Battery control method of tandem type hybrid power vehicle and tandem type hybrid power vehicle

Abstract

In a tandem hybrid vehicle, a controller (6) performs power generation by an internal combustion engine (2) when the SOC of a battery (5) drops to an SOC lower limit target value, and terminates power generation when the SOC reaches an SOC upper limit target value. When a destination is set in the in-vehicle navigation system (14), the maximum required output of the battery (5) predicted in the route to the destination is acquired, and the severity of the battery (5) is acquired in consideration of the association between the SOC corresponding to the battery temperature and the battery output. When the degree of severity is low, a low SOC lower limit target value is selected, and the distance and time at which EV travel can be continued after the start of travel are prolonged.

Description

TECHNICAL FIELD

[0001] The present application relates to battery control of a series hybrid vehicle, which performs power generation by an internal combustion engine when the SOC of a battery falls to a prescribed lower SOC target value, and ends power generation by the internal combustion engine when a prescribed upper SOC target value is reached. BACKGROUND

[0002] In a series hybrid vehicle in which power generation is performed using an internal combustion engine and travel is performed by a motor, in most cases, the travel of the vehicle that consumes the electric power of the battery and the power generation via the internal combustion engine are controlled so that the SOC of the battery is maintained within an appropriate range. For example, a lower SOC target value and an upper SOC target value of the battery are set in advance, power generation by the internal combustion engine is performed when the SOC of the battery falls to the lower SOC target value by travel by the travel motor, and power generation by the internal combustion engine is ended when the SOC recovers to the upper SOC target value. Further, hereinafter, a case in which travel is performed by the travel motor in a state in which the internal combustion engine is stopped will be referred to as "EV travel", and a case in which travel is performed by the travel motor while power generation by the internal combustion engine is performed will be referred to as "HEV travel".

[0003] For a typical user, it is not desirable for the internal combustion engine to be driven frequently when driving the series hybrid vehicle. From the viewpoint of the global environment, it is also desirable for the frequency of operation of the internal combustion engine that emits exhaust gas, i.e., HEV travel, to be as low as possible.

[0004] Therefore, it is desirable that, after the start of driving, EV travel can be performed for as long a time (or distance) as possible, provided that the battery is sufficiently charged at the driving start time point.

[0005] On the other hand, as a characteristic of the battery, the maximum output of the battery decreases if the SOC becomes low. Therefore, if a situation in which high output is required, such as an uphill road, is taken into account, it is necessary to avoid excessive decrease of the SOC, and it is not possible to set the lower SOC target value low enough to continue EV travel for a sufficiently long time. As a result, it is necessary to set the lower SOC target value high, and in most situations, power generation by the internal combustion engine is started at an unnecessarily high lower SOC target value.

[0006] That is, in the case of a constant battery capacity, it is generally difficult to achieve both continuation of EV travel for as long a time as possible and securing of output on an uphill road or the like.

[0007] In Patent Literature 1, battery control is disclosed in which, by cooperating with an on-vehicle navigation system, the SOC is lowered to a low level in advance when a long downhill is predicted, and the SOC is returned to an appropriate intermediate range by regeneration during the downhill.

[0008] However, the technology of Patent Document 1 cannot achieve both of the above-described long-term continuation of EV running and the securing of output on an uphill road and the like.

[0009] Patent Document 1: Japanese Patent Application Publication No. 2002-171603 SUMMARY

[0010] The application has a generator driven by an internal combustion engine, a running motor, and a battery that supplies electric power to the running motor, and performs power generation by the internal combustion engine when the SOC of the battery falls to a prescribed lower SOC target value, and ends power generation by the internal combustion engine when a prescribed upper SOC target value is reached,

[0011] In a battery control method of a series hybrid vehicle,

[0012] It is determined whether a destination is set in a car navigation system,

[0013] When the destination is set, a required maximum output of the battery predicted in a route to the destination is acquired,

[0014] Based on the required maximum output of the battery predicted and the correlation between the SOC and the battery output, a lower SOC target value that satisfies the required maximum output is set.

[0015] For example, when the required maximum output of the battery to be predicted in the route to the destination is high, the lower SOC target value is set to a higher value that can satisfy the required maximum output, considering the correlation between the SOC and the battery output. Therefore, the required maximum output that can occur in the route is reliably satisfied.

[0016] In addition, when the required maximum output of the battery to be predicted in the route is low, the lower SOC target value is set to a lower value. Therefore, when EV running is started from a state in which the battery has been charged to some extent, the time or distance during which EV running can be continued can be made long. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a configuration explanatory diagram showing the system configuration of a series hybrid vehicle that is one embodiment of the application.

[0018] Figure 2 is a characteristic diagram showing the characteristic of the battery output with respect to the battery temperature and the SOC.

[0019] Figure 3 is a flowchart showing the flow of control of one embodiment.

[0020] Figure 4is an explanatory diagram of one example of a change in SOC in the case of severity C.

[0021] Figure 5 is an explanatory diagram of one example of a change in SOC in the case of severity B.

[0022] Figure 6 is an explanatory diagram of one example of a change in SOC in the case of severity A.

[0023] Figure 7 is an explanatory diagram of one example of a change in SOC in the case of no destination setting. DETAILED DESCRIPTION

[0024] Hereinafter, one embodiment of the present application will be explained in detail based on the drawings. Figure 1 The structure of a series hybrid vehicle to which the present application is applied is schematically shown.

[0025] The series hybrid vehicle is configured to have a motor generator 1 for power generation that mainly functions as a generator, an internal combustion engine 2 that is used as a power generation-use internal combustion engine for driving the motor generator 1 for power generation according to a power generation request, a motor generator 4 for traveling that mainly functions as a motor and drives a drive wheel 3, and a battery 5 that is configured from a secondary battery such as a lithium ion battery (liquid lithium ion battery) or an all-solid-state battery that temporarily accumulates generated electric power. In one embodiment, the motor generator 1 for power generation is driven by the internal combustion engine 2 via a gear set 10. Electric power obtained by driving the motor generator 1 for power generation by the internal combustion engine 2 is accumulated in the battery 5 via an inverter device not shown. The motor generator 4 for traveling is drive-controlled using electric power of the battery 5. Electric power at the time of regeneration of the motor generator 4 for traveling is also accumulated in the battery 5 via the inverter device not shown. Further, although not shown in the drawing, it can also be a so-called plug-in hybrid type structure that enables charging of the battery 5 from the outside using a commercial power source or the like.

[0026] The operation of the motor generator 1, 4, the charge and discharge of the battery 5, and the operation of the internal combustion engine 2 are controlled by a controller 6. The controller 6 is constituted by a plurality of controllers, such as a motor controller 7 that controls the motor generator 1, 4, an engine controller 8 that controls the internal combustion engine 2, and a battery controller 9 that manages the battery 5, connected in a communicable manner with each other. The controller 6 is input with information such as the opening degree of an accelerator pedal not shown, the vehicle speed, and the like. In addition, the battery controller 9 acquires the SOC of the battery 5 based on the voltage and the current of the battery 5. In addition, the battery 5 has a battery temperature sensor 12 that detects the battery temperature. The vehicle has an ambient temperature sensor 13 that detects the ambient temperature. The controller 6 acquires information of the battery temperature and the ambient temperature through these sensors 12, 13.

[0027] The vehicle of one embodiment is configured to have an on-vehicle navigation system 14 using a so-called GPS, and to perform route guidance by the driver setting a desired destination. The map data possessed by the on-vehicle navigation system 14 contains the kind of road (whether it is an expressway or a general road, and the like), the speed limit, the gradient information, and the like. In addition, the vehicle of one embodiment has a communication device 11 as a so-called network system that communicates with a cloud server not shown or other vehicles running around. Through the communication device 11, it is possible to acquire information of the environment (weather, and the like) or the congestion situation in the route, and the like.

[0028] As the travel mode of such a series hybrid vehicle, there are an EV travel mode in which travel is performed by the electric power of the battery 5 without combustion operation (i.e., power generation or charging) of the internal combustion engine 2, and an HEV travel mode in which travel is performed while power generation by the combustion operation of the internal combustion engine 2 is performed. The battery controller 9 manages the charge and discharge of the battery 5 so that the SOC of the battery 5 is kept between a prescribed upper target value and a lower target value. For example, the SOC decreases due to EV travel, and when it decreases to the lower target value, the internal combustion engine 2 is started via the engine controller 8, and the travel mode is switched to the HEV travel mode. The power generation by the internal combustion engine 2 is ended, for example, when the SOC reaches the upper target value. For regenerative electric power, too, control is performed by an appropriate method so that the SOC of the battery 5 does not exceed the upper target value.

[0029] Here, in the series hybrid vehicle of one embodiment, the SOC lower limit target value is discretely set to a plurality of levels according to the battery output that should be secured in the route, and a certain level is selected according to the presence or absence of a destination set in the on-vehicle navigation system 14 and the predicted severity. Specifically, a first SOC lower limit target value, a second SOC lower limit target value, a third SOC lower limit target value, and a fourth SOC lower limit target value are sequentially determined from high to low in SOC, and any one of them is selectively used. In the case of the highest first SOC lower limit target value, the highest battery output, or even the vehicle driving force, can be secured.

[0030] In addition, the SOC upper limit target value is determined for each level of the SOC lower limit target value, and the lower the level of the SOC lower limit target value, the lower the SOC upper limit target value. That is, a first SOC upper limit target value, a second SOC upper limit target value, a third SOC upper limit target value, and a fourth SOC upper limit target value are determined corresponding to the first to fourth SOC lower limit target values, respectively, and the fourth SOC upper limit target value is the lowest SOC.

[0031] Furthermore, at least one of the first to fourth SOC lower limit target values and the corresponding first to fourth SOC upper limit target values can also be corrected in such a manner that the SOC control range between the SOC upper limit target value and the SOC lower limit target value is relatively expanded on the high temperature side, according to the temperature of the battery 5. For example, taking the fourth SOC lower limit target value and the fourth SOC upper limit target value as an example, the fourth SOC lower limit target value is made lower as the temperature of the battery 5 is higher, and the fourth SOC upper limit target value is set to a constant value regardless of the temperature, whereby the SOC control range is made larger as the temperature is higher. As for the temperature of the battery 5, in addition to that obtained through the detection value of the battery temperature sensor 12, it can also be obtained through estimation based on the detection value of the outside air temperature sensor 13 or weather information obtained via the communication device 11, and the like.

[0032] Next, the flow of the process of one embodiment performed by the controller 6 will be described with reference to the flowchart of Figure 3 Initially, in step 1, it is determined whether a destination is set in the on-vehicle navigation system 14. In the case where the destination is set, the process proceeds to step 2, and various information of the route to the destination is mainly obtained from the on-vehicle navigation system 14. For example, information such as the distance to the destination, the inclination (slope) of the road in the route, the elevation, whether it is a general road or an expressway, and the like. Next, in step 3, information such as the weather, the air temperature, and the road congestion information of the route to the destination is obtained through the so-called Internet via the communication device 11.

[0033] Next, the process proceeds to step 4, where the severity of the route is determined based on the information obtained from the in-car navigation system 14 in step 2 and the environmental information obtained from the internet in step 3. Severity is a numerical indicator that represents the severity of the demands placed on the battery 5 along the route to the destination. Severity is essentially related to the predicted maximum output required by the battery 5 along the route based on the slope and vehicle speed information. The greater the slope, the higher the maximum output required by the battery 5. The higher the vehicle speed on the highway, the higher the maximum output required by the battery 5. The higher the predicted maximum output required by the battery 5, the higher the severity.

[0034] Preferably, weather information (particularly, rain, snow, etc.) on the route to the destination is obtained, and the severity is calculated by applying a correction related to the road conditions.

[0035] In addition, when calculating the severity, consider Figure 2 The battery characteristics shown are the relationship between the SOC corresponding to the battery temperature and the battery output. Figure 2 The three characteristic lines shown in the figure are representative: characteristic L1 at room temperature (25°C), characteristic L2 at relatively low temperatures, and characteristic L3 at relatively high temperatures. It is clear from these characteristic lines L1, L2, and L3 that the output of battery 5 decreases as the SOC decreases. Furthermore, the relationship between SOC and output is related to the temperature of battery 5: the lower the temperature of battery 5, the lower the output at the same SOC. In other words, to maintain a certain battery output (basically, the output obtained by adding an appropriate margin to the predicted maximum required output) while traveling to the destination, the lower the temperature of battery 5, the higher the SOC must be. Therefore, the lower the temperature of battery 5, the higher the severity.

[0036] The severity level thus digitized is then compared with predetermined thresholds SHc and SHb (where SHc < SHb) in steps 5 and 6, respectively, and classified into three levels of severity: A, B, and C. If the value is less than or equal to threshold SHc in step 5, the system is classified as the lowest severity level, C, and the process proceeds to step 7, where the lowest fourth SOC lower limit target value and the corresponding fourth SOC upper limit target value are selected. If the value is less than or equal to threshold SHb in step 6, the system is classified as the intermediate severity level, B, and the process proceeds to step 8, where the second lowest third SOC lower limit target value and the corresponding third SOC upper limit target value are selected. If the value exceeds threshold SHb, the system is classified as the highest severity level, A, and the process proceeds to step 9, where the second second SOC lower limit target value and the corresponding second SOC upper limit target value are selected.

[0037] On the other hand, when the step 1 proceeds to the step 10 without setting the destination in the in-vehicle navigation system 14, the aforementioned severity is calculated within the driving range of the driver assumed based on the learning. For example, in the case where a certain driver daily commutes from home to the office, it is possible to estimate that the vehicle is driven to the same office depending on the time of use start of the vehicle and its position, and the like. Therefore, even without setting the destination, for a narrow distance range, the required maximum output of the battery 5 being driven is predicted, and the severity is acquired considering the battery characteristics as described above. In the step 10, information whether the driver has selected the acceleration priority mode, so-called sport mode, as the driving mode of the vehicle is also acquired.

[0038] Next, in the step 11, it is determined whether the severity is higher than the threshold SHc or whether the sport mode is selected. In the case where the severity is higher than the threshold SHc or in the case where the sport mode is selected, the step 12 is entered, and the highest first lower SOC target value and the first upper SOC target value are selected. In the step 11, if NO, the step 5 is entered, and any one of the second to fourth lower SOC target values and the second to fourth upper SOC target values is selected depending on the severity.

[0039] Further, as described above, at least one of the first to fourth lower SOC target values and the corresponding first to fourth upper SOC target values (for example, the lower SOC target value) can be corrected in a manner that the SOC control range between the upper SOC target value and the lower SOC target value is relatively expanded on the high temperature side, depending on the temperature of the battery 5.

[0040] In addition, for the upper SOC target value in the case where the destination is set, the driving distance to the destination, the predicted regenerative amount in the downhill, and the required maximum output of the battery predicted in the route depending on the slope information and the vehicle speed information in the route to the destination can be considered, and the upper SOC target value can be variably set.

[0041] Figure 4An example of the change in SOC during travel in the case of stringency C is shown. Basically, the SOC decreases due to EV travel, and the SOC increases by HEV travel or regeneration during downhill travel. The characteristic line in broken line form in the figure is schematically depicted for the purpose of explanation and is not necessarily accurate. Also, the period ΔT in the figure schematically shows the maximum output period. In the case of stringency C, the lowest fourth SOC lower target value and the fourth SOC upper target value are selected among the plurality of levels. At the travel start time point, it is assumed that the battery 5 has been charged to some extent, and the vehicle starts driving as EV travel. Also, EV travel is continued until the SOC of the battery 5 decreases to the fourth SOC lower target value. The fourth SOC lower target value is set low enough so that the distance or time during which EV travel is possible is long. As a result, the frequency of power generation by the internal combustion engine 2 to the destination is less, and the total fuel consumption efficiency including EV travel and HEV travel is improved. Also, it is advantageous in terms of reducing the exhaust emission amount.

[0042] Further, in the case where the SOC lower target value and the SOC upper target value are set low like this, the influence of natural discharge in the case where the vehicle is not used for a long time becomes relatively large. Therefore, for example, it is also possible to control so that the amount of power generation by the internal combustion engine 2 is made large when approaching the destination, and the SOC of the battery 5 at the vehicle stop time point is raised to some extent in advance.

[0043] Figure 5 An example of the change in SOC during travel in the case of stringency B is shown. In this case, the third SOC lower target value and the third SOC upper target value which are the second lowest among the plurality of levels are used, and EV travel is continued until it decreases to the third SOC lower target value after the start of travel. Therefore, the distance or time during which EV travel is possible after the start of travel is long. Also, at this time, the SOC lower target value is higher than in the case of stringency C, and thus the battery output to be secured during travel is higher than in the case of stringency C. Therefore, it is possible to cope with some extent of uphill or high-speed travel on the route.

[0044] Figure 6 An example of the change in SOC during travel in the case of stringency A is shown. In this case, the second SOC lower target value and the second SOC upper target value which are higher than in the case of stringency B are selected. Therefore, the distance or time during which EV travel is possible after the start of travel is short. However, at this time, the SOC lower target value is higher than in the case of stringency B, and thus the battery output to be secured during travel is higher than in the case of stringency B. Therefore, it is possible to reliably secure the battery output required for a steep uphill or the like on the route.

[0045] Figure 7One example of a change in SOC at the time of running in a case where the destination is not set and the strictness is higher than the threshold SHc or in a case where the sport mode is set is shown. In this case, the first SOC lower target value and the first SOC upper target value that are higher than in the case where the destination is set are used. Therefore, a high battery output is always ensured, and so-called sport running can be dealt with.

[0046] However, in order to suppress the level of noise in the senses of the occupants including the driver, a control that prohibits the operation of the internal combustion engine 2 at a low vehicle speed at which the so-called implicit noise is small is known, but the vehicle speed threshold in this case can also be corrected based on the above strictness. For example, the higher the strictness, the lower the vehicle speed at which the operation of the internal combustion engine 2 is allowed, and thus early recovery of the SOC is achieved.

[0047] Further, when the destination is set and EV running is performed at the low fourth SOC lower target value and the fourth SOC upper target value as the strictness C, the driver can switch to the sport mode. In this case, as shown in FIG. 6, the setting of the highest first SOC lower target value and the first SOC upper target value is switched to, and thus, in most cases, power generation by the internal combustion engine 2 is started, and a higher battery output is ensured. Here, in a case where the recovery of the SOC does not catch up with the acceleration request of the driver, the maximum output that can be output at present and the achievement time until the required output can be dealt with can also be information-prompted to the driver as sound information or the like. Figure 7

[0048] Thus, in the above embodiment, based on the required maximum output of the battery 5 predicted in the route and the correlation between the SOC and the battery output corresponding to the battery temperature, the SOC lower target value of the lowest level that satisfies the required maximum output is selected from among the levels of the SOC lower target value discretely set to a plurality of levels according to the battery output that should be ensured in the route. Thereby, after the running is started, EV running can be continued for as long as possible, and reliable output on an uphill road or the like can be ensured.

[0049] The above has been described in detail for one embodiment of the application, but the application is not limited to the above embodiment, and various modifications can be made. For example, in the above embodiment, the SOC lower target value is controlled by levels for the sake of simplicity of the control, but the value of the SOC lower target value can also be continuously changed.​

Claims

1. A battery control method for a series hybrid vehicle, the vehicle comprising a generator driven by an internal combustion engine, a traction motor, and a battery for supplying power to the traction motor, the battery control method for a series hybrid vehicle causing the internal combustion engine to generate power when the battery's SOC drops to a predetermined lower SOC target value, and terminating the internal combustion engine's power generation when the battery's SOC reaches a predetermined upper SOC target value. In this battery control method for a series hybrid vehicle, Determine whether the destination is set in the car navigation system. When a destination is set, the maximum output required by the battery predicted on the route to the destination is obtained. Based on the predicted required maximum output of the battery and the correlation between the SOC and the battery output, an SOC lower limit target value that satisfies the required maximum output is set.

2. The battery control method for a series hybrid vehicle according to claim 1, wherein: The SOC lower limit target value is set in advance in a plurality of levels, and the SOC lower limit target value of a certain level is selectively used.

3. The battery control method for a series hybrid vehicle according to claim 2, wherein: The SOC upper limit target value is determined for each level, and the lower the level of the SOC lower limit target value, the lower the SOC upper limit target value.

4. The battery control method for a series hybrid vehicle according to claim 1, wherein: Detect or estimate the battery temperature, The correlation between the SOC corresponding to the battery temperature and the battery output is used.

5. The battery control method for a series hybrid vehicle according to claim 1, wherein: Detect or estimate the battery temperature, At least one of the SOC lower limit target value and the SOC upper limit target value is corrected according to the battery temperature so that the SOC control range between the SOC upper limit target value and the SOC lower limit target value is relatively expanded on the high temperature side.

6. The battery control method for a series hybrid vehicle according to claim 1, wherein: The required maximum output is obtained based on the slope information and the vehicle speed information on the path to the destination.

7. The battery control method for a series hybrid vehicle according to claim 1, wherein: Weather information on the route to the destination is obtained, correction related to road conditions is applied, and the SOC lower limit target value is set.

8. The battery control method for a series hybrid vehicle according to claim 1, wherein: When the destination is not set, the SOC lower limit target value is set relatively higher than when the destination is set.

9. The battery control method for a series hybrid vehicle according to claim 1, wherein: When no destination is set, the battery's required maximum output is predicted within the driver's assumed driving range based on learning. Based on the predicted battery's required maximum output and the relationship between SOC and battery output, a lower limit target SOC value is set that satisfies the required maximum output.

10. The battery control method for a series hybrid vehicle according to claim 3, wherein: When a destination is set, the SOC upper limit target value is variably set taking into account the travel distance to the destination, the predicted regeneration amount on the downhill road, and the required maximum output of the battery predicted on the route to the destination based on the slope information and vehicle speed information on the route to the destination.

11. A series hybrid vehicle comprising: a generator driven by an internal combustion engine; a traction electric motor; a battery for supplying electric power to the traction electric motor; and a control device for starting power generation by the internal combustion engine when the SOC of the battery drops to a predetermined lower SOC target value, and for stopping power generation by the internal combustion engine when the SOC reaches a predetermined upper SOC target value. In this series hybrid vehicle, The control device determines whether a destination is set in the in-vehicle navigation system. When a destination is set, the control device obtains a required maximum output of the battery predicted on the route to the destination. The control device sets an SOC lower limit target value that satisfies the requested maximum output based on the predicted requested maximum output of the battery and the correlation between the SOC and the battery output.

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