JP2009113581A - Exhaust emission control device for hybrid electric vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device for a hybrid electric vehicle, allowing improvement of exhaust emission control efficiency of an ammonia selective reduction type NOx catalyst without generating an ammonia slip at engine start-up of the series hybrid electric vehicle. <P>SOLUTION: The ammonia selective reduction type NOx catalyst 48 is interposed in an exhaust passage of an engine 2 loaded in the series hybrid electric vehicle 1, and an urea water injector 52 supplying urea water is provided on the upstream side thereof. The engine 2 is started or stopped according to a state of charge of a battery 8, the urea water injector 52 is controlled according to an operation state of the engine 2, and adsorption amount increase operation increasing an ammonia adsorption amount to the ammonia selective reduction type NOx catalyst 48 is performed over a prescribed period before the stop when stopping the engine 2. When newly starting the engine 2, a load and an engine speed of the engine 2 are gradually brought close to target values to slow a rise degree of exhaust emission temperature of the engine 2 down. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to an exhaust emission control device for an engine used in a hybrid electric vehicle. In particular, the engine is exclusively used for driving a generator, and the electric power generated by the generator is stored in a battery and is driven by a motor that operates with electric power supplied from the battery. The present invention relates to an exhaust emission control device for a series hybrid electric vehicle that drives a wheel.

Conventionally, the engine is used exclusively for driving the generator to store the generated power of the generator in the battery, and the battery power is supplied to the motor to drive the driving wheels of the vehicle by the driving force of the motor. Series hybrid electric vehicles have been developed and put into practical use.
In such a series hybrid electric vehicle, the engine is operated when the charging rate of the battery is reduced, and the battery is charged with the power generated by the generator driven by the engine. Then, the engine is stopped when the charging rate of the battery returns to the predetermined charging rate by the power generated by the generator.

  The engine used in the series hybrid electric vehicle can be operated in an operation region in which the pollutants contained in the exhaust gas are relatively small as compared with the case where the engine is one of driving power sources. Since exhaust gas still contains contaminants, an exhaust gas purification device for purifying the exhaust gas is used. Patent Document 1 proposes an exhaust gas purification apparatus for a hybrid electric vehicle in which exhaust gas is favorably purified by maintaining a catalyst provided in the exhaust gas purification apparatus at an appropriate temperature.

  Further, NOx (nitrogen oxide) which is one of the pollutants is contained in the exhaust of the engine. In order to purify the exhaust by reducing this NOx, the ammonia selective reduction type NOx is disposed in the exhaust passage of the engine. 2. Description of the Related Art An exhaust gas purification device in which a catalyst is disposed is known. Therefore, it is conceivable to use such an ammonia selective reduction type NOx catalyst also in the exhaust gas purification device of a hybrid electric vehicle.

  When an ammonia selective reduction type NOx catalyst is used in an exhaust purification device, in order to supply ammonia as a reducing agent to the ammonia selective reduction type NOx catalyst, urea water that is easier to handle than ammonia is supplied into the exhaust gas. In this case, urea water is injected into the exhaust gas using a urea water injector or the like. The atomized urea water supplied into the exhaust gas from the urea water injector is hydrolyzed by the heat of the exhaust gas, and the resulting ammonia is supplied to the ammonia selective reduction type NOx catalyst. The supplied ammonia is once adsorbed by the ammonia selective reduction type NOx catalyst, and the NOx reduction reaction between this ammonia and NOx in the exhaust is promoted by the NOx catalyst, whereby the NOx is reduced and the exhaust gas is purified.

  In the case of such an exhaust purification device equipped with an ammonia selective reduction type NOx catalyst, the temperature of the ammonia selective reduction type NOx catalyst and the urea water injector is low immediately after the start of the engine, and the injected urea water is well hydrolyzed in the exhaust gas. It cannot be disassembled. For this reason, it is necessary to stop the urea water injection from the urea water injector until the exhaust gas temperature rises to a certain temperature after the engine is started.

  However, if the supply of urea water is stopped until the temperature of the ammonia selective reduction NOx catalyst or urea water injector rises after the engine is started in this way, it is generated from the urea water while the supply of urea water is stopped. The selective reduction of NOx by the ammonia selective reduction type NOx catalyst using the reduced ammonia as a reducing agent is not performed, and there is a problem that the exhaust gas cannot be purified.

In particular, in the case of a series hybrid electric vehicle, since the operation and stop of the engine are repeated according to the state of charge of the battery as described above, the state where the exhaust cannot be purified by selectively reducing NOx is the engine start. This is repeated every time, and the exhaust gas purification efficiency of the ammonia selective reduction type NOx catalyst is greatly reduced.
Therefore, in order to solve such a problem, when the battery is fully charged and the engine is stopped, the ammonia adsorption amount to the ammonia selective reduction type NOx catalyst is increased over a predetermined period before the engine is stopped. The exhaust gas is purified by selectively reducing NOx in the exhaust gas using ammonia that has been adsorbed on the ammonia selective reduction type NOx catalyst until the urea water supply becomes possible from the urea water injector when the engine is started. It is possible to do.
JP 2005-248875 A

  However, the amount of ammonia that can be adsorbed on the ammonia selective reduction type NOx catalyst depends on the catalyst temperature of the ammonia selective reduction type NOx catalyst, and the amount of ammonia that can be adsorbed decreases as the catalyst temperature rises. For this reason, when the exhaust gas temperature rapidly rises after the engine is started, the amount of ammonia that can be adsorbed on the ammonia selective reduction type NOx catalyst also sharply decreases, and the amount of ammonia that has been adsorbed on the ammonia selective reduction type NOx catalyst so far May be less than In such a case, there is a problem that a part of the ammonia adsorbed on the ammonia selective reduction type NOx catalyst is released from the ammonia selective reduction type NOx catalyst and is released into the atmosphere as it is, so-called ammonia slip occurs. is there.

  The present invention has been made in view of such problems, and the object of the present invention is to provide an exhaust gas purification efficiency of an ammonia selective reduction type NOx catalyst without causing ammonia slip when starting an engine of a series hybrid electric vehicle. An object of the present invention is to provide an exhaust emission control device for a hybrid electric vehicle capable of improving the above.

  In order to achieve the above object, an exhaust emission control device for a hybrid electric vehicle according to the present invention uses an engine exclusively for driving a generator, stores electric power generated by the generator in a battery, and operates with electric power supplied from the battery. In an exhaust emission control device for a hybrid electric vehicle, in which driving wheels are driven by a motor that performs, an ammonia selective reduction type NOx catalyst that is interposed in the exhaust passage of the engine and selectively reduces NOx in the exhaust gas using ammonia as a reducing agent; A urea water supply means for supplying urea water into the exhaust gas upstream of the ammonia selective reduction type NOx catalyst, and the engine is started or stopped according to the state of charge of the battery. And controlling the engine with a target control amount of the urea water supply means according to the operating state of the engine. In the case of stopping the engine in operation, the adsorption amount that increases the adsorption amount of ammonia to the ammonia selective reduction type NOx catalyst over a predetermined period before the engine stop over the state before the predetermined period. Control means for stopping the engine after performing an increase operation, the control means, after starting the engine, the exhaust temperature of the engine when the control amount of the engine immediately becomes the target control amount The engine control amount is gradually brought close to the target control amount so that the exhaust gas temperature rises more slowly than the rise degree (Claim 1).

  According to the exhaust gas purification apparatus for a hybrid electric vehicle configured as described above, the engine is dedicated to driving the generator, and is controlled by the control means according to the state of charge of the battery for supplying power to the motor that drives the drive wheels. The engine is started or stopped. Further, the control means controls the engine with a predetermined target control amount during the operation of the engine, and also controls the urea water supply means according to the operating state of the engine, and the ammonia selective reduction type NOx catalyst is controlled from the urea water supply means. Urea water is supplied into the exhaust on the upstream side. The urea water supplied into the exhaust gas from the urea water supply means is hydrolyzed by the heat of the exhaust gas discharged from the engine, and the resulting ammonia is supplied to the ammonia selective reduction type NOx catalyst. The supplied ammonia is once adsorbed by the ammonia selective reduction type NOx catalyst, and the NOx reduction reaction between this ammonia and NOx in the exhaust is promoted by the NOx catalyst, whereby the NOx is reduced and the exhaust gas is purified.

  When the control means stops the engine, an adsorption amount increasing operation for increasing the adsorption amount of ammonia on the ammonia selective reduction type NOx catalyst over a predetermined period before the engine stop over the state before the predetermined period is performed. After doing so, stop the engine. As a result, the engine stops with a large amount of ammonia adsorbed on the ammonia selective reduction type NOx catalyst. When the engine is started again in accordance with the state of charge of the battery, the control means determines the degree of increase in the exhaust gas temperature more gradual than the degree of increase in the engine exhaust temperature when the engine control amount is immediately set to the target control amount. Thus, the engine control amount is gradually brought closer to the target control amount. At this time, due to the low temperature of the ammonia selective reduction type NOx catalyst, urea water supply means, etc., even if it is difficult to supply urea water from the urea water supply means, it is adsorbed to the ammonia selective reduction type NOx catalyst. Exhaust gas purification is performed by using a large amount of ammonia used for selective reduction of NOx in the exhaust gas.

Specifically, in the exhaust gas purification apparatus of the hybrid electric vehicle, the control means sets the target engine speed of the engine as the target control amount, starts the engine, and then sets the engine speed to the target engine speed. (Claim 2).
According to the exhaust gas purification apparatus for a hybrid electric vehicle configured as described above, when the engine is started, the control means gradually increases the engine speed toward the target speed that is the target control amount. As a result, the exhaust temperature of the engine rises at a gentler degree of increase than the degree of increase in the exhaust temperature of the engine when the engine speed is immediately increased to the target speed.

  Alternatively, in the exhaust gas purification apparatus of the hybrid electric vehicle, the control means sets the control amount of the engine when the generator generates target power as the target control amount, starts the engine, and then generates the generator The control amount of the engine is changed toward the target control amount so as to gradually increase the generated power to the target power (claim 3).

  According to the exhaust gas purification apparatus for a hybrid electric vehicle configured as described above, when the engine is started, the control means sets the engine control amount to the target power so that the generated power of the generator gradually increases toward the target power. Change toward the corresponding target control amount. As a result, the exhaust temperature of the engine rises at a gentler degree of increase than the degree of increase in the exhaust temperature of the engine when the power generated by the generator is immediately increased to the target power.

  Alternatively, the exhaust gas purification apparatus of the hybrid electric vehicle further includes catalyst temperature detection means for detecting the temperature of the ammonia selective reduction type NOx catalyst, and the control means is detected by the catalyst temperature detection means after starting the engine. Based on the obtained catalyst temperature, the maximum adsorption amount of ammonia that can be adsorbed on the ammonia selective reduction type NOx catalyst corresponding to the temperature of the ammonia selective reduction type NOx catalyst at that time is adsorbed on the ammonia selective reduction type NOx catalyst. The control amount of the engine is gradually brought close to the target control amount so that the exhaust temperature of the engine rises while maintaining a temperature that is equal to or higher than the amount of ammonia that is present (claim 4). .

  The maximum adsorption amount of ammonia that can be adsorbed on the ammonia selective reduction type NOx catalyst decreases as the catalyst temperature of the ammonia selective reduction type NOx catalyst increases. Therefore, according to the exhaust gas purification apparatus for a hybrid electric vehicle configured as described above, when the control unit starts the engine, based on the catalyst temperature detected by the catalyst temperature detection unit, the ammonia selective reduction type NOx catalyst at that time is controlled. While maintaining the temperature at which the maximum amount of ammonia that can be adsorbed to the ammonia selective reduction type NOx catalyst in accordance with the temperature is equal to or greater than the amount of ammonia that is adsorbed to the ammonia selective reduction type NOx catalyst, the exhaust temperature of the engine The engine control amount is gradually brought closer to the target control amount in order to increase the engine speed.

Further, in the exhaust gas purification apparatus for a hybrid electric vehicle, the temperature of the exhaust gas flowing into the ammonia selective reduction type NOx catalyst is reduced as compared with a state before the predetermined period during operation of the engine. The engine is controlled so as to perform the adsorption amount increasing operation (Claim 5).
According to the exhaust gas purification apparatus for a hybrid electric vehicle configured as described above, when the control unit performs the adsorption amount increasing operation, the exhaust gas flowing into the ammonia selective reduction type NOx catalyst is more than before the adsorption amount increasing operation. By reducing the temperature, the adsorption amount of ammonia on the ammonia selective reduction type NOx catalyst is increased.

According to the exhaust gas purification apparatus for a hybrid electric vehicle of the present invention, when the control unit stops the engine, the ammonia is selectively reduced by stopping the engine after performing the adsorption amount increasing operation over a predetermined period before stopping the engine. The engine stops with a large amount of ammonia adsorbed on the NOx catalyst.
When the engine is started again according to the state of charge of the battery, the control means causes the exhaust gas temperature to rise more slowly than the engine exhaust temperature rise when the engine control amount is immediately set as the target control amount. Furthermore, since the engine control amount is gradually brought closer to the target control amount, the decrease in the maximum ammonia adsorption amount that can be adsorbed on the ammonia selective reduction type NOx catalyst accompanying the increase in the exhaust gas temperature becomes moderate. For this reason, it is possible to prevent the actual ammonia adsorption amount that decreases with the selective reduction of NOx from exceeding the maximum adsorption amount of ammonia that decreases as the exhaust temperature rises. It is possible to prevent the occurrence of ammonia slip due to the rise in the temperature.

  Further, when the engine is restarted in this way, it is difficult to supply urea water from the urea water supply means due to the low temperatures of the ammonia selective reduction type NOx catalyst, urea water supply means, and the like. However, ammonia adsorbed on the ammonia selective reduction type NOx catalyst is used for selective reduction of NOx in the exhaust gas, and the exhaust gas is purified. Therefore, it is possible to prevent a decrease in the purification efficiency of the ammonia selective reduction type NOx catalyst while preventing the occurrence of ammonia slip after the engine is started.

  In order to mitigate the increase in the exhaust temperature at the time of starting the engine, the engine rotational speed gradually increases toward the target rotational speed that is the target control amount, as in the exhaust gas purification device for a hybrid electric vehicle according to claim 2. Or the engine control amount is set to a target control amount corresponding to the target power so that the generated power of the generator gradually increases toward the target power, as in the exhaust gas purification device of the hybrid electric vehicle according to claim 3. It can be easily realized by changing.

  According to the exhaust gas purification apparatus for a hybrid electric vehicle according to claim 4, the control means is based on the catalyst temperature detected by the catalyst temperature detection means and corresponds to the temperature of the ammonia selective reduction type NOx catalyst at that time. In order to increase the exhaust temperature of the engine while maintaining a temperature at which the maximum adsorption amount of ammonia that can be adsorbed on the selective reduction type NOx catalyst is equal to or greater than the amount of ammonia adsorbed on the selective ammonia reduction type catalyst, The control amount is gradually brought closer to the target control amount. Therefore, the exhaust gas temperature can be gradually increased so that the maximum ammonia adsorption amount decreases without falling below the actual ammonia adsorption amount that decreases due to the selective reduction of NOx in the ammonia selective reduction type NOx catalyst. Thus, it is possible to reliably prevent the occurrence of ammonia slip when starting the engine. Further, since it is not necessary to delay the exhaust temperature rise more than necessary, the exhaust temperature can be raised as early as possible to the temperature at which urea water can be supplied.

  According to the exhaust gas purification apparatus for a hybrid electric vehicle of claim 5, when the control means performs the adsorption amount increasing operation, the exhaust gas flowing into the ammonia selective reduction type NOx catalyst is more than before performing the adsorption amount increasing operation. By reducing the temperature, the adsorption amount of ammonia on the ammonia selective reduction type NOx catalyst is increased. The amount of ammonia that can be adsorbed to the ammonia selective reduction type NOx catalyst increases as the temperature of the ammonia selective reduction type NOx catalyst decreases. Therefore, by reducing the temperature of the exhaust gas flowing into the ammonia selective reduction type NOx catalyst, ammonia selection If the temperature of the reduced NOx catalyst is lowered, the amount of ammonia adsorbed on the ammonia selective reducing NOx catalyst can be increased.

  Therefore, it is possible to previously adsorb an amount of ammonia sufficient for the selective reduction of NOx performed before the urea water can be supplied after the engine start to the ammonia selective reduction type NOx catalyst. However, if the engine control amount is set to the target control amount immediately after the engine is started next time, ammonia slip easily occurs. However, as described above, the engine control amount is gradually increased to the target control amount. Thus, the rise in the exhaust gas temperature is mitigated and the occurrence of ammonia slip can be prevented. Thus, the temperature of the exhaust gas flowing into the ammonia selective reduction type NOx catalyst is lowered in this way by increasing the adsorption amount, and the ammonia selective reduction type NOx It is possible to obtain a further excellent effect that the amount of ammonia adsorbed on the catalyst can be increased.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an overall configuration diagram of a series-type hybrid electric vehicle 1 to which an exhaust emission control device according to an embodiment of the present invention is applied.
The output shaft of the engine 2, which is a diesel engine, is connected to the rotating shaft of the generator 4, and the output of the engine 2 is exclusively used for driving the generator 4. The power generated by the generator 4 driven by the engine 2 is stored in the battery 8 via the inverter 6. The inverter 6 adjusts the generated power of the generator 4 by controlling the current flowing between the generator 4 and the battery 8 so that the battery 8 is appropriately charged by the power supplied from the generator 4. . Further, the generator 4 operates as a motor when electric power is supplied from the battery 8 via the inverter 6 when the engine 2 is stopped, and also has a function of cranking the engine 2.

  On the other hand, the hybrid electric vehicle 1 is equipped with a motor 10 for traveling, and the output shaft of the motor 10 is connected to left and right drive wheels 18 via a speed reducer 12, a differential device 14 and a pair of drive shafts 16. It is connected. The electric power of the battery 8 is supplied to the motor 10 via the inverter 6, and the driving force transmitted from the motor 10 to the driving wheel 18 can be adjusted by adjusting the electric power supplied to the motor 10 by the inverter 6. It can be done.

  Further, at the time of vehicle braking, the motor 10 operates as a generator, and kinetic energy generated by the rotation of the drive wheels 18 is transmitted to the motor 10 and converted into AC power, thereby generating regenerative braking torque. Then, this AC power is converted into DC power by the inverter 6 and then charged to the battery 8, and the kinetic energy due to the rotation of the drive wheels 18 is recovered as electric energy.

  The HEV-ECU (control means) 20 indicates the operating state of the engine 2, the generator 4, the inverter 6, the motor 10 and the vehicle, the engine ECU (control means) 22 for controlling the engine 2, and the state of the battery 8. Information is collected from the battery ECU 24 or the like to be monitored, and based on these information, integrated control is performed while sending commands to the engine ECU 22 and the battery ECU 24 so that the engine 2, the generator 4, the inverter 6 and the motor 10 operate properly. .

  That is, the HEV-ECU 20 is connected to an accelerator opening sensor 28 that detects an operation amount of the accelerator pedal 26, and controls the inverter 6 according to the operation amount of the accelerator pedal 26 detected by the accelerator opening sensor 28. Thus, the driving force transmitted from the motor 10 to the driving wheels 18 is adjusted according to the driver's request. Further, the HEV-ECU 20 controls the regenerative braking force generated by the motor 10 by controlling the inverter 6 during vehicle braking and adjusting the power supplied from the motor 10 operating as a generator to the battery 8. Further, the HEV-ECU 20 sends a command to the engine ECU 22 to start the engine 2 and drive the generator 4 by the engine 2 when the battery 8 needs to be charged. The inverter 6 is controlled so that the battery 8 is appropriately charged by generating electric power.

  The engine ECU 22 is provided to perform overall operation control of the engine 2, and based on a command from the HEV-ECU 20, the generator 4 is driven to obtain generated power necessary for charging the battery 8 from the generator 4. The engine 2 is controlled for operation to adjust the fuel injection amount and injection timing of the engine 2, and various information obtained from the engine 2 is sent to the HEV-ECU 20.

Further, the battery ECU 24 detects the temperature and voltage of the battery 8, the current flowing between the inverter 6 and the battery 8, and the like, obtains the charging rate SOC of the battery 18 from these detection results, and HEV− together with the detection results. It is sent to ECU20.
When the driver depresses the accelerator pedal 26 in the hybrid electric vehicle 1 configured as described above, the HEV-ECU 20 detects the operation amount of the accelerator pedal 26 detected by the accelerator opening sensor 28 and the vehicle detected by a travel speed sensor (not shown). Based on the traveling speed, a driving torque to be transmitted to the driving wheel 18 is obtained, and the inverter 6 is controlled so that the motor 10 generates this driving torque. As a result, the electric power of the battery 8 is supplied to the motor 10 via the inverter 6, and the drive torque generated by the motor 10 is transmitted to the left and right drive wheels 18 via the speed reducer 12, the differential device 14 and the drive shaft 16. The vehicle runs.

Since the charging rate of the battery 8 gradually decreases due to the power supply to the motor 10, the HEV-ECU 20 responds to the charging rate SOC of the battery 8 sent from the battery ECU 24 in order to prevent the battery 8 from being overdischarged. Then, a command is sent to the engine ECU 22 to drive the generator 4 by operating the engine 2.
The engine ECU 22 controls the operation of the engine 2 in accordance with a command from the HEV-ECU 20, starts the engine 2 when the charging rate of the battery 8 decreases and needs to be charged, and drives the generator 4 by the engine 2. I do. At this time, the HEV-ECU 20 controls the inverter 6 so that the generated power of the predetermined target power is obtained by the generator 4 at the predetermined rotational speed, and in response to this, the engine ECU 22 sets the predetermined rotational speed as the target rotational speed. The engine 2 is controlled to operate. The predetermined rotational speed and the predetermined power at this time are determined in advance so that the rotational speed and load of the engine 2 corresponding thereto are in an operation region in which the concentration of NOx in the exhaust gas is minimized.

However, even if the operation control is performed in this way, the exhaust gas from the engine 2 still needs to be purified because the exhaust gas from the engine 2 still contains air pollutants such as NOx and particulates. Therefore, in the following, a configuration for purifying exhaust gas in the engine 2 will be described in detail based on FIG. 2 which is a system configuration diagram of the engine 2.
As shown in FIG. 2, the engine 2 supplies the engine body 30 with an engine body 30 that generates a driving force for driving the generator 4 by burning the fuel in the cylinder, and air for burning the fuel. And an exhaust pipe (exhaust passage) 34 for exhausting exhaust gas generated by the combustion of fuel.

  An exhaust aftertreatment device 36 for purifying exhaust exhausted from the engine body 30 is interposed in the exhaust pipe 34. The exhaust aftertreatment device 36 includes an upstream casing 38 and a downstream casing 42 that is communicated with the downstream side of the upstream casing 38 through a communication passage 40. A pre-stage oxidation catalyst 44 is accommodated in the upstream casing 38, and a particulate filter (hereinafter referred to as a filter) 46 is accommodated on the downstream side of the pre-stage oxidation catalyst 44. The filter 46 is provided for purifying the exhaust discharged from the engine body 30 by collecting particulates in the exhaust.

Since the pre-stage oxidation catalyst 44 oxidizes NO (nitrogen monoxide) in the exhaust gas to generate NO ₂ (nitrogen dioxide), the pre-stage oxidation catalyst 44 and the filter 46 are arranged in this manner, so that the filter 46 captures them. The collected particulates react with NO ₂ supplied from the pre-stage oxidation catalyst 44 to be oxidized, and the filter 46 is continuously regenerated.
On the other hand, an ammonia selective reduction type NOx catalyst (hereinafter referred to as an SCR catalyst) that adsorbs ammonia in the downstream casing 42 and selectively reduces NOx (nitrogen oxide) in the exhaust gas by using the adsorbed ammonia as a reducing agent to purify the exhaust gas. 48) and a downstream oxidation catalyst 50 for removing ammonia flowing out from the SCR catalyst 48 are accommodated downstream of the SCR catalyst 48. The post-stage oxidation catalyst 50 also has a function of oxidizing CO (carbon monoxide) generated when the particulates are incinerated by forced regeneration of the filter 46, which will be described later, and discharging it to the atmosphere as CO ₂ (carbon dioxide). is doing.

  The communication passage 40 is provided with a urea water injector (urea water supply means) 52 for injecting and supplying urea water into the exhaust gas in the communication passage 40. The urea water tank 56 storing urea water is not shown in the figure. The urea water is supplied to the urea water injector 52 via the urea water supply pump, and the urea water is injected from the urea water injector 52 into the exhaust gas in the communication passage 40 by opening and closing the urea water injector 52. Yes.

The mist-like urea water injected from the urea water injector 52 is hydrolyzed by the heat of the exhaust to become ammonia, and is supplied to the SCR catalyst 48. The SCR catalyst 48 once adsorbs the supplied ammonia, and promotes a denitration reaction between the adsorbed ammonia and NOx in the exhaust, thereby making NOx harmless N ₂ . At this time, when ammonia flows out of the SCR catalyst 48 without reacting with NOx, the ammonia is removed by the post-stage oxidation catalyst 50.

Further, an exhaust temperature sensor (catalyst temperature detection means) 54 for detecting the exhaust temperature is provided upstream of the SCR catalyst 48 in the downstream casing 42, and the exhaust temperature sensor 54 flows into the SCR catalyst 48. It is used to detect the temperature of the exhaust gas and estimate the catalyst temperature of the SCR catalyst 48.
The engine ECU 22 controls the engine main body 30 and the urea water injector 52 in response to a command from the HEV-ECU 20, and includes a CPU, a memory, a timer counter, and the like, and detects the rotational speed of the engine main body 30. Various control amounts such as the amount of fuel supplied to each cylinder of the engine body 30 and the amount of urea water supplied from the urea water injector 52 based on information from various sensors provided in the engine body 30 such as the rotational speed sensor 58 And various devices are controlled based on the control amount.

  In the engine 2 configured as described above, the charging rate of the battery 8 is reduced by supplying power to the motor 10, and the HEV-ECU 20 charges the battery 8 based on the charging rate SOC of the battery 8 detected by the battery ECU 24. When it is determined that it is necessary to start, the engine ECU 22 starts the engine. After startup, the engine ECU 22 controls the battery 8 so that the battery 8 is appropriately charged by the power generated by the generator 4 based on a command from the HEV-ECU 20.

  In order to properly maintain the charging rate of the battery 8 by driving the generator 4 by the engine 2 and charging the battery 8 by the power generated by the generator 4, the HEV-ECU 20 performs charge control according to the flowchart of FIG. It is repeatedly executed at a predetermined control cycle. This charging control is started when a start switch (not shown) provided in the passenger compartment of the hybrid electric vehicle 1 is turned on, and is ended when it is turned off.

When charging control is started by turning on the start switch, first, the HEV-ECU 20 determines whether or not the value of the flag F1 is 1 in step S101.
The flag F1 is used to switch between an operation mode of the engine 2 described later and a urea water supply mode by the urea water injector 52, and the HEV-ECU 20 sends the value of the flag F1 to the engine ECU 22. The engine ECU 22 is instructed for the operation mode of the engine 2 and the urea water supply mode. Specifically, when the value of the flag F1 is 0, it indicates that the operation mode of the engine 2 is the first operation mode and the urea water supply mode is the first supply mode, and the value of the flag F1 is 1 Is, the operation mode of the engine 2 is the second operation mode, and the urea water supply mode is the second supply mode. In the present embodiment, the state in which the engine 2 is operated in the second operation mode and the urea water is supplied from the urea water injector 52 in the second supply mode corresponds to the adsorption amount increasing operation of the present invention. Details of the first and second operation modes and the first and second supply modes will be described later.

Since the initial value of the flag F1 at the start of charging control is 0, the HEV-ECU 20 advances the process to step S102 based on the determination in step S101. In step S102, the HEV-ECU 20 determines whether or not the value of the flag F2 is 1.
This flag F2 indicates whether or not the battery 8 needs to be charged. When the charging rate of the battery 8 is reduced and charging is required, it is necessary to operate the engine 2 and drive the generator 4, so the HEV-ECU 20 sends the value of the flag F 2 to the engine ECU 22. Thus, the operation or stop of the engine 2 is commanded. Specifically, when the value of the flag F2 is 0, it indicates that charging of the battery 8 is not necessary, while when the value of the flag F2 is 1, it indicates that charging of the battery 8 is necessary.

Since the initial value of the flag F2 at the start of charging control is 0, the HEV-ECU 20 advances the process to step S103 based on the determination in step S102. In step S103, the HEV-ECU 20 determines whether or not the charging rate SOC of the battery 8 detected by the battery ECU 24 has fallen below a predetermined lower limit charging rate SL.
The lower limit charging rate SL is a determination value for determining whether or not the battery 8 needs to be charged. When the charging rate SOC of the battery 8 is not lower than the lower limit charging rate SL, the HEV-ECU 20 needs to be charged. After determining that the charging rate SOC of the battery 8 has not decreased, the control cycle is ended, and then the processing is started again from step S101 in the next control cycle.

  In the next control cycle, since the values of the flags F1 and F2 remain 0, the process proceeds to step S3 again through steps S101 and S102. Therefore, the HEV-ECU 20 repeats the processes of steps S101 to S103 unless the charging rate SOC of the battery 8 falls below the lower limit charging rate SL, and the discharging of the battery 8 proceeds, so that the charging rate SOC of the battery 8 becomes lower than the lower limit charging rate SL. If it falls, the process proceeds to step S104.

When the process proceeds to step S104, the charging rate SOC of the battery 8 is below the lower limit charging rate SL and the battery 8 needs to be charged. Therefore, the HEV-ECU 20 sets the value of the flag F2 indicating whether charging is necessary to 1 Then, the process proceeds to the next step S105.
In step S105, the HEV-ECU 20 determines whether or not the charging rate SOC of the battery 8 detected by the battery ECU 24 has reached a predetermined first upper limit charging rate SU1. When the charging rate SOC of the battery 8 has not reached the first upper limit charging rate SU1, the HEV-ECU 20 ends its control cycle and starts the process from step S101 again in the next control cycle.

  In the next control cycle, since the value of the flag F1 remains 0 while the value of the flag F2 is changed to 1, the process proceeds to steps S105 through steps S101 and S102, and the HEV-ECU 20 It is determined whether the charging rate SOC of 8 has reached a predetermined first upper limit charging rate SU1. Therefore, unless the charging rate SOC increases due to the charging of the battery 8 to reach the first upper limit charging rate SU1, the processes from step S101 to steps S102 and S105 are repeated.

  When the value of the flag F2 becomes 1, the engine 2 is started by engine operation control described later, and the power generated by the generator 4 driven by the engine 2 is charged in the battery 8. When the charging rate SOC of the battery 8 reaches the first upper limit charging rate SU1, the HEV-ECU 20 advances the process to step S106 according to the determination in step S105, sets the value of the flag F1 to 1, and then in the next step S107. It is determined whether or not the charging rate SOC of the battery 8 detected by the battery ECU 24 has reached a predetermined second upper limit charging rate SU2. The second upper limit charging rate SU2 is higher than the first upper limit charging rate SU1, and the HEV-ECU 20 determines that the charging rate SOC of the battery 8 has reached the second upper limit charging rate SU2 in step S107. By doing so, it is determined that the charging of the battery 8 has been completed. When the charging rate SOC of the battery 8 has not reached the second upper limit charging rate SU2, the HEV-ECU 20 ends its control cycle and starts the process from step S101 again in the next control cycle.

  In the next control cycle, since the value of the flag F1 has already been 1, the HEV-ECU 20 proceeds directly from step S101 to step S107, and the charge rate SOC of the battery 8 again reaches the second upper limit charge rate SU2. It is determined whether it has been reached. Therefore, as long as the charging of the battery 8 proceeds and the charging rate SOC does not increase and reach the second upper limit charging rate SU2, the processes of step S101 and step S107 are repeated.

  When charging of the battery 8 by the power generated by the generator 4 proceeds and the charging rate SOC of the battery 8 reaches the second upper limit charging rate SU2, the HEV-ECU 20 advances the process to step S108 based on the determination in step S107. In step S108, the HEV-ECU 20 resets the value of the flag F2 to 0 because it is no longer necessary to charge the battery 8, and also resets the value of the flag F1 to 0 in preparation for the next charging of the battery 8. End the control cycle. Therefore, after the next control cycle, the processes of steps S101 to S103 are repeated as described above until the charging rate SOC of the battery 8 decreases again and falls below the lower limit charging rate SL.

  As described above, when the HEV-ECU 20 executes the charge control and the charge rate SOC of the battery 8 decreases and falls below the lower limit charge rate SL, the value of the flag F2 is set to 1, and the engine operation described later is performed. The engine 2 is started by the control, and the battery 8 is charged by the generated power of the generator 4 driven by the engine 2. At this time, until the charging rate SOC of the battery 8 reaches the first upper limit charging rate SU1, the value of the flag F1 is set to 0, so that the operation of the engine 2 is performed in engine operation control and urea water supply control described later. The mode is the first operation mode, and the urea water supply mode from the urea water injector 52 is the first supply mode.

When the charging of the battery 8 proceeds and the charging rate SOC reaches the first upper limit charging rate SU1, the value of the flag F1 is set to 1, so that the operation of the engine 2 is performed in engine operation control and urea water supply control described later. The mode is the second operation mode, and the urea water supply mode from the urea water injector 52 is the second supply mode.
Further, when the charging of the battery 8 proceeds and the charging rate SOC reaches the second upper limit charging rate SU2, it is assumed that the charging of the battery 8 is completed, and the engine 2 is stopped in engine control and urea water supply control described later. The urea water supply from the urea water injector 52 is stopped.

  Therefore, after the engine 2 is started and charging of the battery 8 is started, the operation mode of the engine 2 designated by this charge control is the first period until the charging rate SOC reaches the first upper limit charging rate SU1. In addition to the operation mode, the urea water supply mode from the urea water injector 52 is the first supply mode. Further, during the period from when the charge rate SOC reaches the first upper limit charge rate SU1 to when the charge rate SOC further increases to reach the second upper limit charge rate SU2 and the engine 2 stops, the operation mode of the engine 2 is the second operation mode. And the urea water supply mode from the urea water injector 52 is the second supply mode.

  Next, engine operation control for controlling the operation of the engine 2 in accordance with the values of the flags F1 and F2 will be described in detail with reference to FIG. The engine operation control is started by turning on the start switch in the same manner as the charge control described above, and is executed by the HEV-ECU 20 at a predetermined control period in parallel with the charge control according to the flowchart shown in FIG. The engine operation control is also ended by turning off the start switch in the same manner as the charge control described above.

In this engine operation control, the HEV-ECU 20 instructs the engine ECU 22 to start and stop the engine 2 and switch the operation mode during operation of the engine 2 based on the values of the flags F1 and F2 set in the above-described charging control. Based on this command, the engine ECU 22 starts and stops the engine 2 and switches the operation mode.
When engine operation control is started by turning on the start switch, the HEV-ECU 20 determines whether or not the value of the flag F2 is 1 in step S201. The flag F2 indicates whether or not the battery 8 needs to be charged as described above, and the battery 8 needs to be charged when the charge rate SOC of the battery 8 falls below the lower limit charge rate SL in the charge control. The value is set to 1.

  Therefore, when the charge rate SOC of the battery 8 is not lower than the lower limit charge rate SL and the value of the flag F2 is set to 0 because it is not necessary to charge the battery 8 in the charge control, the generator 2 is turned on by the engine 2. Since it is not necessary to drive and generate electricity, the HEV-ECU 20 advances the process to step S202 based on the determination in step S201, and instructs the engine ECU 22 to stop the engine 2. Since the engine 2 is already in the stopped state, the engine ECU 22 receives the command from the HEV-ECU 20 and maintains the engine 2 in the stopped state.

  Further, the HEV-ECU 20 sets the value of the flag F3 to 0 in step S203 and sets the value of the flag F4 to 0 in step S204, and then ends the control cycle. This flag F3 indicates whether or not the engine 2 is in operation. When the value is 0, the engine 2 is in a stopped state, and when the value is 1, the engine 2 is in operation. Indicates that it is inside. The flag F4 indicates whether or not the engine 2 has completed the operation in the ramp mode, which will be described later, and when the value is 1, it indicates that the operation in the lamp mode has been completed.

  In the next control cycle, the HEV-ECU 20 starts the process again from step S201, and determines whether or not the value of the flag F2 is 1. Therefore, unless the charge rate SOC of the battery 8 is lower than the lower limit charge rate SL and the value of the flag F2 is set to 1 because it is necessary to charge the battery 8 in the charge control, the processes of steps S201 to S204 are repeated every control cycle. Accordingly, the engine 2 is maintained in a stopped state.

  When the charging rate SOC of the battery 8 is lower than the lower limit charging rate SL and the value of the flag F2 is set to 1 because charging of the battery 8 is necessary in the charging control, the HEV-ECU 20 makes a determination in step S201 in this engine operation control. The process proceeds to step S205, and it is determined whether or not the value of the flag F3 is 1. At this time, the engine 2 is still in a stopped state, and the value of the flag F3 is 0, so the HEV-ECU 20 advances the process to step S206 according to the determination in step S205.

  In step S206, the engine 2 is started. That is, the HEV-ECU 20 sends a command to the engine ECU 22 to start the engine 2 and controls the inverter 6 so that the generator 4 operates as a motor. In accordance with this, the engine ECU 22 starts supplying fuel to the engine 2 in order to start the engine 2 in accordance with a command from the HEV-ECU 20. Thus, the generator 2 operates as a motor to crank the engine 2 and the engine ECU 22 starts supplying fuel to the engine 2, whereby the engine 2 is started.

  When the start of the engine 2 is completed, the engine ECU 22 notifies the HEV-ECU 20 of information that the start of the engine 2 is completed. In response to this, the HEV-ECU 20 sends a control signal to the inverter 6 so as to end the motor operation of the generator 4, and then proceeds from step S206 to step S207. Since the engine 2 is in an operating state, the flag F3 The value of 1 is assumed to be 1.

The HEV-ECU 20 further proceeds to step S208, and determines whether or not the value of the flag F4 is 1. The flag F4 indicates whether or not the engine 2 has completed the operation in the ramp mode as described above. Since the engine 2 is not operated at the start of the engine operation control, the initial value of the flag F4 is set. Is 0.
When the HEV-ECU 20 advances the process to step S209 based on the determination in step S208, the HEV-ECU 20 instructs the engine ECU 22 to operate the engine 2 in the lamp mode, and changes the power generation amount of the generator 4 in accordance with the lamp mode operation of the engine 2. The inverter 6 is controlled so that

  In the operation of the engine 2 in this ramp mode, the rotational speed (control amount) of the engine 2 is gradually increased from the idle rotational speed after startup to a first target rotational speed (target control amount) N1 in a first operation mode described later. Accordingly, the load (control amount) of the engine 2 is also increased by gradually increasing the generated power of the generator 4 from 0 (watts) to the first target power corresponding to the first operation mode. It gradually increases toward the load (target control amount) when the engine 2 is operated in the first mode and the generator 4 generates the generated power of the first target power corresponding to the first operation mode. Go. The engine ECU 22 increases the amount of fuel supplied to the engine 2 in response to the increase in the rotational speed and the increase in the load.

  The first target generated electric power is generated when the generator 4 charges the battery 8 efficiently and exhausts the engine 2 under the first target rotational speed when the engine 2 is operated in the first operation mode. Is determined in advance as generated electric power that can reduce the concentration of NOx contained in the NOx as much as possible. Further, the degree of change in the rotational speed of the engine 2 and the generated power of the generator 4 is such that the generated power of the generator 4 reaches the first target power when the rotational speed of the engine 2 reaches the first target rotational speed. Each is predetermined.

  Therefore, when the process of step S209 is repeated for each control cycle, the engine ECU 22 receives the command from the HEV-ECU 20 and controls the engine 2 so that the engine 2 is continuously operated in the lamp mode, and the engine 2 The engine speed gradually increases from the idling engine speed toward the first target engine speed N1, the power generated by the generator 4 gradually increases toward the first target power, and the load on the engine 2 increases. Will go.

  When the process proceeds to the next step S210, the HEV-ECU 20 determines whether or not the rotational speed Ne of the engine 2 detected by the rotational speed sensor 58 has reached the first target rotational speed N1. When the rotational speed Ne of the engine 2 has not reached the first target rotational speed N1, the HEV-ECU 20 ends the control cycle after the determination in step S210, and starts the process from step S201 again in the next control cycle.

  Even in the next control cycle, the charging rate SOC of the battery 8 has not yet sufficiently recovered, and the charging of the battery 8 has not been completed. Therefore, the value of the flag F2 remains 1, and the HEV-ECU 20 performs step S201. If so, the process advances to step S205. In step S205, it is determined whether or not the value of the flag F3 is 1. However, since the engine 2 is in operation, the flag F3 is 1, and the HEV-ECU 20 performs the process in step S205. Proceeding to S208, it is again determined whether or not the value of the flag F4 is 1.

  At this time, since the operation of the engine 2 in the lamp mode has not been completed and the value of the flag F4 remains 0, the HEV-ECU 20 advances the process to step S209 based on the determination in step S208, and again as described above. Then, a command is sent to the engine ECU 22 to continuously operate the engine 2 in the ramp mode, and the generated power of the generator 4 is increased correspondingly. Therefore, the process proceeds to step S209 through steps S201, S205, and S208 until the rotation speed Ne of the engine 2 is increased by the ramp mode operation of the engine 2 and reaches the first target rotation speed N1. Will be operated in lamp mode.

  Thus, the engine 2 is operated in the ramp mode until the rotational speed Ne of the engine 2 reaches the first target rotational speed N1, and the generated power of the generator 4 is changed from 0 to the first target accordingly. When the rotational speed of the engine 2 is set to the first target rotational speed N1 immediately after starting by gradually increasing the electric power, and the generated power of the generator 4 is set to the first target power immediately after starting the engine 2. In comparison, the degree of increase in the exhaust temperature of the engine 2 is moderate. The degree of increase in the engine speed and the degree of increase in the generated power of the generator 4 at this time are set in advance so that the exhaust temperature increases at a predetermined degree as will be described later.

  Thus, when the rotation speed Ne of the engine 2 increases and reaches the first target rotation speed N1 by the ramp mode operation of the engine 2, the HEV-ECU 20 advances the process to step S212, and determines whether or not the value of the flag F1 is 1 or not. Determine. The flag F1 determines the operation mode of the engine 2 and the urea water supply mode from the urea water injector 52, as described above, until the charge rate SOC of the battery 8 increases and reaches the first upper limit charge rate SU1. The value is set to 0 in the charge control, and the value is set to 1 in the period from when the charge rate SOC of the battery 8 reaches the first upper limit charge rate SU1 to the second upper limit charge rate SU2. The

Therefore, until the charging rate SOC of the battery 8 reaches the first upper limit charging rate SU1, the HEV-ECU 20 determines that the value of the flag F1 is not 1 in step S212, and the process proceeds to step S213, and the engine 2 The first operation mode is selected as the operation mode.
When the first operation mode is selected in step S213, the HEV-ECU 20 controls the inverter 6 so that the power generated by the generator 4 becomes the first target power under the first target rotational speed N1, and A command is sent to the engine ECU 22 to operate the engine 2 in the first operation mode. The engine ECU 22 receives a command from the HEV-ECU 20, and controls the operation of the engine 2 so that the engine 2 operates at the first target rotational speed N1. The rotational speed of the engine 2 has already reached the first target rotational speed N1 by the ramp mode operation described above, and the power generated by the generator 4 has also reached the first target power correspondingly. The lamp mode smoothly transitions to the first operation mode.

  Thus, when the first operation mode is selected in step S213 and the engine 2 is operated in the first operation mode, the HEV-ECU 20 ends its control cycle and starts the process from step S201 again in the next control cycle. At this time, the charging rate SOC of the battery 8 has not yet recovered sufficiently, and the charging of the battery 8 has not been completed. Therefore, as described above, the process proceeds to step S208 through steps S201 and S205, and the flag F4 is set again. It is determined whether or not the value is 1.

  At this time, since the operation of the engine 2 in the lamp mode has already been completed and the value of the flag F4 is set to 1, the HEV-ECU 20 proceeds with the process to step S212 based on the determination in step S208, and again the flag F1 Whether the value of 1 is 1 or not is determined. Therefore, after the engine 2 shifts from the lamp mode to the first operation mode, the charging of the battery 8 proceeds, and the process proceeds from step S212 to step S213 until the charging rate SOC increases and reaches the first upper limit charging rate SU1. The engine 2 is advanced and operated in the first operation mode, and the generator 4 generates the first target power, and the battery 8 is charged.

When the charging of the battery 8 proceeds and the battery 8 charging rate SOC increases and reaches the first upper limit charging rate SU1, the value of the flag F1 is set to 1 in the charging control, so the HEV-ECU 20 sets the flag F1 in step S212. Is determined to be 1, the process proceeds to step S214, and the operation mode of the engine 2 is switched to the second operation mode.
When the second operation mode is selected in step S214, the HEV-ECU 20 controls the inverter 6 to generate the second target power based on the second target rotation speed N2, and the engine 2 in the second operation mode. A command is sent to the engine ECU 22 to drive the engine. The second target speed N2 is lower than the first target speed N1 when the first operation mode is selected, and the second target power is the first target power when the first operation mode is selected. Is smaller than The engine ECU 22 receives a command from the HEV-ECU 20, and controls the operation of the engine 2 so that the engine 2 operates at the engine speed of the second target speed N2. Therefore, the engine 2 is operated in an operation region at a lower speed and a lower load than in the first operation mode. As a result, the temperature of the exhaust discharged from the engine 2 is lower than that in the first operation mode, and the concentration of NOx contained in the exhaust is also reduced.

  Thus, after the HEV-ECU 20 sets the operation mode of the engine 2 to the second operation mode in step S214, the HEV-ECU 20 ends the control cycle, and starts the process from step S201 again in the next control cycle. At this time, the charging of the battery 8 is not completed yet, and the value of the flag F2 remains 1, and the value of the flag F3 is 1 because the engine 2 is in operation. Since the value of the flag F4 is also 1 because of the completion of the operation, the HEV-ECU 20 advances the process to step S212 according to the determinations in steps S201, S205, and S208.

  Since the value of the flag F1 is set to 1 in the charging control, the HEV-ECU 20 proceeds with the process to step S214 based on the determination in step S212, and continues to set the operation mode of the engine 2 to the second operation mode. Accordingly, during a period from when the charging rate SOC of the battery 8 reaches the first upper limit charging rate SU1 to the second upper limit charging rate SU2, the process proceeds to step S214 and the engine 2 is operated in the second operation mode. At the same time, the second target power is generated by the generator 4 and the battery 8 is charged.

When the charging of the battery 8 further proceeds and the charging rate SOC of the battery 8 reaches the second upper limit charging rate SU2, the values of the flags F1 and F2 are reset to 0 in the charging control as described above, so that the engine operation control When the process proceeds to step S201, the HEV-ECU 20 determines that the value of the flag F2 is not 1 and proceeds the process to step S202.
In step S202, the HEV-ECU 20 instructs the engine ECU 22 to stop the engine 2, and controls the inverter 6 to stop the power generation of the generator 4. The engine ECU 22 receives the command from the HEV-ECU 20 and stops the engine 2 by stopping the fuel supply to the engine 2.

  Since the HEV-ECU 20 has stopped the engine 2 in step S202, it resets the value of the flag F3 to 0 in the next step S203, and further resets the value of the flag F4 to 0 in step S204. Exit. After the next control cycle, as described above, the process of steps S201 to S204 is repeated and the engine 2 is stopped unless the battery 8 needs to be charged again and the value of the flag F2 becomes 1. Maintained in a state.

  By performing the engine operation control as described above, when the charging rate SOC of the battery 8 falls below the lower limit charging rate SL, the engine 2 is started and the engine 2 is operated in the ramp mode, and the rotational speed of the engine 2 is increased. Gradually increase from idle speed to first target speed. In accordance with this, the generated power of the generator 4 is gradually increased from 0 to the first target power, and the load of the engine 2 is gradually increased. As a result, the exhaust temperature of the engine 2 is set to the first target speed N1 immediately after starting the engine 2 and the power generated by the generator 4 is set to the first target power immediately after starting the engine 2. Compared to a moderate increase.

  When the rotational speed of the engine 2 reaches the first target rotational speed N1, the generated power of the generator 4 also reaches the first target power in accordance with this, and the engine 2 smoothly shifts to the first operation mode. In this way, the engine 2 is operated in the first operation mode, and the generator 4 driven by the engine 2 generates the first target power while rotating at the first target rotation speed, whereby the charging of the battery 8 is further advanced. .

  When the charging of the battery 8 proceeds and the charging rate SOC increases and reaches the first upper limit charging rate SU1, the operating state of the engine 2 is switched to the second operating mode. The operation of the engine 2 in the second operation mode continues until the charge rate SOC of the battery 8 further increases and reaches the second upper limit charge rate SU2, and while the engine 2 is operated in the second operation mode, the engine 2 The battery 4 is continuously charged by generating the second target power smaller than the first target power while the generator 4 driven to 2 rotates at the second target speed N2 lower than the first target speed N1. Is done. At this time, since the engine 2 is operated in a lower speed and lower load operation region than in the first operation mode, the temperature of exhaust discharged from the engine 2 is lower than in the first operation mode, and The concentration of NOx contained in the exhaust also decreases.

  When the charging of the battery 8 further progresses and the charging rate of the battery 8 reaches the second upper limit charging rate, the engine 2 is stopped as the charging of the battery 8 is completed, and the power generation by the generator 4 is ended. Therefore, when the operating state of the engine 2 is switched to the second operation mode when the charging rate SOC of the battery 8 reaches the first upper limit charging rate SU1, the engine 2 has the charging rate SOC of the battery 8 set to the second upper limit charging rate. The vehicle is operated in the second operation mode until it reaches SU2 and stops.

  In accordance with the operation of the engine 2, the engine ECU 22 supplies urea water for supplying urea water into the exhaust gas from the urea water injector 52 so as to purify the exhaust gas by reducing NOx in the exhaust gas discharged from the engine 2. Execute supply control. This urea water supply control is also started by turning on the start switch in the same manner as the charge control described above, and is executed by the engine ECU 22 at a predetermined control cycle according to the flowchart shown in FIG. The urea water supply control is also ended by turning off the start switch in the same manner as the charge control described above.

In this urea water supply control, since the urea water supply from the urea water injector 52 is controlled according to the operating state of the engine 2 in the engine operation control described above, the command is set by the HEV-ECU 20 in the charge control described above as a command. Based on the values of the sent flags F1 and F3, the engine ECU 22 controls the urea water injector 52.
When urea water supply control is started by turning on the start switch, the engine ECU 22 determines whether or not the value of the flag F3 is 1 in step S301. The flag F3 indicates whether or not the engine 2 is in an operating state as described above, and its value is set to 1 when the engine 2 is in an operating state.

  When the value of the flag F3 is 0, indicating that the engine 2 is stopped, it is not necessary to supply urea water into the exhaust gas of the engine 2 from the urea water injector 52. The process proceeds to step S302 based on the determination in S301, and after the supply of urea water from the urea water injector 52 is continuously stopped, the control cycle is ended.

In the next control cycle, the engine ECU 22 starts the process again from step S301 and determines whether or not the value of the flag F3 is 1. Therefore, as long as the engine 2 is in a stopped state, the processes of steps S301 and S302 are repeated, and the supply of urea water from the urea water injector 52 is stopped.
When it is determined that the battery 8 needs to be charged in the above-described charging control and the engine 2 is started by the engine operation control, the value of the flag F3 becomes 1. Therefore, the engine ECU 22 proceeds to step S303 according to the determination in step S301. Proceed.

  In step S303, the engine ECU 22 determines whether or not the temperature Tc of the exhaust gas flowing into the SCR catalyst 48 detected by the exhaust temperature sensor 54 has reached a predetermined temperature Ta. The predetermined temperature Ta is set to, for example, 200 ° C. based on a lower limit temperature at which urea contained in the urea water injected into the exhaust gas from the urea water injector 52 can be easily hydrolyzed and converted to ammonia. If the exhaust temperature Tc has not reached the predetermined temperature Ta, the engine ECU 22 determines that urea water cannot be injected from the urea water injector 52 and advances the process to step S302. In step S302, as described above, the supply of urea water from the urea water injector 52 is continuously stopped, and the engine ECU 22 ends its control cycle.

In the next control cycle, when the process is started again from step S301, the engine 2 is already in operation, so the engine ECU 22 advances the process to step S303 based on the determination in step S301, and the engine ECU 22 is controlled by the exhaust temperature sensor 54. It is determined whether or not the detected temperature Tc of the exhaust gas flowing into the SCR catalyst 48 has reached a predetermined temperature Ta.
Therefore, even if the battery 8 needs to be charged and the engine 2 is started, the process of step S302 is repeated from step S301 to step S303 until the exhaust temperature of the engine 2 rises and reaches the predetermined temperature Ta. The urea water is not injected from the urea water injector 52.

When the operation of the engine 2 continues and the exhaust gas temperature Tc rises and reaches the predetermined temperature Ta, the engine ECU 22 determines that the urea water injection from the urea water injector 52 is possible by the determination in step S303. Then, the process proceeds to step S304, and it is determined whether or not the value of the flag F1 is 1.
The flag F1 determines the operation mode of the engine 2 and the urea water supply mode from the urea water injector 52, as described above, until the charge rate SOC of the battery 8 increases and reaches the first upper limit charge rate SU1. The value is set to 0 in the charging control, and the value is set to 1 in the period from when the charging rate SOC of the battery 8 reaches the first upper limit charging rate SU1 to the second upper limit charging rate SU2.

  Therefore, after the charge rate SOC of the battery 8 falls below the lower limit charge rate SL and the engine 2 is started, the charge rate SOC of the battery 8 reaches the first upper limit charge rate SU1 after the exhaust temperature Tc reaches the predetermined temperature Ta. Up to this point, when the engine ECU 22 determines that the value of the flag F1 is not 1 in step S304, the process proceeds to step S305, and the first supply mode is selected as the urea water supply mode.

  In this first supply mode, the engine ECU 22 calculates the NOx emission amount per unit time of the engine 2 from the operating state of the engine 2, and based on the ammonia supply amount necessary to selectively reduce all the NOx of the emission amount, The target supply amount of urea water per unit time is obtained. However, since the exhaust temperature Tc normally reaches the predetermined temperature Ta after the above-described operation of the engine 2 in the ramp mode is completed, the engine ECU 22 in the first supply mode is the engine when operating in the first operation mode. 2 is calculated, and a target supply amount M1 of urea water per unit time is obtained based on the ammonia supply amount necessary for selectively reducing all of the NOx of the discharge amount.

  Based on the target supply amount M1 thus obtained, the engine ECU 22 controls the urea water injector 52 to supply urea water. As described above, the urea in the urea water injected from the urea water injector 52 is hydrolyzed by the heat of the exhaust, and ammonia is generated. Ammonia generated from the urea water flows into the SCR catalyst 48 as a reducing agent and reduces NOx in the exhaust to purify the exhaust.

On the other hand, when the charging of the battery 8 progresses and the charging rate SOC of the battery 8 reaches the first upper limit charging rate SU1, the value of the flag F1 becomes 1 by the charging control, so the ECU 22 performs the process according to the determination in step S304. Then, the second supply mode is selected as the urea water supply mode.
At this time, since the value of the flag F1 is 1, the engine 2 is operated in the second operation mode. As described above, the load and the rotational speed of the engine 2 in the second operation mode are the same as those in the first operation mode. The engine 2 has shifted to a low speed and low load operation as compared with the case of the first operation mode. In this second supply mode, the engine ECU 22 responds to such an operating state of the engine 2 from the urea water injector 52 to increase the adsorption amount of ammonia generated from the urea water onto the SCR catalyst 48. Water is supplied, and the adsorption amount increasing operation is performed together with the operation of the engine 2 in the second mode.

Specifically, urea water is supplied in the second supply mode as follows.
As described above, when the engine 2 shifts to the second operation mode in which the engine 2 is in the low speed and low load operation state than the first operation mode, the exhaust temperature of the engine 2 is lower than that in the first operation mode, and step S303 is performed. The predetermined temperature Ta used in this determination, that is, a temperature slightly higher than the lower limit temperature at which the urea water can be injected from the urea water injector 52. The maximum ammonia adsorption amount per unit catalyst volume in the SCR catalyst 48 tends to increase as the temperature of the SCR catalyst 48 decreases as shown in FIG. 6, and when the engine 2 is operated in the first operation mode. The maximum ammonia adsorption amount Q2 at the catalyst temperature T2 when operating in the second operation mode is larger than the maximum ammonia adsorption amount Q1 at the catalyst temperature T1.

  That is, by shifting the operation state of the engine 2 to the second operation mode, more ammonia can be adsorbed on the SCR catalyst 48. Therefore, in the second supply mode, the engine ECU 22 responds to the increase in the maximum adsorption amount accompanying the transition of the engine 2 to the second operation mode, and increases the amount of ammonia adsorbed on the SCR catalyst 48. The supply of urea water from the injector 52 is controlled.

  Here, the ammonia supplied to the SCR catalyst 48 is consumed for the selective reduction of NOx in the exhaust gas, and the remainder remains adsorbed on the SCR catalyst 48. Therefore, the sum of the amount consumed for the selective reduction of NOx and the maximum adsorption amount to the SCR catalyst 48 is the maximum supply amount of ammonia that does not cause ammonia slip. When supplied to the SCR catalyst 48, ammonia slip occurs.

In order to prevent the occurrence of such ammonia slip, the supply amount of urea water in the second supply mode is set as follows.
That is, first, the ammonia supply amount per unit time required for the selective reduction of NOx is calculated from the NOx emission amount per unit time when the engine 2 is operated in the second operation mode, and this ammonia supply amount is calculated. The urea water supply amount M2 ′ per unit time corresponding to is obtained.

  The engine 2 is exclusively used to drive the generator 4, and after the charge rate SOC of the battery 8 reaches the first upper limit charge rate SU1, the engine 2 is further increased and reaches the second upper limit charge rate SU2. Since the engine 2 is operated under the fixed operation condition of the second operation mode, the period during which the engine 2 is operated in the second operation mode is substantially constant. Therefore, based on the maximum adsorption amount Q2 of ammonia that can be adsorbed to the SCR catalyst 48 when the engine 2 is operating in the second operation mode, ammonia is supplied until the maximum adsorption amount Q2 is reached without causing ammonia slip. The period necessary for the adsorption to be performed is determined as the period during which the engine 2 is operated in the second operation mode, the urea water supply amount corresponding to the maximum adsorption amount Q2, and the engine 2 in the second operation mode. From the operating period, a urea water supply amount M2 ″ per unit time required for adsorbing the maximum adsorption amount Q2 of ammonia on the SCR catalyst 48 is obtained.

In the engine ECU 22, the sum of the urea water supply amount M2 ′ and the urea water supply amount M2 ″ thus determined is set and stored as the second target supply amount M2 in the second supply mode.
In step S306, the engine ECU 22 controls the urea water injector 52 so that the urea water of the second target supply amount M2 set in this way is supplied into the exhaust gas. As a result, the urea water urea injected from the urea water injector 52 is hydrolyzed to generate ammonia, a part of which is consumed for selective reduction of NOx in the SCR catalyst 48, and the remainder is adsorbed to the SCR catalyst 48. To do.

  When the charging of the battery 8 further proceeds and the charging rate SOC of the battery 8 reaches the second upper limit charging rate SU2, it is assumed that the charging of the battery 8 is completed, the engine 2 is stopped in the engine operation control described above, and the flag F3 and The value of F4 is reset to 0, and the values of flags F1 and F2 are also reset to 0 in the charging control. Therefore, in the control period of the urea water supply control after the charging rate SOC of the battery 8 reaches the second upper limit charging rate SU2, the engine ECU 22 determines that the value of the flag F3 is not 1 in step S301. Is advanced to step S302, and the supply of urea water from the urea water injector 52 is stopped.

  As described above, when the battery 8 is being charged with the generated power of the generator 4 driven by the engine 2, the charging rate of the battery 8 increases and reaches the first upper limit charging rate SU2, and then further increases. During the period until the second upper limit charging rate SU2 is reached, the engine 2 is operated in the second operation mode, and urea water is supplied from the urea water injector 52 in the second supply mode.

  At this time, since the engine 2 is operated in the second operation mode, the exhaust gas temperature is lowered, so that the adsorption of ammonia to the SCR catalyst 48 is higher than that when the engine 2 is operated in the first operation mode as described above. The amount can be increased. Further, as described above, the second target supply amount M2 of urea water in the second supply mode is the urea water supply amount M2 ′ corresponding to the ammonia supply amount necessary for the selective reduction of NOx, and the SCR catalyst 48. Since the ammonia adsorption amount is set based on the sum of the urea water supply amount M2 "so that the maximum adsorption amount Q2 is reached, the SCR catalyst can deliver the maximum possible amount of ammonia without causing ammonia slip from the SCR catalyst 48. 48 can be adsorbed.

  The engine 2 is exclusively used for driving the generator 4, and after the charge rate SOC of the battery 8 reaches the first upper limit charge rate SU1, the engine 2 is further increased and reaches the second upper limit charge rate SU2. 2 is operated under a fixed operation condition of the second operation mode, so that the period from when the charge rate SOC of the battery 8 reaches the first upper limit charge rate SU1 to the second upper limit charge rate SU2 is as described above. The length is almost constant.

In each control cycle after the charging of the battery 8 is completed, the processes of steps S301 and S302 are repeated until the engine 2 is started again and the value of the flag F3 is set to 1, as described above. The supply of urea water from is kept stopped.
When the charge rate SOC of the battery 8 decreases again and falls below the lower limit charge rate SL, the engine 2 is started and the value of the flag F3 becomes 1, and the engine ECU 22 advances the process to step S303 according to the determination in step S301. Also in this case, the exhaust temperature of the engine 2 has not increased for a while after the engine 2 is started, and the engine ECU 22 detects the exhaust gas flowing into the SCR catalyst 48 detected by the exhaust temperature sensor 54 as described above. Until it is determined that the temperature Tc has reached the predetermined temperature Ta, the process proceeds from step S303 to step S302, and urea water is not supplied from the urea water injector 52.

  On the other hand, the engine 2 has already been started and is first operated in the lamp mode as described above. In the ramp mode, the rotational speed of the engine 2 is gradually increased from the idle rotational speed after starting toward the first target rotational speed in the first operation mode, and the generated power of the generator 4 is correspondingly increased from 0 to the first. It gradually increases toward the first target generated power in the operation mode, and the load on the engine 2 gradually increases.

  At this time, a large amount of ammonia is adsorbed to the SCR catalyst 48 by the adsorption amount increasing operation performed when the battery 8 was charged last time, the engine 2 is started, the exhaust temperature rises, and the SCR catalyst 48 becomes NOx. Is in a state where it can be selectively reduced, NOx contained in the exhaust of the engine 2 is selectively reduced using ammonia adsorbed by the SCR catalyst 48 as a reducing agent, and exhaust purification is performed. Thus, while the ammonia adsorbed on the SCR catalyst 48 is consumed by selective reduction and gradually decreases, the maximum amount of ammonia that can be adsorbed by the SCR catalyst 48 is as shown in FIG. It gradually decreases as the catalyst temperature increases.

Therefore, in response to such a change in the amount of adsorbed ammonia, the degree of increase in the rotational speed of the engine 2 in the ramp mode and the degree of increase in the generated power of the generator 4 are determined.
That is, the ammonia adsorbed on the SCR catalyst 48 by the operation of increasing the adsorption amount is gradually reduced by being used for selective reduction of NOx in the exhaust after the engine 2 is started. On the other hand, the maximum amount of ammonia that can be adsorbed on the SCR catalyst 48 gradually decreases as the catalyst temperature of the SCR catalyst 48 increases, as shown in FIG. Therefore, the temperature of the SCR catalyst 48 is such that the degree of decrease in ammonia accompanying this selective reduction is determined in advance by experiments, and the degree of decrease in the maximum amount of adsorption of ammonia does not exceed the degree of ammonia decrease due to selective reduction determined by experiments. Determine the degree of increase. In the ramp mode, it corresponds to the degree of increase in the engine 2 speed and the degree of increase in the load of the engine 2 in order to obtain the degree of increase in exhaust gas temperature that achieves the degree of increase in catalyst temperature thus obtained. The degree of increase in the generated power of the generator 4 is set.

  By operating the engine 2 in the ramp mode in this way, the rotational speed and load of the engine 2 gradually increase, and the exhaust of the engine 2 is compared to when the engine 2 is operated in the first operation mode immediately after starting. The rise in temperature becomes gradual, and the degree of increase in the catalyst temperature of the SCR catalyst 48 becomes gradual. As a result, until the engine 2 completes the operation in the ramp mode and shifts to the first operation mode, the ammonia adsorbed on the SCR catalyst 48 is the maximum adsorption of ammonia on the SCR catalyst 48 at the catalyst temperature at that time. The amount is not exceeded, and the operating state of the engine 2 can be shifted to the first operation mode without causing ammonia slip.

  Even after the engine 2 shifts from the operation in the ramp mode to the operation in the first operation mode, the NOx is selectively reduced using ammonia adsorbed on the SCR catalyst 48 as a reducing agent, and the exhaust gas is purified. Thus, while the exhaust gas is purified using the ammonia adsorbed on the SCR catalyst 48, the exhaust temperature of the engine 2 rises, and the exhaust temperature Tc detected by the exhaust temperature sensor 54 in step S303 becomes the predetermined temperature Ta. If it is determined that it has reached, the urea water is supplied from the urea water injector 52 in the first supply mode as described above.

  Therefore, even if the engine 2 is repeatedly started and stopped for charging the battery 8, NOx is selectively reduced by the ammonia adsorbed on the SCR catalyst 48 when the exhaust temperature at the beginning of the engine 2 is low. Therefore, the exhaust of the engine 2 can be well purified immediately after the engine 2 is started. In addition, since the engine 2 is operated in the ramp mode after the engine 2 is started and then shifted to the first operation mode, the exhaust temperature of the engine 2 rises gradually and is adsorbed by the SCR catalyst 48. The ammonia that does not exceed the maximum ammonia adsorption amount of the SCR catalyst 48 at the catalyst temperature at that time is prevented, and the occurrence of ammonia slip is prevented.

When the charging control and engine operation control by the HEV-ECU 20 as described above and the urea water supply control by the engine ECU 22 are performed, the target rotational speed of the engine 2, the temperature of the exhaust gas flowing into the SCR catalyst 48, the urea water FIG. 7 shows temporal changes in the target supply amount and the concentration of NOx discharged from the exhaust aftertreatment device 36, respectively.
In FIG. 7, if the charging rate of the battery 8 decreases and falls below the lower limit charging rate SL at time t1, and the engine 2 is started, the engine 2 is operated in the ramp mode, and the engine speed is calculated from the idle engine speed. The speed is gradually increased toward the first target rotational speed in the first operation mode. Although not shown in the figure, the generated power of the generator 4 is gradually increased from 0 toward the first target generated power in the first operation mode, and the load on the engine 2 is gradually increased. Will increase.

  The change in the exhaust temperature of the engine 2 at this time is shown by a solid line in FIG. 7, and the engine 2 as shown by a two-dot chain line in FIG. It rises more slowly than the exhaust temperature rises when the generated power is the first target power. Due to such a gradual increase in the exhaust temperature, the catalyst temperature of the SCR catalyst 48 also gradually increases. As described above, the ammonia adsorbed on the SCR catalyst 48 is reduced by the ammonia of the SCR catalyst 48 at the catalyst temperature at that time. Generation of ammonia slip is prevented without exceeding the maximum adsorption amount.

When the operation in the ramp mode of the engine 2 is completed and the operation state of the engine 2 shifts to the first operation mode, the rotation speed of the engine 2 is set to the first target rotation speed N1. At this time, the generator 4 is controlled by the HEV-ECU 20 so as to generate the first target power under the first target rotation speed N1.
Although the exhaust temperature of the engine 2 gradually increases as the engine 2 starts, the exhaust temperature at the start of the engine 2 is lower than a predetermined temperature Ta at which urea water can be supplied from the urea water injector 52. Therefore, the target supply amount of urea water from the urea water injector 52 is not set, and urea water is not supplied. For this reason, if the adsorption of ammonia to the SCR catalyst 48 as described above is not performed during the last charging of the battery 8, as shown by a one-dot chain line in FIG. In addition, the exhaust discharged from the exhaust aftertreatment device 36 has a high NOx concentration without being purified. However, in the present embodiment, when the battery 8 is charged last time, a large amount of ammonia is adsorbed on the SCR catalyst 48 as described above. Therefore, even if urea water is not supplied from the urea water injector 52, the SCR NOx is selectively reduced using ammonia adsorbed on the catalyst 48 as a reducing agent, and as shown by a solid line in FIG. 7, the NOx concentration in the exhaust can be kept low from the start of the engine 2, thereby purifying the SCR catalyst 48. A decrease in efficiency can be prevented. The increase in the NOx concentration only for a short period immediately after the start of the engine 2 is due to the increase in the fuel supply amount performed at the start of the engine 2 and the activation of the SCR catalyst 48.

  After the operation in the ramp mode, the operation of the engine 2 in the first operation mode continues to increase the exhaust temperature of the engine 2. When the temperature reaches the predetermined temperature Ta at time t2, the urea water injector 52 performs the first supply mode. The supply of urea water with the target supply amount M1 is started. Ammonia generated from the urea water is supplied to the SCR catalyst 48, and the exhaust gas is purified by continuing selective reduction of NOx. At this time, the exhaust temperature of the engine 2 rises to, for example, about 500 ° C. when the engine 2 is operated in the first operation mode and the generator 4 generates the first target power.

  When the charging of the battery 8 proceeds by the generated power of the generator 4 driven by the engine 2 and the charging rate SOC of the battery 8 reaches the first upper limit charging rate SU1 at time t3, the operation mode of the engine 2 is changed to the first operation mode. Is switched to the second operation mode, and the engine 2 is operated at the second target speed lower than the first target speed N1. At this time, the generator 4 is controlled by the HEV-ECU 20 so as to generate the second target power smaller than the first target power under the second target rotational speed. Therefore, the engine 2 shifts to an operation state at a lower speed and a lower load than in the first operation mode, and the exhaust temperature of the engine 2 is slightly higher than a predetermined temperature Ta at which urea water can be supplied from the urea water injector 52. (For example, 250 ° C.).

  By reducing the exhaust temperature in this way, it becomes possible to adsorb more ammonia to the SCR catalyst 48 than when the engine 2 is operated in the first operation mode. In response to this, the engine ECU 22 switches the urea water supply mode from the urea water injector 52 from the first supply mode to the second supply mode in accordance with the transition of the engine 2 to the second operation mode, and the urea water injector 52. The target supply amount of urea water from is set as a second target supply amount M2.

  In the present embodiment, the second target supply amount M2 is smaller than the first target supply amount M1, but this is because the exhaust temperature decreases due to the engine 2 shifting to the second operation mode, and the engine 2 This is because the concentration of NOx discharged from the exhaust gas greatly decreases, and the second target supply amount M2 depends on the characteristics of the SCR catalyst 48 and the degree of decrease in the exhaust temperature of the engine 2 in the second operation mode. In some cases, the value may be larger than the first target supply amount M1.

  When the engine 2 is operated in the second operation mode, the operation state of the engine 2 is a lower speed and lower load operation than in the first operation mode. Therefore, as described above, the NOx concentration in the exhaust discharged from the engine 2 is This is lower than in the first operation mode, and accordingly, the NOx concentration in the exhaust discharged from the exhaust aftertreatment device 36 also decreases. Further, as the exhaust temperature of the engine 2 decreases, the temperature of the SCR catalyst 48 also decreases. As shown in FIG. 6, a large amount of ammonia is generated compared to when the engine 2 is operated in the first operation mode. To be adsorbed.

  The operation of the engine 2 in the second operation mode and the supply of urea water in the second supply mode are continued until time t4 when the charging of the battery 8 proceeds and the charging rate SOC reaches the second upper limit charging rate SU2, and the charging of the battery 8 is continued. When the rate SOC reaches the second upper limit charging rate SU2, the charging of the battery 8 is completed. Therefore, when the charging of the battery 8 is terminated, the engine 2 is operated in the second operation mode and the second urea water injector 52 performs the second operation for a predetermined period before the charging is completed from time t3 to t4 in FIG. The urea water is supplied in the supply mode, and a large amount of ammonia is adsorbed by the SCR catalyst 48.

  As described above, the engine 2 is exclusively used for driving the generator 4, and after the charging rate SOC of the battery 8 reaches the first upper limit charging rate SU1, it further increases to reach the second upper limit charging rate SU2. In the meantime, the engine 2 is operated under the substantially fixed operation condition of the second operation mode, and therefore, the period from t3 to t4 in FIG. Therefore, the period during which the engine 2 is operated in the second operation mode can be arbitrarily set according to the characteristics of the engine 2 and the SCR catalyst 48 by adjusting the first upper limit charging rate SU1.

  In this way, by operating the engine 2 in the second operation mode and supplying the urea water from the urea water injector 52 in the second supply mode for a predetermined period before the engine 2 stops due to the completion of charging, a large amount of ammonia is generated in the SCR. Since it is adsorbed by the catalyst 48, the charging rate SOC of the battery 8 decreases and again falls below the lower limit charging rate SL, and when charging of the battery 8 is started, the exhaust temperature is low and urea water is supplied from the urea water injector 52 Even in a state where it cannot be performed, the NOx in the exhaust gas can be selectively reduced by the ammonia adsorbed on the SCR catalyst 48 and the exhaust gas can be purified.

  Further, when supplying urea water from the urea water injector 52 in the second supply mode, urea water corresponding to the supply amount of ammonia necessary for selective reduction of NOx when the engine 2 is operated in the second operation mode. Since the urea water target supply amount M2 is set by the sum of the supply amount M2 ′ and the urea water supply amount M2 ″ so that the ammonia adsorption amount to the SCR catalyst 48 becomes the maximum adsorption amount Q2, It is possible to adsorb the maximum possible amount of ammonia to the SCR catalyst 48 without causing ammonia slip from the SCR catalyst 48.

Furthermore, since the adsorption amount increasing operation for increasing the adsorption amount of ammonia on the SCR catalyst 48 is performed while the battery 8 is being charged, in order to increase the adsorption amount of ammonia on the SCR catalyst 48, an extra amount is required. Therefore, it is not necessary to operate the engine 2 and the fuel consumption of the engine 2 is not deteriorated.
Although the description of the exhaust gas purification apparatus for a hybrid electric vehicle according to one embodiment of the present invention has been completed above, the present invention is not limited to the above embodiment.

That is, in the above embodiment, when the engine 2 is operated in the ramp mode, the rotational speed of the engine 2 is changed with a preset increase degree and the generated power of the generator 4 is increased with a preset increase degree. However, the method of increasing the engine speed and the method of increasing the generated power are not limited to this.
For example, the adsorption amount of ammonia in the SCR catalyst 48 is estimated, and the exhaust temperature detected by the exhaust temperature sensor 54 is set so that the estimated ammonia adsorption amount does not exceed the maximum ammonia adsorption amount shown in FIG. Based on this, the degree of increase in engine speed and the degree of increase in generated power may be adjusted.

  In this case, for example, as in the above-described embodiment, when the rotational speed of the engine 2 reaches the first target rotational speed N1 in the first operation mode, the generated power of the generator 4 becomes the first generated power in the first operation mode. In this way, the relationship between the rotational speed of the engine 2 and the generated power of the generator 4 when the rotational speed and the generated power are changed is set in advance by considering the operation efficiency and exhaust characteristics of the engine 2 through experiments. Remember it. Then, based on the amount of ammonia consumed for the selective reduction of NOx when the engine 2 is operated in the ramp mode with the amount of ammonia adsorbed on the SCR catalyst 48 in the operation of increasing the storage amount in the second operation mode as an initial value. The residual adsorption amount of ammonia in the SCR catalyst 48 is estimated.

  The catalyst temperature at which the maximum adsorption amount that can be adsorbed to the SCR catalyst 48 is equal to the estimated residual adsorption amount of ammonia in this way is obtained from the relationship of FIG. The engine ECU 22 controls the engine 2 and the HEV-ECU 20 controls the inverter 6 so as to be equal to the catalyst temperature of the SCR catalyst 48 estimated based on the detected exhaust gas temperature. Change the generated power.

  By performing control based on the exhaust temperature detected by the exhaust temperature sensor 54 in this manner, the amount of ammonia adsorbed on the SCR catalyst 48 does not exceed the maximum ammonia adsorption amount on the SCR catalyst 48. In addition, the rotational speed of the engine 2 gradually increases toward the first target rotational speed N1, the generated power of the generator 4 gradually increases toward the first target power, and the load on the engine 2 gradually increases. As a result, the maximum adsorption amount of ammonia can be reduced by increasing the exhaust temperature of the engine 2 in accordance with the actual ammonia adsorption amount that is decreased due to the selective reduction of NOx in the SCR catalyst 48. Therefore, it is possible to prevent the occurrence of ammonia slip at the time of starting the engine and not to delay the rise of the exhaust temperature more than necessary, and to raise the exhaust temperature as quickly as possible up to a predetermined temperature Ta at which urea water can be supplied. It becomes possible.

  The estimation of the residual adsorption amount of ammonia in the SCR catalyst 48 is performed using the amount of ammonia adsorbed on the SCR catalyst 48 in the previous operation for increasing the storage amount in the second operation mode as an initial value. In the storage amount increasing operation, since the maximum adsorption amount Q2 of ammonia at the catalyst temperature T2 in FIG. 6 is adsorbed by the SCR catalyst 48, the maximum adsorption amount Q2 becomes the initial value of the ammonia adsorption amount.

  On the other hand, when considering the situation where ammonia is not adsorbed to the SCR catalyst 48 until the maximum adsorption amount is reached, this NOx is selected from the NOx emission amount from the engine 2 when operating in the second operation mode. While calculating | requiring the quantity of ammonia consumed in order to reduce | restore, the quantity of ammonia produced | generated with the urea water supplied from the urea water injector 52 in the 2nd supply mode is calculated | required, and it adsorb | sucks to the SCR catalyst 48 from both. The initial value of the ammonia adsorption amount may be obtained by estimating the amount of ammonia.

  In the above embodiment, when the engine 2 is operated in the ramp mode, the rotational speed of the engine 2 is gradually increased and the generated power of the generator 4 is gradually increased to gradually increase the load of the engine 2. Thus, although the degree of increase in the exhaust temperature of the engine 2 is moderated, the method of gradually increasing the degree of increase in the exhaust temperature of the engine 2 is not limited to this. For example, the rotation speed of the engine 2 is set to the first target rotation speed in the first operation mode immediately after the engine 2 is started, and only the power generated by the generator 4 is gradually increased to the first target power generation in the first operation mode. The load of the engine 2 may be gradually increased, or the exhaust gas temperature may be gradually increased by gradually changing a control amount other than the above of the engine 2.

Further, when the engine 2 is operated in the ramp mode, the starting point of the increase in the rotational speed of the engine 2 is set to the idle rotational speed, and the starting point of the generated power increase of the generator 4 is set to 0. It is not limited to these, and can be appropriately changed to a value larger than these.
Further, in the above embodiment, the period of the adsorption amount increasing operation in which the engine 2 is operated in the second operation mode and urea water is supplied in the second supply mode to increase the adsorption amount of ammonia on the SCR catalyst 48 is set in the battery. However, the method of setting the period of the adsorption amount increasing operation is not limited to this.

  For example, the elapsed time after the charging rate SOC of the battery 8 falls below the lower limit charging rate SL and the charging of the battery 8 is started is measured by a timer, and when this elapsed time reaches a predetermined time, the operation proceeds to the adsorption amount increasing operation. You may make it do. That is, since the operating conditions of the engine 2 in the lamp mode, the first operation mode, and the second operation mode are almost the same in each charge of the battery 8, the charging rate of the battery 8 after the charging of the battery 8 is started. The period until the SOC reaches the second upper limit charging rate and completes charging is substantially constant. Therefore, the start and end of charging of the battery 8 are determined based on the charge rate SOC of the battery 8 as in the above embodiment, and the shift to the adsorption amount increasing operation can be performed using a timer.

Further, until the charging of the battery 8 is completed, the engine 2 is operated in the lamp mode and then in the first operation mode, and urea water is supplied in the first supply mode. During the period, the engine 2 may be set in the second operation mode, and urea water may be supplied in the second supply mode to perform the adsorption amount increasing operation.
In this case, during the adsorption amount increasing operation, the HEV-ECU 20 controls the inverter 6 so that the generator 4 does not generate power. Therefore, the power of the engine 2 does not contribute to the charging of the battery 8, and only that much. The fuel consumption of the engine 2 is reduced. However, the period during which the adsorption amount increasing operation is performed can be accurately set by the timer.

  Moreover, in the said embodiment, when it transfers to adsorption amount increase operation, both the load and rotation speed of the engine 2 are made by making the electric power generation of the generator 4 into 2nd target electric power, and making rotation speed into 2nd target rotation speed. Although the exhaust gas temperature of the engine 2 is lowered by decreasing it, the exhaust gas temperature of the engine 2 may be lowered by reducing only the load of the engine 2 or reducing only the rotational speed.

  Furthermore, in the above embodiment, when urea water is supplied from the urea water injector 52 in the second supply mode in the adsorption amount increasing operation, it is necessary for selective reduction of NOx when the engine 2 is operated in the second operation mode. The urea water supply amount M2 ′ corresponding to the ammonia supply amount and the urea water supply amount M2 ″ so that the adsorption amount of ammonia on the SCR catalyst 48 becomes the maximum adsorption amount Q2 Although the amount M2 is set, the method for setting the second target supply amount of urea water in the second supply mode is not limited to this, for example, a period during which urea water at the start of the engine 2 cannot be supplied. When the amount of ammonia that can be adsorbed to the SCR catalyst 48 is more than the amount of ammonia required for the selective reduction of NOx by the SCR catalyst 48, the above-mentioned Less supply amount than the second target supply amount set by the measuring method may be used as the second target supply amount.

  In the above-described embodiment, the exhaust post-treatment device 36 is provided with the filter 46 in addition to the SCR catalyst 48, and the upstream oxidation catalyst 44 is provided on the upstream side of the filter 46 and the downstream side of the SCR catalyst 48. Although the post-stage oxidation catalyst 50 is provided, the configuration and arrangement other than the SCR catalyst 48 are not limited to this, and may be omitted as necessary, and still another exhaust purification device. It is also possible to combine with.

  In the above embodiment, the engine 2 is a diesel engine. However, the type of the engine 2 is not limited to this, and an engine having an SCR catalyst 48 that selectively reduces NOx in exhaust gas using ammonia as a reducing agent. The present invention can be similarly applied to any series-type hybrid electric vehicle equipped with.

1 is an overall configuration diagram of a hybrid electric vehicle to which an exhaust emission control device according to an embodiment of the present invention is applied. It is a system block diagram of the engine mounted in the hybrid electric vehicle of FIG. It is a flowchart of the charge control which HEV-ECU performs. It is a flowchart of the engine operation control which HEV-ECU performs. It is a flowchart of the urea water supply control which engine ECU performs. It is a graph which shows the relationship between the catalyst temperature in an SCR catalyst, and the adsorption amount of ammonia. The target engine speed in the engine operation control in FIG. 4, the target supply amount of urea water in the urea water supply control in FIG. 6, the temperature of the exhaust gas flowing into the SCR catalyst, and the NOx in the exhaust gas discharged from the exhaust aftertreatment device It is a time chart which shows the relationship with a density | concentration by a time change.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hybrid electric vehicle 2 Engine 4 Generator 8 Battery 10 Motor 18 Drive wheel 20 HEV-ECU (control means)
22 Engine ECU (control means)
34 Exhaust pipe (exhaust passage)
48 SCR catalyst (ammonia selective reduction type NOx catalyst)
52 Urea water injector (urea water supply means)
54 Exhaust temperature sensor (catalyst temperature detection means)

Claims (5)

In an exhaust emission control device for a hybrid electric vehicle, the engine is dedicated to driving a generator, the electric power generated by the generator is stored in a battery, and the driving wheels are driven by a motor that operates with the electric power supplied from the battery. ,
An ammonia selective reduction type NOx catalyst that is interposed in the exhaust passage of the engine and selectively reduces NOx in the exhaust gas using ammonia as a reducing agent;
Urea water supply means for supplying urea water into the exhaust gas upstream of the ammonia selective reduction type NOx catalyst;
The engine is started or stopped according to the state of charge of the battery, the engine is controlled with a predetermined target control amount during operation of the engine, and the urea water supply means is controlled according to the operation state of the engine. When the engine in operation is stopped, the adsorption amount increase for increasing the adsorption amount of ammonia to the ammonia selective reduction type NOx catalyst over the predetermined period before the engine stop over the state before the predetermined period. Control means for stopping the engine after operation,
After the engine is started, the control means is configured so that the exhaust gas temperature rises more slowly than the engine exhaust temperature rise when the engine control amount is immediately set to the target control amount. An exhaust emission control device for a hybrid electric vehicle, characterized in that an engine control amount gradually approaches the target control amount.   2. The control means according to claim 1, wherein the control means sets the target engine speed of the engine as the target control amount, and gradually increases the engine speed to the target engine speed after starting the engine. An exhaust purification system for hybrid electric vehicles.   The control means uses the control amount of the engine when the generator generates target power as the target control amount, and after starting the engine, gradually increases the generated power of the generator to the target power. The exhaust emission control device for a hybrid electric vehicle according to claim 1, wherein the control amount of the engine is changed toward the target control amount. A catalyst temperature detecting means for detecting the temperature of the ammonia selective reduction type NOx catalyst;
The control means adsorbs to the ammonia selective reduction type NOx catalyst in accordance with the temperature of the ammonia selective reduction type NOx catalyst based on the catalyst temperature detected by the catalyst temperature detection means after starting the engine. The control amount of the engine is gradually increased so that the exhaust temperature of the engine rises while maintaining a temperature at which the maximum ammonia adsorption amount is equal to or greater than the amount of ammonia adsorbed on the ammonia selective reduction type NOx catalyst. The exhaust emission control device for a hybrid electric vehicle according to claim 1, wherein the exhaust gas purification device is close to the target control amount.   The control means controls the engine so that the temperature of the exhaust gas flowing into the ammonia selective reduction type NOx catalyst is lowered as compared with a state before the predetermined period during operation of the engine, and the adsorption amount 2. The exhaust emission control device for a hybrid electric vehicle according to claim 1, wherein the operation is increased.

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