Air conditioning system for electric vehicles

Abstract

To provide an air conditioning system for electric vehicles that does not require a fuel tank. [Solution] The air conditioning unit 38 of the electric vehicle 12 is equipped with a heat generation control unit 84 that, when there is a heat generation demand, drives the second electric motor MG2 with the lock-up clutch 20 released, thereby raising the temperature of the fluid that transmits power in the torque converter 22 and using it as a heat source for the air conditioning unit 38. This provides an air conditioning unit 38 for the electric vehicle 12 that heats up quickly and provides sufficient heating performance.

Description

Technical Field

[0001] The present invention relates to an air conditioner device for an electric vehicle, and more particularly to a technique using a torque converter as a heat source of the air conditioner device.

Background Art

[0002] Patent Document 1 proposes a heating device for an electric vehicle that, in addition to an electric heater, mounts a combustion heater using combustion heat as a heat source, and operates the combustion heater in the case of driving in extremely cold regions where the temperature of the temperature sensor is lower than a predetermined determination value of about -20°C. According to this, when the temperature is below the predetermined determination value at which the heating function deteriorates, the combustion heater is operated, so that a decrease in the driving distance of the vehicle is prevented.

[0003] However, in the heating device for a vehicle described in Patent Document 1, not only an electric heater but also a fuel tank for storing fuel to be burned by the combustion heater needs to be mounted, so that the air conditioner device mounted on the electric vehicle becomes large, and there is a disadvantage that the vehicle weight increases. In addition, it is necessary to check whether or not fuel is stored in the fuel tank, and the checking work is complicated.

[0004] On the other hand, in Patent Document 2, a heat pump or a PCT heater (postistor) is used as a heat source in the heating mode.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] Electric vehicles such as HEVs and BEVs are primarily designed to maximize driving range by prioritizing fuel efficiency and energy consumption. In the air conditioning systems of such electric vehicles, the output of the PCT heater used as a heat source in heating mode is limited by the output capacity of the DC-DC converter and alternator. As a result, at extremely low temperatures, the air conditioning systems of electric vehicles sometimes have poor heating speed and may not provide sufficient heating performance.

[0007] The present invention was made against the above circumstances, and its objective is to provide an air conditioning system for electric vehicles that provides rapid heating and sufficient heating performance.

[0008] Based on the circumstances described above, the inventors conducted various studies and found that in electric vehicles having a torque converter in the power transmission path, increasing the rotational difference of the torque converter generates heat in the fluid within the torque converter, resulting in a significantly larger amount of heat generation (fluid loss) than that of a PCT heater. This heat can be used as a heat source to meet the heat generation requirements of the air conditioning system of electric vehicles. The present invention is based on this finding. [Means for solving the problem]

[0009] In other words, the gist of the present invention is an air conditioning system for an electric vehicle equipped with a torque converter with a lock-up clutch between an electric motor and a drive wheel, comprising: (a) a torque converter fluid heat exchanger that exchanges heat between a fluid that transmits power in the torque converter and a refrigerant in the air conditioning system; and (c) a heat generation control unit that, when there is a heat generation demand, drives the electric motor with the lock-up clutch released to raise the temperature of the fluid that transmits power in the torque converter and use it as a heat source for the air conditioning system. [Effects of the Invention]

[0010] According to the electric vehicle air conditioning system of the present invention, when there is a demand for heat generation, the electric motor is driven with the lock-up clutch released, thereby increasing the temperature of the fluid that transmits power in the torque converter and using it as a heat source for the air conditioning system. As a result, there is no need to mount a fuel tank on the electric vehicle, and an electric vehicle air conditioning system is obtained that provides rapid heating and sufficient heating performance. [Brief explanation of the drawing]

[0011] [Figure 1] This document illustrates an example of a power transmission device for an electric vehicle, a circuit configuration for an air conditioning system mounted on the electric vehicle, and a control device for controlling the air conditioning system. [Figure 2] This figure illustrates the heat generation (fluid loss) characteristics of the torque converter included in the power transmission device shown in Figure 1, in relation to the input torque. [Figure 3] This figure illustrates the heat generation (fluid loss) characteristics of the torque converter included in the power transmission device shown in Figure 1, in relation to the differential rotation. [Figure 4] Figure 1 is a flowchart illustrating the control differential of the control device, where (a) shows the heat generation control while the vehicle is in motion, and (b) shows the heat generation control while the vehicle is stationary. [Modes for carrying out the invention]

[0012] The electric vehicles of the present invention include a two-motor hybrid vehicle (HEV) in which the engine is connected to the first rotating element of a differential gear system, the first electric motor is connected to the second rotating element, and the second electric motor is connected to the third rotating element; a one-motor hybrid vehicle (HEV) in which the engine, a disengaging clutch, and an electric motor are connected in series; a series hybrid vehicle (HEV) equipped with a first electric motor that is rotationally driven by the engine and functions exclusively as a generator, and a second electric motor that rotationally drives the drive wheels; and an electric vehicle (BEV) in which an electric motor is exclusively mounted as the prime mover. The electric vehicles of the present invention are equipped with a torque converter with a lock-up clutch between the electric motor and the drive wheels.

[0013] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. [Examples]

[0014] Figure 1 is a schematic diagram illustrating the configuration of the power transmission device 16 of an electric vehicle 12 equipped with an engine 10, a first electric motor MG1, and a second electric motor MG2 as power sources. The power transmission device 16 consists of the first electric motor MG1, a differential gear device 18, a second electric motor MG2, a torque converter 22 with a lock-up clutch 20, a reverse gear device 24, and a reduction gear device 26, all arranged sequentially on a common rotation axis CL1. The differential gear device 18 has a first rotating element connected to an input shaft 28 connected to the engine 10, a second rotating element connected to the first electric motor MG1, and a third rotating element connected to an output shaft 30. When the lock-up clutch 20 is released, the torque converter 22 amplifies the torque from the second electric motor MG2 and outputs it to the sleeve shaft 32. When the reverse brake B1 is engaged, the reverse gear device 24 reverses the rotation of the sleeve shaft 32 and transmits it to the output shaft 30. When the reduction brake B2 is engaged, the reduction gear 26 reduces the rotation of the sleeve shaft 32 and transmits it to the output shaft 30.

[0015] The torque converter 22 is a fluid transmission device that transmits power from the pump impeller to the turbine impeller via fluid (ATF). For example, during stalling (when the vehicle is stopped), it exhibits the heat generation characteristics shown in Figure 2. Figure 2 shows the fluid loss (kW) with respect to the input torque (Nm) during stalling. Compared to the approximately 1 kW of PTC heaters used in typical air conditioning systems, it can be seen that a significantly larger amount of heat generation (fluid loss) is obtained. Figure 3 shows the fluid loss (kW) of the torque converter 22 with respect to the differential rotation ΔN (rpm) during vehicle acceleration and deceleration. The differential rotation ΔN of the torque converter 22 is the rotational speed of the second electric motor MG2 as seen from the sleeve shaft 32.

[0016] Returning to FIG. 1, the air conditioner device 38 mounted to thermally condition the interior of the electric vehicle 12 includes a torque converter fluid heat exchanger 40, a refrigeration circuit 50, a low-temperature circuit 60, a high-temperature circuit 70, and an air conditioner control device 80. Further, the electric vehicle 12 includes an engine 10, a first electric motor MG1, a second electric motor MG2, a lock-up clutch 20, a torque converter 22, a reverse brake B1, and a deceleration brake B2 in a power transmission device 16, and a hybrid drive control device 86 that controls the required driving force based on the accelerator opening θacc so as to obtain optimal fuel efficiency and electricity cost. The hybrid drive control device 86 is an electronic control unit (ECU) composed of a so-called microcomputer.

[0017] The torque converter fluid heat exchanger 40, also referred to as an ATF warmer, is a heat exchanger that performs heat exchange between the fluid in the torque converter 22 and the refrigerant in the air conditioner device 38, that is, the cooling water in the high-temperature circuit 70. When the cooling water in the high-temperature circuit 70 is at an extremely low temperature, the fluid in the torque converter 22 is actively agitated using the second electric motor MG2 to generate heat in the fluid in the torque converter 22.

[0018] The refrigeration circuit 50 includes a condenser 52, a receiver 53, a first expansion valve 54, a second expansion valve 55, an evaporator 56, a chiller 57, a first electromagnetic control valve 58, and a second electromagnetic control valve 59 in a refrigerant circulation path by a compressor 51 to realize a refrigeration cycle.

[0019] The low-temperature circuit 60 includes a chiller 57, a low-temperature radiator 62, a first three-way valve 63, a second three-way valve 64, a battery heat exchanger 65, an MG heat exchanger 66, and a PCU heat exchanger 67 in a circulation path of cooling water (LLC) by a first pump 61, and cools the battery, the first electric motor MG1, the second electric motor MG2, and a PCU (power control unit) of the electric vehicle 12 with the cooling water, respectively. The low-temperature radiator 62 dissipates heat to the outside air when the temperature of the cooling water is higher than the outside air, and absorbs heat from the outside air when it is lower.

[0020] The high-temperature circuit 70 includes a condenser 52, a high-temperature radiator 72, a third three-way valve 73, a PCT heater 74, and a heater core 75 in the cooling water circulation path by the second pump 71. The heater core 75 exchanges heat between the cooling water and the air around the heater core 75 to perform heating and cooling in the vehicle interior. The PCT heater 74 heats the cooling water when, for example, the outside air temperature is extremely low and the refrigerant does not function properly in the refrigeration circuit 50. And in an extremely low temperature such as when the calorific value of the PCT heater 74 is insufficient and the refrigerant does not function properly in the refrigeration circuit 50, heat exchange is performed between the fluid heat loss generated in the torque converter 22 and the refrigerant in the air conditioner device 38, that is, the cooling water in the high-temperature circuit 70 through the torque converter fluid heat exchanger 40, and the torque converter 22 is used as a heating element.

[0021] The air conditioner control device 80 is an electronic control unit (ECU) composed of a so-called microcomputer mounted on the electric vehicle 12 and functioning as a control device for the air conditioner device 38. The air conditioner control device 80 functionally includes a stop mode control unit 81, a cooling mode control unit 82, a heating mode control unit 83, and a heat generation control unit 84.

[0022] When the stop mode is selected, the stop mode control unit 81 stops the operation of the compressor 51 and the second pump 71, and drives the first pump 61 to circulate the cooling water in the low-temperature circuit 60. Further, the stop mode control unit 81 switches the first three-way valve 63 so that the cooling water passes through the battery heat exchanger 65, and switches the second three-way valve 64 so that the cooling water passes through the MG heat exchanger 66 and the PCU heat exchanger 67.

[0023] When the cooling mode is selected, the cooling mode control unit 82 activates the compressor 51, the first pump 61, and the second pump 71 to circulate refrigerant in the refrigeration circuit 50 and coolant in the low-temperature circuit 60. The cooling mode control unit 82 also opens the first electromagnetic regulating valve 58 and closes the second electromagnetic regulating valve 59. In this cooling mode, the surrounding air is cooled by the evaporator 56, while the heat from the refrigerant via the condenser 52 warms the coolant in the high-temperature circuit 70. In addition, the battery heat exchanger 65, MG heat exchanger 66, and PCU heat exchanger 67 are cooled by the coolant, and the heat absorbed from them is released from the high-temperature radiator 72.

[0024] The heating mode control unit 83 operates the compressor 51, the first pump 61, and the second pump 71 to circulate refrigerant in the refrigeration circuit 50 and coolant in the low-temperature circuit 60 and high-temperature circuit 70. The heating mode control unit 83 also closes the first electromagnetic control valve 58 and opens the second electromagnetic control valve 59 to prevent refrigerant from passing through the evaporator 56 but to allow refrigerant to pass through the chiller 57. The heating mode control unit 83 also switches the third three-way valve 73 so that the coolant passes through the PCT heater 74 and heater core 75. As a result, the coolant in the low-temperature circuit 60 is cooled below the ambient temperature by the chiller 57, and the coolant in the high-temperature circuit 70 is heated by the condenser 52. Subsequently, the air around the heater core 75 is heated by the coolant in the high-temperature circuit 70. In this heating mode, heat is absorbed from the outside air in the low-temperature radiator 62 and released in the heater core 75. In the first heating mode of this heating mode, the switching valve 78 is closed and the coolant in the low-temperature circuit 60 passes only through the low-temperature radiator 62, so heat is absorbed from the outside air in the low-temperature radiator 62. However, in the second heating mode, the switching valve 78 is opened and the coolant in the low-temperature circuit 60 passes through both the low-temperature radiator 62 and the high-temperature radiator 72, so heat is absorbed from the outside air in both the low-temperature radiator 62 and the high-temperature radiator 72.

[0025] In the heating mode, if there is a heat generation request that arises when the refrigerant in the refrigeration circuit 50 becomes extremely cold and does not function properly, the heat generation control unit 84 controls the second electric motor MG2 to drive with the lock-up clutch 20 released via the hybrid drive control device 86, thereby increasing the temperature of the fluid that transmits power within the torque converter 22 through agitation and utilizing it as a new heat source for the high-temperature circuit 70 of the air conditioner 38.

[0026] In step S1 of Figure 4(a) (the steps are omitted hereafter), it is determined whether there is a heating request based on the fact that the set temperature of the air conditioner 38 is higher than the room temperature. If the determination in S1 is affirmative, in S2 it is determined whether the room temperature is below a preset specified temperature, for example, such as a temperature at which the refrigerant of the refrigeration circuit 50 would not function properly. If the determination in S2 is affirmative, in S3 it is determined whether the vehicle has been shifted to a driving range (D or R range). If the determination in S3 is affirmative, in S4 it is determined whether there is an acceleration request or a braking request based on accelerator or brake operation. If the determination in S4 is affirmative, in S5, which corresponds to the heat generation control unit 84, torque converter heat generation control during vehicle operation, as indicated by the affirmation in S3 and S4, is started in response to the heat generation request indicated by the affirmation in S1 and S2. If any of S1 to S4 is negative, in S6 the torque converter heat generation control during vehicle operation is terminated.

[0027] In S11 and S12 of Figure 4(b), similar to S1 and S2, it is determined whether there is a heating request and whether the room temperature is below a preset specified temperature at which, for example, the refrigerant in the refrigeration circuit 50 would cease to function properly. If the determinations in S11 and S12 are affirmative, S13 determines whether the vehicle has been shifted to the P range. If the determination in S13 is affirmative, S14 determines whether there is an acceleration request or a braking request based on accelerator or brake operation. If the determination in S14 is affirmative, S15, which corresponds to the heat generation control unit 84, starts torque converter heat generation control while the vehicle is stopped, as indicated by the affirmation in S13 and S14, in response to the heat generation request indicated by the affirmation in S11 and S12. If any of S11 to S14 is negative, S16 terminates the torque converter heat generation control while the vehicle is stopped.

[0028] As described above, the air conditioning unit 38 of the electric vehicle 12 in this embodiment includes a heat generation control unit 84 that, when there is a heat generation demand, drives the second electric motor MG2 with the lock-up clutch 20 released to raise the temperature of the fluid that transmits power in the torque converter 22, thereby using it as a heat source for the air conditioning unit 38. This provides an air conditioning unit 38 for the electric vehicle 12 that heats up quickly and provides sufficient heating performance.

[0029] The above-described examples are embodiments of the present invention, and the present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art, without departing from its spirit. [Explanation of Symbols]

[0030] 12: Electric vehicle, 20: Lock-up clutch, 22: Torque converter, 38: Air conditioning system, 40: Torque converter fluid heat exchanger, 84: Heat generation control unit, MG2: Second electric motor (electric motor)

Claims

[Claim 1] An air conditioning system for an electric vehicle equipped with a torque converter with a lock-up clutch between the electric motor and the drive wheels, A torque converter fluid heat exchanger that exchanges heat between the power-transmitting fluid and the refrigerant in the air conditioner within the torque converter, The system includes a heat generation control unit that, when there is a heat generation requirement, drives the electric motor with the lock-up clutch released to raise the temperature of the fluid transmitting power within the torque converter, thereby using it as a heat source for the air conditioner. An air conditioning system for electric vehicles characterized by the following features.

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