Hybrid vehicles

Abstract

To properly adjust whether fuel reduction efficiency by EV travel is considered significant or regenerative electric power recovery at vehicle deceleration time is considered significant when selecting engine travel and the EV travel in a hybrid vehicle.SOLUTION: A hybrid vehicle travels in any one travel mode of engine travel in which the vehicle travels using power of a diesel engine without using power of a motor generator and EV travel in which the vehicle travels using power of the motor generator without using power of the diesel engine. A control circuit calculates fuel reduction amount by the EV travel, calculates power consumption amount required for the EV travel, and calculates the ratio of fuel reduction amount to power consumption amount Cq as a fuel evaluation index. When the fuel evaluation index is larger than a threshold, the EV travel is selected. When the fuel evaluation index is not larger than the threshold, the engine travel is selected. The control circuit sets the threshold to be compared with the fuel evaluation index to a smaller value as SOC of a battery is higher.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a hybrid vehicle that runs using power from at least one of a motor generator and a diesel engine. [Background technology]

[0002] Japanese Patent Application Laid-Open Publication No. 2015-77923 (Patent Document 1) discloses a hybrid vehicle that runs using at least one of the power sources of a motor generator and an engine. This hybrid vehicle runs in either EV running (EV running mode), in which the engine is stopped and the vehicle runs using the power of the motor generator, or engine running (engine running mode or engine power generation mode), in which the vehicle runs with the engine running. The hybrid vehicle compares the engine power generation cost with the EV effect, and if the EV effect is greater than the engine power generation cost, EV running is selected, and if not, engine running is selected. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-77923 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the hybrid vehicle disclosed in Patent Document 1, as described above, whether to select EV running or engine running is determined based on the results of a comparison between the engine power generation cost and the EV effect.

[0005] However, if the SOC (State Of Charge, a value indicating the amount of stored electricity) of the battery electrically connected to the motor generator is high, there is a concern that the regenerative power generated by the motor generator during vehicle deceleration may not be properly recovered by the battery. The hybrid vehicle disclosed in Patent Document 1 does not mention such an issue or how to address it, leaving room for improvement.

[0006] The present disclosure has been made to solve the above-mentioned problems, and its purpose is to appropriately adjust whether to prioritize fuel saving efficiency through motor driving or to prioritize recovery of regenerative power when decelerating the vehicle when selecting between engine driving and motor driving in a hybrid vehicle that can select between engine driving and motor driving. [Means for solving the problem]

[0007] (Item 1) A hybrid vehicle according to the present disclosure runs using power from at least one of a diesel engine and a motor generator. The hybrid vehicle includes a battery electrically connected to the motor generator, and a control circuit that runs the hybrid vehicle in either engine running, in which the hybrid vehicle runs using power from the diesel engine without using power from the motor generator, or motor running, in which the hybrid vehicle runs using power from at least the motor generator. The control circuit calculates a fuel reduction amount, which is the amount of fuel consumption reduced by motor running compared to engine running, calculates the amount of power consumption required for motor running, and calculates an evaluation index as the ratio of the fuel reduction amount to the amount of power consumption. If the evaluation index is greater than a threshold, the control circuit selects motor running, and if the evaluation index is smaller than the threshold, the control circuit selects engine running. The control circuit sets a smaller threshold value as the amount of charge stored in the battery increases.

[0008] According to the above configuration, the ratio of the fuel consumption reduction amount to the power consumption due to motor driving is calculated as an evaluation index. When the evaluation index is greater than a threshold, motor driving is selected; otherwise, engine driving is selected. Furthermore, the greater the amount of charge stored in the battery, the smaller the threshold value compared to the evaluation index. Therefore, when the amount of charge stored in the battery is large, EV driving is made more likely to be selected and the battery is actively discharged, thereby emphasizing the recovery of regenerative power during vehicle deceleration. On the other hand, when the amount of charge stored in the battery is low, the threshold value compared to the evaluation index is made larger, so that EV driving is selected only when fuel consumption reduction efficiency is higher, thereby emphasizing the fuel saving efficiency of motor driving. As a result, when selecting between engine driving and motor driving, it is possible to appropriately adjust whether to emphasize the fuel saving efficiency of motor driving or the recovery of regenerative power during vehicle deceleration.

[0009] (2) In the hybrid vehicle described in paragraph 1, the control circuit is configured to: raw The larger the amount of power, the smaller the threshold value is set.

[0010] (Item 3) In the hybrid vehicle described in item 2, the predetermined period is the period from when the control system of the hybrid vehicle is started to when it is stopped next time. [Effects of the Invention]

[0011] According to the present disclosure, in a hybrid vehicle that can select between engine running and motor running, when selecting between engine running and motor running, it is possible to appropriately adjust whether to prioritize fuel reduction efficiency through motor running or to prioritize recovery of regenerative power when the vehicle decelerates. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is an overall configuration diagram of a vehicle. [Figure 2]10 is a flowchart illustrating an example of a processing procedure of a control circuit. [Figure 3] FIG. 10 is a diagram showing an example of a correspondence relationship between the SOC of a battery and a threshold value to be compared with a fuel efficiency evaluation index. [Figure 4] FIG. 4 is a diagram showing an example of a pattern of the amount of regenerative power of the motor generator during one trip. [Figure 5] FIG. 10 is a diagram showing an example in which the correspondence relationship between the SOC of the battery and the threshold value to be compared with the fuel efficiency evaluation index is defined for each pattern of the amount of regenerative power during one trip. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated.

[0014] [Overall configuration of vehicle 1] 1 is an overall configuration diagram of a vehicle 1 according to this embodiment. Vehicle 1 includes an engine 10, a clutch 15, a motor generator 20, an inverter 21, a battery 22, an automatic transmission 40, drive wheels 50, and a control circuit 100.

[0015] The engine 10 is a diesel engine that uses diesel as fuel. The crankshaft of the engine 10 and the rotating shaft of the motor generator 20 are connected via a clutch 15.

[0016] The battery 22 is an electricity storage device that stores the power supplied to the motor generator 20. The output voltage of the battery 22 is set to a voltage (for example, about several hundred volts) higher than the voltage (for example, about 12 volts) used for low-voltage auxiliary devices.

[0017] Motor generator 20 is, for example, a three-phase AC rotating electric machine. A rotating shaft (rotor) of motor generator 20 is connected to a power transmission path between the crankshaft of engine 10 and an input shaft of automatic transmission 40. A torque converter may be provided between motor generator 20 and automatic transmission 40. An output shaft of automatic transmission 40 is connected to left and right drive wheels 50 via a differential gear.

[0018] The inverter 21 performs power conversion between the motor generator 20 and the battery 22. Specifically, the inverter 21 converts DC power from the battery 22 into three-phase AC power and supplies it to the motor generator 20, and converts three-phase AC power regenerated by the motor generator 20 into DC power and supplies it to the battery 22. The motor generator 20 is driven by power supplied from the battery 22 via the inverter 21. The battery 22 is charged by power supplied from the motor generator 20 via the inverter 21. A voltage converter (step-up / step-down converter) may be provided between the motor generator 20 and the inverter 21.

[0019] The power of at least one of the engine 10 and the motor generator 20 is transmitted to the drive wheels 50 via the automatic transmission 40. In other words, the vehicle 1 is a hybrid vehicle that can run using the power of at least one of the engine 10 and the motor generator 20.

[0020] The driving mode of the vehicle 1 can be switched between engine driving and EV (Electric Vehicle) driving. During engine driving, the clutch 15 is engaged, and the vehicle 1 drives using the power of the engine 10 without using the power of the motor generator 20. During EV driving, the clutch 15 is released, and the vehicle 1 drives using the power of the motor generator 20 without using the power of the engine 10.

[0021] The control circuit 100 includes a processor such as a CPU (Central Processing Unit), memories such as a ROM (Read Only Memory) and a RAM (Random Access Memory), and ports for inputting and outputting various signals (none of which are shown). The control circuit 100 controls the engine 10, the clutch 15, the motor generator 20 (inverter 21), and the automatic transmission 40 based on programs and maps stored in the memory, as well as signals received from various sensors (not shown).

[0022] [Switching of vehicle 1's driving mode] As described above, the driving mode of vehicle 1 can be switched between engine driving and EV driving. During engine driving, the vehicle runs on the power of engine 10 without using the power of motor generator 20, whereas during EV driving, the vehicle runs on the power of motor generator 20 without using the power of engine 10. Therefore, when EV driving is selected, the fuel consumption of engine 10 tends to be reduced while the power consumption of motor generator 20 tends to be increased compared to when engine driving is selected.

[0023] Taking this into consideration, when driving the vehicle 1, the control circuit 100 according to this embodiment calculates the amount of fuel consumption of the engine 10 that is reduced by EV driving compared to engine driving (hereinafter referred to as "fuel consumption reduction amount Rf by EV driving" or simply "fuel consumption reduction amount Rf") and the amount of power consumption of the motor generator 20 required for EV driving (hereinafter referred to as "power consumption Cp required for EV driving" or simply "power consumption Cp"). The control circuit 100 then calculates the ratio of fuel consumption reduction amount Rf to power consumption Cp (= Rf / Cp) as a fuel efficiency evaluation index, and if the fuel efficiency evaluation index is greater than a threshold value, it determines that EV driving is efficient in reducing fuel consumption and selects EV driving, and if the fuel efficiency evaluation index is less than the threshold value, it determines that EV driving is not very efficient in reducing fuel consumption and selects engine driving.

[0024] 2 is a flowchart showing an example of a processing procedure executed by the control circuit 100 when switching the driving mode of the vehicle 1. This flowchart is repeatedly executed every time a predetermined condition is met (for example, every predetermined period) while the vehicle 1 is driving.

[0025] First, the control circuit 100 calculates the fuel consumption reduction amount Rf (unit: g / sec) due to EV driving using the following formula (1) (step S10).

[0026] Rf = NE × FV × FD / K … (1) In the formula (1), "NE" is the rotation speed of the engine 10 (unit: rpm), and "FV" is the fuel injection amount for the engine 10 (unit: mm 3 / stroke), and "FD" is the fuel density (unit: g / cm 3 ) and "K" is a coefficient for converting units. The fuel density FD and the unit conversion coefficient K can be stored in advance in the memory of the control circuit 100 as physical specification values.

[0027] The control circuit 100 determines the rotation speed NE and the fuel injection amount FV of the engine 10 according to the running mode of the vehicle 1 as follows.

[0028] During engine running, the engine 10 is operated, and therefore the control circuit 100 sets the rotation speed NE and fuel injection amount FV of the engine 10 as their respective actual values ​​(measured values ​​or control command values).

[0029] On the other hand, during EV running, the engine 10 is stopped, so the control circuit 100 uses estimated values ​​for the rotation speed NE and fuel injection amount FV of the engine 10 as what would occur if the engine were running, rather than actual values. For example, the control circuit 100 estimates the rotation speed NE of the engine 10 from the vehicle speed, the differential gear ratio, and the gear ratio of the automatic transmission 40. The control circuit 100 then estimates an engine operating point from the driving force required for the vehicle 1 and the estimated value of the rotation speed NE of the engine 10, and reverse-calculates the fuel injection amount FV from the estimated engine operating point and a pre-stored fuel economy map.

[0030] The control circuit 100 calculates the fuel consumption reduction amount Rf due to EV driving by substituting the rotation speed NE of the engine 10 and the fuel injection amount FV calculated as described above into the above equation (1).

[0031] Next, the control circuit 100 calculates the power consumption Cp (unit: kW) required for EV running (step S12).

[0032] During EV driving, power is actually supplied from the battery 22 to the motor generator 20, so the control circuit 100 calculates the actual power control amount from the voltage and current of the battery 22 and sets the calculated power control amount as the power consumption Cp.

[0033] On the other hand, during engine running, the motor generator 20 is stopped, so the power consumption Cp is not the actual power control amount, but an estimated value that would be obtained if the vehicle were running in EV mode. For example, the control circuit 100 calculates the power consumption Cp using the following equation (2).

[0034] Cp=Preq+Lbat+Lmg …(2) In equation (2), "Preq" is the required driving force (unit: kW) for the vehicle 1, "Lbat" is the loss (unit: kW) when transmitting power from the battery 22 to the motor generator 20, and "Lmg" is the loss (unit: kW) when converting electrical energy into power in the motor generator 20. The required driving force Preq can be used as an actual control value. The loss Lbat can be set in advance as a specification value once the hardware configuration is determined. The loss Lmg can be calculated according to an operating point determined from the rotational speed and required driving force of the motor generator 20.

[0035] Next, the control circuit 100 calculates the fuel efficiency evaluation index using the following equation (3) (step S14).

[0036] Fuel efficiency evaluation index = Rf / Cp ... (3) By calculating the fuel economy evaluation index in this way, the fuel economy evaluation index becomes an index that indicates that the larger the value, the more efficient the fuel saving achieved by EV driving.

[0037] Next, the control circuit 100 sets a threshold value to be compared with the fuel efficiency evaluation index (step S20). The method for setting the threshold value will be described in detail later.

[0038] Next, the control circuit 100 determines whether the fuel efficiency evaluation index calculated in step S14 is greater than the threshold value set in step S20 (step S30).

[0039] If the fuel efficiency evaluation index is greater than the threshold value (YES in step S30), the control circuit 100 selects EV running (step S32).

[0040] If the fuel economy evaluation index is not greater than the threshold value (NO in step S30), the control circuit 100 selects engine running (step S34).

[0041] [Setting the threshold value to be compared with the fuel efficiency evaluation index] As described above, in vehicle 1, the ratio of fuel consumption reduction Rf to power consumption Cp (=Rf / Cp) is calculated as a fuel efficiency evaluation index, and if the fuel efficiency evaluation index is greater than a threshold value, EV driving is selected, and if not, engine driving is selected.

[0042] However, if the SOC (State Of Charge) of the battery 22 electrically connected to the motor generator is high, there is a concern that the regenerative power generated by the motor generator 20 when the vehicle 1 subsequently decelerates may not be properly recovered by the battery 22.

[0043] Therefore, the control circuit 100 according to this embodiment: Threshold By changing the SOC of the battery 22, it is possible to appropriately adjust whether to prioritize fuel saving efficiency through EV driving or to prioritize recovery of regenerative power during deceleration of the vehicle.

[0044] 3 is a diagram showing an example of the correspondence relationship between the SOC of the battery 22 and a threshold value to be compared with the fuel efficiency evaluation index. In FIG. 3, the horizontal axis represents the SOC of the battery 22, and the vertical axis represents the threshold value.

[0045] As shown in Fig. 3, when the SOC of the battery 22 is high (the amount of stored electricity is large), the threshold value is set to a small value. This makes it easier to determine that the fuel efficiency evaluation index is greater than the threshold value, and makes it easier to select EV driving. Therefore, it is possible to proactively discharge the battery 22 and lower the SOC of the battery 22 in advance in preparation for future recovery of regenerative power. In other words, it is possible to emphasize recovery of regenerative power during vehicle deceleration.

[0046] On the other hand, when the SOC of the battery 22 is low (the amount of stored electricity is small), the threshold value is set to a large value. This allows EV driving to be selected only when the fuel efficiency evaluation index is large (when the fuel efficiency reduction efficiency by EV driving is higher). In other words, it is possible to emphasize the fuel saving efficiency by EV driving.

[0047] As a result of the above, in the vehicle 1 according to this embodiment, when selecting between engine running and EV running, it is possible to appropriately adjust whether to prioritize fuel saving efficiency through EV running or to prioritize recovery of regenerative power during vehicle deceleration, depending on the SOC (amount of stored electricity) of the battery 22.

[0048] <Variation 1> While vehicle 1 is traveling, the amount of regenerative power of motor generator 20 may vary depending on the driving tendencies of the driver of vehicle 1. In view of this, the threshold value to be compared with the fuel efficiency evaluation index may be learned to change in accordance with the amount of regenerative power of motor generator 20 during a predetermined period (for example, one trip, as described below) instead of or in addition to the battery SOC.

[0049] For example, the control circuit 100 measures the amount of regenerative power of the motor generator 20 during the period from when the control system of the vehicle 1 is started until when it is stopped again (hereinafter also referred to as "one trip") and stores the measured amount in memory. Then, each time the control system of the vehicle 1 is started, the control circuit 100 reads out from memory the amount of regenerative power during the immediately preceding one trip, and the larger the amount of regenerative power read out, the smaller the threshold value to be compared with the fuel efficiency evaluation index may be set to.

[0050] 4 is a diagram showing an example of a pattern of the amount of regenerative power during one trip of motor generator 20. In the example shown in FIG. 4, the amount of regenerative power during one trip gradually increases in the order of patterns A, B, and C.

[0051] 5 is a diagram showing an example in which the correspondence relationship between the SOC of battery 22 and the threshold value to be compared with the fuel efficiency evaluation index is defined for each pattern of the amount of regenerative power during one trip (each of patterns A, B, and C shown in FIG. 4). As shown in FIG. 5, for pattern C, in which the amount of regenerative power during one trip is large, the threshold value is set to a smaller value than for patterns A and B. This makes it possible to increase the frequency of EV driving for drivers who tend to regenerate a large amount of power during one trip, thereby actively discharging battery 22 and prioritizing the recovery of regenerative power during vehicle deceleration.

[0052] Furthermore, for pattern A, where the amount of regenerated power during one trip is small, the threshold is set to a higher value than for patterns B and C. This allows drivers who tend to drive with a low amount of regenerated power during one trip to select EV driving only when the fuel efficiency evaluation index is larger, making it possible to emphasize the fuel saving efficiency achieved by EV driving.

[0053] In this way, the amount of regenerative power during one trip may be stored, and learning may be performed to vary the threshold value depending on the amount of regenerative power. In this way, as a strategy to improve fuel efficiency, it is possible to change, depending on the driver's driving tendencies, whether to perform efficient EV driving with limited regenerative resources, or to increase the frequency of EV driving with abundant regenerative resources.

[0054] <Variation 2> In the above embodiment, the case where engine running and EV running, which does not use the power of the engine 10, are switched in accordance with the comparison result between the fuel efficiency evaluation index and the threshold value has been described.

[0055] However, it is also possible to switch between engine running and assist running using the power of the motor generator 20 and the power of the engine 10 depending on the result of comparison between the fuel economy evaluation index and a threshold value.

[0056] Furthermore, the above-described embodiments and their modifications can be combined as appropriate. The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0057] 1 Vehicle, 10 Engine, 15 Clutch, 20 Motor Generator, 21 Inverter, 22 Battery, 40 Automatic Transmission, 50 Drive Wheel, 100 Control Circuit.

Claims

1. A hybrid vehicle that runs using power from at least one of a diesel engine and a motor generator, a battery electrically connected to the motor generator; a control circuit that causes the hybrid vehicle to run in either an engine running mode in which the hybrid vehicle runs using power from the diesel engine without using power from the motor generator, or a motor running mode in which the hybrid vehicle runs using power from at least the motor generator, The control circuit calculating a fuel reduction amount, which is a reduction in fuel consumption due to the motor traveling compared to the engine traveling; Calculating the amount of power consumption required for the motor running; calculating a ratio of the fuel reduction amount to the power consumption amount as an evaluation index; When the evaluation index is greater than a threshold value, the motor running is selected regardless of other conditions, and when the evaluation index is smaller than the threshold value, the engine running is selected regardless of other conditions; The control circuit sets the threshold to a smaller value as the amount of stored electricity in the battery increases.

2. 2. The hybrid vehicle according to claim 1, wherein the control circuit reduces the threshold value as the amount of stored electricity in the battery increases and as the amount of regenerated power by the motor generator during a predetermined period increases.

3. 3. The hybrid vehicle according to claim 2, wherein the predetermined period is a period from when the control system of the hybrid vehicle is started to when the control system is stopped next.

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