JP2012091728A - Plug-in hybrid electric vehicle and control method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To strike a balance between the antifreezing of urea aqueous solution as a reducing agent for exhaust purification and securing the charging amount of a battery under situation that electric energy which can charge per unit time is restricted in a plug-in hybrid electric vehicle.SOLUTION: The plug-in hybrid electric vehicle (1) includes: a means (24) to heat the urea aqueous solution as the reducing agent; a means (17) to detect outside air temperature; a means (26) to detect a charged amount of a battery (11); a means (26) to determine a charged mode of a battery (11); and a means (26) to operate a heating means, when outside air temperature is under a predetermined temperature, and when the charged amount of the battery is less than a predetermined charged amount and a first charging mode (normal charging mode) is chosen, while switching the charging mode to the second charging mode (quick charging mode).

Description

  The present invention relates to a plug-in hybrid electric vehicle that can be driven by power output from at least one of an internal combustion engine and an electric motor that can be driven by using electric power stored in a battery that can be charged from an external power source, and the plug-in hybrid electric The present invention relates to the technical field of automobile control methods.

  2. Description of the Related Art In recent years, a plug-in hybrid electric vehicle that can run using at least one of an internal combustion engine and an electric motor as motive power and can charge a battery from an external power source has attracted attention. In a plug-in hybrid electric vehicle, the electric power supplied from an external power source is stored in a battery, and the electric power stored in the battery is driven to drive the motor, thereby suppressing the fuel consumption of the internal combustion engine, An improvement in fuel consumption efficiency is achieved.

  When a plug-in hybrid electric vehicle is used in a low-temperature environment such as a cold region, a block heater that can be operated with electric power is provided in the internal combustion engine in order to ensure the startability of the internal combustion engine, and the internal combustion engine is warmed up at the time of starting. It is known. For example, in Patent Document 1, when it is determined that warming up of the internal combustion engine is necessary, the power supplied from the external power source is preferentially used for the operation of the block heater rather than the battery charging or the pre-air conditioning operation. A technique for ensuring startability of an internal combustion engine is disclosed.

JP 2009-274470 A

  Here, the exhaust passage of the internal combustion engine is provided with a selective reduction catalyst system (hereinafter referred to as “urea SCR system”) that uses an aqueous urea solution as a reducing agent in order to purify nitrogen oxides contained in the exhaust gas. May be. In a urea SCR system, an exhaust nozzle is provided upstream of a selective reduction type NOx catalyst (hereinafter referred to as “SCR catalyst”) provided in an exhaust passage of an internal combustion engine, and an aqueous urea solution is injected from the injection nozzle to exhaust gas. Aqueous urea solution is supplied. The supplied urea aqueous solution is hydrolyzed to generate ammonia, and the ammonia reduces nitrogen oxides contained in the exhaust gas into harmless nitrogen and water in the SCR catalyst.

  In the urea SCR system, a urea aqueous solution as a reducing agent is stored in a storage tank in advance. Technology in which when a plug-in hybrid electric vehicle equipped with a urea SCR system is in a low-temperature environment, the urea aqueous solution stored in the storage tank freezes, making it impossible to inject from the injection nozzle, and the exhaust purification capability significantly decreases. There is a problem. As a solution to such a problem, a heater that can be operated by electric power supplied from an external power source is installed in the storage tank, such as the block heater for warming up the internal combustion engine described above, and the urea aqueous solution in the storage tank is removed. It is effective to prevent freezing by heating.

  However, in Patent Document 1, the power supplied from the external power source is always used preferentially for the operation of the block heater over the battery charging or the pre-air-conditioning operation. May be insufficient. Therefore, if the technique of Patent Document 1 is applied as it is to a heater for preventing freezing of an aqueous urea solution, there is a risk that such a shortage of battery charge will occur. In this case, by using the electric power charged in the battery from the external power source, it becomes impossible to make use of the merit of the plug-in hybrid electric vehicle that suppresses the fuel consumption of the internal combustion engine.

  In plug-in hybrid electric vehicles, when charging a battery from an external power supply, the normal charge mode has a small amount of power that can be charged per unit time, and the power that can be charged per unit time compared to the normal charge mode. There is one that can select a quick charge mode with a large amount. When the quick charge mode is selected as the charge mode, the amount of electric power that can be supplied from the external power source is large, so that the battery can be charged while operating the heater for preventing the urea aqueous solution from freezing. However, when the normal charging mode is selected as the charging mode, the amount of electric power that can be supplied from the external power source is small. Therefore, when the heater is operated to prevent the urea aqueous solution from freezing, the battery is sufficiently charged. This makes it more likely that the above-described battery charge shortage will occur more easily.

  The present invention has been made in view of the above-described problems. Even in a situation where the amount of power that can be charged per unit time is limited, freezing of the reducing agent for exhaust purification and the amount of charge of the battery can be prevented. It is an object of the present invention to provide a plug-in hybrid electric vehicle that can be secured and a method for controlling the plug-in hybrid electric vehicle.

  In order to solve the above-described problems, the plug-in hybrid electric vehicle of the present invention is driven by power output from at least one of an internal combustion engine and an electric motor that can be driven using power stored in a battery that can be charged from an external power source as a power source. In a plug-in hybrid electric vehicle that travels and can select a first charging mode and a second charging mode in which the amount of power that can be charged per unit time is larger than that in the first charging mode as the charging mode of the battery A urea water tank that stores a urea aqueous solution that is supplied as a reducing agent upstream of the urea reduction catalyst installed in the exhaust passage of the internal combustion engine, and a heating unit that heats the urea aqueous solution stored in the urea water tank; An outside air temperature detecting means for detecting an outside air temperature, a battery charge amount detecting means for detecting a charge amount of the battery, and the battery The charge mode determination means for determining which of the first charge mode and the second charge mode is selected as the battery charge mode, and the outside air temperature detected by the outside air temperature detection means is less than a predetermined temperature If the charge amount detected by the battery charge amount detection means is less than a predetermined charge amount, and the charge mode determination means determines that the first charge mode is selected. Comprises a control means for switching the charging mode of the battery from the first charging mode to the second charging mode and operating the heating means.

  According to the present invention, when it is necessary to prevent the aqueous urea solution from being frozen because the outside air temperature is lower than the predetermined temperature, the battery charge amount is small and the amount of power that can be charged per unit time is small. When the charging mode is selected, the charging mode is switched from the first charging mode to the second charging mode. In the second charging mode, the amount of electric power that can be charged per unit time is larger than that in the first charging mode. Therefore, it is possible to charge the battery while operating the heater to prevent the urea aqueous solution from freezing. Become. This makes it possible to achieve both prevention of freezing of the reducing agent for exhaust purification and securing of the charge amount of the battery even in a situation where a charge mode with a small amount of power that can be charged per unit time is set.

  In one aspect of the plug-in hybrid electric vehicle of the present invention, the control unit stops charging the battery when the charge amount detected by the battery charge amount detection unit is equal to or greater than the predetermined charge amount. It is characterized by.

  According to this aspect, since the charging to the battery is stopped when the charging amount of the battery becomes equal to or higher than the predetermined charging amount, it is possible to prevent the battery life from being shortened by overcharging the battery. Also, when the battery charge amount is greater than or equal to the predetermined charge amount, it is assumed that the battery charge amount has already been sufficiently secured, and the power supplied from the external power source can be used exclusively for the operation of the heating means. By means, it is possible to more quickly prevent the urea aqueous solution from freezing.

  In another aspect of the plug-in hybrid electric vehicle of the present invention, according to the time measuring means for measuring the elapsed time from the time when the heating means started operation, the outside air temperature detected by the outside air temperature detecting means, An operation continuation period setting means for setting an operation continuation period for continuously operating the heating means, and the control means sets the elapsed time measured by the time measurement means by the operation continuation period setting means. When the operation continuation period is reached, the operation of the heating means is stopped for a predetermined period.

  According to this aspect, the heating unit performs a so-called interval operation in which an operation pattern of being stopped for a predetermined period after being operated for the operation duration set by the operation duration setting unit is repeated. In the predetermined period in which the heating means is stopped, the electric power supplied from the external power source can be used exclusively for charging the battery, so that the reducing agent can be prevented from freezing for exhaust purification. Here, the operation duration setting means sets the operation duration according to the outside air temperature. For example, the temperature of the urea aqueous solution also decreases as the outside air temperature decreases, so that the operation continuation period is set longer, and the temperature of the urea aqueous solution increases as the outside air temperature increases, so the operation continuation period may be set short.

  In order to solve the above problems, a control method for a plug-in hybrid electric vehicle of the present invention is output from at least one of an internal combustion engine and an electric motor that can be driven by using electric power stored in a battery that can be charged from an external power source as a power source. A urea water tank that stores a urea aqueous solution that is supplied as a reducing agent upstream of the urea reduction catalyst installed in the exhaust passage of the internal combustion engine, and a urea aqueous solution that is stored in the urea water tank. Heating means for heating, and the charging mode of the battery can be selected from a first charging mode and a second charging mode in which the amount of electric power that can be charged per unit time is larger than in the first charging mode. In a control method for a plug-in hybrid electric vehicle, an outside air temperature detecting step for detecting an outside air temperature, and a battery for detecting a charge amount of the battery A charge amount detection step; a charge mode determination step for determining which of the first charge mode and the second charge mode is selected as a charge mode of the battery; and the detected outside air temperature is predetermined. When it is determined that the detected charge amount is less than a predetermined charge amount and the first charge mode is selected when the temperature is less than the temperature, the charge mode of the battery is changed to the first charge mode. And a control step of operating the heating means while switching from the first charging mode to the second charging mode.

  According to the control method of the plug-in hybrid electric vehicle of the present invention, the above-described plug-in hybrid electric vehicle (including the above-described various aspects) is preferably realized, thereby preventing the reducing agent from freezing and purifying the battery. The amount of charge can be secured at the same time.

  According to the present invention, when it is necessary to prevent the aqueous urea solution from being frozen because the outside air temperature is lower than the predetermined temperature, the battery charge amount is small and the amount of power that can be charged per unit time is small. When the charging mode is selected, the charging mode is switched from the first charging mode to the second charging mode. In the second charging mode, the amount of electric power that can be charged per unit time is larger than that in the first charging mode. Therefore, it is possible to charge the battery while operating the heater to prevent the urea aqueous solution from freezing. Become. This makes it possible to achieve both prevention of freezing of the reducing agent for exhaust purification and securing of the charge amount of the battery even in a situation where a charge mode with a small amount of power that can be charged per unit time is set.

1 is a block diagram conceptually showing an overall configuration of a plug-in hybrid electric vehicle according to an embodiment. It is a flowchart figure which shows the basic flow of urea water freezing prevention control. It is a flowchart figure which shows the detailed control content of urea water freezing prevention control shown in FIG. It is a graph which shows the correspondence of an operation continuation period and external temperature.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Not too much.

  First, the overall configuration of the plug-in hybrid electric vehicle according to the present embodiment will be described with reference to FIG. FIG. 1 is a block diagram conceptually showing the overall configuration of the plug-in hybrid electric vehicle.

  The plug-in hybrid electric vehicle 1 is a parallel plug-in hybrid electric vehicle, and an input shaft of the clutch 3 is connected to an output shaft of a diesel engine 2 (hereinafter referred to as “engine 2”). Further, the input shaft of the transmission 5 is connected to the motor 4 through the rotation shaft. Left and right drive wheels 9 are connected to the output shaft of the transmission 5 via a propeller shaft 6, a differential 7 and a drive shaft 8.

  The engine 2 is an internal combustion engine that functions as one of the power sources of the plug-in hybrid electric vehicle 1. The engine 2 is a diesel engine. For example, by reciprocating the air at high temperature and injecting fuel in the combustion chamber, the reciprocating motion of the piston caused by the explosive force by combustion using spontaneous ignition can be converted into the rotational motion of the output shaft. It is configured to be possible.

  The clutch 3 is provided between the output shaft of the engine 2 and the rotating shaft of the motor 4, and is a power transmission mechanism configured to be able to switch these mechanical connection states. When the clutch 3 is connected, since the output shaft of the engine 2 is mechanically connected to the rotation shaft of the motor 4, the drive wheel 9 is connected to both the output shaft of the engine 2 and the rotation shaft of the motor 4. It will be. On the other hand, when the clutch 3 is disengaged, the output shaft of the engine 2 is mechanically disconnected from the rotating shaft of the motor 4, so that only the rotating shaft of the motor 4 is connected to the drive wheel 9 via the transmission 5. Will be connected.

  The motor 4 functions as one of the power sources of the plug-in hybrid electric vehicle 1 by rotating using electric power stored in the battery 11 during power running, and generates electric power for charging the battery 11 during regeneration. It is an electric motor that functions as a generator.

  The transmission 5 is a transmission that converts power output from the engine 2 and the motor 4 and transmits the power to the left and right drive wheels 9 via the propeller shaft 6, the differential device 7, and the drive shaft 8. Note that the transmission ratio of the transmission 5 may be variable stepwise or continuously.

  The battery 11 is a rechargeable storage battery that functions as a power supply source for powering the motor 4. Direct current power is stored in the battery 11, and the direct current power is AC converted by the inverter 10 and then supplied to the motor 4. On the other hand, the battery 11 can be charged using electric power from an external power source 14 provided outside the vehicle or electric power generated during regeneration of the motor 4. When the battery 11 is charged using the external power source 14, charging power can be taken in by connecting the charging connector 13 connected to the charger 12 to the external power source 14. Further, the electric power generated during regeneration of the motor 4 is DC-converted by the inverter 10 and then charged by being supplied to the battery 11.

  When the clutch 3 is in the connected state, the output shaft of the engine 2 is mechanically connected to the rotating shaft of the motor 4, so that the drive wheel 9 is connected to both the output shaft of the engine 2 and the rotating shaft of the motor 4. . In this case, when the motor 4 is powered, both the output torque of the engine 2 and the output torque of the motor 4 are transmitted to the drive wheels 9 via the transmission 5. That is, a part of the torque for driving the drive wheels 9 is supplied from the engine 2 and the rest is supplied from the motor 4. Further, when the charge amount of the battery 11 decreases during traveling, the motor 4 is driven using the remaining output torque of the engine 2 while driving the drive wheels 9 using a part of the output torque of the engine 2. The battery 11 can be charged by regenerative driving. On the other hand, when the plug-in hybrid electric vehicle 1 is braked, the motor 4 can be regeneratively driven to function as a generator and the battery 11 can be charged.

  When the clutch is disengaged (that is, when the clutch is not connected), the output shaft of the engine 2 is mechanically disconnected from the rotating shaft of the motor 4 and only the rotating shaft of the motor 4 is shifted to the drive wheels 9. It is mechanically connected via the machine 5. In this case, when the motor 4 is powered, the output torque of the engine 2 is not transmitted to the drive wheels 9 and only the output torque of the motor 4 is transmitted. In other words, the travel of the plug-in hybrid electric vehicle 1 is performed exclusively by driving the motor 4 using the electric power stored in the battery 11. On the other hand, when the plug-in hybrid electric vehicle 1 is braked, the motor 4 is regeneratively driven to function as a generator, and the battery 11 can be charged.

  An exhaust passage 19 of the engine 2 is provided with a diesel particulate filter (hereinafter referred to as DPF 20) and a urea SCR system 21 in order to purify the exhaust gas. The DPF 20 collects particulate matter (hereinafter referred to as PM) in the exhaust, and the urea SCR system 21 reduces the NOx contained in the exhaust by using an aqueous urea solution as a NOx reducing agent.

  The DPF 20 is an exhaust filter for collecting PM in the exhaust gas, and typically has a structure in which a ceramic filter carrier such as cordierite or SiC is accommodated in a metal housing. The DPF 20 is provided with a DPF regeneration device (not shown) for burning the accumulated PM in order to prevent clogging due to accumulation of PM in the exhaust gas and deterioration of the power performance of the engine 2 and the like. ing.

The urea SCR system 21 includes a urea water tank 22 for storing a urea aqueous solution as a NOx reducing agent, an introduction pipe 23 for introducing the urea aqueous solution into the exhaust passage 19, and urea provided at the tip of the introduction pipe 23 on the exhaust passage side. It includes a water addition nozzle (not shown), a heater 24 for preventing freezing of the urea aqueous solution stored in the urea water tank 22, and a selective reduction type NOx catalyst (hereinafter referred to as “SCR catalyst 25”). The NOx contained in the exhaust gas is decomposed into harmless N ₂ and H ₂ O by passing through the urea aqueous solution added (injected) to the exhaust passage 19 from the urea water addition nozzle, thereby purifying the exhaust gas. Done.

  The heater 24 is a heating unit that is installed in a urea water tank 22 in which a urea aqueous solution is stored, and can be operated (heated) by electric power stored in the battery 11 or electric power supplied from an external power source 14.

  The battery current sensor 15 and the battery voltage sensor 16 are sensors that can detect the current and voltage of the battery 11, respectively. The outside air temperature sensor 17 is a sensor that is installed at a predetermined position away from the urea water tank 22 and can detect the outside air temperature. The time counter 18 is a counter capable of measuring the elapsed time from the time when the operation of the heater 24 is started.

  The vehicle ECU 26 is a plug-in hybrid electric vehicle 1 based on information obtained from various sensors including an engine ECU 27, an inverter ECU 28, a battery ECU 29, a battery current sensor 15, a battery voltage sensor 16, an outside air temperature sensor 17, and a time counter 18. It is the electronic control unit comprised so that control of the whole operation | movement of this was possible. Specifically, the vehicle ECU 26 configures the plug-in hybrid electric vehicle 1 including the engine 2, the clutch 3, the motor 4, and the transmission 5 by transmitting and receiving control signals to and from the engine ECU 27, the inverter ECU 28, and the battery ECU 29. The operation state of each part to be controlled is controlled.

  The engine ECU 27 is an electronic control unit for performing various controls necessary for the operation of the engine 2. For example, fuel injection in the engine 2 is performed so that torque to be output from the engine 2 set by the vehicle ECU 26 can be output. Control the amount and injection timing.

  The inverter ECU 28 is an electronic control unit for performing various controls necessary for the operation of the inverter 10. For example, the inverter ECU 28 controls the inverter 10 so that torque to be output from the motor 4 set by the vehicle ECU 26 can be output. Thus, the motor 4 is controlled to be powered or regeneratively operated.

  The battery ECU 29 obtains information from the battery current sensor 15 and the battery voltage sensor 16 via the vehicle ECU 26 to obtain a charge amount (hereinafter referred to as “SOC” as appropriate) of the battery 11 and obtains the obtained SOC. Is transmitted to the vehicle ECU 26.

  The vehicle ECU 26, the engine ECU 27, the inverter ECU 28, and the battery ECU 29 described above are electronic control units each including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. In accordance with the control program stored in the program, various controls described later can be executed. The physical, mechanical and electrical configurations of these various controls are not limited to this.

  Particularly in this embodiment, when the battery 11 is charged using the external power source 14, the normal charge mode in which the amount of power that can be charged per unit time is small and the charge can be charged per unit time compared to the normal charge mode. The quick charge mode with a large amount of electric power can be selected. That is, the normal charging mode is an example of the “first charging mode” according to the present invention, and the quick charging mode is an example of the “second charging mode” according to the present invention.

  The charging mode is selected by operating the touch panel displayed on the monitor 30 by the user. Specifically, two touch icons corresponding to the normal charging mode and the quick charging mode are displayed on the monitor 30, and the charging mode is pressed by pressing the touch icon corresponding to the charging mode intended by the user. Can be selected. In the present embodiment, the description will be given assuming that the selection of the charging mode is performed via the monitor 30, but such a charging mode selection means is provided on the external power source 14 (for example, a desk lamp) side, for example. May be.

  In the plug-in hybrid electric vehicle 1 configured as above, the urea aqueous solution stored in the urea SCR system 21 is prevented from being frozen by executing the urea water freeze prevention control. Here, the basic flow of urea water freezing prevention control is demonstrated with reference to FIG. FIG. 2 is a flowchart showing the basic flow of urea water freezing prevention control.

  When the urea water freeze prevention control is executed, the vehicle ECU 26 first executes an outside air temperature determination process (step S100), and determines whether or not the urea aqueous solution freeze prevention process needs to be executed based on the outside air temperature. To do. Next, the vehicle ECU 26 determines whether or not charging is necessary based on the amount of charge of the battery of the plug-in hybrid electric vehicle 1 and the selected charging mode (step S200). Subsequently, the vehicle ECU 26 executes urea water freeze prevention processing according to the determination results in the outside air temperature determination processing and the battery charging processing (step S300).

  Next, with reference to FIG. 3, the detailed control content of the urea water freeze prevention control shown in FIG. 2 will be described. FIG. 3 is a flowchart showing the detailed control contents of the urea water freeze prevention control shown in FIG.

  First, in the outside air temperature determination process (step S100), the vehicle ECU 26 detects the outside air temperature T from the outside air temperature sensor 17 (step S101), and determines whether or not the detected outside air temperature T is lower than a predetermined temperature T1. (Step S102). Here, the predetermined temperature T1 is a threshold value defined as an outside air temperature at which the urea aqueous solution stored in the urea water tank 17 may be frozen. Since the typical freezing temperature of the urea aqueous solution is about −11 ° C., the predetermined temperature T1 may be set as the freezing temperature. However, more preferably, since the outside air temperature sensor 17 is installed at a position away from the urea water tank 22, there is little difference between the original temperature of the urea aqueous solution stored in the urea water tank 22 and the outside air temperature. There is a gap. Therefore, in consideration of the temperature gap, it is preferable to set the predetermined temperature T1 to a temperature (for example, −6 ° C. to −8 ° C.) slightly higher than the actual urea water freezing temperature.

  If the outside air temperature T is not lower than the predetermined temperature T1 (step S102: NO), the vehicle ECU 26 sets the heater 24 to be off and terminates the process (step S306), assuming that it is not necessary to prevent the urea aqueous solution from being frozen. On the other hand, when the outside air temperature T is lower than the predetermined temperature T1 (step S102: YES), the vehicle ECU 26 proceeds to the battery charging process (step S200), assuming that the urea aqueous solution needs to be prevented from freezing.

  In the battery charging process (step S200), the vehicle ECU 26 first determines whether or not the charge amount of the battery 11 is less than the predetermined charge amount SOC1 (step S201). Here, the predetermined charge amount SOC1 is a threshold value defined as a charge amount necessary for starting the plug-in hybrid electric vehicle 1. Specifically, the SOC value at the time of full charge of the battery 11 may be used as the predetermined charge amount SOC1, but when the time required to fully charge the battery 11 is expected to be long, at the time of full charge It is preferable to set a value smaller than the SOC value. In the present embodiment, a value that is 70% of the SOC value when the battery 11 is fully charged is set as the predetermined charge amount SOC1.

  When the charge amount of the battery 11 is less than the predetermined charge amount SOC1 (step S201: YES), the vehicle ECU 26 determines whether or not the charge mode selected by the user via the monitor 30 is the normal power mode (step). S202). When the charging mode is the normal charging mode (step S202: YES), the vehicle ECU 26 switches the charging mode from the normal charging mode to the quick charging mode (step S203), and starts charging the battery 11 (step S204). In the subsequent step S301, the urea aqueous solution stored in the urea water tank 22 is heated by turning on the heater 24 to prevent freezing. In the quick charge mode, the amount of electric power that can be charged per unit time is larger than that in the normal charge mode. Therefore, it is possible to charge the battery while operating the heater 24 to prevent the urea aqueous solution from freezing. This makes it possible to achieve both prevention of freezing of the urea aqueous solution and securing of the charge amount of the battery 11 even in a state where the normal charge mode with a small amount of power that can be charged per unit time is set.

  On the other hand, when the charge amount of the battery 11 is equal to or greater than the predetermined charge amount SOC1 (step S201: NO), the vehicle ECU 26 stops charging because the charge amount of the battery 11 is sufficient (step S205), and turns on the heater 24. (Step S301). As described above, when the charge amount of the battery 11 is sufficient, by stopping the charge, the battery 11 can be prevented from being overcharged and the life of the battery 11 can be extended.

  In the urea water freeze prevention process (step S300), the urea aqueous solution stored in the urea water tank 22 is heated by turning on the heater 24 to prevent freezing. First, the vehicle ECU 26 acquires an elapsed period t from the time point when the heater 24 is set to ON in step S301 (step S302), and the acquired elapsed period t is a preset operation continuation period t1. It is determined whether it is larger (step S303). The determination in step S303 is performed at predetermined intervals (typically according to a constant sampling frequency), and is repeated until the elapsed time t becomes greater than the operation duration t1.

  Here, the operation continuation period t1 used in step S303 is set depending on the outside air temperature T detected in step S101. FIG. 4 is a graph showing a correspondence relationship between the operation continuation period t1 and the outside air temperature T. As shown in FIG. 4, the operation continuation period t1 is set to become longer as the outside air temperature T decreases. This is because the temperature of the urea aqueous solution also decreases as the outside air temperature T decreases, so that it is necessary to provide a longer period for operating the heater 24 in order to prevent freezing.

  When the elapsed time t becomes longer than the operation continuation period t1 (step S303: YES), the vehicle ECU 26 turns off the heater 24 for a predetermined period t2 (step S304). As described above, since the urea aqueous solution in the urea tank 22 is heated by the heater 24, there is no fear of freezing at least temporarily, so the heater 24 stops for a predetermined period t2.

  The predetermined period t2 is set in advance as a constant value that does not depend on the outside air temperature T. Specifically, during the predetermined period t2, the temperature of the urea aqueous solution or the outside air temperature T at the time when the operation period t of the heater 24 reaches the operation continuation period t1 is concerned that the temperature of the urea aqueous solution may freeze again. It may be set as a period that is expected to decrease to the temperature. The predetermined period t2 can be set to depend on the outside air temperature T. In this case, it is preferable to set the predetermined period t2 in consideration of the balance with the operation continuation period t1. That is, the operation continuation period t1 and the predetermined period t2 can be set in a well-balanced manner so that the power supplied from the external power source 14 is not used extremely biased to either charge the battery 11 or the heater 24. preferable.

  After setting the heater 24 to OFF in step S304, the vehicle ECU 26 resets the elapsed time t counted by the time counter 18 (step S305) and returns the process (RETURN). Then, the above steps are executed again, and charging of the battery 11 and prevention of freezing of the urea aqueous solution by the heater 24 are repeatedly performed.

  According to the urea water freeze prevention control described above, even when the normal charge mode with a small amount of power that can be charged per unit time is selected, by switching to the quick charge mode, the urea aqueous solution is controlled. The battery 11 can be charged while operating the heater 24 to prevent freezing. This makes it possible to achieve both prevention of freezing of the urea aqueous solution and securing of the charge amount of the battery 11 even in a state where a charge mode with a small amount of power that can be charged per unit time is set.

  INDUSTRIAL APPLICABILITY The present invention can be used for, for example, a plug-in hybrid electric vehicle that can be driven by power output from at least one of an internal combustion engine and an electric motor that can be driven by using electric power stored in a battery that can be charged from an external power source. It is.

DESCRIPTION OF SYMBOLS 1 Plug-in hybrid electric vehicle 2 Engine 3 Clutch 4 Motor 5 Transmission 9 Drive wheel 11 Battery 14 External power supply 17 Outside temperature sensor 19 Exhaust passage 20 DPF
21 Urea SCR system 22 Urea water tank 24 Heater 26 Vehicle ECU
27 Engine ECU
28 Inverter ECU
29 Battery ECU

Claims (4)

The vehicle is driven by power output from at least one of an internal combustion engine and an electric motor that can be driven using a power source stored in a battery that can be charged from an external power source. In a plug-in hybrid electric vehicle capable of selecting a second charging mode in which the amount of power that can be charged per unit time is larger than that in the first charging mode,
A urea water tank for storing a urea aqueous solution supplied as a reducing agent to the upstream side of the urea reduction catalyst installed in the exhaust passage of the internal combustion engine;
Heating means for heating the urea aqueous solution stored in the urea water tank;
Outside temperature detecting means for detecting outside temperature;
Battery charge amount detecting means for detecting the charge amount of the battery;
Charging mode determination means for determining which of the first charging mode and the second charging mode is selected as the charging mode of the battery;
When the outside air temperature detected by the outside air temperature detection means is less than a predetermined temperature, the charge amount detected by the battery charge amount detection means is less than a predetermined charge amount, and the charge mode determination means causes the first charge amount to be detected. When it is determined that the first charging mode is selected, the charging mode of the battery is switched from the first charging mode to the second charging mode, and a control unit that operates the heating unit is provided. A plug-in hybrid electric vehicle characterized by comprising.   2. The plug-in hybrid according to claim 1, wherein the control unit stops charging the battery when a charge amount detected by the battery charge amount detection unit is equal to or greater than the predetermined charge amount. 3. Electric car. A time measuring means for measuring an elapsed time from the time when the heating means starts operating;
An operation continuation period setting means for setting an operation continuation period in which the heating means is continuously operated according to the outside air temperature detected by the outside air temperature detection means, and
The said control means stops the operation | movement of the said heating means for a predetermined period, when the elapsed time time-measured by the said time measuring means reaches the operation | movement continuation period set by the said operation continuation period setting means. Item 3. The plug-in hybrid electric vehicle according to Item 1 or 2. A urea reduction catalyst installed in the exhaust passage of the internal combustion engine is driven by power output from at least one of an internal combustion engine and an electric motor that can be driven by using electric power stored in a battery that can be charged from an external power source. A urea water tank for storing a urea aqueous solution supplied as a reducing agent to the upstream side; and a heating means for heating the urea aqueous solution stored in the urea water tank. In a control method for a plug-in hybrid electric vehicle capable of selecting a mode and a second charging mode in which the amount of power that can be charged per unit time is larger than that in the first charging mode,
An outside air temperature detecting step for detecting the outside air temperature;
A battery charge amount detecting step for detecting a charge amount of the battery;
A charging mode determination step for determining which of the first charging mode and the second charging mode is selected as the charging mode of the battery;
When the detected outside air temperature is less than a predetermined temperature, when it is determined that the detected charge amount is less than a predetermined charge amount and the first charge mode is selected, A control method for a plug-in hybrid electric vehicle, comprising: a control step of switching the charging mode of the battery from the first charging mode to the second charging mode and operating the heating means.

Images