JP2016155410A - Control method of hybrid vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control method of a hybrid vehicle that can surely perform reduction and purification of NOx in exhaust gas while improving a fuel economy more than before.SOLUTION: According to a control method of a hybrid vehicle, when a measured value by a temperature sensor 20 arranged in the vicinity of an inlet of a catalytic converter 15 becomes less than a lower limit value of activation temperatures of a SCR catalyst 17 during travelling a HEV1, a clutch 12 for a motor is brought into an engaged state to rotate and drive an electric power generator 5, while a wet multiple disc clutch 32 is brought into a disengaged state; when measured values by a SOC sensor 13 of a battery 11 become equal to a lower limit value, the wet multiple disc clutch 32 is brought into an engaged state and required travel torque is determined from measured values by a rotation sensor 34 and a vehicle speed sensor 35 and first map data; and the electric power generator 5 is regenerated to generate power at required regenerative torque determined by the required travel torque and second map data so as to charge the battery 11.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for controlling a hybrid vehicle, and more particularly to a method for controlling a hybrid vehicle that can reliably reduce and purify NOx in exhaust gas while improving fuel efficiency as compared with the related art.

  In recent years, from the viewpoint of improving fuel efficiency and environmental measures, part of the driving force generated by the engine is replaced by a motor-driven generator that uses a battery as a power source, and surplus energy during normal driving and regenerative energy during braking are collected. Hybrid vehicles that store electricity as electric power in batteries are attracting attention.

  When a diesel engine is used for the engine of this hybrid vehicle, an exhaust gas purification system for removing harmful substances such as particulate matter (PM) and nitrogen oxide (NOx) contained in the exhaust gas is required. As for the former PM, a PM collecting filter that mainly collects PM by a ceramic honeycomb porous filter is mainly used. As for the latter NOx, a urea SCR system using urea water and a selective reduction catalyst (hereinafter referred to as “SCR catalyst”) has attracted attention (for example, see Patent Document 1).

This urea SCR system converts NOx in exhaust gas by SCR reaction in which ammonia (NH ₃ ) generated by hydrolysis of urea water heated by being injected into exhaust gas acts as a reducing agent in the presence of an SCR catalyst. It is something to purify.

  However, in the SCR catalyst described above, when the catalyst temperature falls below the lower limit value of the activation temperature (for example, about 150 to 200 ° C.), the NOx purification rate decreases, so most of the NOx in the exhaust gas is not purified. May be released into the atmosphere.

  Here, it is generally known that in a diesel engine, a reduction in the amount of NOx generated and fuel consumption are in a trade-off relationship. Therefore, if an attempt is made to reduce the amount of NOx generated in the diesel engine in accordance with the decrease in the NOx purification rate in the SCR catalyst as described above, the fuel efficiency will be deteriorated.

JP 2001-37008 A

  An object of the present invention is to provide a control method for a hybrid vehicle capable of reliably reducing and purifying NOx in exhaust gas while improving fuel efficiency as compared with the conventional art.

  A control method for a hybrid vehicle of the present invention that achieves the above object includes a hybrid system capable of connecting and disconnecting a motor generator and an engine connected to a battery and a drive shaft, and an exhaust passage through which exhaust gas from the engine flows. A control method of a hybrid vehicle comprising an injection nozzle for supplying urea water sequentially provided from the side and an exhaust gas purification system having a selective catalytic reduction catalyst, wherein the hybrid vehicle is running and from the injection nozzle When the urea water is injected, and the temperature of the exhaust gas flowing into the selective catalytic reduction catalyst becomes less than the lower limit value of the activation temperature of the selective catalytic reduction catalyst, the motor generator and the drive While rotating the motor generator by feeding from the battery with the shaft in contact, the engine and the drive shaft are disconnected, When the storage rate of the battery reaches a preset lower limit, the engine and the drive shaft are brought into contact with each other, and the engine speed of the engine and the vehicle speed of the hybrid vehicle are preset. The required travel torque is determined from the map data of 1, and the battery is charged by regenerating the motor generator with the required regeneration torque determined from the required travel torque and preset second map data. It is characterized by this.

  According to the method for controlling a hybrid vehicle of the present invention, a load is applied to the diesel engine not only by the torque required for traveling of the hybrid vehicle but also by regenerative power generation of the motor generator. An opportunity to reliably increase the temperature of the inflowing exhaust gas can be obtained. Further, it is not necessary to reduce the amount of NOx generated in order to cover the decrease in the NOx purification rate of the selective catalytic reduction catalyst due to the temperature rise of the exhaust gas, and a part of the load applied to the diesel engine is reduced. The regenerative power generation of the motor generator can be recovered as electric energy and charged to the battery. Therefore, in a hybrid vehicle, NOx reduction in exhaust gas can be reliably reduced and improved while improving fuel efficiency.

It is a block diagram which shows the example of a hybrid vehicle. It is a flowchart explaining the control method of the hybrid vehicle which consists of the 1st Embodiment of this invention. It is a graph which shows the example of the map data which concerns on determination of request | requirement regenerative torque. It is a flowchart explaining the control method of the hybrid vehicle which consists of the 2nd Embodiment of this invention. It is a flowchart explaining the control method of the hybrid vehicle which consists of the 3rd Embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a configuration example of a hybrid vehicle.

  This hybrid vehicle (hereinafter referred to as “HEV”) 1 includes a diesel engine 4 and a motor generator 5 via a transmission 6 on a drive shaft 3 that transmits driving force to a pair of left and right drive wheels 2 and 2, respectively. A hybrid system 7 that can be connected and disconnected and an exhaust gas purification system 9 provided in an exhaust passage 8 of the diesel engine 4 are provided.

  The hybrid system 7 includes a battery 11 that is electrically connected to the motor generator 5 through an inverter 10, and a motor clutch 12 that is interposed between the transmission 6 and the motor generator 5. Further, the battery 11 is provided with an SOC sensor 13 for measuring a storage rate (SOC). The hybrid system 7 is controlled by the HCU 14.

  The exhaust gas purification system 9 includes a large-diameter catalytic converter 15 interposed in the exhaust passage 8 and a urea water injection nozzle 16 installed in the exhaust passage 8 upstream of the catalytic converter 15. An SCR catalyst 17 is stored in the catalytic converter 15.

  The SCR catalyst 17 is formed by supporting a zeolite catalyst such as iron ion exchange aluminosilicate or copper ion exchange aluminosilicate on a carrier having a honeycomb structure formed of cordierite, aluminum oxide, titanium oxide or the like.

  A temperature sensor 20 for measuring the temperature of the exhaust gas G flowing into the SCR catalyst 17 is provided in the vicinity of the inlet of the catalytic converter 15.

The exhaust gas purification system 9 may be provided with an oxidation catalyst (not shown) in the exhaust passage 8 on the downstream side of the catalytic converter 15 in order to prevent NH ₃ slip.

  In the engine body 22 of the diesel engine 4, the intake air supplied into each of the plurality of cylinders 19 when the intake valve 23 is opened is mixed and burned with the fuel injected from the injector 24, and is stored in the cylinder 25. After the piston 26 is reciprocated and the crankshaft 27 is rotationally driven, when the exhaust valve 28 is opened, it becomes exhaust gas G and is exhausted from the exhaust manifold 29 to the exhaust passage 8. The exhaust gas G passes through an exhaust throttle valve 30 provided in the exhaust passage 8, and is then purified by the exhaust gas purification system 9 described above and released to the outside. The exhaust throttle valve 30 may be provided on the downstream side of the catalytic converter 15. The rotational power of the crankshaft 27 is transmitted from the transmission 6 to the drive shaft 3 via the fluid coupling 31 and the wet multi-plate clutch 32.

  Each part of the engine main body 22 and the exhaust gas purification system 9 are controlled by an ECU 33 connected to the HCU 14 through an in-vehicle network (indicated by a one-dot chain line). The ECU 33 is connected to a rotation sensor 34 that measures the engine speed of the diesel engine 4, a vehicle speed sensor 35 that measures the vehicle speed of the HEV 1, and an accelerator opening sensor 36 that detects the opening of the accelerator.

  A hybrid vehicle control method (hereinafter simply referred to as “control method”) according to the first embodiment of the present invention in the HEV 1 will be described below as control contents of the ECU 33 and the HCU 14 with reference to FIG. .

  The ECU 33 injects urea water from the injection nozzle 16 and performs NOx reduction purification by the SCR catalyst 17 during the HEV1 travel (S10), and at the same time the measured value F of the temperature sensor 20 is activated. Is compared with the lower limit value Z (S12). Examples of the lower limit value Z of the activation temperature include values in the range of about 150 to 200 ° C.

  When the measured value F becomes less than the lower limit value Z, it is determined that the NOx purification rate in the SCR catalyst 17 has decreased to an insufficient level (S14), and that fact is transmitted to the HCU 14.

  Receiving this transmission, the HCU 14 puts the motor clutch 12 into the engaged state (S16), rotates the motor generator 5 by power feeding from the battery 11 through the inverter 10, and puts the wet multi-plate clutch 32 in the disengaged state. (S18). Thereby, HEV1 will be in the state which drive | works only with the driving force of the motor generator 5. FIG. Next, the detection value V of the SOC sensor 13 is compared with a preset lower limit value X (S20), and when the detection value V becomes equal to the lower limit value X, it is determined that the discharge of the battery 11 is completed. (S22), to that effect is transmitted to the ECU 33. As the lower limit value X, it is desirable to use a value in which the SOC exceeds 0% and is in a range of 40% or less which is the lower limit of the normal use range of the battery 11.

  Receiving this transmission, the ECU 33 brings the wet multi-plate clutch 32 into a contact state (S24). Thereby, HEV1 will be in the state which drive | works with the driving force of the diesel engine 4 mainly. Next, the measured value of the rotation sensor 34 and the measured value of the vehicle speed sensor 35 are input (S26), and the required travel required for the travel of the HEV 1 based on the measured values and the first map data set in advance The torque is determined (S28) and transmitted to the HCU 14. As this 1st map data, what is called a torque curve set for every diesel engine 4 is illustrated.

  The HCU 14 determines the required regenerative torque based on the transmitted required travel torque and preset second map data (S30), and performs regenerative power generation of the motor generator 5 at the required regenerative torque. The battery 11 is charged through the inverter 10 (S32).

  FIG. 3 shows an example of the second map data. This map data is obtained in advance by experiments and calculations for the relationship between the engine speed of the diesel engine 4 and the torque for setting the temperature of the exhaust gas G in the vicinity of the inlet of the catalytic converter 15 to a preset value. is there. In this map data, when the required running torque H is obtained, the required regenerative torque D for obtaining the temperature T of the exhaust gas G in the vicinity of the inlet of the catalytic converter 15 (for example, about 150 ° C. or more) and the optimum point of fuel consumption This is the difference between the required travel torque H in the number K and the map data. The determination of the required travel torque, the determination of the required regenerative torque, and the charging of the battery 11 by regenerative power generation are repeatedly performed according to the change in the travel state of the HEV 1 (S26 to S32).

  By performing the control as described above, a load is applied to the diesel engine 4 by the regenerative power generation of the motor generator 5 in addition to the required travel torque, so that the temperature of the exhaust gas G flowing into the SCR catalyst 17 is surely activated. The lower limit value Z can be increased. Further, since the temperature of the exhaust gas G rises, it is not necessary to reduce the amount of NOx generated in the diesel engine 4 in order to cover the decrease in the NOx purification rate in the SCR catalyst 17, and the NOx in the SCR catalyst 17. A part of the load applied to the diesel engine 4 during the reduction purification can be recovered as electric energy by the regenerative power generation of the motor generator 5 and charged to the battery 11.

  For these reasons, the HEV 1 can reliably reduce and purify NOx in the exhaust gas G while improving the fuel efficiency as compared with the prior art.

  Furthermore, since the temperature of the exhaust gas G rises, all of the urea water injected from the injection nozzle 16 is hydrolyzed and reaches the SCR catalyst 17 in a gas phase state, so that NOx in the SCR catalyst 17 is increased. It is also possible to suppress a decrease in the purification rate.

  The control method which consists of the 2nd Embodiment of this invention is demonstrated below based on FIG. In FIG. 4, the same control numbers as in FIG. 2 are assigned the same step numbers, and the description thereof is omitted.

  In the control method according to the first embodiment described above, the SOC of the battery 11 is set in advance for charging the battery 11 by regenerative power generation of the motor generator 5 (S32) from the viewpoint of preventing the deterioration of the battery 11. It is necessary to stop when the upper limit is reached. The upper limit value is preferably the rated maximum capacity of the battery 11. The rated maximum capacity is a value defined in advance according to the manufacturing specifications of the battery 11, and is normally a state in which the SOC of the battery 11 is 70 to 90%.

  However, if the charging of the battery 11 is stopped in step 32, the control by the ECU 33 and the HCU 14 is terminated, and there is a possibility that the NOx purification rate in the SCR catalyst 17 is interrupted in a state where it does not increase to a sufficient level.

  Therefore, in order to continue the reliable reduction and purification of NOx in the exhaust gas G even after the SOC of the battery 11 reaches a preset upper limit value, in addition to the control method according to the first embodiment, Implement the control method.

  After charging the battery 11 (S32), the HCU 14 compares the detection value V of the SOC sensor 13 with a preset upper limit value Y (S34). When the detected value V becomes equal to the upper limit value Y, it is determined that the charging of the battery 11 has been completed (S36), and the motor generator 5 is driven to rotate by power feeding from the battery 11 through the inverter 10. The wet multi-plate clutch 32 is disengaged (S38), and the fact is transmitted to the ECU 33.

  Receiving this transmission, the ECU 33 adjusts the fuel injection amount of the injector 24 to set the engine speed of the diesel engine 4 to a preset value, and closes the exhaust throttle valve 30 (S40). As a preset value related to the engine speed, the idle speed when the vehicle is stopped is set so that torque fluctuation is less likely to occur when the wet multi-plate clutch 32 is reconnected when the HEV 1 is suddenly accelerated. A higher value is preferable.

  By performing the control as described above, the HEV 1 performs the motor traveling by the motor generator 5 while maintaining the idle operation state of the diesel engine 4 during the traveling after the battery 11 is charged to the upper limit value Y, Since the exhaust pressure is increased by closing the exhaust throttle valve 30 and a new load is applied to the diesel engine 4, it is possible to suppress a decrease in the temperature of the exhaust gas G and to continue reduction and purification of NOx. is there.

  The control method which consists of the 3rd Embodiment of this invention is demonstrated below based on FIG. In FIG. 5, the same control numbers as those in FIGS. 2 and 4 are denoted by the same step numbers, and the description thereof is omitted.

  In the control method according to the first embodiment described above, when the driver turns off the accelerator and the HEV 1 enters the inertial running state during NOx reduction purification (S24 to S32) in the SCR catalyst 17, the SCR catalyst 17 Since the temperature of the inflowing exhaust gas G is lowered, there is a possibility that the NOx purification rate in the SCR catalyst 17 is interrupted without increasing to a sufficient level.

  Therefore, in order to continue the reliable reduction and purification of NOx in the exhaust gas G even after HEV1 enters the inertial running state during the reduction and purification of NOx by the SCR catalyst 17, the control method according to the first embodiment is used. In addition, the following control method is implemented.

  In parallel with the determination of the required travel torque, the determination of the required regenerative torque, and the charging of the battery 11 by regenerative power generation according to the change in the travel state of the HEV 1 (S26 to S32), the ECU 33 detects the accelerator opening sensor. It is determined from the detected value of 36 whether or not the accelerator is off (S42).

  When the accelerator is off, it is determined that the HEV 1 is in an inertial running state due to deceleration or downhill (S44), and that fact is transmitted to the HCU 14. Then, the wet multi-plate clutch 32 is disengaged (S46), the fuel injection amount of the injector 24 is adjusted to set the engine speed of the diesel engine 4 to a preset value, and the exhaust throttle valve 30 is closed. (S48). The preset value related to the engine speed is the same as that in step 40 in the control method according to the second embodiment described above.

  The HCU 14 that has received the above transmission performs regenerative power generation of the motor generator 5 at the maximum required regenerative torque Dmax in parallel and charges the battery 11 through the inverter 10 (S50). The maximum required regenerative torque Dmax corresponds to the case where the required travel torque H is zero in the second map data shown in FIG.

  By performing the control as described above, the HEV 1 is exhausted by closing the exhaust throttle valve 30 while maintaining the idle operation state of the diesel engine 4 during the travel after the HEV 1 is in an inertia traveling state due to a downhill or the like. Since the pressure is increased and a load is newly applied to the diesel engine 4, it is possible to suppress a decrease in the temperature of the exhaust gas G, and to continue the reduction and purification of NOx and to continue the regenerative power generation. It is.

1 HEV
3 Drive shaft 4 Diesel engine 5 Motor generator 7 Hybrid system 8 Exhaust passage 9 Exhaust gas purification system 11 Battery 12 Motor clutch 13 SOC sensor 14 HCU
17 SCR catalyst 32 Wet multi-plate clutch 33 ECU
34 Rotation sensor 35 Vehicle speed sensor 36 Accelerator opening sensor

Claims (5)

A motor-driven generator connected to a battery and a hybrid system capable of connecting / disconnecting an engine and a drive shaft, an injection nozzle for supplying urea water sequentially installed from the upstream side to an exhaust passage through which exhaust gas from the engine flows, and selection A control method for a hybrid vehicle including an exhaust gas purification system having a reduction catalyst,
When the hybrid vehicle is running and the urea water is injected from the injection nozzle, the temperature of the exhaust gas flowing into the selective catalytic reduction catalyst is less than the lower limit value of the activation temperature of the selective catalytic reduction catalyst. When the motor generator and the drive shaft are in contact with each other, the motor generator is rotationally driven by power supply from the battery, while the engine and the drive shaft are in a disconnected state,
When the storage rate of the battery reaches a preset lower limit, the engine and the drive shaft are brought into contact with each other, and the engine speed of the engine and the vehicle speed of the hybrid vehicle are preset. The required running torque is determined from the map data of 1,
A control method for a hybrid vehicle, wherein the motor generator is regeneratively generated with a required regenerative torque determined from the required running torque and preset second map data to charge the battery. An exhaust throttle valve interposed in the exhaust passage,
After the battery is charged, when the storage rate of the battery reaches a preset upper limit, the motor generator and the drive shaft are in contact with each other and the motor generator is supplied with power from the battery. Rotate and drive
The hybrid vehicle control method according to claim 1, wherein the engine and the drive shaft are disconnected, the engine speed of the engine is set to a preset value, and the exhaust throttle valve is closed.   The hybrid vehicle control method according to claim 2, wherein the preset upper limit value is a rated maximum capacity of the battery. An exhaust throttle valve interposed in the exhaust passage,
When the hybrid vehicle enters an inertial running state after charging the battery, the motor generator is regeneratively generated with the maximum required regenerative torque to charge the battery, and the engine and the drive shaft are disconnected. 2. The method for controlling a hybrid vehicle according to claim 1, wherein the engine speed of the engine is set to a preset value and the exhaust throttle valve is closed.   The hybrid vehicle control method according to any one of claims 1 to 4, wherein the preset lower limit value is a value in a range of more than 0 and 40% or less.

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