Vehicle control device

Abstract

To provide a vehicle control device that can prevent a lack of power for driving a motor when a driving request of the motor is made.SOLUTION: A control unit charges a smooth capacitor by raising a target voltage of a boost capacitor when predetermined conditions including a condition that a driving request of a motor is expected are met (YES in step S1, YES in step S2, and YES in step S3) (step S4). The control unit controls the smooth capacitor to discharge by lowering the target voltage of the boost capacitor when the driving request of the morot is made (step S6). The predetermined conditions include a condition that outputtable power of a battery is decreased to be lower than a predetermined value.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a vehicle control device. [Background technology]

[0002] Patent Document 1 describes a technology for achieving high output without increasing the size of the motor or inverter in an electric vehicle that runs by driving a motor with battery power. This technology boosts the voltage output from the battery using a boost converter and then applies it to an inverter. In the technology described in Patent Document 1, the boost converter determines a target voltage for achieving the output required of the motor depending on the driving state, and executes boost control. A smoothing capacitor is connected in parallel to the input of the inverter to smooth out and stabilize voltage fluctuations. The smoothing capacitor performs smoothing by utilizing the capacitor's properties of charging until the voltage exceeds a certain value and discharging when the voltage falls below a certain value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-278794 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the technology described in Patent Document 1, when the boost converter boosts the voltage in response to a motor drive request, part of the power output from the battery is used not only to drive the motor but also to charge the smoothing capacitor, so the power supplied to the motor is reduced by the amount of power charged to the smoothing capacitor. Furthermore, because the boost converter is controlled to maintain a target voltage according to the motor's required output, if the target voltage is higher than the terminal voltage of the smoothing capacitor, the power charged in the smoothing capacitor cannot be discharged and used to drive the motor, and the discharged power of the smoothing capacitor cannot be utilized. For these reasons, the technology described in Patent Document 1 may result in a shortage of power to drive the motor when a drive request is made.

[0005] The present invention has been made in light of the above-mentioned circumstances, and aims to provide a vehicle control device that can prevent a shortage of power for driving a motor when there is a demand for driving the motor. [Means for solving the problem]

[0006] The present invention provides a vehicle control device that is mounted on a vehicle that includes a battery, a boost converter that boosts the DC power output from the battery, an inverter that converts the DC power output from the boost converter into AC power, a motor that is driven by the AC power output from the inverter and generates motor torque for driving, and a smoothing capacitor connected between the boost converter and the inverter, and that includes a control unit that controls the boost converter and the inverter in accordance with a drive request for the motor, wherein the control unit controls the boost converter and the inverter in accordance with a drive request for the motor when predetermined conditions are met, including that a drive request for the motor is predicted, so as to increase the target voltage of the boost converter to charge the smoothing capacitor, and when a drive request for the motor is made, so as to decrease the target voltage of the boost converter to discharge the smoothing capacitor. [Effects of the Invention]

[0007] As described above, according to the present invention, it is possible to provide a vehicle control device that can prevent a shortage of power for driving the motor when a drive request for the motor is made. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a block diagram showing the configuration of a vehicle equipped with a vehicle control device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a control block diagram illustrating details of the control unit of the vehicle control device according to one embodiment of the present invention. [Figure 3] FIG. 3 is a flowchart illustrating the operation of the vehicle control device according to one embodiment of the present invention. [Figure 4] FIG. 4 is a timing chart showing the transition of the vehicle state due to the smoothing capacitor control operation of the vehicle control device according to one embodiment of the present invention. [Figure 5] FIG. 5 is a timing chart showing the transition of the vehicle state due to the operation of the vehicle control device according to the comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0009] A vehicle control device according to one embodiment of the present invention is mounted on a vehicle including a battery, a boost converter that boosts DC power output from the battery, an inverter that converts the DC power output from the boost converter into AC power, a motor driven by the AC power output from the inverter and generating motor torque for driving, and a smoothing capacitor connected between the boost converter and the inverter, and the vehicle control device includes a control unit that controls the boost converter and the inverter in response to a drive request for the motor, wherein the control unit controls the boost converter and the inverter to increase a target voltage of the boost converter to charge the smoothing capacitor when predetermined conditions are met, including a prediction of a drive request for the motor, and to decrease the target voltage of the boost converter to discharge the smoothing capacitor when a drive request for the motor is made. This makes it possible for the vehicle control device according to one embodiment of the present invention to prevent a shortage of power for driving the motor when a drive request for the motor is made. [Example]

[0010] Hereinafter, a vehicle equipped with a vehicle control device according to an embodiment of the present invention will be described with reference to the drawings.

[0011] As shown in FIG. 1, the vehicle 1 includes a battery 2, a boost converter 3 that boosts the DC power output from the battery 2, an inverter 4 that converts the DC power output from the boost converter 3 into AC power, and a motor 5 that is driven by the AC power output from the inverter 4 and generates motor torque for driving.

[0012] The motor 5 functions as a motor generator that generates driving force for traveling and also functions as a generator that regenerates power using traveling energy. The motor 5 is connected to the battery 2 via the boost converter 3 and the inverter 4.

[0013] The vehicle 1 is equipped with a smoothing capacitor 6. The smoothing capacitor 6 is connected in parallel between the boost converter 3 and the inverter 4, and smoothes the voltage supplied from the boost converter 3 to the inverter 4.

[0014] The vehicle 1 includes a control unit 10. The control unit 10 controls the boost converter 3 and the inverter 4 in response to a drive request for the motor 5.

[0015] The control unit 10 is configured by a computer unit that includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an input port, and an output port.

[0016] The ROM of the computer unit stores various constants, various maps, and the like, as well as a program for causing the computer unit to function as the control unit 10. That is, in the computer unit, the CPU executes the program stored in the ROM, causing the computer unit to function as the control unit 10 in this embodiment.

[0017] The control unit 10 receives an input of the battery state from the battery 2. The battery state includes the state of charge (SOC) of the battery 2 and the battery output power that is the power that the battery 2 can output. The control unit 10 controls the boost converter 3 by transmitting a boost converter control signal to the boost converter 3. The boost converter control signal includes a target voltage that is a target value for the output voltage of the boost converter 3. The control unit 10 controls the inverter 4 by transmitting an inverter control signal to the inverter 4.

[0018] In vehicle 1 configured as above, when the voltage output from battery 2 is V1, the voltage boosted by boost converter 3 is V2, and the charging power of smoothing capacitor 6 is P4, P4 changes depending on V2.

[0019] Furthermore, if the output power of battery 2 is P1, the output power of boost converter 3 is P2, and the input power of inverter 4 is P3, P1 and P2 are equal, but P3 is the value obtained by adding or subtracting P4 from P2. In other words, P3, the input power of inverter 4, is the value obtained by subtracting P4 from P2 when smoothing capacitor 6 is charging, and is the value obtained by adding P4 to P2 when smoothing capacitor 6 is discharging.

[0020] When predetermined conditions are met, including the prediction of a drive request for the motor 5, the control unit 10 increases the target voltage of the boost converter 3 to charge the smoothing capacitor 6. Then, when a drive request for the motor 5 is made, the control unit 10 controls the boost converter 3 to decrease the target voltage to discharge the smoothing capacitor 6.

[0021] In this way, in this embodiment, the smoothing capacitor 6 is precharged by increasing the target voltage prior to a request to drive the motor 5, and when a request to drive the motor 5 is made, the target voltage is decreased to discharge the precharged smoothing capacitor 6, and the discharged power is added and supplied to the motor 5.

[0022] Here, the value of the target voltage of the boost converter 3, which is increased in order to charge the smoothing capacitor 6, is greater than the voltage value for driving the motor 5. Also, the value of the target voltage of the boost converter 3, which is decreased when a drive request is made, is equal to the voltage value for driving the motor 5. Note that the control for charging the smoothing capacitor 6 is also referred to as smoothing capacitor charging control. Also, the control for discharging the smoothing capacitor 6 is also referred to as smoothing capacitor discharging control.

[0023] The predetermined condition includes that the available output power of the battery 2 has fallen below a predetermined value.

[0024] Here, it is possible to arbitrarily set the conditions for determining whether a drive request for motor 5 is predicted. For example, when an engine (not shown) is started for the first time from a cold-stop state or when the engine is started by depressing an accelerator pedal (not shown) from a stopped state of the engine at a predetermined vehicle speed or above, the amount of power required for motor 5 increases, and the amount of charge in smoothing capacitor 6 is insufficient, so that it is predicted that the amount of power supplied to motor 5 will be insufficient. In such cases, control unit 10 determines whether a drive request for motor 5 is predicted, and charges smoothing capacitor 6 by increasing the target voltage, and discharges smoothing capacitor 6 by decreasing the target voltage.

[0025] Furthermore, it is possible to arbitrarily set the conditions for determining whether or not the available output power of the battery 2 has decreased. For example, it is preferable to set various factors such as the state of health (SOH) and state of charge (SOC) of the battery 2, the temperature of the battery 2, and the ambient temperature around the battery 2 as the conditions for determination, and determine whether or not the available output power of the battery 2 has decreased.

[0026] The control unit 10 will be described in detail with reference to FIG.

[0027] As shown in FIG. 2, the control unit 10 includes a battery output power reduction determination unit 11, a motor drive request prediction unit 12, a smoothing capacitor discharge control necessity determination unit 13, and a smoothing capacitor discharge control possibility determination unit 14.

[0028] The battery output power reduction determination unit 11 determines whether the battery output power reduction is reduced.

[0029] The motor drive request prediction unit 12 determines whether or not a drive request for the motor 5 is predicted.

[0030] The smoothing capacitor discharge control necessity determination unit 13 determines whether or not discharge control of the smoothing capacitor 6 is necessary.

[0031] The smoothing capacitor discharge controllability determining unit 14 determines whether or not discharge control of the smoothing capacitor 6 is possible.

[0032] The control unit 10 also includes a smoothing capacitor charge control execution determination unit 15 and a smoothing capacitor discharge control execution determination unit 16.

[0033] The smoothing capacitor charge control execution determination unit 15 determines whether to execute smoothing capacitor charge control based on the determination results of the available battery output power decrease determination unit 11 and the motor drive request prediction unit 12. The smoothing capacitor charge control execution determination unit 15 determines to execute smoothing capacitor charge control when predetermined conditions are met, including the prediction of a drive request for the motor 5. In detail, the smoothing capacitor charge control execution determination unit 15 determines to execute smoothing capacitor charge control when the determination result that the available battery output power is decreasing is input from the available battery output power decrease determination unit 11 and the determination result that a drive request for the motor 5 is predicted is input from the motor drive request prediction unit 12.

[0034] The smoothing capacitor discharge control execution determination unit 16 determines whether or not to execute smoothing capacitor discharge control. The smoothing capacitor discharge control execution determination unit 16 determines to execute smoothing capacitor discharge control when a drive request for the motor 5 is made. More specifically, the smoothing capacitor discharge control execution determination unit 16 determines to execute smoothing capacitor discharge control when a determination result that discharge control of the smoothing capacitor 6 is necessary is input from the smoothing capacitor discharge control necessity determination unit 13 and a determination result that discharge control of the smoothing capacitor 6 is possible is input from the smoothing capacitor discharge control feasibility determination unit 14.

[0035] The control unit 10 also includes a target voltage calculation unit 17 and a boost converter control unit 18.

[0036] Target voltage calculation unit 17 calculates a target voltage according to the determination results of smoothing capacitor charge control execution determination unit 15 and smoothing capacitor discharge control execution determination unit 16. Boost converter control unit 18 controls boost converter 3 to output the target voltage.

[0037] The smoothing capacitor control operation by the control unit 10 will be described with reference to Fig. 3. This smoothing capacitor control operation is repeatedly performed at predetermined intervals.

[0038] As shown in FIG. 3, the control unit 10 determines whether the available output power of the battery 2 has decreased (step S1).

[0039] When the control unit 10 determines that the available output power of the battery 2 has decreased (YES in step S1), it determines whether or not discharge control of the smoothing capacitor 6 is necessary (step S2).

[0040] When the control unit 10 determines that the discharge control of the smoothing capacitor 6 is not necessary (NO in step S2), the control unit 10 determines whether or not a request to drive the motor 5 is predicted (step S3).

[0041] When the control unit 10 determines that a drive request for the motor 5 is predicted (YES in step S3), it performs smoothing capacitor charging control (step S4) and ends the current operation.

[0042] When the control unit 10 determines that discharge control of the smoothing capacitor 6 is necessary (YES in step S2), it determines whether or not discharge by the smoothing capacitor 6 is possible (step S5).

[0043] When the control unit 10 determines that the smoothing capacitor 6 can discharge (YES in step S5), it performs smoothing capacitor discharge control (step S6) and ends the current operation.

[0044] If the control unit 10 determines that the available output power of the battery 2 has not decreased (NO in step S1), or if it determines that a drive request for the motor 5 is not predicted (NO in step S3), or if it determines that discharging by the smoothing capacitor 6 is not possible (NO in step S5), it performs normal smoothing capacitor control (step S7) and ends the current operation. Normal smoothing capacitor control is control that does not aim to charge or discharge the smoothing capacitor 6.

[0045] The transition of the vehicle state due to the smoothing capacitor control operation will be described with reference to Fig. 4. In Fig. 4, the vertical axis represents whether or not smoothing capacitor charging control is performed, whether or not smoothing capacitor discharging control is performed, the target voltage of the boost converter 3, the discharge power of the smoothing capacitor 6, the discharge power of the battery 2, and the input power of the inverter 4, and the horizontal axis represents the transition of time.

[0046] 4, at time t0, the discharge power of the smoothing capacitor 6, the discharge power of the battery 2, and the input power of the inverter 4 are all 0. Furthermore, smoothing capacitor charging control and smoothing capacitor discharging control are not being performed.

[0047] After that, at time t1, smoothing capacitor charging control is performed. Also, the target voltage starts to rise, and the discharge power of the battery 2 increases. Also, the discharge power of the smoothing capacitor 6 increases in the negative direction, and the smoothing capacitor 6 is charged.

[0048] After that, at time t2, the target voltage maintains a constant value after increasing. The increased target voltage value is greater than the voltage value for driving the motor 5. In addition, the discharge power of the smoothing capacitor 6 becomes 0, and charging of the smoothing capacitor 6 is completed. In addition, the discharge power of the battery 2 becomes 0.

[0049] Subsequently, at time t3, a request to drive the motor 5 is made, causing the smoothing capacitor charge control to be disabled and the smoothing capacitor discharge control to be enabled. At this time t3, the discharge power of the battery 2 increases to the available output power. The target voltage also starts to drop toward a value for driving the motor 5. The discharge power of the smoothing capacitor 6 then increases in the positive direction, causing the smoothing capacitor 6 to be discharged. In this state, the discharge of the smoothing capacitor 6 is added to the discharge power of the battery 2, resulting in a large increase in the input power of the inverter 4.

[0050] After that, at time t4, the smoothing capacitor discharge control is changed to non-execution. As a result, the discharge power of the smoothing capacitor 6 becomes 0, and the discharge of the smoothing capacitor 6 is completed. Therefore, the input power of the inverter 4 decreases to the value of the discharge power of the battery 2.

[0051] In this case, the smoothing capacitor charging control preferably increases the target voltage at a set increase rate. It is preferable to limit this target voltage increase rate [V / s] so that it does not exceed the available output power [W] of the battery 2. The charging current [A] of the smoothing capacitor 6 is the product of the voltage increase rate [V / s] and the capacitance [F] of the smoothing capacitor 6. Therefore, the available output power [W] of the boost converter 3 is divided by the input voltage [V] of the inverter 4 to obtain the available output current [A], and the available output current [A] is then divided by the capacitance [F] of the smoothing capacitor 6 to obtain the upper limit value [V / s] of the target voltage increase rate. Here, the available output power [W] of the boost converter 3 is calculated by subtracting the power loss [W] of the boost converter 3 from the available output power [W] of the battery 2.

[0052] When the target voltage is higher than the minimum voltage required to drive the motor 5 and the smoothing capacitor 6 needs to be discharged to drive the motor 5, smoothing capacitor discharge control is performed.

[0053] Whether or not smoothing capacitor discharge control is necessary for driving the motor 5 is determined based on the margin of the output power that the boost converter 3 can output relative to the required output value of the motor 5, as well as the control mode of the function to be realized by driving the motor 5. For example, it is preferable to be able to select whether or not to perform smoothing capacitor discharge control depending on the control mode; for example, smoothing capacitor discharge control is required in a control mode in which the engine is started by driving the motor 5, smoothing capacitor discharge control is not required in a control mode in which the vehicle is driven to run steadily by driving the motor 5, and smoothing capacitor discharge control is required in a control mode in which the vehicle 1 is driven to go over bumps by driving the motor 5.

[0054] In smoothing capacitor discharge control, it is preferable to decrease the target voltage at a set decrease rate. This target voltage decrease rate [V / s] can be calculated based on the discharge power [W] desired to drive the motor 5. The charging current [A] of the smoothing capacitor 6 is the product of the target voltage decrease rate [V / s] and the capacitance [F] of the smoothing capacitor 6. Therefore, the discharge power [W] desired to drive the motor 5 is divided by the inverter 4 input voltage [V] to obtain the set discharge current [A], and the set discharge current [A] is then divided by the capacitance [F] of the smoothing capacitor 6 to obtain the set value [V / s] of the target voltage decrease rate. Here, the discharge power [W] desired to drive the motor 5 can be calculated by subtracting the output power [W] of the battery 2 from the power [W] required to drive the motor 5.

[0055] The smoothing capacitor discharge control is terminated when the target voltage can no longer be lowered, and the smoothing capacitor charge control is determined to be complete when the target voltage can no longer be increased.

[0056] In an electric vehicle system in which the engine is started by driving the motor 5, when it is determined that the discharge control of the smoothing capacitor 6 is necessary for starting the engine, it is preferable to allow the engine to start after the smoothing capacitor charge control is completed.

[0057] In an electric vehicle system that starts the engine by driving the motor 5, if it is determined during engine start that engine start by driving the motor 5 cannot be completed, it is preferable to suspend engine start and resume engine start after smoothing capacitor charging control is completed. This operation can be repeated until engine start is completed, but it is preferable to suspend engine start after repeating it a predetermined number of times.

[0058] If a situation continues in which it is not predicted that the motor 5 will be driven after the smoothing capacitor charging control has been performed, it is preferable to perform the smoothing capacitor 6 discharging control.

[0059] When the driver performs an operation intending to end driving, it is preferable to perform smoothing capacitor discharge control before opening a power cutoff relay (not shown) of the battery 2. By performing smoothing capacitor charge control, the energy charged in the smoothing capacitor 6 can be recovered and charged into the battery 2.

[0060] In this way, in this embodiment, at time t3 when a request to drive the motor 5 is made, power is discharged from the pre-charged smoothing capacitor 6, so that both the power discharged from the smoothing capacitor 6 and the power discharged from the battery 2 can be supplied to the motor 5, thereby preventing a shortage of power for driving the motor 5.

[0061] A transition of the vehicle state according to a comparative example will be described with reference to Fig. 5. This comparative example shows an example in which smoothing capacitor charging control and smoothing capacitor discharging control are not performed. In Fig. 5, the vertical axis represents the target voltage of the boost converter 3, the discharge power of the smoothing capacitor 6, the discharge power of the battery 2, and the input power of the inverter 4, and the horizontal axis represents the transition of time.

[0062] As shown in FIG. 5, at time t10, the discharge power of the smoothing capacitor 6, the discharge power of the battery 2, and the input power of the inverter 4 are all zero.

[0063] After that, at time t11, a request to drive the motor 5 is made, and the target voltage starts to rise toward a value for driving the motor 5. Furthermore, the discharge power of the battery 2 increases. At this time t11, the input power of the inverter 4 increases in accordance with the increase in the discharge power of the battery 2. Furthermore, the discharge power of the smoothing capacitor 6 increases in the negative direction, and the smoothing capacitor 6 is charged.

[0064] After that, at time t12, the target voltage is maintained at a value for driving the motor 5. In addition, the discharge power of the smoothing capacitor 6 becomes 0, and charging of the smoothing capacitor 6 is completed. At this time t12, the discharge power of the battery 2 has increased to the available output power. The input power of the inverter 4 increases to a value equivalent to the available output power of the discharge power of the battery 2.

[0065] As described above, in the comparative example, at time t11 when a request to drive the motor 5 is made, part of the discharged power of the battery 2 is used to charge the smoothing capacitor 6, which prevents an increase in the input power of the inverter 4. As a result, the power required to drive the motor 5 is insufficient.

[0066] As described above, in the vehicle control device according to this embodiment, when predetermined conditions are met, including the prediction of a drive request for the motor 5, the control unit 10 increases the target voltage of the boost converter 3 to charge the smoothing capacitor 6. Furthermore, when a drive request for the motor 5 is made, the control unit 10 controls the boost converter 3 to decrease the target voltage to discharge the smoothing capacitor 6.

[0067] As a result, when a request to drive the motor 5 is predicted, the target voltage of the boost converter 3 is increased in advance to charge the smoothing capacitor 6, and when a request to drive the motor 5 is made, the target voltage is decreased to discharge the smoothing capacitor 6, and the discharged power can be supplied to the motor 5. Therefore, when a request to drive the motor 5 is made, both the power stored in the battery 2 and the power stored in the smoothing capacitor 6 can be supplied to the motor 5. As a result, it is possible to prevent a shortage of power for driving the motor 5 when a request to drive the motor 5 is made.

[0068] In the vehicle control device according to this embodiment, the predetermined conditions include the available output power of the battery 2 being reduced to less than a predetermined value.

[0069] As a result, in a situation where, for example, the battery 2 is unable to output the power required to drive the motor 5 due to a low temperature or the like, causing a decrease in the available output power, and there is a high possibility of a power shortage occurring due to the charging of the smoothing capacitor 6, the discharged power of the smoothing capacitor 6 can be utilized to drive the motor 5. This makes it possible to effectively prevent a shortage of power for driving the motor 5. Furthermore, because the charge control and discharge control of the smoothing capacitor 6 can be executed only when the available output voltage of the battery 2 is low, it is possible to prevent unnecessary consumption of power for charging the smoothing capacitor 6 in a situation where there is no risk of a shortage of power for driving the motor 5.

[0070] While an embodiment of the present invention has been disclosed, it will be apparent to one skilled in the art that modifications may be made thereto without departing from the scope of the present invention, and it is intended that all such modifications and equivalents be included in the following claims. [Explanation of symbols]

[0071] 1 vehicle 2 Battery 3. Boost Converter 4 inverters 5 motors 6 smoothing capacitors 10 Control Unit

Claims

1. A battery, a boost converter that boosts the DC power output from the battery; an inverter that converts the DC power output from the boost converter into AC power; a motor that is driven by AC power output from the inverter and generates motor torque for traveling; a smoothing capacitor connected between the boost converter and the inverter, A vehicle control device including a control unit that controls the boost converter and the inverter in response to a drive request of the motor, The control unit When a predetermined condition including a prediction of a drive request for the motor is satisfied, the target voltage of the boost converter is increased to charge the smoothing capacitor; A vehicle control device comprising: a control unit that controls the smoothing capacitor to discharge by lowering a target voltage of the boost converter when a drive request is made for the motor.

2. 2. The vehicle control device according to claim 1, wherein the predetermined condition includes a condition in which the available output power of the battery falls below a predetermined value.

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