JP4432999B2 - Hybrid electric vehicle - Google Patents

Description

  The present invention relates to a hybrid electric vehicle including an engine and a motor as drive sources.

  The hybrid electric vehicle includes a drive motor (electric motor) as a drive source in addition to the engine (internal combustion engine). The drive motor is an AC motor that is driven by an AC current. When the AC motor is driven by a DC current, a power conversion device such as an inverter is required. In the power conversion device such as an inverter, the drive motor performs power conversion for high power by switching at a high frequency, so that the power transistor may be heated. Accordingly, when controlling the drive motor, it is necessary to take measures to suppress heat generated in the power transistor.

  As one of measures for preventing heating, there is known a technique for suppressing heat generated in an inverter by reducing a carrier frequency of a PWM (pulse width modulation) signal, that is, a switching frequency of a power transistor. For example, when the motor speed is sufficiently low, the carrier frequency is reduced when the accelerator is stepped on with the side brake turned on when starting on a slope, or when the accelerator is stepped on while the wheel is hitting the vehicle stop. Thus, it is performed when it can be considered that it is locked by external force. In addition, a technique is known in which the temperature of the power transistor is detected and the carrier frequency is changed in accordance with the change in temperature to suppress heat generated in the inverter.

  Patent Document 1 includes a propulsion operation for retracting a train that has failed and stuck on a track with another train, a unit cut operation in which the failed unit is separated and operated with only the remaining units, and a low speed during car washing. A technique is disclosed in which a switching frequency is set low when switching from a normal operation mode to a special operation mode such as a constant speed operation to suppress loss of the switching element.

  Patent Document 2 discloses a technique in which an inverter device having a control board in a casing is provided with a temperature detection means on the control board and detects the ambient temperature in the casing to grasp the operation status of the inverter apparatus. ing.

JP-A-5-308704 JP 2003-324967 A

  By the way, the inverter provided in the hybrid electric vehicle has a limited mounting space, and therefore often has to be arranged in the vicinity of the engine. In addition, the inverter is often cooled by cooling water in order to suppress heating of the internal control board and the like. However, when the engine is left idling or running at a low speed after running on a high load such as on a hill, the cooling water temperature increases due to the influence of the high load running and the cooling efficiency of the inverter device decreases. Sometimes. Further, when the vehicle travels at a low speed, the cooling air taken into the engine room is reduced, so that the cooling effect of the inverter is lowered.

  An object of the present invention is to suppress heat generation of an inverter even when a hybrid electric vehicle travels at a high load and the engine is left in an idling state or continues to travel at a low speed.

A hybrid electric vehicle according to the present invention includes an engine and a motor as driving sources, and the engine is left in an idling state, and intermittently repeats an idling state operation period and an engine stop state rest period. In a hybrid electric vehicle that operates and generates electric power to the motor by the power of the engine during the operation period, a motor control unit that supplies a pulse modulation signal having a predetermined carrier frequency to an inverter connected to the motor. A motor control unit configured to set the carrier frequency of the inverter during the idle period lower than the carrier frequency of the inverter during the operation period when the engine is intermittently operated and the vehicle speed is lower than a predetermined threshold speed. And

  In one aspect of the hybrid electric vehicle according to the present invention, the motor control unit stops supplying the pulse modulation signal to the inverter during the pause period when the engine is intermittently operated and the vehicle speed is zero. It is characterized by that.

  In one aspect of the hybrid electric vehicle according to the present invention, the motor control unit sets the motor frequency lower than the carrier frequency of the inverter only when the load of the motor immediately before the engine performs intermittent operation is larger than a predetermined threshold. Alternatively, the supply of the pulse modulation signal to the inverter is stopped.

  According to the present invention, when the vehicle speed is smaller than the predetermined threshold speed, the hybrid electric vehicle is loaded at a high load by setting the carrier frequency of the inverter during the engine idle period to be lower than the carrier frequency of the inverter during the engine operation period. Even when the engine is left in an idling state after traveling or when traveling is continued at a low speed, heat generation of the inverter can be suppressed.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments that specifically show the best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram illustrating a schematic configuration of a hybrid electric vehicle 10 according to the present embodiment. The hybrid electric vehicle 10 is connected to an engine 22, a three-shaft power distribution mechanism 30 connected via a damper to a crankshaft 26 serving as an output shaft of the engine 22, and the power distribution mechanism 30. A motor MG1 capable of generating power, a motor MG2 connected to the power distribution mechanism 30 via a drive shaft 32, and a hybrid electronic control unit (hereinafter referred to as a hybrid ECU) 70 for controlling the entire power output apparatus. The drive shaft 32 transmits the power from the engine 22 and the motors MG1, MG2 to the drive wheels via the speed reducer 34 and the drive shaft 36.

  The engine 22 is an internal combustion engine that outputs power upon receiving a supply of hydrocarbon fuel such as gasoline or light oil from a fuel tank (not shown). The engine 22 performs operation control such as fuel injection control, ignition control, and intake air amount adjustment control by an engine electronic control unit (hereinafter referred to as an engine ECU) 24 that inputs signals from various sensors that detect the operation state of the engine 22. is recieving. The engine ECU 24 communicates with the hybrid ECU 70 and controls the operation of the engine 22 by a control signal from the hybrid ECU 70. Further, the engine ECU 24 outputs data relating to the operating state such as the engine speed of the engine 22 to the hybrid ECU 70 as necessary.

  The power distribution mechanism 30 appropriately divides the vehicle driving force for directly driving the driving wheels by the power of the engine 22 and the power generation driving force for operating the motor MG1 by the power of the engine 22 to generate power. A well-known planetary gear mechanism is provided. The power distribution mechanism 30 further includes a mechanism capable of transmitting rotation via the rotor shaft of the motor MG2 and the drive shaft 32.

  Both the motor MG1 and the motor MG2 are configured as well-known synchronous generator motors that can be driven by a three-phase alternating current as a generator and that can be driven as an electric motor. Communicate. The motors MG1, MG2 are both driven and controlled by a motor electronic control unit (hereinafter referred to as motor ECU) 40 via inverters 41, 42. The motor ECU 40 receives signals necessary for controlling the motors MG1 and MG2, such as signals from a rotational position detection sensor that detects the rotational position of the rotor of the motors MG1 and MG2, and motors MG1 and MG2 detected by a current sensor. The current applied to is input. Further, the motor ECU 40 outputs a switching signal (pulse width modulation signal) to the inverters 41 and 42. Motor ECU 40 includes motor speeds of motor MG1 and motor MG2 from each speed sensor for detecting the speeds of motor MG1 and motor MG2, and inverter currents I1 and I2, motor MG1 and motors input from current sensors to inverters 41 and 42. A torque command value that is a value of torque to be output from MG 2 is input from hybrid ECU 70, a carrier frequency is calculated, and a switching signal is output to inverters 41 and 42.

  The battery 50 is managed by a battery electronic control unit (hereinafter referred to as a battery ECU) 52. The battery ECU 52 is attached to a signal necessary for managing the battery 50, for example, a voltage between terminals from a voltage sensor installed between terminals of the battery 50, and a power line connected to an output terminal of the battery 50. The charge / discharge current from the current sensor, the battery temperature from the temperature sensor attached to the battery 50, and the like are input. Further, the battery ECU 52 calculates data relating to the state of the battery 50 based on each input signal as necessary, and outputs the data to the hybrid ECU 70 through communication. The battery ECU 52 also calculates the state of charge (SOC) based on the integrated value of the charge / discharge current detected by the current sensor in order to manage the battery 50.

  The hybrid ECU 70 receives an ignition signal from the ignition switch 80, an engine speed Rev of the engine 22 from the engine ECU 24, and the like via an input port. The hybrid ECU 70 further detects the shift position SP from the shift position sensor that detects the operation position of the shift lever, the accelerator opening Acc from the accelerator pedal position sensor that detects the depression amount of the accelerator pedal, and the depression amount of the brake pedal. The brake pedal position BP from the brake pedal position sensor and the vehicle speed V from the vehicle speed sensor are input via the input port. As described above, the hybrid ECU 70 is connected to the engine ECU 24, the motor ECU 40, and the battery ECU 52 via the communication port, and exchanges various control signals and data with the engine ECU 24, the motor ECU 40, and the battery ECU 52.

  In the present embodiment, when the hybrid electric vehicle 10 configured as described above is left in an idling state, the hybrid ECU 70 intermittently operates the engine 22 and drives the motor MG1 with the power of the engine 22. The battery 50 is charged intermittently. That is, the hybrid ECU 70 outputs a control signal to the engine ECU 24 and the motor ECU 40 so that the engine 22 performs intermittent operation in which the operation period and the rest period are alternately repeated. By charging the battery 50 during idling in this way, it is possible to prevent the motor MG1 from being driven due to insufficient charging of the battery 50 at the next start. However, when the hybrid electric vehicle is left in an idling state as described above after traveling at a high load such as on a slope, the temperature of the cooling water for cooling the inverters 41 and 42 is also increased due to the high load traveling. The cooling efficiency of the inverters 41 and 42 may decrease. Further, when the hybrid electric vehicle travels at a low speed, the cooling air taken into the engine room is reduced, so that the cooling effect of the inverters 41 and 42 is reduced.

  On the other hand, as the carrier frequency of the switching signal is higher, the inverters 41 and 42 are more stable in driving the motor and can suppress the generation of abnormal noise. However, the higher the carrier frequency, the easier the power transistors included in the inverters 41 and 42 are heated. In other words, the heating of the power transistor can be suppressed as the carrier frequency is lower. Therefore, when leaving the hybrid electric vehicle 10 in an idling state, it is conceivable to always set the carrier frequency low to suppress heating of the power transistor. However, as described above, during idling, the motor MG1 is driven and the battery 50 is charged. That is, if the carrier frequency is always set low when left in the idling state, there is a possibility that abnormal noise may be generated from the motor MG1 or the motor MG2 that is driven when the battery 50 is charged.

  Therefore, in the present embodiment, when the hybrid electric vehicle 10 is left in an idling state, the motor ECU 40 is connected to the inverters 41 and 42 while the engine 22 is at rest, that is, while the torque of the motor MG1 and the motor MG2 is zero. On the other hand, the heat generated in the inverters 41 and 42 is suppressed by setting the carrier frequency to be output low.

FIG. 2 shows a timing chart relating to the carrier frequency corresponding to the operating state of the engine 22 in the idling state. As shown in FIG. 2, the motor ECU 40 determines that the motor MG <b> 1 and the motor MG <b> 2 are not driven during the idling state in which the engine 22 performs intermittent operation, and the engine 22 is not driven. Set the carrier frequency lower than the operating period. More specifically, when the carrier frequency during the operation period of the engine 22 is set to 20 kHz, for example, the motor ECU 40 sets the carrier frequency during the idle period of the engine 22 to 10 kHz or 1 kHz, for example. 2A shows the ambient temperature (electronic component temperature inside the inverter) in the inverter 41 or the inverter 42 when the carrier frequency is set to 20 kHz in both the operation period and the rest period of the engine 22. (B) shows the ambient temperature (electronic component temperature inside the inverter) when the carrier frequency during the operation period of the engine 22 is 20 kHz and the carrier frequency during the idle period of the engine 22 is 10 kHz. (C) shows the ambient temperature (electronic component temperature inside the inverter) when the carrier frequency during the operation period of the engine 22 is 20 kHz and the carrier frequency during the idle period of the engine 22 is 1 kHz. That is, as shown in FIG. 2, it can be seen that the lower the carrier frequency during the idle period of the engine 22, the more the increase in the atmospheric temperature inside the inverter (the temperature of the electronic components inside the inverter) can be suppressed.

In the above embodiment, the example in which the carrier frequency is lowered during the idle period of the engine 22 has been described. However, for example, as shown in FIG. 3, the motor ECU 40 may turn off the switching signal, that is, prevent the switching signal from being output to the inverters 41 and 42 during the stop period of the engine 22. As a result, as shown in FIG. 3 (d), it is possible to suppress an increase in the atmospheric temperature inside the inverter (electronic component temperature inside the inverter) compared to when the switching signal is turned on also during the idle period of the engine 22. it can.

  As described above, the idling can be performed by lowering the carrier frequency of the switching signal input to the inverter or not inputting the switching signal to the inverter during the idling period of the engine 22 during idling where the inverter temperature rise is likely to occur. The temperature rise of the inverter at the time can be suppressed.

  Inverters mounted on hybrid electric vehicles are often placed in a high-temperature environment such as in the vicinity of an engine room due to space limitations. Therefore, there is a high possibility that the circuit included in the inverter is also high in temperature, and it is necessary to consider the heat resistance performance of the circuit. In order to improve the heat resistance performance, the circuit may be increased in size. However, according to the present embodiment, since the carrier frequency is set low or the switching signal is turned off during the idle period of the engine 22 during idling, the temperature rise inside the inverter can be suppressed. Therefore, there is no problem even if the heat resistance of the circuit provided in the inverter is lowered to some extent. Therefore, an increase in the size of the circuit for improving the heat resistance can be suppressed. Further, by setting the carrier frequency low during the idle period of the engine 22 in which the motor is not driven, or turning off the switching signal, it is possible to suppress abnormal noise that occurs when the motor rotates.

  In the above-described embodiment, an example in which the value of the carrier frequency is changed or the switching signal is turned off when the hybrid electric vehicle is idling, that is, when the engine 22 is intermittently operated while the vehicle is stopped has been described. . However, for example, the carrier frequency value may be changed or the switching signal may be turned off according to the vehicle speed while the engine 22 is intermittently operating. That is, the motor ECU 40 sets the carrier frequency low when the vehicle speed is smaller than the predetermined threshold speed during the pause period when the engine 22 is intermittently operated, and when the vehicle speed becomes zero, that is, the hybrid electric vehicle is When the vehicle stops, the switching signal may be turned off.

  Furthermore, in the above-described embodiment, an example has been described in which the carrier frequency is set low or the switching signal is turned off during the idle period when the engine 22 is intermittently operated, regardless of the traveling state immediately before shifting to the idling state. .

  However, it is preferable to suppress the heat generation of the inverter when the engine is left in an idling state or continued to travel at a low speed after traveling at a high load such as traveling on a slope. Therefore, the carrier frequency is set low or the switching signal is turned off during the idle period when the engine 22 is intermittently operated (idling state) immediately after the hybrid electric vehicle is traveling at a high load. May be. In this case, for example, the motor ECU 40 determines whether or not the load (torque or inverter current) of the motors MG1 and MG2 immediately before the engine 22 shifts to the intermittent operation (idling state) is larger than a predetermined threshold. Only in this case, the carrier frequency may be set low or the switching signal may be turned off during the pause period during intermittent operation of the engine 22.

It is a figure which shows the functional block of the hybrid electric vehicle which concerns on this embodiment. It is a figure which shows an example of the timing chart regarding the carrier frequency corresponding to the driving | running state of the engine in the idling state. It is a figure which shows an example of the timing chart regarding the switching signal corresponding to the driving | running state of the engine in the idling state.

Explanation of symbols

  10 Hybrid Electric Vehicle, 22 Engine, 24 Engine ECU, 26 Crankshaft, 30 Power Distribution Mechanism, 32 Drive Shaft, 34 Reducer, 36 Driveshaft, 40 Motor ECU, 41, 42 Inverter, 50 Battery, 52 Battery ECU, 70 Hybrid ECU, 80 ignition switch.

Claims (4)

An engine and a motor are provided as drive sources, and when the engine is left in an idling state, an intermittent operation in which an operation period in an idling state and a pause period in an engine stop state are alternately repeated is performed. In a hybrid electric vehicle that causes the motor to generate electric power using engine power,
A motor controller for supplying a pulse modulation signal having a predetermined carrier frequency to an inverter connected to the motor, wherein the engine is intermittently operated and a vehicle speed is lower than a predetermined threshold speed; A hybrid electric vehicle comprising: a motor control unit that sets a carrier frequency of an inverter lower than a carrier frequency of the inverter during the operation period. The hybrid electric vehicle according to claim 1,
The motor controller is
Wherein when the vehicle speed engine is in said intermittent operation is zero, stopping the supply of the pulse modulation signal to the inverter in the idle period,
A hybrid electric vehicle characterized by that. The hybrid electric vehicle according to claim 1 or 2,
The motor controller is
The engine load of the motor immediately before performing the intermittent operation in the case which has been left in an idling state is greater than a predetermined threshold value only, is set lower than the carrier frequency of the inverter, or the to the inverter Stop supplying the pulse modulation signal,
A hybrid electric vehicle characterized by that. An engine and a motor are provided as drive sources, and the control is performed when the vehicle is stopped and the engine is left in the idling operation so as to alternately repeat the operation period in the idling state and the rest period in the engine stop state , In a hybrid electric vehicle that causes the motor to generate power using the power of the engine during the operation period
A motor control unit for supplying a pulse modulation signal having a predetermined carrier frequency to an inverter connected to the motor, wherein a carrier frequency of the inverter in the idle period is lower than a carrier frequency of the inverter in the operation period A hybrid electric vehicle including a motor control unit to be set.

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