Vehicle control device

Abstract

To effectively utilize heat generated within a vehicle while suppressing a decrease in energy efficiency of the entire vehicle.SOLUTION: A vehicle control device 4 calculates a maximum powertrain braking power, which is a maximum value of braking power in a vehicle drive device 8 on the basis of a chargeable electric energy amount of a DC power source 6 and powertrain losses including at least mechanical loss and electrical loss in the vehicle drive device 8 including a rotary electric machine 2, a power transmission mechanism 5, and an inverter 3, and a maximum powertrain braking torque, which is a maximum value of braking torque generated by the vehicle drive device 8, on the basis of the maximum powertrain braking power and a rotational speed of the rotary electric machine 2, and provides the maximum powertrain braking torque to a brake control device 7 that controls a friction brake 71 of a wheel 9.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a vehicle control device that controls a vehicle drive device equipped with a rotating electric machine. [Background technology]

[0002] In recent years, the number of electric vehicles that do not have an internal combustion engine as a driving force source for the wheels, or that have a low-output internal combustion engine for generating electricity and use a rotating electric machine as the main driving force source for the wheels, has been increasing. In such electric vehicles, it is difficult to use the exhaust heat of the internal combustion engine as a heat source for heating the vehicle cabin or warming up the equipment, as in conventional vehicles. Japanese Patent Application Laid-Open Publication No. 2018-98857 discloses that in an electric vehicle, heat from a drive circuit that drives and controls a rotating electric machine is used as a heat source. According to this document, when there is no heat conversion request, the drive circuit drives and controls the rotating electric machine in a loss reduction mode, and when there is a heat conversion request, the drive circuit drives and controls the rotating electric machine in a loss increase mode, and the heat generated by the increased loss is used as a heat source. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-98857 Summary of the Invention [Problem to be solved by the invention]

[0004] The technology disclosed in the above document is excellent in that it can utilize the heat generated in the drive circuit that drives and controls the rotating electric machine as a heat source without providing a separate heater or the like. However, some vehicles generate heat in addition to the drive circuit of the rotating electric machine, and this heat is dissipated without being utilized. Furthermore, operating the drive circuit in a loss-increasing mode naturally results in poor energy efficiency.

[0005] Therefore, it is desirable to effectively utilize the heat generated within the vehicle while suppressing a decrease in the energy efficiency of the entire vehicle. [Means for solving the problem]

[0006] In view of the above, a vehicle control device is a vehicle control device that controls at least a vehicle drive device that includes an AC rotating electric machine that serves as a driving force source for the wheels of an electric vehicle, an inverter that is arranged between a DC power source and the rotating electric machine and converts power between DC and multi-phase AC, and a power transmission mechanism that transmits power between the rotating electric machine and the wheels, and calculates a maximum powertrain brake power, which is the maximum value of the brake power in the vehicle drive device, based on the chargeable power amount of the DC power source and powertrain losses that include at least mechanical losses and electrical losses in the rotating electric machine, the power transmission mechanism, and the inverter, calculates a maximum powertrain brake torque, which is the maximum value of the brake torque by the vehicle drive device, based on the maximum powertrain brake power and the rotational speed of the rotating electric machine, and provides the maximum powertrain brake torque to a brake control device that controls the friction brakes of the wheels.

[0007] By having the vehicle drive system output a powertrain brake torque corresponding to a power up to the maximum powertrain brake power, it becomes easier to reduce the proportion of the brake torque applied to the wheels determined by, for example, the driver's operation that is handled by the friction brake. As a result, it is possible to reduce the heat lost to the atmosphere as friction heat in the friction brake and increase the heat generated in the process of driving the vehicle drive system and available for use inside the vehicle. Therefore, this configuration makes it possible to effectively utilize the heat generated inside the vehicle while suppressing a decrease in the energy efficiency of the entire vehicle.

[0008] Further features and advantages of the vehicle control device will become apparent from the following description of exemplary, non-limiting embodiments thereof, which are given with reference to the drawings. [Brief explanation of the drawings]

[0009] [Figure 1] Block diagram showing an example of a vehicle control system [Figure 2] A circuit block diagram showing an example of a control system for driving and controlling a rotating electric machine. [Figure 3] Block diagram showing an example of a cooperative braking system [Figure 4] A diagram showing the relationship between the brake operation amount and the required brake torque. [Figure 5] Diagram showing the relationship between chargeable power and regenerative power [Figure 6] A diagram showing the relationship between chargeable power and regenerative power depending on the control mode [Figure 7] Torque map for rotating electrical machine control DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of a vehicle control device will be described with reference to the drawings. FIG. 1 is a block diagram showing an example of a vehicle control system. FIG. 2 is a circuit block diagram showing an example of a control system that drives and controls a rotating electric machine 2. The vehicle control device of this embodiment is a control device configured around a rotating electric machine control device 4 that drives and controls the rotating electric machine 2 via an inverter 3. The rotating electric machine 2 constitutes a part of a vehicle drive device 8 as a driving power source for wheels 9 of an electric vehicle. The vehicle drive device 8 includes at least the rotating electric machine 2, an inverter 3, and a power transmission mechanism 5. Since the vehicle control device of this embodiment is a control device that controls at least the vehicle drive device 8, it is preferable that the rotating electric machine control device 4 also controls the power transmission mechanism 5 in addition to the rotating electric machine 2 and the inverter 3. Alternatively, the vehicle control device of this embodiment may be configured by combining the rotating electric machine control device 4 with a control device (not shown) that controls the power transmission mechanism 5.

[0011] The rotating electric machine 2 is an AC rotating electric machine. The inverter 3 is an electric circuit centered on a power switching element that drives the rotating electric machine 2. The inverter 3 is disposed between a DC power source 6 and the rotating electric machine 2 and converts power between DC and multi-phase (here, three-phase) AC. The DC power source 6 is a high-voltage DC power source with a rated voltage of approximately 200 to 800 volts. The power transmission mechanism 5 is a mechanical mechanism centered on a gear mechanism and transmits power between the rotating electric machine 2 and wheels 9. In this embodiment, an electric vehicle equipped only with the rotating electric machine 2 as a driving power source for the wheels 9 is illustrated, but this does not preclude a hybrid vehicle also equipped with an internal combustion engine. The power transmission mechanism 5 may also include an engagement device that can switch the power transmission path. If a control device (not shown) that controls the power transmission mechanism 5 is provided, the control device preferably controls the engagement device and the supply of oil to the rotating electric machine 2 and the power transmission mechanism 5. Naturally, if the control device is not provided, the rotary electric machine control device 4 may control the engagement devices and the supply of oil.

[0012] As shown in FIG. 1 , the vehicle control system includes an integrated control device 1, which is a higher-level control device than the rotating electric machine control device 4. An accelerator sensor 15 detects the amount of operation of, for example, an accelerator pedal 17 by the driver (accelerator operation amount S17). The detected accelerator operation amount S17 is transmitted to the integrated control device 1 via an in-vehicle network such as a CAN (Controller Area Network). A vehicle speed sensor 19 is provided on the wheels 9, and vehicle speed information detected by the vehicle speed sensor 19 is also transmitted to the integrated control device 1 via the in-vehicle network. The integrated control device 1 calculates a driving force request (here, a torque command for the rotating electric machine 2) for the vehicle drive device 8 based on the vehicle speed, the accelerator operation amount S17, and other information as needed (road gradient information detected by a sensor not shown, weather information such as the presence or absence of obstacles ahead, and rainfall), and transmits the calculated driving force request to the rotating electric machine control device 4. The rotating electric machine control device 4 drives and controls the rotating electric machine 2 via an inverter 3 based on the torque command. The power transmission mechanism 5 includes a reducer (or transmission) that reduces the speed of the rotating electric machine 2 and amplifies the torque, and a differential gear mechanism that distributes the power to a pair of wheels 9. The power from the rotating electric machine 2 is transmitted to the wheels 9 via the power transmission mechanism 5.

[0013] Here, an example has been shown in which a driving force request to the vehicle driving device 8 (rotating electric machine 2) is determined based on the driver's operation of the accelerator pedal 17. However, in the case of automatic driving including cruise control, for example, the driving force request may be calculated without the accelerator pedal 17 being operated.

[0014] The rotating electric machine 2 includes a stator with a stator coil and a rotor with a field magnet. If the rotating electric machine 2 is a permanent magnet synchronous motor (PMSM), the rotor includes a permanent magnet. Alternatively, the rotating electric machine 2 may be an electrically excited field synchronous motor (EESM) that includes an electromagnet using a field winding (rotor coil) instead of a permanent magnet as a field source.

[0015] As described above, the rotating electric machine 2 is drive-controlled based on the target torque of the rotating electric machine 2, which is set in accordance with a torque command from the integrated control device 1, which is a higher-level control device than the rotating electric machine control device 4. As shown in FIG. 2 , the stator coil is connected to a DC power source 6 via an inverter 3. A DC link capacitor 63 (smoothing capacitor) that smoothes the voltage on the DC side of the inverter 3 is provided on the DC side of the inverter 3, i.e., between the inverter 3 and the DC power source 6. The rotating electric machine control device 4 controls the switching of the inverter 3, which is made up of a plurality of switching elements, to cause the inverter 3 to convert power between DC and multi-phase (three-phase in this embodiment) AC.

[0016] The inverter 3 is configured with a plurality of switching elements. The inverter 3 has a plurality of sets (three sets in this example) of arms for one AC phase, each set being a series circuit of an upper-stage switching element on the positive side of DC and a lower-stage switching element on the negative side. The switching elements are power transistors such as IGBTs (Insulated Gate Bipolar Transistors), power MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), and HEMTs (High Electron Mobility Transistors).

[0017] The rotating electric machine control device 4 performs current feedback control using, for example, a vector control method based on the target torque, the rotational position of the rotor (magnetic pole position of the field), the rotational speed of the rotor, and the current flowing through the stator coils of each of the three phases, and drives and controls the rotating electric machine 2 via the inverter 3. In the vector control method, feedback control is performed by converting the current flowing through the stator coils of each phase into vector components with respect to the d-axis, which is the direction of the magnetic field in the rotor, and the q-axis, which is in a direction perpendicular to the d-axis (a direction leading the magnetic field direction by an electrical angle of π / 2). The coordinate system after the coordinate conversion is called a dq-axis orthogonal vector coordinate system.

[0018] Switching modes of the inverter 3 include pulse-width modulation control and square-wave control. Square-wave control is often performed when the rotating electric machine 2 is rotating at a high speed, and the inverter 3 is switched by pulse-width modulation control for most of the operating time of the rotating electric machine 2. In pulse-width modulation control, the inverter 3 is driven and controlled by controlling the armature current, which is a composite vector of the field current (d-axis current Id) and the drive current (q-axis current Iq) along each axis of the dq-axis orthogonal vector. In other words, the rotating electric machine control device 4 drives and controls the inverter 3 by controlling the current phase angle of the armature current in the dq-axis orthogonal vector coordinate system (the angle between the q-axis current vector and the armature current vector) (current phase control). The rotating electric machine control device 4 basically controls the switching of the inverter 3 at a current phase angle that minimizes loss and allows the rotating electric machine 2 to be driven most efficiently.

[0019] The current flowing through the stator coil is detected by a current sensor 41. The rotational position and rotational speed of the rotor are detected by a rotation sensor 42, such as a resolver or an inductive position sensor. The rotating electric machine control device 4 is configured with various functional units for current feedback control, and each functional unit is realized by the cooperation of hardware such as a microcomputer configured with an electronic circuit as its core and software (program). The integrated control device 1 is also configured with various functional units, and each functional unit is realized by the cooperation of hardware such as a microcomputer configured with an electronic circuit as its core and software (program). The operating voltage of the integrated control device 1 and the rotating electric machine control device 4 is approximately 3.3 to 5 volts.

[0020] The voltage of the switching control signal for the power transistors that make up the inverter 3 needs to be about 15 to 24 volts. For this reason, a drive circuit (not shown) is provided between the rotating electric machine control device 4 and the inverter 3 to amplify the voltage amplitude of the switching control signal output from the rotating electric machine control device 4, increase the driving force, and supply it to the inverter 3. Alternatively, it may be considered that the rotating electric machine control device 4 includes the drive circuit.

[0021] The rotating electric machine 2 has a function as a motor that receives power from the DC power supply 6 to generate power, and a function as a generator that receives power from the wheels 9 to generate power. That is, the rotating electric machine 2 generates driving force by running using the power stored in the DC power supply 6, and also generates power using the driving force transmitted from the pair of wheels 9 to charge the DC power supply 6.

[0022] The DC power supply 6 is configured by, for example, a rechargeable secondary battery (battery) such as a lithium ion battery, an electric double layer capacitor, or the like. When the rotating electric machine 2 is a driving power source for a vehicle as in this embodiment, the DC power supply 6 is a high-voltage, large-capacity DC power supply. As described above, the rated power supply voltage of the DC power supply 6 is, for example, 200 to 800 volts.

[0023] For example, when the DC power supply 6 is a lithium-ion battery, a battery management system 61 (BMS: Battery Management System) is often provided. A secondary battery such as a lithium-ion battery is composed of multiple cells (battery cells). The battery management system 61 is a battery management control system that (1) prevents overcharging and overdischarging of the cells, (2) prevents excessive current from flowing through the cells, (3) manages the cell temperature, (4) calculates the state of charge (SOC), and (5) equalizes the cell voltages. The battery management system 61 preferably includes a battery current sensor that detects the input / output current (battery current) to / from the DC power supply 6 and a battery voltage sensor that detects the terminal voltage (battery voltage Vbat: see FIG. 4, etc.) of the DC power supply 6. To prevent overcharging of the cells, the battery management system 61 determines and outputs, for example, a chargeable energy Bmnp (see FIG. 3, FIG. 5, FIG. 6, etc.).

[0024] Next, vehicle braking will be described. Here, braking based on the driver's operation of the brake pedal 77 will be exemplified. However, as described above with respect to the driving force request, in the case of automatic driving including cruise control, automatic braking, etc., the braking force request may be determined without the brake pedal 77 being operated.

[0025] The amount of operation of the brake pedal 77 by the driver (brake operation amount S77) is detected by a brake sensor 75. The detected brake operation amount S77 is transmitted to the brake control device 7, for example, via an in-vehicle network. The brake system of this embodiment is a so-called brake-by-wire system, which applies a braking force corresponding to the brake operation amount S77 to the brake device 71 using an actuator. The brake control device 7 calculates a required brake power to be applied to the brake device 71 based on the vehicle speed, the brake operation amount S77, and other information as needed. For example, when a braking force corresponding to the brake operation amount S77 is to be realized only by a friction brake such as a disc brake that acts to prevent rotation of a rotating body that rotates integrally with the wheel 9, an actuator of the friction brake such as the disc brake is controlled to realize a friction force corresponding to the required brake power.

[0026] As described above, the rotating electric machine 2 is capable of not only power running but also regenerative operation. When the rotating electric machine 2 performs regenerative operation, mechanical energy transmitted from the wheels 9 is converted into electrical energy, and a braking force acts on the wheels 9. Here, the braking force when the rotating electric machine 2 performs regenerative operation is referred to as regenerative braking. Therefore, the electric vehicle of this embodiment can utilize both the friction brake and the regenerative brake described above. Hereinafter, braking in which the required brake power is shared between the friction brake and the regenerative brake will be referred to as "friction regenerative cooperative braking," or simply "cooperative braking."

[0027] FIG. 3 is a circuit block diagram showing an example of a cooperative braking system for realizing cooperative braking, and FIG. 4 shows the relationship between the amount of brake operation on the brake pedal 77 and the brake torque (required brake torque BTrq) required for the vehicle brakes (cooperative braking). Here, braking based on operation of the brake pedal 77 will be described as an example. The brake operation amount S77 detected by the brake sensor 75 corresponds to the requested brake torque BTrq for the vehicle brakes (cooperative braking). For ease of understanding, FIG. 3 illustrates the requested brake torque BTrq being provided from the brake sensor 75 to the brake control device 7, but the brake control device 7 may also calculate the requested brake torque BTrq based on the brake operation amount S77.

[0028] The rotating electric machine control device 4 sequentially transmits to the integrated control device 1 the rotational speed ω of the rotating electric machine 2 and the regenerative brake torque (maximum regenerative brake torque Tmg) that the rotating electric machine 2 can output when the rotating electric machine 2 performs regenerative operation at this rotational speed ω. Furthermore, the rotating electric machine control device 4 adds brake torque due to the mechanical load in the vehicle drive device 8, electrical loss in the inverter 3, etc. to the maximum regenerative brake torque Tmg, and sequentially transmits the brake torque (maximum powertrain brake torque BTptx) that the vehicle drive device 8 can output to the integrated control device 1. The integrated control device 1 sequentially transmits the maximum powertrain brake torque BTptx received from the rotating electric machine control device 4 to the brake control device 7. Naturally, the maximum powertrain brake torque BTptx may also be sequentially transmitted from the rotating electric machine control device 4 to the brake control device 7 via an in-vehicle network. Furthermore, nothing prevents the integrated control device 1 from adding brake torque due to the mechanical load in the vehicle drive device 8 and electrical loss in the inverter 3, etc., to the maximum regenerative brake torque Tmg received from the rotating electric machine control device 4, and sequentially transmitting the maximum powertrain brake torque BTptx to the brake control device 7. Based on the required brake torque BTrq and the maximum powertrain brake torque BTptx, the brake control device 7 proportionally divides the required brake torque BTrq into brake torque to be borne by the vehicle drive device 8 (powertrain required brake torque BTptrq) and brake torque by the brake device 71.

[0029] The brake control device 7 allocates the required brake torque BTrq and requests the integrated control device 1 to provide a powertrain required brake torque BTptrq, which is the brake torque to be provided to the vehicle drive device 8. The integrated control device 1 determines the powertrain brake torque BTpt, which is the brake torque to be provided to the vehicle drive device 8, based on the maximum powertrain brake torque BTptx and the powertrain required brake torque BTptrq, and transmits it to the brake control device 7. Specifically, the integrated control device 1 determines the powertrain brake torque BTpt based on the powertrain required brake torque BTptrq within a range not exceeding the maximum powertrain brake torque BTptx. If the powertrain required brake torque BTptrq is equal to or less than the maximum powertrain brake torque BTptx, the powertrain brake torque BTpt is determined according to the powertrain required brake torque BTptrq. If the powertrain required brake torque BTptrq exceeds the maximum powertrain brake torque BTptx, the powertrain brake torque BTpt is determined so as to be limited to the value of the maximum powertrain brake torque BTptx. At the same time, the integrated control device 1 determines the powertrain brake torque BTpt and transmits it to the brake control device 7, and outputs a torque command for regenerative operation (regenerative torque command Trq) to the rotating electrical machine control device 4 based on the powertrain brake torque BTpt.

[0030] The rotating electric machine control device 4 controls the driving of the rotating electric machine 2 via the inverter 3 based on the regenerative torque command Trq. As a result, a regenerative brake torque is generated by the rotating electric machine 2, and a powertrain brake torque BTpt is realized, including other brake torques in the vehicle drive device 8. The brake control device 7 again proportionally divides the requested brake torque BTrq based on the powertrain brake torque BTpt to determine a friction brake torque BTfr. The brake control device 7 drives the brake device 71, for example, by hydraulic control, based on the friction brake torque BTfr. As a result, the friction brake torque BTfr is realized. A brake torque BT corresponding to a brake operation amount S77 acts on the vehicle based on the powertrain brake torque BTpt and the friction brake torque BTfr (see FIG. 4).

[0031] Such cooperative control of the powertrain brake torque BTpt and the friction brake torque BTfr is so-called feedback control, but it is more preferable to realize the cooperative control by feedforward control as described below, as this has high responsiveness.

[0032] As described above, the maximum powertrain brake torque BTptx is sequentially transmitted to the brake control device 7. Therefore, the brake control device 7 can request the powertrain required brake torque BTptrq from the integrated control device 1. Specifically, when allocating the required brake torque BTrq to the powertrain required brake torque BTptrq and the friction brake torque BTfr, the brake control device 7 can determine the powertrain required brake torque BTptrq within the range of the maximum powertrain brake torque BTptx.

[0033] Because the powertrain required brake torque BTptrq is within a range that does not exceed the maximum powertrain brake torque BTptx, the integrated control device 1 determines the powertrain brake torque BTpt according to the powertrain required brake torque BTptrq. Then, based on the powertrain brake torque BTpt, the integrated control device 1 outputs a torque command for regenerative operation (regenerative torque command Trq) to the rotating electrical machine control device 4. Note that even in this case, this does not prevent the determined powertrain brake torque BTpt from being transmitted to the brake control device 7 in response to the powertrain required brake torque BTptrq.

[0034] Furthermore, although the above describes an example in which the brake control device 7 requests the integrated control device 1 for the powertrain required brake torque BTptrq, this does not preclude a configuration in which the brake control device 7 requests the powertrain required brake torque BTptrq from the rotating electric machine control device 4 via an in-vehicle network. In this case, the determined powertrain brake torque BTpt may be transmitted from the rotating electric machine control device 4 to the brake control device 7 via the in-vehicle network in response to the powertrain required brake torque BTptrq.

[0035] When the rotating electric machine 2 performs regenerative operation, the electric power generated by the rotating electric machine 2 charges the DC power supply 6 via the inverter 3. When the SOC of the DC power supply 6 is sufficiently high, the electric power that the DC power supply 6 can accept is limited, and accordingly, the electric power generated by the rotating electric machine 2 is also limited. Here, the electric power that the DC power supply 6 can accept is defined as the chargeable electric energy Bmnp. As shown in FIG. 5 , when the chargeable electric energy Bmnp is limited, the charging power Pmgr, which corresponds to the charging power generated by the rotating electric machine 2 and supplied to the DC power supply 6, is preferably limited to a value less than the chargeable electric energy Bmnp. However, the electric power generated in the stator coil of the rotating electric machine 2 is consumed through losses due to transmission through the inverter 3 and the like. Furthermore, because losses also occur in the power transmission mechanism 5, the rotating electric machine 2 itself can generate electric power exceeding the charging power Pmgr. Here, losses in the vehicle drive device 8, including the inverter 3, are referred to as powertrain losses Ploss. The rotating electric machine 2 can be controlled to output a maximum powertrain brake power (maximum regenerative power Pmg) that corresponds to the sum of the charging power Pmgr and the powertrain loss Ploss. The above-mentioned maximum powertrain brake torque BTptx is a brake torque that corresponds to this maximum regenerative power Pmg, and is determined by the maximum regenerative power Pmg and the rotational speed ω of the rotating electric machine 2.

[0036] As is clear from the above, when the chargeable energy Bmnp is low and the amount of power that can be supplied from the rotating electric machine 2 to the DC power supply 6 is limited, the maximum regenerative power Pmg decreases. Therefore, the maximum powertrain brake torque BTptx also decreases. When the maximum powertrain brake torque BTptx decreases, the amount of brake torque BT that can be borne by the powertrain brake torque BTpt decreases, and the friction brake torque BTfr by the brake device 71 increases. The brake device 71 generates heat due to friction when generating the friction brake torque BTfr. This heat is released into the atmosphere.

[0037] Electric vehicles have fewer heat sources than conventional vehicles that use an internal combustion engine as a driving force source for the wheels. Conventional vehicles use exhaust heat from the internal combustion engine as a heat source for heating the vehicle, but electric vehicles without an internal combustion engine naturally cannot utilize the exhaust heat of the internal combustion engine. While plug-in hybrid vehicles and the like may be equipped with an internal combustion engine for power generation, the internal combustion engine operates only when the SOC of the DC power supply 6 is low. Unlike conventional internal combustion engine vehicles, the internal combustion engine does not operate constantly. Furthermore, the size of the internal combustion engine is smaller than that of a vehicle that drives the wheels, and therefore the amount of heat generated is smaller than that of conventional vehicles. Therefore, it is preferable to efficiently utilize the heat generated within the vehicle, especially when heating is required (including warming up the DC power supply 6). Frictional heat generated in the brake device 71 is difficult to recover, and most of it is released into the atmosphere. On the other hand, heat generated in the vehicle drive device 8 can be easily recovered through oil that lubricates the bearings and meshing parts of gears and cools the stator coil of the rotating electrical machine 2, and cooling water that cools the inverter 3. Therefore, by increasing the torque that is borne by the powertrain brake torque BTpt out of the brake torque BT that acts on the vehicle, more heat can be recovered.

[0038] As described above, in this embodiment, the brake control device 7, the rotating electric machine control device 4, and the integrated control device 1 cooperate to control the rotating electric machine 2 and the brake device 71 so as to achieve friction regenerative cooperative braking. That is, the rotating electric machine control device 4, which is the core of the vehicle control device that controls at least the vehicle drive device 8 including the rotating electric machine 2, the inverter 3, and the power train mechanism 5, calculates the maximum powertrain brake power (maximum regenerative power Pmg), which is the maximum value of the brake power in the vehicle drive device 8, based on the chargeable energy Bmnp of the DC power supply 6 and the powertrain loss Ploss, which includes mechanical loss and electrical loss in at least the rotating electric machine 2, the power train mechanism 5, and the inverter 3. As described above, the brake torque corresponding to this maximum regenerative power Pmg is the maximum powertrain brake torque BTptx. The rotating electric machine control device 4 provides this maximum powertrain brake torque BTptx to the brake control device 7.

[0039] In one aspect, the integrated control device 1 commands the rotating electric machine control device 4 to change the control mode based on the chargeable energy Bmnp of the DC power supply 6, the state of the vehicle drive device 8, and the value of the maximum powertrain brake torque BTptx. The rotating electric machine control device 4 receives the control mode change command and calculates and updates the maximum powertrain brake power (maximum regenerative power Pmg), which is the maximum value of the brake power in the vehicle drive device 8, based on the powertrain loss Ploss, which includes mechanical losses in at least the rotating electric machine 2, the power transmission mechanism 5, and the inverter 3, and electrical losses that change with the control change, and notifies the integrated control device 1 of the updated value. As described above, the brake torque corresponding to this maximum regenerative power Pmg is the maximum powertrain brake torque BTptx. The integrated control device 1 provides the brake control device 7 with this maximum powertrain brake torque BTptx received from the rotating electric machine control device 4.

[0040] As shown in FIG. 6, increasing the powertrain loss Ploss from “Ploss1” to “Ploss2” can increase the maximum powertrain brake power (maximum regenerative power Pmg) from “Pmg1” to “Pmg2.” Note that, for convenience, the charging powers Pmgr are referred to as “Pmgr1” and “Pmgr2,” but they are the same power. Typically, the inverter 3 is switched to achieve high power conversion efficiency. For example, in the case of pulse-width modulation control, as described above, the inverter 3 is switched at a current phase angle that minimizes loss and enables the rotating electric machine 2 to be driven most efficiently. By shifting the current phase angle from the optimal phase angle, the current flowing through the inverter 3 and the stator coil can be increased, thereby increasing the powertrain loss Ploss. Typically, the inverter 3 is switched at an appropriate switching frequency to minimize losses in the switching elements. The rotating electric machine control device 4 can increase the powertrain loss Ploss by controlling the inverter 3 at a higher switching frequency, for example, to increase losses in the switching elements.

[0041] Control with high power conversion efficiency and low loss, such as the former, is called normal control, while control with low power conversion efficiency and high loss, such as the latter, is called high-loss control (inefficient control). Losses in the switching elements and stator coils become heat, so the heat due to the increased powertrain loss Ploss can be recovered through heat exchange with the cooling water that cools the inverter 3 or the oil that cools the stator coils, and used for heating or warming up the engine. In this way, the powertrain loss Ploss can include losses when the rotating electrical machine control device 4 performs switching control of the inverter 3 using high-loss control, which involves higher losses than normal control, which is the normal control used when running an electric vehicle.

[0042] As shown in FIG. 3 , the integrated control device 1 can provide the rotating electric machine control device 4 with mode instruction information MD that specifies a control mode for controlling the switching of the inverter 3. For example, the integrated control device 1 can determine, based on information from a BMS or the like, whether the chargeable energy Bmnp is low and power generation by the rotating electric machine 2 is limited. The integrated control device 1 can also determine whether heat is needed in the vehicle. Based on such a determination, the integrated control device 1 preferably provides the mode instruction information MD to the rotating electric machine control device 4. By increasing the powertrain loss Ploss, the charging to the DC power supply 6 can be limited while the rotating electric machine 2 generates power in an amount exceeding the chargeable energy Bmnp, and the heat generated by the loss can be utilized.

[0043] If the rotating electric machine control device 4 can acquire information that serves as a determination condition for the mode instruction information MD, the above determination may be made by the rotating electric machine control device 4 (vehicle control device). In this case, the rotating electric machine control device 4 may be configured to be able to autonomously change the control mode.

[0044] That is, the high-loss control is preferably executed when the chargeable energy Bmnp is less than a predetermined limit energy. Considering the use of heat, the high-loss control is preferably executed when the chargeable energy Bmnp is less than the limit energy and the ambient temperature around the vehicle or a temperature linked to the ambient temperature is less than a predetermined reference temperature. Furthermore, when the demand for heat is high, the high-loss control may be executed regardless of the chargeable energy Bmnp. That is, the high-loss control is preferably executed when the ambient temperature around the vehicle or a temperature linked to the ambient temperature is less than a predetermined reference temperature. Because both high-loss controls are executed to generate a powertrain brake torque BTpt used as the brake torque BT, the high-loss control is executed when the rotating electric machine 2 is in regenerative operation. When the above-described conditions are met, the integrated control device 1 requests the rotating electric machine control device 4, which drives and controls the inverter 3, to execute the high-loss control. For example, the integrated control device 1 transmits mode instruction information MD instructing the execution of high-loss control to the rotating electrical machine control device 4. Alternatively, the rotating electrical machine control device 4 may autonomously execute high-loss control when it determines that the above-described conditions are met.

[0045] The temperature linked to the outside air temperature is, for example, the temperature of the DC power supply 6 (battery temperature Tbat shown in FIG. 3), which is greatly affected by temperature. It is preferable to perform high-loss control when the temperature of the DC power supply 6 drops, especially after parking in cold weather. Similarly, it is preferable to perform high-loss control when the temperature of the oil stored in the case of the vehicle drive system 8 drops, or when the temperature of the coolant drops, after parking in cold weather. Therefore, such oil temperature and coolant temperature can also be said to be temperatures linked to the outside air temperature. It is obvious from the examples of the temperatures of the DC power supply 6, oil, and coolant, but the temperature linked to the outside air temperature does not always need to be linked to the outside air temperature, and may be the temperature of an object whose temperature tends to drop in conjunction with the outside air temperature, especially when the temperature is low.

[0046] FIG. 7 shows a torque map for rotating electric machine control. "Tmgmax" indicates the maximum torque of the rotating electric machine 2. The first curve A1 shows the relationship between the rotation speed ω and the maximum regenerative braking torque Tmg when the chargeable energy Bmnp is sufficiently large and there is no limit to the amount of power generated by the rotating electric machine 2. The second curve A2 and the third curve A3 show the relationship between the rotation speed ω and the maximum regenerative braking torque Tmg when the chargeable energy Bmnp is small and the amount of power generated by the rotating electric machine 2 is limited. The second curve A2 shows the case when the maximum regenerative power Pmg (maximum powertrain braking power) in FIG. 6 is "Pmg1," and the third curve A3 shows the case when the maximum regenerative power Pmg is "Pmg2." The powertrain loss "Ploss1" when the maximum regenerative power Pmg is "Pmg1" is smaller than the powertrain loss "Ploss2" when the maximum regenerative power Pmg is "Pmg2."

[0047] As shown in FIG. 7, of the three curves, the first curve A1 can output the highest torque at the same rotational speed ω. On the other hand, the second curve A2 can only output the lowest torque at the same rotational speed ω. Here, as described above with reference to FIG. 6, by increasing the powertrain loss Ploss from "Ploss1" to "Ploss2," the second curve A2 can be shifted toward the first curve A1, as shown by the third curve A3. As a result, the torque that can be output at the same rotational speed ω can be made larger than that of the second curve A2.

[0048] As shown in FIG. 2 , an auxiliary device 100, which is an on-board device separate from the rotating electric machine 2 that is the driving force source for the wheels 9, may be connected to the DC power supply 6. The auxiliary device 100 may be, for example, an oil pump that draws and discharges lubricating oil, a cooling water pump that circulates cooling water, or a compressor that compresses the refrigerant of an on-board air conditioner. The electric power generated by the rotating electric machine 2 may be used for such an auxiliary device 100, rather than for charging the DC power supply 6. By including the electric power used by the auxiliary device 100 in the powertrain loss Ploss, the maximum powertrain braking power (maximum regenerative power Pmg) can be increased. In other words, it is preferable that the powertrain loss Ploss includes the power consumption of the auxiliary device 100, which is an on-board device separate from the rotating electric machine 2 and receives power from the DC power supply 6. In this case, temporarily increasing the output of the auxiliary device 100 can further increase the maximum powertrain braking power (maximum regenerative power Pmg). Note that Figure 1 illustrates an example in which the auxiliary equipment 100 is controlled by the integrated control device 1, but in cases where the auxiliary equipment 100 is, for example, an oil pump that draws in and discharges oil for lubrication of the vehicle drive device 8, the auxiliary equipment 100 may be controlled by a rotating electrical machine control device 4 or a control device (not shown) that controls the power transmission mechanism 5.

[0049] The control device for an electric vehicle described above will be briefly summarized below.

[0050] In one aspect, the vehicle control device controls at least a vehicle drive device that includes an AC rotating electric machine that serves as a driving force source for the wheels of an electric vehicle, an inverter arranged between a DC power source and the rotating electric machine to convert power between DC and multi-phase AC, and a power transmission mechanism that transmits power between the rotating electric machine and the wheels.The vehicle control device calculates a maximum powertrain brake power, which is the maximum value of the brake power in the vehicle drive device, based on the chargeable power amount of the DC power source and powertrain losses, which include at least mechanical losses and electrical losses in the rotating electric machine, the power transmission mechanism, and the inverter, calculates a maximum powertrain brake torque, which is the maximum value of the brake torque by the vehicle drive device, based on the maximum powertrain brake power and the rotational speed of the rotating electric machine, and provides the maximum powertrain brake torque to a brake control device that controls the friction brakes of the wheels.

[0051] By having the vehicle drive system output a powertrain brake torque corresponding to a power up to the maximum powertrain brake power, it becomes easier to reduce the proportion of the brake torque applied to the wheels determined by, for example, the driver's operation that is handled by the friction brake. As a result, it is possible to reduce the heat lost to the atmosphere as friction heat in the friction brake and increase the heat generated in the process of driving the vehicle drive system and available for use inside the vehicle. Therefore, this configuration makes it possible to effectively utilize the heat generated inside the vehicle while suppressing a decrease in the energy efficiency of the entire vehicle.

[0052] Here, it is preferable that the powertrain loss includes loss when switching control of the inverter is performed by high-loss control, which is larger in loss than normal control, which is normal control when running the electric vehicle.

[0053] According to this configuration, by performing high-loss control, the value of the maximum powertrain brake power is increased, and it is easy to increase the proportion of the powertrain brake torque in the brake torque applied to the wheels.

[0054] Preferably, the high-loss control is executed when the ambient temperature around the electric vehicle or a temperature linked to the ambient temperature is lower than a predetermined reference temperature and the rotating electric machine is in regenerative operation.

[0055] According to this configuration, when it is required to utilize more heat, the maximum powertrain braking power can be increased, and the heat generated at that time can be utilized effectively.

[0056] Preferably, the power train loss includes power consumption of auxiliary equipment, which is on-board equipment other than the rotating electrical machine and which receives power from the DC power supply.

[0057] By including the power consumed by on-board devices that use power supplied from a DC power supply, which is the power source for the vehicle drive system, in the powertrain loss, it becomes easier to reduce the proportion of braking torque applied to the wheels that is borne by the friction brakes.This makes it easier to effectively utilize the heat generated within the vehicle while suppressing a decrease in the energy efficiency of the entire vehicle. [Explanation of symbols]

[0058] 1: Integrated control device 2: Rotating electric machine 3: Inverter 4: Rotating electric machine control device (vehicle control device) 5: Power transmission mechanism 6:DC power supply 7: Brake control device 8: Vehicle drive unit 9: Wheels 71: Brake device (friction brake) 100: Auxiliary BT: Brake torque BTpt: Powertrain brake torque BTptx: Maximum powertrain brake torque Ploss: Powertrain loss Pmg: Maximum regenerative power (maximum powertrain brake power) Bmnp: Charging possible power ω: rotation speed

Claims

1. A vehicle control device that controls at least a vehicle drive device including an AC rotating electric machine that serves as a drive power source for wheels of an electric vehicle, an inverter that is disposed between a DC power source and the rotating electric machine and converts power between DC and multi-phase AC, and a power transmission mechanism that transmits power between the rotating electric machine and the wheels, calculating a maximum powertrain brake power, which is a maximum value of brake power in the vehicle drive device, based on a chargeable electric energy amount of the DC power supply and a powertrain loss including at least a mechanical loss and an electrical loss in the rotating electric machine, the power transmission mechanism, and the inverter; calculating a maximum powertrain brake torque, which is a maximum value of a brake torque by the vehicle drive device, based on the maximum powertrain brake power and the rotational speed of the rotating electric machine; A control device for a vehicle that provides the maximum powertrain braking torque to a brake control device that controls friction brakes on the wheels.

2. 2. The vehicle control device according to claim 1, wherein the powertrain loss includes a loss that occurs when switching control of the inverter is performed by high-loss control that has a larger loss than normal control that is normal control when running the electric vehicle.

3. 3. The vehicle control device according to claim 2, wherein the high-loss control is executed when an outside air temperature around the electric vehicle or a temperature linked to the outside air temperature is lower than a predetermined reference temperature and the rotating electric machine is performing a regenerative operation.

4. The vehicle control device according to claim 1 , wherein the powertrain loss includes power consumption of an auxiliary device that is an on-board device separate from the rotating electric machine and that receives power from the DC power supply.

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