JP7578080B2 - Electric vehicles - Google Patents

Description

The technology disclosed in this specification relates to electric vehicles.

The electric vehicle in Patent Document 1 discloses energy management technology for use when traveling on a circuit. Specifically, a set value that limits the power supplied to the motor is set in advance for each section of travel. By controlling the motor based on the set value, energy management is performed to balance the charge and discharge balance for each lap. This allows more power to be supplied to the motor in places where it is highly necessary to output torque from the motor, making it possible to optimize time.

JP 2009-18699 A

The actual amount of power regenerated and consumed while driving may vary from the set value that limits the power supplied to the motor. This causes the charge/discharge balance for each lap to become unbalanced, making energy management difficult.

The technology disclosed in this specification is embodied in an electric vehicle. The electric vehicle includes a motor. The electric vehicle includes a power storage device that supplies power to the motor and accumulates regenerative power generated by the motor. The electric vehicle includes a traveling position acquisition means that acquires the traveling position of the electric vehicle on a circuit. The electric vehicle includes a power limiting means that limits the supply power supplied to the motor for each section of the circuit divided into multiple sections. The power limiting means limits the supply power so that the charging rate of the power storage device at a specific point on the circuit becomes a predetermined target charging rate. The power limiting means is configured to execute a process of setting a limit setting value for each of the multiple sections, a process of limiting the supply power according to the limit setting value based on the traveling position acquired by the traveling position acquisition means, a process of calculating the difference between a measured charging rate, which is a charging rate measured when passing through a specific point, and the target charging rate, and a process of correcting the limit setting value based on the difference so that the measured charging rate approaches the target charging rate.

With the above configuration, the difference between the measured charging rate and the target charging rate can be calculated to calculate the variation that the actual charging/discharging amount has against the limit setting value. Then, by correcting the limit setting value so that the measured charging rate approaches the target charging rate, the variation can be suppressed, making it possible to balance the charge/discharge balance for each lap. Time optimization becomes possible.

1 is a schematic diagram of a configuration of a hybrid vehicle 10 according to an embodiment of the present invention. FIG. 13 is an operational flow diagram of energy management implemented by the power limiting means. FIG. 13 is a diagram showing an example of a circular route. 1 is a first example of a graph showing the relationship between the amount of discharged power, the charging rate, the upper limit setting value, etc.; 13 is a second example of a graph showing the relationship between the amount of discharged power, the charging rate, the upper limit setting value, etc.;

(Configuration of Hybrid Vehicle 10)
A hybrid vehicle 10 according to the embodiment will be described with reference to FIG. 1. The hybrid vehicle 10 according to the embodiment belongs to an electric vehicle, and is typically an electric vehicle (a so-called automobile) that runs on a road surface. However, some or all of the technology described in the embodiment can be similarly adopted in an electric vehicle that runs on a track, for example. The hybrid vehicle 10 includes a vehicle body 12, a pair of front wheels 14 provided at the front of the vehicle body 12, and a pair of rear wheels 16 provided at the rear of the vehicle body 12. The specific configuration of the vehicle body 12 and the number of wheels provided on the hybrid vehicle 10 are not particularly limited. In addition, the hybrid vehicle 10 is not limited to one that is driven and operated by a user, and may be one that is remotely operated by an external device or one that runs autonomously.

The hybrid vehicle 10 further includes an engine 18, a first motor generator (hereinafter referred to as the "first motor") 20, a clutch 22, a transmission 24, and a first power transmission path 26. The engine 18 is connected to a pair of rear wheels 16 via the first power transmission path 26. The engine 18 is an internal combustion engine that burns fuel to generate power, and examples of the engine 18 include, but are not limited to, a gasoline engine, a diesel engine, a hydrogen engine, etc.

The first motor 20 is provided in the first power transmission path 26. The first motor 20 is located between the engine 18 and the rear wheels 16, and functions as a prime mover that drives the rear wheels 16 together with the engine 18. The first motor 20 can also function as a generator in addition to functioning as a prime mover. That is, the hybrid vehicle 10 can generate power using the first motor 20 by driving the first motor 20 with the engine 18. Alternatively, when the hybrid vehicle 10 needs to decelerate, it can perform regenerative braking of the pair of rear wheels 16 by making the first motor 20 function as a generator.

The clutch 22 is provided in the first power transmission path 26. The clutch 22 is located between the engine 18 and the first motor 20 and the pair of rear wheels 16. The clutch 22 can connect and disconnect the power transmission between the engine 18 and the first motor 20 and the rear wheels 16 by mechanically connecting and disconnecting the first power transmission path 26. With this configuration, the hybrid vehicle 10 can generate power using the first motor 20 by driving the first motor 20 with the engine 18 in a state where the engine 18 is mechanically disconnected from the pair of rear wheels 16. In other words, the hybrid vehicle 10 can generate power using the first motor 20 regardless of its speed.

The transmission 24 is provided in the first power transmission path 26. The transmission 24 is located between the clutch 22 and the pair of rear wheels 16. The transmission 24 changes the rotational motion input from the clutch 22 at a gear ratio corresponding to the selected gear stage, and outputs the rotational motion to the pair of rear wheels 16. The rotational motion (i.e., torque) output by the transmission 24 is distributed to the pair of rear wheels 16 via a differential gear (not shown).

The hybrid vehicle 10 further includes a second motor generator (hereinafter referred to as the "second motor") 30. The second motor 30 is connected to the pair of front wheels 14 via a second power transmission path 32, and functions as a prime mover that drives the pair of front wheels 14. A differential gear 34 is provided in the second power transmission path 32, and the rotational motion (i.e., torque) output by the second motor 30 is distributed to the pair of front wheels 14 via the differential gear 34. The second motor 30 can also function as a generator for regenerative braking of the front wheels 14, in addition to the prime mover. That is, when the hybrid vehicle 10 needs to decelerate, the second motor 30 can function as a generator to perform regenerative braking of the front wheels 14. Although not shown, the second power transmission path 32 may be provided with a reducer or a clutch as necessary.

The hybrid vehicle 10 further includes a battery 40, a first power control unit (hereinafter referred to as the "first PCU") 36, and a second power control unit (hereinafter referred to as the "second PCU") 38. The battery 40 is a power supply device for the first motor 20 and the second motor 30. The battery 40 has multiple secondary battery cells and is configured to be capable of repeated charging and discharging. The secondary battery cells referred to here are not particularly limited, but may be, for example, lithium ion battery cells or nickel metal hydride battery cells.

The first PCU 36 is a power conversion device and is interposed between the battery 40 and the first motor 20. That is, the battery 40 is connected to the first motor 20 via the first PCU 36. When the first motor 20 functions as a prime mover, the first PCU 36 converts the DC power output from the battery 40 into three-phase AC power and supplies it to the first motor 20. On the other hand, when the first motor 20 functions as a generator, the first PCU 36 converts the three-phase AC power output from the first motor 20 into DC power and supplies it to the battery 40. In this way, the battery 40 is charged by the power generated by the first motor 20.

The specific configuration of the first PCU 36 is not particularly limited. As an example, the first PCU 36 in this embodiment includes a voltage converter connected to the battery 40, an inverter located between the voltage converter and the first motor 20, and a power controller that controls the operation of these components. The voltage converter is configured to be capable of stepping up and stepping down DC power, and the inverter is configured to be capable of converting power between DC power and AC power.

The second PCU 38 is also a power conversion device and is interposed between the battery 40 and the second motor 30. That is, the battery 40 is connected to the second motor 30 via the second PCU 38. When the second motor 30 functions as a prime mover, the second PCU 38 converts the DC power output from the battery 40 into three-phase AC power and supplies it to the second motor 30. On the other hand, when the second motor 30 functions as a generator, the second PCU 38 converts the three-phase AC power output from the second motor 30 into DC power and supplies it to the battery 40. As a result, the battery 40 is charged by the power generated by the second motor 30. There is no particular limitation on the specific configuration of the second PCU 38. As an example, the second PCU 38 in this embodiment includes a voltage converter, an inverter, and a power controller, similar to the first PCU 36.

(Configuration and Function of Control Device 50)
The hybrid vehicle 10 further includes a control device 50. The control device 50 is configured using a computer device, and includes a memory 51 that stores various control programs, a processor 52 that executes the control programs, a traveling position acquisition unit 53 that acquires the traveling position of the hybrid vehicle 10, and the like. The control device 50 is electrically connected to the engine 18, the first PCU 36, the second PCU 38, the clutch 22, and the transmission 24, and is configured to be able to control the operations of these. For example, operation information by a user and vehicle information indicating the state of the hybrid vehicle 10 are input to the control device 50. The operation information is, for example, accelerator opening information indicating the amount of operation of the accelerator pedal by the user, and brake depression force information indicating the amount of operation of the brake pedal by the user. The vehicle information is, for example, vehicle speed information indicating the speed of the hybrid vehicle 10 and battery information indicating the charging rate (SOC: State of Charge) of the battery 40. The control device 50 controls the operation of each part of the hybrid vehicle 10 described above according to the input operation information and vehicle information. In other words, the control device 50 realizes a system that can accurately manage inputs and outputs such as the remaining amount of releasable energy, released energy, and recovered energy in a power system including the battery 40, the first motor 20, and the second motor 30.

The memory 51 includes, for example, an EEPROM. The memory 51 stores various programs (e.g., an energy management program) and various data (e.g., a course map of the circuit CC, sections, an upper limit setting value US, a target charging rate Tsoc, etc.).

The traveling position acquisition unit 53 is a device capable of identifying the current vehicle position of the hybrid vehicle 10. The traveling position acquisition unit 53 may be equipped with a GPS, for example. Alternatively, the traveling position acquisition unit 53 may identify the vehicle position on the circuit based on the traveling distance from a specific point SP or the acceleration measured by an acceleration sensor (not shown).

When the processor 52 executes the energy management program stored in the memory 51, the control device 50 functions as a power limiting means for limiting the power supplied to the first motor 20 and the second motor 30. The power limiting means is a means for performing energy management so that the charge/discharge balance of the battery 40 is balanced for each lap in order to travel around the circuit faster and with a more stable time. The energy required for discharge is provided by braking regeneration during travel and power generation from the engine's reserve power, but in circuit travel where the proportion of high-load travel is high, it is difficult to secure enough discharge resources to satisfy all of the driving force requirements required by the driver. Therefore, the charge/discharge balance can be balanced by appropriately limiting discharge using the power limiting means.

In this embodiment, the power limiting means limits the power supply so that the charging rate of the battery 40 at a specific point SP on the circuit becomes a predetermined target charging rate Tsoc. This makes it possible to balance the charge and discharge balance. Further specific operations of the power limiting means will be described later.

(Operation of power limiting means)
The operation flow of the energy management performed by the power limiting means will be described with reference to Fig. 2. The flow of Fig. 2 is started, for example, when the hybrid vehicle 10 is powered on.

In step S10, the control device 50 divides the circuit into predetermined sections. This process may be performed inside the control device 50, or may be performed by a computer or the like external to the hybrid vehicle 10. The sections may be divided in various ways. For example, the sections may be divided by corners, or by predetermined distances. The divided sections may also be stored in the memory 51. This makes it possible to omit the process of step S10 from the next time onwards.

The sections will be explained using the example of the closed circuit CC in Figure 3. The closed circuit CC has five corners C1 to C5. Each vertex of these corners serves as a boundary to divide the circuit into sections SE1 to SE5.

In step S20, the control device 50 sets a specific point SP. The specific point SP can be set at any position on the circular route. In the example of FIG. 3, the specific point SP is set at the start point of section SE1.

In step S30, the control device 50 sets an initial value for the upper limit setting value US of the discharge amount. The upper limit setting value US determines the upper limit value of the amount of power discharged by the first motor 20 and the second motor 30 for each of the multiple sections. In other words, the upper limit setting value US sets the optimal amount of energy discharged for each of the multiple sections. Note that the upper limit setting value US that was set when the circuit was previously traveled may be stored in the memory 51 and read out in step S30. This can simplify the processing of step S30.

The setting of the upper limit setting value US will be explained using the example of Figure 4. Figure 4 is a graph of the first and second laps of the circular circuit CC. Figure 4(A) is a graph showing the amount of discharged power in the first motor 20 and the second motor 30. The horizontal axis is the travel distance from departure from a specific point SP on the circular circuit CC to returning to the specific point SP. The solid line indicates the upper limit setting value US_C for the current lap. The dashed and dotted line indicates the upper limit setting value US_P for the previous lap. The dotted line indicates the actual discharge amount AD, which is a value obtained by measuring the actual discharge amount during travel.

Figure 4 (B) is a graph showing the charging rate of the battery 40. The charging rate Msoc indicates the measured value of the actual charging rate during driving. The measured charging rate Msoc_SP is the measured value of the charging rate when passing a specific point SP. The target charging rate Tsoc is the target value of the measured charging rate Msoc_SP.

Figure 4 (C) is a table showing the upper limit setting value US_P of the previous lap, the correction amount CA, the upper limit setting value US_C of the current lap, and the time sensitivity TS. The upper limit setting value US_P of the previous lap is the upper limit setting value used during the previous lap. The upper limit setting value US_C of the current lap is the upper limit setting value US_P of the previous lap corrected using the correction amount CA, and is the upper limit setting value used during the current lap. Note that in the case of the first lap, the upper limit setting value US_P and correction amount CA of the previous lap do not exist.

Time sensitivity TS is the percentage improvement in driving time per input energy. The higher the time sensitivity, the greater the reduction in driving time for the same amount of discharge. In this embodiment, time sensitivity TS is high in sections with long straights such as sections SE1 and SE5. Time sensitivity TS is low in sections sandwiched between sharp corners such as section SE4. Time sensitivity TS for sections SE2 and SE3 is medium.

As described above, in step S30, the initial value of the upper limit setting value US_C for the current lap is set (see region R1 in FIG. 4C). At this time, the higher the time sensitivity TS of the section, the higher the upper limit setting value US_C is set. In the example of FIGS. 4A and 4C, the upper limit setting value US_C of section SE1, which has the longest straight section and has a time sensitivity TS of "large", is set to the highest 1.4 [MJ]. The upper limit setting value US_C of section SE5, which has the next longest straight section and has a time sensitivity TS of "large", is set to the second highest 1.0 [MJ]. Meanwhile, the upper limit setting values US_C of sections SE2 and SE3, which have a time sensitivity TS of "medium", are set to 0.6 [MJ] and 0.3 [MJ], respectively. The upper limit setting value US_C of section SE4, which has a time sensitivity TS of "small", is set to 0 [MJ], so no motor assist is generated in section SE4.

The upper limit setting value US_C for each section set in this control may be set to provide optimal energy management when the vehicle is driven by a driver with a certain level of skill.

In step S40, the control device 50 judges whether or not traveling on the closed circuit CC has started. This judgment may be made based on the traveling position acquired by the traveling position acquisition unit 53. If the judgment is negative, the process returns to step S40 and waits, and if the judgment is positive, the process proceeds to step S50.

In step S50, the control device 50 limits the amount of discharge to the first motor 20 and the second motor 30 in accordance with the upper limit setting value US_C for the current lap. This process is performed based on the traveling position acquired by the traveling position acquisition unit 53. Specifically, it is determined which of the sections SE1 to SE5 the vehicle is traveling in based on the traveling position. Then, the amount of discharge from the motor is limited so as not to exceed the upper limit setting value US_C corresponding to the section in which the vehicle is traveling.

An example will be explained using Figure 4 (A). In section SE1, the actual discharge amount AD increases in response to acceleration on the straight (region R2). When the upper limit set value US_C is reached, the actual discharge amount AD is limited to a constant value of 1.4 [MJ] and does not increase any further (region R3). Similarly, the upper limit value of the actual discharge amount AD in each of sections SE2 to SE5 is set to a value corresponding to the upper limit set value US_C. In other words, energy management is performed so that the discharge amount does not exceed the upper limit set value US_C in response to the driver's driving force request.

In step S60, the control device 50 determines whether or not the vehicle has completed one lap around the closed circuit CC and returned to the specific point SP. If the determination is negative, the control device 50 proceeds to step S70, where it determines whether or not the vehicle should end its journey. If the vehicle should continue to travel (S70: NO), the control device 50 returns to S60. If the vehicle should end its journey (S70: YES), the control device 50 ends the flow.

If it is determined that one lap has been completed around the circuit CC (S60: YES), the process proceeds to step S80. In step S80, the control device 50 acquires the measured charging rate Msoc_SP measured when passing through the specific point SP. Then, the control device 50 calculates the difference DF between the measured charging rate Msoc_SP and the predetermined target charging rate Tsoc. In the example of FIG. 4(B), at the end of the first lap, the measured charging rate Msoc_SP(1) is acquired, and the difference DF1 is calculated.

In step S90, the control device 50 calculates the upper limit setting value US_C for the current lap by correcting the upper limit setting value US_P for the previous lap based on the difference DF. This correction is performed so that the measured charging rate Msoc_SP approaches the target charging rate Tsoc.

A first example of the specific content of the correction will be described with reference to FIG. 4. The first example is a case where the measured charging rate Msoc_SP(1) is smaller than the target charging rate Tsoc by the difference DF1 at the end of the first lap. In other words, since the charging rate is insufficient by the difference DF1, it is determined that the upper limit set value US_C needs to be lowered in the next lap (i.e., the discharge amount needs to be further reduced).

First, the correction rate CR is calculated based on the difference DF1. The correction rate CR is the rate of increase or decrease of the maximum amount of power that can be supplied at the upper limit setting value US_C (the area surrounded by the upper limit setting value US_C in FIG. 4(A)). There may be various methods for calculating the correction rate CR. For example, it may be found using a table showing the relationship between the difference DF and the correction rate CR, or it may be calculated by substituting the difference DF into a formula prepared in advance. In the example of FIG. 4, a case will be described where the correction rate CR calculated based on the difference DF1 is "0.7".

Next, a correction is performed to lower the upper limit setting value US_C based on the calculated correction rate CR. Specifically, the correction is performed so that the maximum power amount after correction (the area surrounded by the upper limit setting value US_C for the current lap) is 0.7 times the maximum power amount before correction (the area surrounded by the upper limit setting value US_P for the previous lap). Furthermore, the correction to lower the upper limit setting value US_C is performed preferentially for sections with low time sensitivity TS. Then, if the reduction in the maximum power amount is insufficient with only the correction for sections with low time sensitivity TS, a correction is also performed for sections with high time sensitivity TS.

In the example of FIG. 4, in section SE4 where time sensitivity TS is "low", the upper limit setting value US_C is already 0, so no correction is made. Then, the upper limit setting values US_C of sections SE2 and SE3 where time sensitivity TS is "medium" are corrected to 0 (arrow Y1). And because this correction alone is not enough to reduce the maximum power consumption to 0.7 times, the upper limit setting values US_C of sections SE1 and SE5 where time sensitivity TS is "high" are corrected (arrow Y2).

A second example of the specific content of the correction will be described with reference to FIG. 5. The second example is a case where, at the end of the first lap, the measured charging rate Msoc_SP(1) is greater than the target charging rate Tsoc by the difference DF1. In other words, since the charging rate has been exceeded by the difference DF1, it is determined that the upper limit setting value US_C needs to be increased in the next lap (i.e., the discharge amount needs to be further increased).

The correction rate CR is calculated based on the difference DF1 using the method described above. In the example of FIG. 5, the correction rate CR calculated based on the difference DF1 is 1.2. Then, a correction is performed so that the maximum power amount after correction is 1.2 times the maximum power amount before correction. The correction to increase the upper limit setting value US_C is performed preferentially for sections with a large time sensitivity TS. In the example of FIG. 5, the upper limit setting value US_C for sections SE1 and SE5, where the time sensitivity TS is "large", is corrected (arrow Y3).

When the upper limit setting value US_C for the current lap is calculated in step S90, the process returns to step S50. Then, the discharge amount for the current lap is limited based on the upper limit setting value US_C for the current lap. In the example of Figures 4 and 5, the discharge amount for the second lap is limited. Then, at the end of the second lap, the measured charging rate Msoc_SP(2) is obtained and the difference DF2 is calculated (step S80). The upper limit setting value US_C for the third lap is calculated based on the difference DF2 (step S90). Thereafter, the processes of steps S60 to S90 are repeated for each lap.

(effect)
During the running of the circuit, various factors of variation (e.g., vehicle condition such as tires, road surface condition such as dry or wet, conditions of other vehicles on the course, and skill difference of the driver itself) exist. Therefore, even if a limit value is set in advance so that the charging rate of the battery 40 converges to the target charging rate Tsoc and the power supply to the motor is limited based on this limit value, the charging rate may deviate from the target charging rate Tsoc. The charge and discharge balance for each lap is not balanced, making energy management difficult. Therefore, in the technology of this specification, the difference DF between the measured charging rate Msoc_SP and the target charging rate Tsoc is calculated for each lap (step S80), thereby calculating the variation of the actual charging and discharging amount with respect to the upper limit setting value US. Then, the upper limit setting value US is corrected so that the measured charging rate Msoc_SP approaches the target charging rate Tsoc (step S90), thereby suppressing the variation, and therefore it is possible to balance the charging and discharging balance for each lap. Time optimization is possible.

In the technology of this specification, the correction to lower the upper limit setting value US_C is performed preferentially for sections with a small time sensitivity TS. The correction to raise the upper limit setting value US_C is performed preferentially for sections with a large time sensitivity TS (step S90). This allows the upper limit setting value US_C to be corrected higher for sections with a larger time sensitivity TS, making it possible to further improve times.

It is conceivable to limit the power supplied to the motor based on the battery charge rate and vehicle speed. This is because concentrating the limited amount of discharge at a lower speed range has better time sensitivity per energy, and is therefore expected to lead to improved times. However, with the above method, the amount of discharge is determined by the starting vehicle speed. Therefore, on the same circuit, it is not possible to change the amount of discharge between a long straight with high time sensitivity and a short straight with low time sensitivity. Therefore, in the technology of this specification, the circuit is divided into multiple sections (step S10). The higher the time sensitivity TS of the section, the higher the upper limit setting value US is set (step S30). This allows the amount of power supply limit to be optimized according to the time sensitivity TS. This allows for further improvements in time.

Although the embodiments of the present technology have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. The technical elements described in this specification or drawings demonstrate technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technology exemplified in this specification or drawings achieves multiple objectives simultaneously, and achieving one of these objectives is itself technically useful.

The correction of the upper limit setting value US_P in step S90 is not limited to a form in which a priority is determined based on time sensitivity TS, but can be performed in various forms. For example, it may be a form in which a weight is assigned based on time sensitivity TS. Also, the correction may be based on other indicators, not limited to time sensitivity TS. Also, all sections may be corrected at the same rate.

In this embodiment, the difference DF is calculated for each lap and the upper limit setting value US_C for the next lap is corrected, but this is not the only possible mode. For a long course with many sections, the course may be divided into sections every few sections, and the difference DF may be calculated at the end of each section. Then, the upper limit setting value US_C for the next section may be corrected.

The electric vehicles to which the technology of this specification can be applied are not limited to hybrid electric vehicles (HEVs). For example, it can also be applied to battery electric vehicles (BEVs), plug-in hybrid electric vehicles (PHEVs), fuel cell electric vehicles (FCEVs), etc. For example, if the technology of this specification is applied to an electric vehicle, it can improve the time by completing a specified number of laps from full charge to depletion.

In this embodiment, the power storage device is a battery 40, but this is not limited to the above. For example, the power storage device may be a capacitor.

10: Hybrid vehicle 20: First motor 30: Second motor 40: Battery 50: Control device 51 Memory 52 Processor 53 Travel position acquisition unit CC: Circuit DF: Difference Msoc: Charge rate Msoc_SP: Measured charge rate Tsoc: Target charge rate TS: Time sensitivity SE1 to SE5: Section US_P: Upper limit setting value for previous lap US_C: Upper limit setting value for current lap

Claims (1)

An electric vehicle,
A motor;
a power storage device that supplies power to the motor and stores regenerative power generated by the motor;
a traveling position acquisition means for acquiring a traveling position of the electric vehicle on a circular route;
a power limiting means for limiting a supply power to be supplied to the motor for each section of the circuit divided into a plurality of sections, the power limiting means limiting the supply power so that a charging rate of the power storage device at a specific point of the circuit becomes a predetermined target charging rate;
Equipped with
The power limiting means includes:
A process of setting a limit setting value for each of the plurality of sections;
A process of limiting the supply power in accordance with the limit setting value based on the traveling position acquired by the traveling position acquisition means;
A process of calculating a difference between a measured charging rate, which is a charging rate measured when passing through the specific point, and the target charging rate;
correcting the limit setting value based on the difference so that the measured charging rate approaches the target charging rate;
The electric vehicle is configured to be able to execute the above steps.

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