Control unit of vehicle

Abstract

To provide a control unit of a vehicle which can prevent traveling only by an engine as a power source due to over-voltage from being stopped.SOLUTION: A vehicle 10 comprises: an engine 12; an electric motor MG which is connected to the engine 12; a high-voltage battery 52; a low-voltage battery 56 which supplies an auxiliary machine 58 with electric power; and a DC / DC converter 54 which is disposed between the high-voltage battery 52 and the low-voltage battery 56. An electric control unit 90 controls the vehicle in which: (a) when the high-voltage battery 52 fails, a relay 60 is disconnected and the vehicle travels in a battery-less traveling mode; and (b) when an engine speed Ne is a determination value Ne_jdg or less in the battery-less traveling mode, the electric motor MG is brought into a regenerative state and counter electromotive force Vemf of the electric motor MG is stepped-down by the DC / DC converter 54 to charge the low-voltage battery 56, otherwise, the electric motor MG is brought into a non-regenerative state.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a control device for a vehicle that includes an engine, a generator connected to the engine, and a DC / DC converter provided between the generator and a high-voltage battery that can exchange power with the generator, and a low-voltage battery that supplies power to auxiliary equipment. [Background technology]

[0002] There are known control devices for vehicles that include an engine, a generator connected to the engine, and a DC / DC converter provided between the generator and a high-voltage battery that can exchange power with the generator and a low-voltage battery that supplies power to auxiliary equipment. For example, the control device described in Patent Document 1 controls the amount of power generation by adjusting the regenerative torque generated by the generator connected to the engine. In other words, the power generation voltage of the generator is controlled to a predetermined target value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2021-180587 Summary of the Invention [Problem to be solved by the invention]

[0004] In the control device described in Patent Document 1, if the high-voltage battery fails, the vehicle travels using only the engine as a power source. In this case, if the regenerative torque of the generator is not adjusted, the voltage generated by the generator will depend on its rotational speed. As a result, when the engine rotational speed is high, the generator rotational speed also increases, resulting in a high generated voltage. In this case, the step-down capability of the DC / DC converter that supplies charging current to the low-voltage battery may be insufficient compared to the amount of power generated by the generator, causing an overvoltage and potentially halting travel using only the engine as a power source.

[0005] The present invention has been made against the background of the above circumstances, and its purpose is to provide a vehicle control device that can prevent overvoltage from causing the vehicle to stop running when using only the engine as a power source for running. [Means for solving the problem]

[0006] The gist of the present invention is a control device for a vehicle that includes an engine, a generator connected to the engine, a high-voltage battery that can supply and receive power from the generator, a low-voltage battery that supplies power to accessories and has a lower voltage than the high-voltage battery, a DC / DC converter provided between the high-voltage battery and the low-voltage battery, and a relay that disconnects the generator and the high-voltage battery, wherein (a) when the high-voltage battery fails, the relay is disconnected and the vehicle is driven using only the engine as a power source for driving, and (b) when driving using only the engine as a power source for driving, if the engine rotation speed is below a predetermined judgment value, the generator is put into a regenerative state and the voltage generated by the generator is reduced by the DC / DC converter to charge the low-voltage battery, and otherwise the generator is put into a non-regenerative state. [Effects of the Invention]

[0007] According to the present invention, (a) if the high-voltage battery fails, the relay is disconnected and the vehicle is driven using only the engine as a power source for traveling; (b) when the vehicle is driven using only the engine as a power source for traveling, if the engine rotation speed is equal to or lower than a predetermined threshold, the generator is put into a regenerative state and the voltage generated by the generator is stepped down by the DC / DC converter to charge the low-voltage battery; otherwise, the generator is put into a non-regenerative state. When the engine rotation speed is equal to or lower than the predetermined threshold, the low-voltage battery is charged, thereby preventing the vehicle from being unable to travel due to a drop in the battery voltage of the low-voltage battery. On the other hand, when the engine rotation speed exceeds the predetermined threshold, the generator is put into a non-regenerative state and no overvoltage occurs due to power generation by the generator, thereby preventing the vehicle from being unable to travel using only the engine as a power source for traveling. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic configuration diagram of a vehicle equipped with an electronic control device according to an embodiment of the present invention. [Figure 2] 2 is an explanatory diagram of a high-voltage battery, an inverter, an electric motor, a DC / DC converter, a low-voltage battery, and an electronic control device. FIG. [Figure 3] 3 is an example of a flowchart illustrating a main part of the control operation of the electronic control device. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings. In the drawings, the dimensions and shapes of the components are not necessarily accurately depicted, and the drawings are simplified or modified as appropriate. [Example]

[0010] 1 is a schematic diagram of a vehicle 10 equipped with an electronic control device 90 according to an embodiment of the present invention. The vehicle 10 includes, in order from the engine 12 side, a transmission 14 and a differential 16 in a power transmission path between an engine 12 and a pair of drive wheels 18, which are well-known components. The vehicle 10 also includes a belt transmission 40, an electric motor MG, an inverter 50, a high-voltage battery 52, a DC / DC converter 54, a low-voltage battery 56, accessories 58, a relay 60, and an air compressor AC, which are well-known components. The vehicle 10 also includes the electronic control device 90.

[0011] The engine 12 is a well-known internal combustion engine and is a power source for driving a pair of drive wheels 18 of the vehicle 10 .

[0012] The electric motor MG is a rotating electric machine that has at least the generator function of both the electric motor function and the generator function. The electric motor MG includes a stator (not shown) and a rotor (not shown). For example, in the electric motor MG, a stator coil Cs (see FIG. 2) is wound around the stator, and the rotor is provided with a surface magnet type or embedded magnet type permanent magnet and is wound with a rotor coil Cr (see FIG. 2). The electric motor MG corresponds to the "generator" in this invention.

[0013] The belt transmission 40 interconnects the engine 12, the electric motor MG, and the air compressor AC. The air compressor AC is a well-known air compressor. The belt transmission 40 is a well-known belt-type transmission device that includes a crank pulley 42 connected to the crankshaft 32 of the engine 12 so as not to rotate relative to the crankshaft 32, an electric motor pulley 44 connected to the rotor shaft 34, which is the rotating shaft of the rotor of the electric motor MG, so as not to rotate relative to the rotor, an AC pulley 46 connected to the drive shaft 36 of the air compressor AC so as not to rotate relative to the rotor, and a belt 48 wound around the crank pulley 42, the electric motor pulley 44, and the AC pulley 46.

[0014] The electric motor MG is connected to a high-voltage battery 52 via an inverter 50. The inverter 50 is a power supply circuit that converts direct current to alternating current and vice versa under the control of an electronic control device 90. The high-voltage battery 52 is used to supply power to the electric motor MG and to charge the generated power Wmg [W] of the electric motor MG. The high-voltage battery 52 is a battery that can exchange power with the electric motor MG. The low-voltage battery 56 is used to supply power to auxiliary devices 58. The auxiliary devices 58 include accessories such as headlamps, power window drive motors, a navigation system, an audio system, and an ETC (electronic toll collection system), all of which are not shown, as well as the electronic control device 90. Due to the difference in use, the low-voltage battery 56 has a lower voltage than the high-voltage battery 52. ​​Thus, the low-voltage battery 56 supplies power to the auxiliary devices 58 and has a lower voltage than the high-voltage battery 52.

[0015] The DC / DC converter 54 is a power supply circuit that is provided between the high-voltage battery 52 and the low-voltage battery 56 and that increases or decreases the voltage of direct current. For example, the DC / DC converter 54 decreases the voltage of direct current supplied from the high-voltage battery 52 or the inverter 50, and outputs direct current having a lower voltage than that of the high-voltage battery 52 to the low-voltage battery 56. The relay 60 is a switch that connects or disconnects the power supply between the high-voltage battery 52 and the inverter 50 and the DC / DC converter 54.

[0016] FIG. 2 is an explanatory diagram of the high-voltage battery 52, the inverter 50, the electric motor MG, the DC / DC converter 54, the low-voltage battery 56, and the electronic control device 90. As shown in FIG.

[0017] The inverter 50 includes a rotor coil control circuit 50a and a stator coil control circuit 50b.

[0018] The rotor coil control circuit 50a controls the excitation current Icr [A] of the rotor coil Cr. For example, the rotor coil control circuit 50a controls the excitation current Icr to a predetermined value using PWM control. As shown in FIG. 2, for example, the rotor coil control circuit 50a includes two pairs of switching elements connected in series between the positive and negative pole lines of the power line pair 62. A diode is connected in parallel to each switching element. The connection point between each pair of serially connected switching elements is connected to one terminal and the other terminal of the rotor coil Cr of the electric motor MG. A smoothing capacitor C1 is connected between the positive and negative pole lines of the power line pair 62.

[0019] The stator coil control circuit 50b is a circuit that controls the excitation current Ics [A] of the stator coil Cs. As shown in Fig. 2, for example, the stator coil control circuit 50b is provided with three pairs of switching elements connected in series between the positive and negative pole lines of the power line pair 62. A diode is connected in parallel to each switching element. The connection points of each pair of serially connected switching elements are connected to the connection terminals of the U-phase, V-phase, and W-phase of the stator coil Cs of the electric motor MG.

[0020] For example, in an excited state where the excitation current Icr is controlled to a predetermined magnitude, when the rotor is rotated, a rotating magnetic field is generated in which the magnetic flux from the permanent magnets and the magnetic flux from the electromagnets formed by the excitation current Icr rotate. For example, in a non-excited state where the excitation current Icr is set to zero, when the rotor is rotated, a rotating magnetic field is generated in which only the magnetic flux from the permanent magnets rotates. The magnetic flux from the electromagnets is configured to be significantly larger than the magnetic flux from the permanent magnets when the excitation current Icr is set to a predetermined magnitude. Therefore, in the excited state, a back electromotive force V emf [V] sufficient to supply the power required by the auxiliary equipment 58 is generated in the stator coil Cs, and the low-voltage battery 56 is charged by the DC / DC converter 54, placing the electric motor MG in a regenerative state. In the non-excitation state, a back electromotive force V emf sufficient to supply the power required by the auxiliary equipment 58 is not generated in the stator coil Cs, placing the electric motor MG in a non-regenerative state. The back electromotive force V emf corresponds to the "generated voltage" in this invention. In both the regenerative and non-regenerative states, all of the switching elements of the stator coil control circuit 50b are turned off.

[0021] For example, when a three-phase alternating current flows through the stator coil Cs, the rotor of the electric motor MG is rotated.

[0022] In the vehicle 10, for example, an engine driving mode in which only the engine 12 is used as a power source for driving, and an HEV driving mode in which both the engine 12 and the electric motor MG are used as power sources for driving, and an HEV (Hybrid Electric Vehicle) driving mode in which the vehicle is driven.

[0023] Here, the crank pulley 42 has a radius R1 [mm], the electric motor pulley 44 has a radius R2 [mm], and the value obtained by dividing the radius R2 by the radius R1 is the predetermined rotation ratio α (= R2 / R1) of the belt transmission device 40. In a state in which the electric motor MG is normally rotated by the engine 12 by the belt transmission device 40 (i.e., in a state in which the belt 48 is not bent, the belt 48 is not slipping relative to at least one of the crank pulley 42 and the electric motor pulley 44, and the tension of the belt 48 is not changing), the engine rotation speed Ne [rpm], which is the rotation speed of the engine 12, matches the product (= Nmg × α) of the electric motor rotation speed Nmg [rpm], which is the rotation speed of the electric motor MG, and the predetermined rotation ratio α.

[0024] The electronic control device 90 includes, for example, a so-called microcomputer, and executes various controls of the vehicle 10 by performing signal processing in accordance with pre-stored programs. The electronic control device 90 corresponds to the "control device" of the present invention. Various signals (e.g., engine rotation speed Ne, motor rotation speed Nmg, battery charge / discharge current Ibat [A], battery voltage Vbat [V], battery temperature THbat [°C] of the high-voltage battery 52, motor temperature THmg [°C] that is the temperature of the motor MG, converter temperature THcon [°C] that is the temperature of the DC / DC converter 54, accelerator pedal position θacc [%] that is the acceleration operation amount indicating the magnitude of the acceleration operation by the driver, vehicle speed V [km / h], etc.) are input to the electronic control device 90. The electronic control device 90 outputs various command signals (e.g., an engine control signal Se for controlling the engine 12, a shift control signal Stm for executing shift control of the transmission 14, an inverter control signal Sinv for controlling the inverter 50, a relay control signal Srly for controlling the opening and closing of the relay 60, a converter control signal Scon for controlling the voltage conversion of the DC / DC converter 54, etc.) to each device provided in the vehicle 10 (e.g., the engine 12, the transmission 14, the inverter 50, the relay 60, the DC / DC converter 54, etc.).

[0025] Next, we will explain the case where the high-voltage battery 52 fails and the vehicle is driven in battery-less driving mode. The "battery-less driving mode" is an engine driving mode in which the relay 60 is disconnected. Driving in battery-less driving mode corresponds to "driving using only the engine as the power source for driving" in this invention.

[0026] The electronic control device 90 determines whether or not there is a malfunction in the high-voltage battery 52. ​​For example, if the battery charge / discharge current Ibat, the battery voltage Vbat, or the battery temperature THbat is at a predetermined abnormal value, it is determined that there is a malfunction in the high-voltage battery 52.

[0027] When the electronic control unit 90 determines that the high-voltage battery 52 has failed, it controls the relay 60 to a disconnected state and drives the vehicle in a batteryless driving mode. When driving in this batteryless driving mode, the electronic control unit 90 controls the engine 12 and the transmission 14 so as to achieve a required driving torque Trdem [N·m] for the vehicle 10. The required driving torque Trdem is a driving torque that the driver requests for the vehicle 10. The required driving torque Trdem is calculated, for example, by applying the actual accelerator opening θacc and the actual vehicle speed V to a map in which the relationship between the accelerator opening θacc, the vehicle speed V, and the required driving torque Trdem is determined in advance experimentally or by design and stored.

[0028] When the vehicle is traveling in the batteryless traveling mode, the electronic control device 90 determines whether the engine rotation speed Ne exceeds a determination value Ne_jdg. The "determination value Ne_jdg" is an upper limit value of the engine rotation speed Ne that is predetermined experimentally or by design, at which the back electromotive force Vemf does not become an overvoltage even when the electric motor MG is in a regenerative state. The engine rotation speed Ne and the electric motor rotation speed Nmg can be converted into each other using a predetermined rotation ratio α. Therefore, "determining whether the engine rotation speed Ne exceeds the determination value Ne_jdg" is the same as "determining whether the electric motor rotation speed Nmg exceeds the quotient (=Ne_jdg / α) obtained by dividing the determination value Ne_jdg by the predetermined rotation ratio α." The "determination value Ne_jdg" corresponds to the "predetermined determination value" in this invention.

[0029] When the electronic control device 90 determines that the engine rotation speed Ne exceeds the determination value Ne_jdg, it places the electric motor MG in a non-regenerative state. Specifically, the electric motor MG is placed in a non-excitation state. When the electronic control device 90 determines that the engine rotation speed Ne is equal to or lower than the determination value Ne_jdg, it places the electric motor MG in a regenerative state. Specifically, the electric motor MG is placed in an excitation state.

[0030] When the electric motor MG is put into either the regenerative state or the non-regenerative state according to the engine rotation speed Ne, the electronic control device 90 determines whether or not it is acceptable to continue traveling in the batteryless traveling mode. For example, if the electric motor temperature THmg or the converter temperature THcon reaches a predetermined abnormal value, it is determined that traveling in the batteryless traveling mode cannot be continued.

[0031] Fig. 3 is an example of a flowchart illustrating the main control operations of the electronic control device 90. The flowchart in Fig. 3 is executed when the high-voltage battery 52 has failed.

[0032] First, in step S10 (hereinafter, "step" will be omitted), the relay 60 is controlled to a disconnected state, and in S20, it is determined whether the engine rotation speed Ne exceeds the determination value Ne_jdg. If the determination in S20 is YES, in S30, the electric motor MG is put into a non-regenerative state. If the determination in S20 is NO, in S40, the electric motor MG is put into a regenerative state. After both S30 and S40 are executed, in S50, it is determined whether or not it is acceptable to continue driving in the batteryless driving mode. If the determination in S50 is YES, S20 is executed again. If the determination in S50 is NO, the process ends.

[0033] According to this embodiment, (a) if the high-voltage battery 52 fails, the relay 60 is disconnected and the vehicle is driven in the batteryless driving mode; (b) during driving in the batteryless driving mode, if the engine rotation speed Ne is equal to or less than the determination value Ne_jdg, the electric motor MG is driven in the regenerative state and the back electromotive force Vemf of the electric motor MG is stepped down by the DC / DC converter 54 to charge the low-voltage battery 56; otherwise, the electric motor MG is driven in the non-regenerative state. When the engine rotation speed Ne is equal to or less than the determination value Ne_jdg, the low-voltage battery 56 is charged, thereby preventing the vehicle from being unable to drive due to a drop in the battery voltage Vbat of the low-voltage battery 56. On the other hand, when the engine rotation speed Ne exceeds the determination value Ne_jdg, the electric motor MG is driven in the non-regenerative state and no overvoltage occurs due to power generation by the electric motor MG, thereby preventing the vehicle from halting driving in the batteryless driving mode.

[0034] The above-described embodiments of the present invention are merely examples, and the present invention can be embodied in various forms with various modifications and improvements based on the knowledge of those skilled in the art without departing from the spirit of the present invention.

[0035] In the above-described embodiment, the belt transmission device 40 connects the engine 12, the electric motor MG, and the air compressor AC to one another. However, for example, the belt transmission device 40 may connect the engine 12 and the electric motor MG to one another but not the air compressor AC.

[0036] In the above-described embodiment, the electric motor MG has a rotor provided with a permanent magnet and wound with a rotor coil Cr, but the electric motor MG is not limited to this configuration. The electric motor MG may be of another configuration, such as a brushless synchronous generator, as long as it is configured to be controllable between an excited state, which is a regenerative state, and a non-excited state, which is a non-regenerative state. [Explanation of symbols]

[0037] 10: vehicle, 12: engine, 52: high-voltage battery, 54: DC / DC converter, 56: low-voltage battery, 58: auxiliary equipment, 60: relay, 90: electronic control device (control device), MG: electric motor (generator), Ne: engine rotation speed (engine rotation speed), Ne_jdg: judgment value (predetermined judgment value), Vemf: back electromotive force (generated voltage)

Claims

[Claim 1] A control device for a vehicle including an engine, a generator connected to the engine, a high-voltage battery capable of supplying and receiving electric power to and from the generator, a low-voltage battery that supplies electric power to an auxiliary device and has a lower voltage than the high-voltage battery, a DC / DC converter provided between the high-voltage battery and the low-voltage battery, and a relay that connects and disconnects the generator and the high-voltage battery, When the high-voltage battery fails, the relay is disconnected and the vehicle is driven using only the engine as a power source. When the vehicle is traveling using only the engine as a power source for traveling, if the rotation speed of the engine is equal to or lower than a predetermined judgment value, the generator is put into a regenerative state and the voltage generated by the generator is stepped down by the DC / DC converter to charge the low-voltage battery, and otherwise the generator is put into a non-regenerative state. A vehicle control device characterized by:

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