Vehicle control device

Abstract

To provide a vehicle control device which reduces a frequency of turning an engine on by controlling a target regenerative electric power amount, even in a situation where an actual regenerative electric power amount is restricted.SOLUTION: A vehicle control device includes an engine 14, a motor 16 for performing regenerative power generation utilizing kinetic energy of a rotation axis of the engine 14, a battery 18 charged by the regenerative power generation, and a motor cooling circuit 20 for cooling the motor 16, wherein when a SOC value indicating a charging state of the battery 18 is higher than a predetermined value, and a temperature of the battery 18 and a water temperature of the motor cooling circuit 20 are lower than a predetermined temperature, the vehicle control device performs control so as to reduce a target regenerative electric power amount.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a vehicle control device, and more particularly to control of regenerative power of a vehicle. [Background technology]

[0002] For hybrid vehicles, in order to reduce exhaust gas emissions and improve fuel efficiency, technology has been proposed to maintain a mode in which the vehicle runs solely on electricity without turning on the engine (hereinafter referred to as "EV mode" as appropriate).

[0003] For example, Patent Document 1 discloses a control device for a hybrid vehicle that prevents a switch from regenerative braking to engine braking when there is a possibility of such a switch while traveling down a steep slope with a sharp curve. Patent Document 1 describes how a switch from regenerative braking to engine braking can be prevented in the middle of a downhill slope by connecting the engine and the drive wheels in advance with a clutch before the vehicle reaches a point where there is a possibility of switching from regenerative braking to engine braking. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-020663 A Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, when the actual amount of regenerative power based on the vehicle's driving state and the like reaches the target amount of regenerative power to be generated by regenerative power generation (i.e., the target amount of regenerative power, which is the target value of the amount of regenerative power of the motor), a braking force equivalent to engine braking is applied to the vehicle by regenerative braking, so that the vehicle's EV driving is maintained. On the other hand, under certain circumstances, such as when there is a concern about overcharging the battery, the generation of actual regenerative power is limited to protect the battery. As a result, since the actual amount of regenerative power does not reach the target amount of regenerative power, the regenerative braking is switched to the engine braking. In other words, the engine is turned on in order to use the engine braking.

[0006] As described above, when regenerative braking is not possible, the engine is turned on, which is undesirable from the viewpoints of the environment and fuel efficiency. Therefore, this specification realizes a vehicle control device that can reduce the frequency of turning on the engine by controlling the target amount of regenerative power even in a situation where the actual amount of regenerative power is limited. [Means for solving the problem]

[0007] The vehicle control device disclosed in this specification comprises an engine, a motor that generates regenerative power by utilizing the kinetic energy of the engine's rotating shaft, a battery that is charged by the regenerative power, and a motor cooling circuit that cools the motor, and is characterized in that it controls the target amount of regenerative power to be reduced when a SOC value indicating the state of charge of the battery is higher than a predetermined value and when the temperature of the battery and the water temperature of the motor cooling circuit are lower than a predetermined temperature. Effect of the Invention

[0008] According to the vehicle control device disclosed in this specification, since the target regenerative electric power amount is controlled to be small under certain conditions, it is possible to avoid a state in which the actual regenerative electric power amount falls short of the target regenerative electric power amount. In other words, it is possible to prevent switching from regenerative braking to engine braking, and as a result, it is possible to suppress the engine from being turned on for the purpose of using engine braking. [Brief description of the drawings]

[0009] [Figure 1] 1 is a block diagram conceptually showing a configuration of a control device for a vehicle. [Diagram 2] 4 is a graph showing the relationship between vehicle speed and the required amount of regenerative power. [Diagram 3] 4 is a flowchart showing an example of processing in a control device for a vehicle. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the vehicle control device will be described with reference to the drawings.

[0011] Fig. 1 is a block diagram conceptually showing the configuration of a vehicle control device. As shown in Fig. 1, a vehicle 10 is provided with a control unit 12 as a control device for the vehicle 10. In this example, the vehicle 10 is a plug-in hybrid vehicle (PHEV) equipped with an engine, a battery for driving, and a regenerative braking system. The control device for the vehicle 10 further includes an engine 14, a motor 16, a battery 18, a motor cooling circuit 20, a power converter 22, a power conversion unit 24, and an output shaft 26.

[0012] The control unit 12 is an electronic control unit that controls the running of the vehicle 10, including the control of regenerative power, and has at least a CPU that performs various arithmetic processing, and a memory in which control programs and data are stored. The control unit 12 controls the operation of each part of the control device of the vehicle 10. For example, the control unit 12 controls the driving of the engine 14 and the motor 16. In addition, for example, the control unit 12 controls the power converter 22 to adjust the amount of power exchanged between the motor 16 and the battery 18, and further controls the power conversion unit 24 to control the exchange of power between the engine 14, the motor 16, and the output shaft 26.

[0013] The engine 14 functions as a power source for the vehicle 10 and also as a power source for generating electricity.

[0014] The motor 16 rotates the output shaft 26 via the power conversion unit 24, and also functions as a generator that performs regenerative power generation by converting the kinetic energy of the rotating shaft of the output shaft 26 into electrical energy. Furthermore, the motor 16 can generate power by receiving the driving force of the engine 14 via the power conversion unit 24.

[0015] The battery 18 supplies electric power to various electric devices provided in the vehicle 10. That is, the battery 18 is a member that functions as a power supply source. The battery 18 can also be charged by regenerative power.

[0016] The motor cooling circuit 20 is a circuit that cools the motor 16. More specifically, coolant is circulated in the motor cooling circuit 20 by an electric water pump (not shown) operated by an electric motor. The motor cooling circuit 20 uses the coolant circulating inside to cool the motor 16, which generates heat during operation, and maintains the temperature of the motor 16 at a predetermined temperature. The coolant in the motor cooling circuit 20 may be circulated to the battery 18 so that the battery 18 can be cooled.

[0017] The power converter 22 is an inverter that converts the DC power of the battery 18 into AC power suitable for driving the motor 16. Note that the power converter 22 may include a boost converter that boosts the output voltage of the battery 18.

[0018] The power conversion unit 24 controls the exchange of power (i.e., driving force) between the engine 14, the motor 16, and the output shaft 26. For example, the power conversion unit 24 may include a planetary gear mechanism to control the transmission of power and may include a clutch to disconnect the engine 14.

[0019] The output shaft 26 is connected to the drive wheels via a predetermined gear or the like. When the vehicle 10 is powered, the drive force of the engine 14 or the motor 16 is transmitted to the drive wheels via the output shaft 26 to cause the vehicle 10 to travel, and when braking, the drive force of the output shaft 26 causes the motor 16 to generate power, thereby applying a braking force to the vehicle 10 through regenerative braking. The regenerative power obtained by the power generation of the motor 16 is charged into the battery 18. Furthermore, the output shaft 26 can be connected to the engine 14 to perform braking through engine braking by the engine 14.

[0020] Next, the required regenerative power amount will be described with reference to FIG. 2. FIG. 2 is a graph showing the relationship between the vehicle speed and the required regenerative power amount. In FIG. 2, "high SOC value / low temperature" refers to a case where the SOC value of the battery 18 is high, and the temperature of the battery 18 and the water temperature of the motor cooling circuit 20 are low. For example, a predetermined value (i.e., a threshold value) such as a high SOC value of 70% or more and a low SOC value of 5° C. or less may be set for judgment. Note that since the conditions for limiting charging differ depending on the vehicle and the battery, the above threshold value may also be set individually for each vehicle. "Normal" refers to a case where the SOC value of the battery 18 is equal to or less than a predetermined value, and the temperature of the battery 18 or the water temperature of the motor cooling circuit 20 is equal to or more than a predetermined temperature. Here, the "required regenerative power amount" in FIG. 2 refers to the regenerative power amount required when performing deceleration equivalent to engine braking by regenerative braking during coasting, etc. The required regenerative power amount increases as the vehicle speed increases.

[0021] Here, when the SOC value of the battery 18 is high, the amount of regenerative power accepted is small in order to prevent overcharging, etc. Also, the battery 18 accepts a small amount of regenerative power at low temperatures in order to prevent deterioration of the battery 18. For example, a lithium-ion battery cannot be charged with a large current because metallic lithium is easily generated by charging at low temperatures. Therefore, at low temperatures, the appropriate charging current is small, and there is a limit to the acceptance of regenerative power.

[0022] Therefore, when the battery 18 is in a "high SOC value / low temperature" state, the amount of regenerative power that can actually be performed falls below the target amount of regenerative power due to the above-mentioned restrictions. When the amount of actual regenerative power falls below the target amount of regenerative power, the control unit 12 starts the engine 14 and connects the output shaft 26 to the engine 14 via the power conversion unit 24. This causes the vehicle 10 to decelerate due to engine braking by the engine 14.

[0023] Therefore, in this example, when the SOC value is high and the temperature is low, the target regenerative power amount is set small, and the target regenerative braking force is reduced. As shown in FIG. 2, when the SOC value is high and the temperature is low, the required regenerative power amount is lower than in normal times. For example, when the vehicle 10 is started, the temperature of the battery 18 and the water temperature of the motor cooling circuit 20 are generally lower than when the vehicle 10 is running. Also, when the temperature is low, such as when the vehicle 10 is started (hereinafter referred to as "low-temperature start"), friction of the motor 16 and the like is large, so it is easy to ensure deceleration. Therefore, when the vehicle is started at a low temperature, the braking force due to regenerative braking may be smaller than in normal times.

[0024] In this example, an appropriate regenerative power (i.e., an upper limit value of regenerative power that the battery 18 can accept without problems) that changes according to temperature is set. Then, a target amount of regenerative power corresponding to the braking force required for braking the vehicle is calculated, and it is determined whether or not this target amount of regenerative power exceeds the appropriate regenerative power. If the target amount of regenerative power exceeds the appropriate amount of regenerative power, the engine 14 is started and engine braking and mechanical braking are used since the required braking force cannot be obtained by regenerative braking. However, compared to engine braking and mechanical braking, it is actually more desirable to use regenerative braking that can convert braking force into electric power and charge the battery 18. Therefore, in this example, the control unit 12 controls the regenerative power in order to use regenerative braking, which is an effective brake. To explain the control of regenerative power performed by the control unit 12, reference is made to FIG. 3. FIG. 3 is a flowchart showing an example of processing in a control device for a vehicle.

[0025] First, the control unit 12 acquires the SOC value, which is an index representing the state of charge of the battery 18, and compares the SOC value with a predetermined value (S10). The predetermined value is a value determined to maintain the battery 18 in a preferable state in terms of battery characteristics. If the SOC value is greater than the predetermined value as a result of the comparison between the SOC value and the predetermined value (Yes in S10), the process proceeds to step S12. On the other hand, if the SOC value is equal to or less than the predetermined value (No in S10), the process proceeds to step S18. Here, if the SOC value is greater than the predetermined value, the battery 18 may be overcharged, and some measure, i.e., some control, is required to protect the battery 18 (i.e., suppress Li deposition). The control will be described later.

[0026] Next, the control unit 12 acquires the temperature of the battery 18 and compares the temperature of the battery 18 with a predetermined temperature (S12). If the comparison of the two temperatures shows that the temperature of the battery 18 is lower than the predetermined temperature (Yes in S12), the process proceeds to step S14. On the other hand, if the temperature of the battery 18 is equal to or higher than the predetermined temperature (No in S12), the process proceeds to step S18.

[0027] Next, the control unit 12 obtains the water temperature of the motor cooling circuit 20, and compares the water temperature of the motor cooling circuit 20 with a predetermined temperature (S14). If the comparison of the two temperatures shows that the water temperature of the motor cooling circuit 20 is lower than the predetermined temperature (Yes in S14), the process proceeds to step S16. On the other hand, if the water temperature of the motor cooling circuit 20 is equal to or higher than the predetermined temperature (No in S14), the process proceeds to step S18.

[0028] As described above, in a state where the SOC value is greater than a predetermined value and the battery 18 may be overcharged, some control is required in the control device of the vehicle 10. Therefore, in the control device of the vehicle 10, the generation of actual regenerative power is limited. That is, in such a state, it is determined that the generation of regenerative power is unnecessary. Here, it is also determined that the generation of regenerative power is unnecessary when the temperature of the battery 18 is lower than a predetermined temperature (i.e., when Yes is determined in S12) and when the water temperature of the motor cooling circuit 20 is lower than a predetermined temperature (i.e., when Yes is determined in S14). Therefore, when it is determined that the generation of regenerative power is unnecessary (i.e., when the process proceeds to step S16 in the above-mentioned flowchart), the control unit 12 controls the target regenerative power amount to be smaller (S16). On the other hand, when the process proceeds to step S18 in the above-mentioned flowchart, there is no need to change the target regenerative power amount, so no control is performed (S18).

[0029] As described above, the control unit 12 controls the target regenerative power amount to be smaller under certain conditions, and therefore, it is possible to avoid a state in which the actual regenerative power amount falls short of the target regenerative power amount. In other words, it is possible to prevent switching from regenerative braking to engine braking, and as a result, it is possible to suppress the engine from being turned on for the purpose of using engine braking.

[0030] The above description is merely an example, and the vehicle control device disclosed in this specification may be configured to control the target regenerative power amount to be reduced under certain conditions, and other configurations may be changed as appropriate. In the embodiment, the motor cooling circuit 20 cools the motor 16, but this is not limited to the above. For example, the motor cooling circuit 20 may be a circuit that cools an e-Axle, which is a packaged driving unit that is a main component required to drive the vehicle 10, such as a gear, a motor, and an inverter, by water cooling. In the embodiment, the target regenerative power amount is reduced at the time of low-temperature start, but the control of the target regenerative power amount is not limited to the time of start of the vehicle 10 if the temperature of the battery and the water temperature of the motor cooling circuit are low. [Explanation of symbols]

[0031] 10 vehicle, 12 control unit, 14 engine, 16 motor, 18 battery, 20 motor cooling circuit, 22 power converter, 24 power conversion unit, 26 power shaft.

Claims

[Claim 1] The engine, a motor that uses kinetic energy of a rotating shaft of the engine to generate regenerative power; a battery that is charged by the regenerative power generation; a motor cooling circuit for cooling the motor; Equipped with When an SOC value indicating a state of charge of the battery is higher than a predetermined value and the temperature of the battery and the water temperature of the motor cooling circuit are lower than predetermined temperatures, the target regenerative power amount is controlled to be smaller. A vehicle control device comprising:

Images