JP6769891B2 - Electric vehicle - Google Patents

Description

The present disclosure relates to an electric vehicle, and more particularly to a technique for preventing deterioration of a battery mounted on the electric vehicle.

According to Japanese Patent Application Laid-Open No. 11-11743 (Patent Document 1), in an electric vehicle including a motor generator mechanically connected to a drive wheel and a battery electrically connected to the motor generator, the drive wheel is on a road surface. On the other hand, a technique for prohibiting regenerative braking by the motor generator after the slip is detected is disclosed.

JP-A-11-15743 Japanese Unexamined Patent Publication No. 2013-20293 Japanese Unexamined Patent Publication No. 2008-312400

In an electric vehicle, when a phenomenon that the grip is restored after the drive wheels slip against the road surface (hereinafter, also referred to as "slip grip") occurs, an excessive current pulse may be input to the battery by regenerative power generation by the motor generator at the time of gripping. ..

In particular, in a low temperature environment where the outside air temperature is 0 ° C. or lower, the slip grip may easily deteriorate the battery. Specifically, in a low temperature environment, when an excessive current pulse due to regenerative power generation during grip recovery is input to the battery, granular dendrites are deposited on the surface of the battery electrode and excessive heat is generated inside the battery. There is a concern that the battery will deteriorate.

In the above-mentioned Patent Document 1, since regenerative braking is prohibited after slip is detected, for example, when gripping immediately after slip, regenerative braking cannot be prohibited in time at the time of gripping, and deterioration of the battery is appropriately suppressed. You may not be able to.

The present disclosure has been made to solve the above-mentioned problems, and an object of the present disclosure is to appropriately suppress deterioration of a battery due to slip grip in an electric vehicle.

The electric vehicle according to the present disclosure includes a motor generator mechanically connected to a drive wheel, a battery electrically connected to the motor generator, and a first detection device configured to be able to detect the outside air temperature around the electric vehicle. A second detection device configured to be able to detect the road surface condition ahead in the traveling direction of the electric vehicle, and a control device configured to be able to control the regenerative power generation by the motor generator. The control device determines whether or not the outside air temperature detected by the first detection device is 0 ° C. or lower. When the outside air temperature is 0 ° C. or lower, the control device determines whether or not the slip location where the drive wheels are predicted to slip with respect to the road surface exists in front of the electric vehicle in the traveling direction based on the detection result of the second detection device. Judge by using. When it is determined that the slip location is in front of the electric vehicle in the traveling direction, the control device performs regenerative power generation by the motor generator during the period from before the electric vehicle reaches the slip location until the electric vehicle passes through the slip location. Try not to.

According to the above configuration, when the outside air temperature is 0 ° C. or lower, it is determined whether or not the slip location exists in front of the electric vehicle in the traveling direction in view of the fact that the battery may be easily deteriorated by the slip grip. When it is determined that the slip location exists in front of the electric vehicle in the traveling direction, the motor generator is prevented from performing regenerative power generation in advance before the electric vehicle reaches the slip location. As a result, it is possible to suppress the generation of an excessive current pulse due to regenerative power generation when the grip is restored. As a result, deterioration of the battery due to the slip grip can be appropriately suppressed in the electric vehicle.

It is a figure which shows an example of the whole structure of an electric vehicle schematically. It is a figure which shows an example of the detectable range by a millimeter wave radar and the detectable range by a camera schematically. It is a figure which shows an example of the correspondence relationship between the temperature of a battery and the amount of heat generation. It is a flowchart which shows an example of the processing procedure of an ECU. It is a figure which shows an example of the correspondence relationship between the reflection intensity on a dry road (a place where slip is hard) and the reflection intensity on a snow-packed road (a place where slip is easy). It is a figure for demonstrating an example of the method of determining whether or not the rear wheel of an electric vehicle has passed a slip place. It is a figure for demonstrating an example of the start timing of the regenerative power generation prohibition processing.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are designated by the same reference numerals, and the description thereof will not be repeated.

<Overall configuration of electric vehicle>
FIG. 1 is a diagram schematically showing an example of the overall configuration of the electric vehicle 1 according to the present embodiment. The electric vehicle 1 includes an engine 10, a first motor generator 20, a second motor generator 30, a power dividing device 40, a speed reducer 50, a PCU (Power Control Unit) 60, a battery 70, and front wheels (driving). It includes a wheel) 80, a rear wheel (driving wheel) 81, and an ECU (Electronic Control Unit) 200.

The electric vehicle 1 shown in FIG. 1 is a hybrid vehicle including an engine 10 and two motor generators 20 and 30, but the vehicle to which the present disclosure is applicable is a motor generator mechanically connected to a drive wheel. Any electric vehicle may include a battery electrically connected to the motor generator, and the vehicle is not limited to the electric vehicle 1 shown in FIG. For example, the present disclosure is also applicable to a hybrid vehicle including an engine and one motor generator. The disclosure is also applicable to electric vehicles equipped with only a motor generator.

The engine 10, the first motor generator 20, and the second motor generator 30 are connected via the power dividing device 40. Then, the electric vehicle 1 travels by a driving force output from at least one of the engine 10 and the second motor generator 30. The power generated by the engine 10 is divided by the power splitting device 40 into a path transmitted to the front wheels (driving wheels) 80 and a path transmitted to the first motor generator 20.

Although FIG. 1 shows an example in which the front wheels 80 are driving wheels, the rear wheels 81 may be driving wheels.

The engine 10 is controlled by a control signal from the ECU 200. The first motor generator 20 and the second motor generator 30 are, for example, three-phase AC synchronous motors.

The first motor generator 20 generates electricity by using the power of the engine 10 divided by the power dividing device 40.

The second motor generator 30 generates a driving force by using at least one of the electric power stored in the battery 70 and the electric power generated by the first motor generator 20. The second motor generator 30 is mechanically connected to the drive wheels 80 via the speed reducer 50. Therefore, the driving force of the second motor generator 30 is transmitted to the drive wheels 80 via the speed reducer 50. When braking the electric vehicle 1, the drive wheels 80 drive the second motor generator 30, and the second motor generator 30 operates as a generator. The regenerative power generated by the second motor generator 30 is stored in the battery 70.

The power splitting device 40 includes planetary gears including a sun gear, a pinion gear, a carrier, and a ring gear. The pinion gear engages the sun gear and ring gear. The carrier supports the pinion gear so as to rotate on its axis and is connected to the crankshaft of the engine 10. The sun gear is connected to the rotating shaft of the first motor generator 20. The ring gear is connected to the rotating shaft of the second motor generator 30 and the speed reducer 50.

The PCU 60 is controlled by a control signal from the ECU 200. The PCU 60 converts the DC power stored in the battery 70 into driveable AC power for the first motor generator 20 and the second motor generator 30 and outputs the DC power to the first motor generator 20 and / or the second motor generator 30. As a result, the first motor generator 20 and / or the second motor generator 30 is driven by the electric power stored in the battery 70. Further, the PCU 60 converts the AC power generated by the first motor generator 20 and / or the second motor generator 30 into DC power that can be charged to the battery 70 and outputs the AC power to the battery 70. As a result, the battery 70 is charged with the electric power generated by the first motor generator 20 and / or the second motor generator 30.

The battery 70 is electrically connected to the first motor generator 20 and the second motor generator 30. The battery 70 stores electric power for driving the first motor generator 20 and the second motor generator 30. In this embodiment, the battery 70 is a lithium ion battery.

The electric vehicle 1 further includes a millimeter wave radar 11 and a camera 12. The millimeter-wave radar 11 and the camera 12 are provided in front of the vehicle and are configured to be capable of detecting an object in front of the vehicle and a road surface condition.

The millimeter wave radar 11 emits a millimeter wave for detection (for example, a radio wave in the 30 to 300 GHz band) toward a predetermined range in front of the vehicle, and the emitted millimeter wave emits a reflected wave reflected on an object or a road surface in front of the vehicle. Receive. The millimeter wave radar 11 outputs the received reflected wave information D1 to the ECU 200. The ECU 200 can detect the road surface condition in front of the vehicle from the reflected wave information from the millimeter wave radar 11.

The camera 12 captures an image in a predetermined range in front of the vehicle, and outputs information D2 of the captured image to the ECU 200. The ECU 200 can detect the road surface condition in front of the vehicle from the image information from the camera 12.

FIG. 2 is a diagram schematically showing an example of a detectable range by the millimeter wave radar 11 and a detectable range by the camera 12. As shown in FIG. 2, the detectable distance by the millimeter wave radar 11 is longer than the detectable distance by the camera 12, but the detectable width by the camera 12 is larger than the detectable width by the millimeter wave radar 11.

In the present embodiment, a case where the road surface condition in front of the vehicle is detected by using the millimeter wave radar 11 and the camera 12 will be described. However, instead of or in addition to the millimeter wave radar 11 and the camera 12, the laser and infrared are used. A floodlight, sonar, a thermoviewer, or the like may be used to detect the road surface condition in front of the vehicle.

The electric vehicle 1 further includes an outside air temperature sensor 13 and a vehicle speed sensor 14. The outside air temperature sensor 13 detects the outside air temperature THout around the electric vehicle 1. The vehicle speed sensor 14 detects the vehicle speed V from the rotation speed of the drive shaft. Each of these sensors transmits a signal representing the detection result to the ECU 200.

The ECU 200 has a built-in CPU (Central Processing Unit) and a memory (not shown), and is configured to execute a predetermined arithmetic process based on the information stored in the memory and the information from each sensor.

<Suppression of battery deterioration caused by slip grip>
In the electric vehicle 1 having the above-described configuration, when a "slip grip" occurs in which the grip recovers after the drive wheels 80 slip against the road surface, an excessive current is generated by the regenerative power generation by the second motor generator 30 at the time of grip recovery. A pulse can be input to the battery 70.

In particular, in a low temperature environment where the outside air temperature is 0 ° C. or lower, the slip grip may easily deteriorate the battery. Specifically, when an excessive current pulse due to regenerative power generation during grip recovery is input to the battery 70 in a low temperature environment, granular Li (lithium) dendrites are deposited on the surface of the electrodes of the battery 70 to deposit the battery. Since excessive heat may be generated inside the 70, there is a concern that the battery will deteriorate. It should be noted that the above-mentioned Li precipitation is particularly likely to occur in a state where the SOC (State Of Charge) of the battery 70 is high.

FIG. 3 is a diagram showing an example of a correspondence relationship between the temperature of the battery 70 and the amount of heat generated by Li precipitation when charging the battery 70. As shown in FIG. 3, when the temperature of the battery 70 is 0 ° C. or lower, Li precipitation due to charging is very large, and there is a concern that the battery 70 may be deteriorated.

In view of the above points, the ECU 200 according to the present embodiment predicts that the drive wheels 80 will slip with respect to the road surface using the information from the millimeter wave radar 11 and the camera 12 when the outside air temperature THout is 0 ° C. or lower. It is determined whether or not the place to be moved (hereinafter, also simply referred to as “slip place”) exists in front of the traveling direction. Then, when it is determined that the slip location exists in the front in the traveling direction, the ECU 200 prohibits the regenerative power generation by the second motor generator 30 in advance before the electric vehicle 1 reaches the slip location. The ECU 200 continues to prohibit the regenerative power generation by the second motor generator 30 until the electric vehicle 1 passes the slip location. As a result, even if a slip grip occurs when the electric vehicle 1 passes through the slip location, it is possible to suppress the generation of an excessive current pulse due to the regenerative power generation. As a result, deterioration of the battery 70 due to the slip grip in the electric vehicle 1 can be appropriately suppressed.

FIG. 4 is a flowchart showing an example of a processing procedure executed when the ECU 200 suppresses deterioration of the battery 70 due to the slip grip. This flowchart is repeatedly executed during the forward travel of the electric vehicle 1.

In step 10 (hereinafter, step is abbreviated as “S”) 10, the ECU 200 determines whether or not the outside air temperature THout detected by the outside air temperature sensor 13 is 0 ° C. or lower. When the outside air temperature THout is not 0 ° C. or lower (NO in S10), the ECU 200 skips the subsequent processing and shifts the processing to the return.

Next, the ECU 200 uses the information from the millimeter wave radar 11 and the camera 12 to have the above-mentioned slip location (a location where the drive wheels 80 are predicted to slip with respect to the road surface) in front of the electric vehicle 1 in the traveling direction. Whether or not it is determined (S12).

As the slip location, unpaved roads, Belgian roads (cobblestone roads), frozen roads, snow-packed roads, puddles, metal objects installed on roads (manholes, etc.) are assumed.

For example, when the slip location is specified by using the image information from the camera 12, image matching can be used. Specifically, images of a plurality of slip locations are stored in advance in the internal memory of the ECU 200. The slip locations to be remembered in advance include locations that are predicted to exceed the limit of the friction circle from the specifications of the electric vehicle 1 (the above-mentioned unpaved road, Belgian road, etc.), or locations that actually slipped in the past. is assumed.

Then, the ECU 200 collates the image from the camera 12 with the image of the slip location stored in the internal memory, and there is a place where the image from the camera 12 matches the image of the slip location stored in the internal memory. If so, the location can be identified as a slip location.

Further, when the slip location is specified by using the reflected wave information from the millimeter wave radar 11, the intensity of the reflected wave received by the millimeter wave radar 11 can be used.

FIG. 5 is a diagram showing an example of the correspondence relationship between the reflection intensity on a dry road (a place where slip is difficult) and the reflection intensity on a snow-packed road (a place where slip is easy). As shown in FIG. 5, the reflection intensity on the dry road is almost 0, while the reflection intensity on the snow-packed road is large. By utilizing this point, it is possible to determine the presence or absence of a snow-packed road (slip location) from the reflected wave information from the millimeter wave radar 11. Specifically, the reflection intensity of the snow-packed road (slip location) is stored in advance as a determination value in the internal memory of the ECU 200. Then, when the intensity of the reflected wave from the millimeter wave radar 11 is at a level close to the determination value stored in the internal memory, the ECU 200 can specify the location as a snow-packed road (slip location). Even when the slip location is specified using a laser, the presence or absence of the slip location can be determined by the same method.

Returning to FIG. 4, when it is not determined that the slip location exists (NO in S12), the ECU 200 skips the subsequent processing and shifts the processing to the return.

When it is determined that the slip location exists (YES in S12), the ECU 200 prohibits the regenerative power generation by the second motor generator 30 before the electric vehicle 1 reaches the slip location (S14). Specifically, the ECU 200 controls the PCU 60 so that regenerative power generation by the second motor generator 30 does not occur. If a braking force is required while regenerative power generation is prohibited, the regenerative brake cannot be generated. Therefore, if another friction brake (not shown) or the like is used to generate the braking force. Good.

While the regenerative power generation is prohibited, the ECU 200 determines whether or not the electric vehicle 1 has passed the slip location (S16). For example, the ECU 200 can determine that the electric vehicle 1 has passed the slip location when at least the rear wheels 81 are predicted to have passed the slip location.

FIG. 6 is a diagram for explaining an example of a method for determining whether or not the rear wheel 81 of the electric vehicle 1 has passed the slip location.

As shown in FIG. 6, the distance from the mounting position of the sensor (millimeter wave radar 11 or camera 12) to the shortest position in the detectable range of the sensor is defined as “α”, and the distance from the mounting position of the sensor to the rear wheel 81 is defined as “α”. When "β" is set, the rear wheel is when the time (= (α + β) / V) obtained by dividing the total distance between α and β by the vehicle speed V has elapsed after the slip location is no longer detected by the sensor. It can be determined that 81 has passed the slip location.

In the present embodiment, considering that the front wheels (driving wheels) 80 generate regenerative power generation by the second motor generator 30 when the grip is restored, it is said that the front wheels 80, not the rear wheels 81, have passed the slip location. If it is predicted, it may be determined that the electric vehicle 1 has passed the slip location. As a method for determining whether or not the front wheel 80 has passed the slip location, the same concept as the method described with reference to FIG. 6 can be adopted.

Returning to FIG. 4, when it is not determined that the electric vehicle 1 has passed the slip location (NO in S16), the ECU 200 returns the process to S14 and continues to prohibit the regenerative power generation by the second motor generator 30.

When it is determined that the electric vehicle 1 has passed the slip location (YES in S16), the ECU 200 releases the prohibition of regenerative power generation by the second motor generator 30 (S18).

As described above, when the outside air temperature THout is 0 ° C. or lower, the ECU 200 according to the present embodiment uses the information from the millimeter wave radar 11 and the camera 12 to determine whether or not the slip location exists in front of the traveling direction. judge. Then, when it is determined that the slip location exists ahead in the traveling direction, the ECU 200 generates regenerative power generation by the second motor generator 30 during the period from before the electric vehicle 1 reaches the slip location until it passes through the slip location. Ban. As a result, even if a slip grip occurs when the electric vehicle 1 passes through the slip location, it is possible to suppress the generation of an excessive current pulse due to the regenerative power generation. As a result, deterioration of the battery 70 due to the slip grip in the electric vehicle 1 can be appropriately suppressed.

<Modification example>
In the above-described embodiment, an example of starting the regenerative power generation prohibition process (process of S14 in FIG. 4) at the timing when it is determined that the slip location exists in front of the traveling direction has been described.

On the other hand, as described below, the start timing of the regenerative power generation prohibition process may be delayed from the timing when it is determined that the slip location exists.

FIG. 7 is a diagram for explaining an example of the start timing of the regenerative power generation prohibition process according to this modification. As shown in FIG. 7, it is assumed that the electric vehicle 1 is moving forward at the vehicle speed V, and the slip location is detected by the millimeter wave radar 11 ahead of the distance D. In this case, the time T until the electric vehicle 1 reaches the slip location is a value (= D / V) obtained by dividing the distance D to the slip location by the vehicle speed V.

The time required to start the regenerative power generation prohibition process is the total time of the millimeter wave processing time, the communication time, the determination time, the regenerative prohibition control time, and the like.

Therefore, the start timing of the regenerative power generation prohibition process can be delayed until the time T (= D / V) until the electric vehicle 1 reaches the slip location reaches the time required to start the regenerative power generation prohibition process. .. By doing so, it is possible to suppress the generation of an excessive current pulse due to the regenerative power generation at the time of slip grip without wasting the required regenerative energy.

It should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present disclosure is indicated by the scope of claims rather than the above description, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

1 vehicle, 10 engine, 11 mm wave radar, 12 camera, 13 outside temperature sensor, 14 vehicle speed sensor, 20 1st motor generator, 30 2nd motor generator, 40 power divider, 50 reducer, 70 battery, 80 front wheels ( Drive wheels), 81 rear wheels (driven wheels), 200 ECU.

Claims (2)

It ’s an electric vehicle,
With a motor generator mechanically connected to the drive wheels,
A battery electrically connected to the motor generator and
A first detection device configured to detect the outside air temperature around the electric vehicle, and
A second detection device configured to be able to detect the road surface condition in front of the electric vehicle in the traveling direction, and
It is equipped with a control device configured to be able to control regenerative power generation by the motor generator.
The control device is
It is determined whether or not the outside air temperature detected by the first detection device is 0 ° C. or lower.
When the outside air temperature is 0 ° C. or lower, the detection result of the second detection device indicates whether or not the slip location where the drive wheels are predicted to slip with respect to the road surface exists in front of the electric vehicle in the traveling direction. Judgment using
When it is determined that the slip location exists in front of the electric vehicle in the traveling direction, regeneration by the motor generator is performed during a period from before the electric vehicle reaches the slip location until the electric vehicle passes through the slip location. An electric vehicle that prevents power generation. The drive wheels are front wheels
The control device is
When it is determined that the slip location exists in front of the electric vehicle in the traveling direction, the period from before the electric vehicle reaches the slip location until at least the rear wheels, which are the trailing wheels, pass through the slip location. The electric vehicle according to claim 1, wherein the motor generator does not generate regenerative power generation.

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