side reaches the refrigerant flow rate (uniform) (step 8). Specifically, the increase amount of the pump output to compensate for the reduction amount may be determined using a map that is prepared in advance through experiments or the like and that inputs the reduction amount to give the increase amount of the pump output to compensate for the reduction amount. The value of the pump output before the increase may be determined in the same manner as in step 3.

[0023] Thus, in the configuration of the present embodiment described above, when the loads on the drive motors for the left and right wheels are different, the pump output is increased, so that the refrigerant flows through the refrigerant flow path on the side with the smaller load at a flow rate that is sufficient to provide a sufficient cooling effect, thereby ensuring the cooling effect of the system.

[0024] The above description has been given in relation to the embodiment of the present invention, but it will be apparent to those skilled in the art that many modifications and changes can be easily made thereto, and that the present invention is not limited to the embodiment exemplified above, but can be applied to various devices without departing from the concept of the present invention.

Claims

[Claim 1] A refrigerant flow control device for a cooling system in an electric vehicle in which left and right wheels are each provided with a drive motor and an inverter therefor, in which refrigerant flow paths for cooling inverters and motor oil for left and right wheels are connected in parallel to a radiator and a pump that pumps the refrigerant, a refrigerant temperature acquisition means for acquiring refrigerant temperatures in the refrigerant flow paths for the left and right wheels; a refrigerant flow rate estimating means for estimating a refrigerant flow rate in the refrigerant flow path based on a refrigerant temperature of a wheel that has a lower refrigerant temperature in the refrigerant flow path for the left and right wheels; a pump pressure-feed amount control means for increasing a pressure-feed amount of the refrigerant from the pump so that a refrigerant flow rate in the refrigerant flow path for the wheel having a lower refrigerant temperature reaches a refrigerant flow rate in the refrigerant flow path when the loads on the drive motors for the left and right wheels are substantially equal; An apparatus comprising:

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