Electric vehicle

Abstract

To restrain the occurrence of polarization of a battery in an electric vehicle which travels with electric power of the battery.SOLUTION: An electric vehicle which uses a battery as a power source and a motor as a driving source, comprises a travel control device which adjusts travel speed. The travel control device repeatedly executes gentle acceleration travel and coasting travel alternatively if detecting a high load state of the battery, and increases and decreases the travel speed within a prescribed speed range interposing setting speed when traveling in constant speed by adjusting the travel speed to the setting speed.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to driving control of an electric vehicle.

Background Art

[0002] In recent years, a cruise control that allows a vehicle to travel at a set speed on a highway or the like has been used. In addition, in recent years, when a preceding vehicle is captured in front of the host vehicle by radar means, imaging means, or a combination of these radar means and imaging means, when the speed of the preceding vehicle is equal to or lower than the set speed, the vehicle follows the preceding vehicle while maintaining a predetermined inter-vehicle distance, and when the speed of the preceding vehicle is higher than the set vehicle speed or when the preceding vehicle is not captured, the vehicle travels at a constant speed at the set vehicle speed (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in recent years, electric vehicles using a battery as a power source and a motor as a drive source have been used. In such an electric vehicle, when traveling at a high speed for a long time, the input / output current of the battery may become only on the discharge side during traveling. In this case, the ions in the battery may be biased and polarization may occur, the internal resistance may increase, and the heat generation amount of the battery may increase. Further, this may lead to insufficient cooling capacity of the battery and result in driving output limitation or battery deterioration.

[0005] Therefore, an object of the present invention is to suppress the occurrence of polarization of a battery in an electric vehicle that travels using the power of the battery.

Means for Solving the Problems

[0006] The electric vehicle of the present invention is an electric vehicle that uses a battery as a power source and a motor as a drive source, and is provided with a travel control device for adjusting the travel speed. When the travel control device adjusts the travel speed to a set speed and performs constant-speed travel, if a high-load state of the battery is detected, it alternately repeats gentle acceleration travel and coasting travel, and increases and decreases the travel speed within a predetermined speed range sandwiching the set speed.

[0007] In this way, by alternately repeating gentle acceleration travel and coasting travel, it is possible to balance the discharge and charge of the battery, suppress the situation where the input / output of the battery becomes only on the discharge side, and suppress the occurrence of polarization of the battery. As a result, an increase in the heat generation amount of the battery, deterioration of the battery, etc. can be suppressed.

[0008] In the electric vehicle of the present invention, when the travel control device detects the release of the high-load state of the battery, it may perform constant-speed travel at the set speed.

[0009] When the battery changes from a high-load state to a low-load state where almost no polarization occurs even when the input / output of the battery becomes only on the discharge side, the travel that alternately repeats gentle acceleration travel and coasting travel is stopped and the vehicle returns to constant-speed travel. As a result, in the case of a low-load state, smooth constant-speed travel can be performed.

[0010] The electric vehicle of the present invention is provided with a current sensor for detecting the output current value of the battery. When the square value of the output current value of the battery detected by the current sensor exceeds a first threshold, the travel control device detects the high-load state of the battery, and when the square value of the output current value becomes equal to or less than a second threshold smaller than the first threshold, the detection of the high-load state of the battery may be released.

[0011] Thereby, it is possible to detect and release the high-load state of the battery by a simple method.

[0012] In the electric vehicle of the present invention, a current sensor for detecting the output current value of the battery and a voltage sensor for detecting the voltage value of the battery are provided. The travel control device calculates the output power value of the battery based on the output current value of the battery detected by the current sensor and the voltage value of the battery detected by the voltage sensor. When the output power value exceeds a first reference value, a high load state of the battery is detected. When the output power value becomes equal to or less than a second reference value smaller than the first reference value, detection of the release of the high load state of the battery may be performed.

[0013] Thereby, it is possible to detect and release the high load state of the battery by a simple method.

Effects of the Invention

[0014] The present invention can suppress the generation of polarization of the battery in an electric vehicle that travels using the power of the battery.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0016] As shown in FIG. 1, the electric vehicle 100 of the embodiment includes a battery 11, an inverter 12, a motor 15 as a drive source of the electric vehicle 100, and a travel control device 30.

[0017] The battery 11 is a power source that supplies DC power. The inverter 12 is connected to the battery 11, converts the DC power input from the battery 11 into three-phase AC power and supplies it to the motor 15, and also converts the three-phase AC power input from the motor 15 into DC power to charge the battery 11. The inverter 12 performs power conversion by turning on and off a plurality of switching elements provided inside. The driving force of the motor 15 is transmitted from the output shaft 16 of the motor 15 to the transaxle 18 via the gear 17 to drive the wheels 19 of the electric vehicle 100.

[0018] Between the battery 11 and the inverter 12, a current sensor 21 that detects the output current value IB of the battery 11 and a voltage sensor 22 that detects the voltage value VB of the battery 11 are arranged. Also, on the high-voltage cable between the inverter 12 and the motor 15, a V-phase current sensor 23 that detects the V-phase current value Iv of the three-phase AC power and a W-phase current sensor 24 that detects the W-phase current value Iw are attached. Further, a resolver 25 that detects the rotational angle position θ of the output shaft 16 is attached to the output shaft 16 of the motor 15. Also, a vehicle speed sensor 26 that detects the vehicle speed V of the electric vehicle 100 is attached to the transaxle 18.

[0019] The cruise control device 30 is a computer including a CPU 31, which is a processor for performing internal information processing, and a memory 32 for storing operation programs, control data, and the like. The output current value IB, voltage value VB, V-phase current value Iv, and W-phase current value Iw of the battery 11, the rotation angle position θ of the output shaft 16 of the motor 15, and the vehicle speed V detected by the current sensor 21, the voltage sensor 22, the V-phase current sensor 23, the W-phase current sensor 24, the resolver 25, and the vehicle speed sensor 26 are input to the cruise control device 30. The accelerator opening and the brake opening of the electric vehicle 100 are also input to the cruise control device 30. Furthermore, the cruise control device 30 is input with a cruise control ON / OFF signal from a cruise control switch, a set speed Vs for constant speed travel from a speed setting switch, and a preceding vehicle speed and a preceding vehicle distance from a preceding vehicle monitoring device. The cruise control switch and the speed setting switch are attached to, for example, a steering wheel, and the ON / OFF signal of the cruise control and the set speed Vs are input by the driver operating each switch. The preceding vehicle monitoring device may be, for example, a radar, or may be configured with a radar and a camera. A detailed configuration of the cruise control device 30 will be described later with reference to FIG.

[0020] The driving control device 30 stores in the memory 32 a square value IB of the output current value IB of the battery 11 as shown in FIG. 2 and the load state of the battery 11. The map 33 stores a square value IB of the output current value IB of the battery 11 detected by the current sensor 21. 2 When the square value IB of the output current IB exceeds the first threshold, a high load state of the battery 11 is detected. 2 becomes equal to or less than a second threshold value smaller than the first threshold value, the detection of the high load state of the battery 11 is cancelled and a low load state is detected. The high load state is a load state in which polarization may occur when the input and output of the battery 11 are mostly on the discharge side. The low load state is a load state in which polarization hardly occurs even when the input and output of the battery 11 are mostly on the discharge side.

[0021] Next, the detailed configuration of the travel control device 30 will be described with reference to FIG. 3. As shown in FIG. 3, the travel control device 30 includes four functional blocks: a cruise control unit 35, a battery monitoring unit 36, a gentle acceleration / deceleration control unit 37, and an inverter control unit 38. Each functional block can be realized by the CPU 31 shown in FIG. 1 executing a program stored in the memory 32.

[0022] The inverter control unit 38 receives the output current value IB, voltage value VB of the battery 11, V-phase current value Iv, W-phase current value Iw, rotational angle position θ of the output shaft 16 of the motor 15, vehicle speed V, accelerator opening, and brake opening. Based on these input data, the inverter control unit 38 generates an inverter drive command for turning on / off a plurality of switching elements provided inside the inverter 12 and outputs it to the inverter 12. The inverter 12 turns on / off a plurality of switching elements provided inside based on the inverter drive command input from the inverter control unit 38 to convert DC power into three-phase AC power and drive the motor 15.

[0023] The cruise control unit 35 receives an ON / OFF signal for cruise control, a set speed Vs for constant-speed driving, the speed of the preceding vehicle, and the distance to the preceding vehicle. Based on these input data, the cruise control unit 35 generates a driving speed signal and outputs it to the inverter control unit 38 and the gentle acceleration / deceleration control unit 37. When the cruise control unit 35 captures the preceding vehicle while the ON signal for cruise control and the set speed Vs are input, if the speed of the preceding vehicle is equal to or lower than the set speed Vs, the cruise control unit 35 performs follow-up driving control to drive the electric vehicle 100 while maintaining a predetermined inter-vehicle distance and following the preceding vehicle. Also, when the ON signal for cruise control and the set speed Vs are input, and the speed of the preceding vehicle is higher than the set speed Vs or the preceding vehicle has not been captured, the cruise control unit 35 performs constant-speed driving control to drive the electric vehicle 100 at the set speed Vs. In the case of follow-up driving control, the cruise control unit 35 outputs a variable speed corresponding to the speed of the preceding vehicle as the driving speed signal to the inverter control unit 38 and the gentle acceleration / deceleration control unit 37. Also, in the case of constant-speed driving control, the cruise control unit 35 outputs the set speed Vs as the driving speed signal to the inverter control unit 38 and the gentle acceleration / deceleration control unit 37. When the inverter control unit 38 receives the variable speed from the cruise control unit 35, it generates and outputs an inverter drive command such that the vehicle speed V becomes the variable speed without using the accelerator opening and the brake opening. As a result, the electric vehicle 100 follows the preceding vehicle at the variable speed input from the cruise control unit 35. When the inverter control unit 38 receives the set speed Vs from the cruise control unit 35, it generates and outputs an inverter drive command such that the vehicle speed V becomes the set speed Vs without using the accelerator opening and the brake opening. As a result, the electric vehicle 100 drives at a constant speed of the set speed Vs.

[0024] The battery monitoring unit 36 receives the output current value IB and the voltage value VB of the battery 11. The battery monitoring unit 36 calculates the square value IB 2 of the input output current value IB of the battery 11, detects whether the load state of the battery 11 is a high load state or a low load state using the map 33 described with reference to FIG. 2, and outputs the detected state of the battery 11 as a battery state signal to the gentle acceleration / deceleration control unit 37.

[0025] When the traveling speed signal input from the cruise control unit 35 is the set speed Vs and the battery state signal input from the battery monitoring unit 36 is in a high load state, the gentle acceleration / deceleration control unit 37 generates a gentle acceleration traveling command or a coasting command based on the set speed Vs and the vehicle speed V input from the inverter control unit 38, and outputs it to the inverter control unit 38. When a gentle acceleration traveling command or a coasting command is input from the gentle acceleration / deceleration control unit 38, the inverter control unit 38 does not use the accelerator opening, the brake opening, and the traveling speed signal input from the cruise control unit 35, and generates an inverter drive command based on the gentle acceleration traveling command or the coasting command input from the gentle acceleration / deceleration control unit 37 to drive the inverter 12.

[0026] Next, the traveling operation of the electric vehicle 100 according to the embodiment will be described with reference to FIGS. 4 and 5.

[0027] As shown in step S101 of FIG. 4, the cruise control unit 35 determines whether a cruise control ON signal is input from the cruise control switch. If it is determined NO in step S101 of FIG. 4, step S101 of FIG. 3 is repeatedly executed. When it is determined YES in step S101 of FIG. 4, the cruise control unit 35 starts cruise control. When performing constant speed traveling control, the cruise control unit 35 outputs the set speed Vs as a traveling speed signal to the gentle acceleration / deceleration control unit 37 and the inverter control unit 38. When performing following traveling control, the cruise control unit 35 outputs the variable speed as a traveling speed signal to the gentle acceleration / deceleration control unit 37 and the inverter control unit 38. The inverter control unit 38 generates an inverter drive command based on the traveling speed signal and outputs it to the inverter 12 to cause the electric vehicle 100 to perform constant speed traveling or following traveling.

[0028] The gentle acceleration / deceleration control unit 37 determines whether the electric vehicle 100 is in a constant speed running state. When the set speed Vs is input as a running speed signal from the cruise control unit 35, the gentle acceleration / deceleration control unit 37 determines YES in step S102 of FIG. 4 and proceeds to step S103 of FIG. 4. On the other hand, when a variable speed is input as a running speed signal from the cruise control unit 35, the gentle acceleration / deceleration control unit 37 determines NO in step S102 of FIG. 4 and waits until the set speed Vs is input as a running speed signal from the cruise control unit 35.

[0029] In step S103 of FIG. 4, the gentle acceleration / deceleration control unit 37 determines whether a battery state signal in a high load state is input from the battery monitoring unit 36. When the gentle acceleration / deceleration control unit 37 determines YES in step S103 of FIG. 4, it proceeds to step S104 of FIG. 4, and based on the set speed Vs and the vehicle speed V input from the inverter control unit 38, generates a gentle acceleration running command or a coasting running command and outputs it to the inverter control unit 38.

[0030] As shown in the upper graph of FIG. 5, the gentle acceleration running command is a command to gently increase or decrease the vehicle speed V so that the vehicle speed V falls within a predetermined speed range sandwiching the set speed Vs. As shown in the upper graph of FIG. 5, the gentle acceleration / deceleration control unit 37 outputs a gentle acceleration running command to gently accelerate the vehicle speed V from the set speed Vs to the upper limit speed V1 of the predetermined speed range from the time t0 when it determines YES in step S103 of FIG. 4 to the time t1. The inverter control unit 38 outputs an inverter drive command to the inverter 12 to control the on / off operation of the switching elements of the inverter 12 so as to increase the power supplied from the battery 11 to the motor 15 based on this gentle acceleration running command. As a result, the power supplied from the battery 11 to the motor 15 increases, and the vehicle speed V of the electric vehicle 100 rises. At this time, as shown in the lower graph of FIG. 5, the output current value IB of the battery 11 gradually increases on the discharge side.

[0031] As shown in the upper graph of FIG. 5, when the vehicle speed V reaches the upper limit speed V1 at time t1, the gentle acceleration / deceleration control unit 37 outputs to the inverter control unit 38 a coasting command such that the vehicle speed V gently decreases from the upper limit speed V1. Due to this coasting command, as shown in the lower graph of FIG. 5, the inverter control unit 38 generates an inverter drive command for controlling the on / off operation of the switching elements of the inverter 12 such that the output current value IB of the battery 11 becomes the charging current IBc from the discharge current IB1 at time t1, and outputs it to the inverter 12. Thereby, the motor 15 enters a gentle regenerative drive state and a predetermined charging current IBc is charged to the battery 11. Then, the electric vehicle 100 enters a coasting running state in which the vehicle speed V gently decreases from the upper limit speed V1. When the vehicle speed V decreases to the lower limit speed V2, the gentle acceleration / deceleration control unit 37 outputs to the inverter control unit 38 a gentle acceleration command for gently increasing the vehicle speed V from the lower limit speed V2 to the upper limit speed V1. Thereby, the inverter control unit 38 outputs to the inverter 12 an inverter drive command for controlling the on / off operation of the switching elements of the inverter 12 so as to increase the power supplied from the battery 11 to the motor 15. Thereby, at time t2, the output current value IB of the battery 11 becomes the discharge current IB2 from the charging current IBc, and then increases as the vehicle speed V increases. Then, the electric vehicle 100 gently accelerates.

[0032] In this way, due to the gentle acceleration command and the coasting command output by the gentle acceleration / deceleration control unit 37, the inverter control unit 38 alternately repeats gentle acceleration running and coasting running to increase and decrease the vehicle speed V within a predetermined range, and the battery 11 is alternately discharged and charged.

[0033] The gentle acceleration / deceleration control unit 37 determines whether the battery state signal input from the battery monitoring unit 36 in step S105 of FIG. 4 is in a low load state. If it is determined as NO in step S105 of FIG. 4, it returns to step S104 of FIG. 5 and continues to generate and output the gentle acceleration command and the coasting command. On the other hand, if it is determined as YES in step S105 of FIG. 5, the gentle acceleration / deceleration control unit 37 stops the gentle acceleration command and the coasting command.

[0034] Further, when the gentle acceleration / deceleration control unit 37 determines NO in step S103 of FIG. 4, it does not generate and output a gentle acceleration travel command and a coasting travel command.

[0035] Thus, when the gentle acceleration / deceleration control unit 37 does not generate and output a gentle acceleration travel command and a coasting travel command, a set speed Vs is input to the inverter control unit 38 as a travel speed signal from the cruise control unit 35. Then, in step S106 of FIG. 5, the inverter control unit 38 outputs an inverter drive command for controlling the inverter 12 so that the electric vehicle 100 travels at a constant speed of the set speed Vs.

[0036] When the set speed Vs is input to the inverter control unit 38 as a travel command signal from the cruise control unit 35, the inverter control unit 38 determines NO in step S107 of FIG. 7 and returns to step S103 of FIG. 5. On the other hand, when a variable speed is input to the inverter control unit 38 as a travel command signal from the cruise control unit 35, the inverter control unit 38 determines YES in step S107 of FIG. 7, proceeds to step S108 of FIG. 4, generates an inverter drive command for changing the vehicle speed V according to the variable speed, and outputs it to the inverter 12. As a result, the electric vehicle 100 follows.

[0037] When the input of the travel speed signal from the cruise control unit 35 continues, the inverter control unit 38 determines NO in step S109 of FIG. 4, returns to step S102 of FIG. 4, and continues to operate. On the other hand, when the input of the travel speed signal from the cruise control unit 35 stops, the inverter control unit 38 determines YES in step S109 of FIG. 4 and ends the process.

[0038] As described above, the electric vehicle 100 can balance the discharge and charge of the battery 11 by alternately repeating gentle acceleration travel and coasting travel, suppress the situation where the input / output of the battery 11 becomes only on the discharge side, and suppress the occurrence of polarization of the battery 11. Thereby, an increase in the heat generation amount of the battery 11, deterioration of the battery 11, etc. can be suppressed.

[0039] Further, when the electric vehicle 100 transitions from a high-load state of the battery 11 to a low-load state where almost no polarization occurs even when the input / output of the battery 11 becomes only on the discharge side, the electric vehicle 100 stops the running that alternately repeats gentle acceleration running and coasting running and returns to constant-speed running. Thereby, in the case of a low-load state, smooth constant-speed running can be performed.

[0040] Although the travel control device 30 described above has been described on the assumption that it stores the map 33 described with reference to FIG. 2 in the memory 32, it is not limited to this. For example, as shown in FIG. 6, a map 34 showing the relationship between the output power value WB of the battery 11 and the load state of the battery 11 may be stored in the memory 32. In this case, the battery monitoring unit 36 calculates the output power value WB of the battery 11 based on the output current value IB of the battery 11 detected by the current sensor 21 and the voltage value VB of the battery 11 detected by the voltage sensor 22. Then, based on the map 34, the battery monitoring unit 36 detects a high-load state of the battery 11 when the output power value WB exceeds a first reference value, and detects that the high-load state of the battery 11 has been released and the battery 11 has entered a low-load state when the output power value WB becomes equal to or less than a second reference value that is smaller than the first reference value.

[0041] Also, although the cruise control unit 35 of the travel control device 30 has been described as performing follow-up travel control and constant-speed travel control, it is not limited to this, and it may be configured to perform only constant-speed travel control. Further, instead of the cruise control unit 35, an automatic driving device that automatically controls operations such as steering, acceleration, and deceleration of the electric vehicle 100 may be provided, and the gentle acceleration / deceleration control unit 37 and the inverter control unit 38 may be configured to receive a travel speed signal from the automatic driving device when the automatic driving device is set to the automatic driving mode.

Description of Reference Numerals

[0042] 11 Battery, 12 Inverter, 15 Motor, 16 Output shaft, 17 Gear, 18 Transaxle, 19 Wheel, 21 Current sensor, 22 Voltage sensor, 23 V-phase current sensor, 24 W-phase current sensor, 25 Resolver, 26 Vehicle speed sensor, 30 Travel control device, 31 CPU, 32 Memory, 33, 34 Map, 35 Cruise control unit, 36 Battery monitoring unit, 37 Gentle acceleration and deceleration control unit, 38 Inverter control unit, 100 Electric vehicle.

Claims

1. An electric vehicle having a battery as a power source and a motor as a drive source, comprising a travel control device for adjusting the travel speed, wherein when the travel control device detects a high load state of the battery while adjusting the travel speed to a set speed and performing constant speed travel, it alternately repeats gentle acceleration travel and coasting travel, and increases and decreases the travel speed within a predetermined speed range sandwiching the set speed, characterized in that it is an electric vehicle.

2. The electric vehicle according to Claim 1, wherein when the travel control device detects the release of the high load state of the battery, it performs constant speed travel at the set speed, characterized in that it is an electric vehicle.

3. The electric vehicle according to Claim 1 or 2, comprising a current sensor for detecting an output current value of the battery, wherein the travel control device detects a high load state of the battery when the square value of the output current value of the battery detected by the current sensor exceeds a first threshold value, and cancels the detection of the high load state of the battery when the square value of the output current value becomes equal to or less than a second threshold value smaller than the first threshold value, characterized in that it is an electric vehicle.

4. The electric vehicle according to Claim 1 or 2, comprising a current sensor for detecting an output current value of the battery and a voltage sensor for detecting a voltage value of the battery, wherein the travel control device calculates an output power value of the battery based on the output current value of the battery detected by the current sensor and the voltage value of the battery detected by the voltage sensor, detects a high load state of the battery when the output power value exceeds a first reference value, and detects the release of the high load state of the battery when the output power value becomes equal to or less than a second reference value smaller than the first reference value, characterized in that it is an electric vehicle.

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