Hybrid vehicle control device

Abstract

To suppress atmospheric release of NOx due to combustion in an engine.SOLUTION: While a catalyst device 18 has not been warmed up, a hybrid vehicle control device causes a generator 13 to perform: regenerative drive when demand drive force of a hybrid vehicle is equal to or less than maximum lean combustion drive force; and power drive when the same exceeds the maximum lean combustion drive force. The maximum lean combustion drive force represents drive force of the hybrid vehicle generated with an engine 10 when the same is operated at maximum output achievable through lean combustion.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a control device for a hybrid vehicle. [Background technology]

[0002] Patent Document 1 describes a control device for a hybrid vehicle equipped with an engine that uses hydrogen gas as fuel and has an air-fuel ratio sensor installed in the exhaust passage. When hydrogen gas is burned, water is produced. When the engine is cold, the water produced by combustion is difficult to vaporize, making the air-fuel ratio sensor more susceptible to water damage. The control device in Patent Document 1 suppresses water damage to the air-fuel ratio sensor by performing lean combustion when the engine is cold. Furthermore, the control device promotes engine warm-up by applying a load to the engine using a generator motor when the engine is cold. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-047282 Summary of the Invention [Problem to be solved by the invention]

[0004] When an engine is cold, the catalytic converter for purifying exhaust gases is inactive and cannot sufficiently purify the NOx in the exhaust. Even in this state, if the air-fuel ratio of the mixture burned in the engine is made leaner until the amount of NOx produced by combustion decreases, the amount of NOx released into the outside air can be kept to an acceptable level. However, if the air-fuel ratio is made leaner until the amount of NOx produced decreases, the engine's output performance will decrease.

[0005] On the other hand, as in the above document, if a load is applied to the engine by the generator motor, the power that can be extracted as driving force for the vehicle is reduced by the amount of the load. Therefore, if an attempt is made to promote engine warm-up by applying a load by the generator motor while suppressing NOx emissions by making the air-fuel ratio lean, there is a risk that the power performance of the hybrid vehicle will be insufficient when the engine is cold. [Means for solving the problem]

[0006] The control device for a hybrid vehicle that solves the above problems is: A control device for a hybrid vehicle including an engine equipped with a catalytic converter that purifies nitrogen oxides in exhaust, a generator motor connected to the engine, a battery that exchanges electric power with the generator motor, and a heater that generates heat in response to the supply of electric power to heat the catalytic converter, wherein the driving force of the hybrid vehicle generated by the engine when the engine is operated at the maximum output at which lean combustion is possible is defined as lean combustion maximum driving force, the driving force of the hybrid vehicle based on the operation amount of the accelerator pedal is defined as driver requested power, an upper limit value of electric power that can be charged to the battery is defined as an input limit, and a requested value of electric power requested to the heater is defined as heater requested power, and when the catalytic converter reaches a temperature below a predetermined temperature, At this time, when the driver requested power is equal to or less than a value obtained by subtracting the heater requested power and the input limit from the lean-combustion maximum driving force, the sum of the driver requested power, the input limit, and the heater requested power is set as the target power of the engine, the heater requested power is supplied from the battery to the heater, and the generator motor is regeneratively driven to generate the sum of the input limit and the heater requested power, and when the driver requested power exceeds the lean-combustion maximum driving force, the lean-combustion maximum driving force is set as the target power of the engine, and the generator motor is power-driven to output a value obtained by subtracting the lean-combustion maximum driving force from the driver requested power. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram schematically illustrating the configuration of a drive system of a hybrid vehicle. [Figure 2] FIG. 2 is a diagram schematically illustrating the configuration of a control device for the hybrid vehicle of FIG. [Figure 3] 2 is a graph showing the relationship between the excess air ratio and the amount of NOx produced in the engine mounted on the hybrid vehicle of FIG. 1. [Figure 4] 2 is a graph showing the relationship between engine speed and maximum engine torque when the engine mounted on the hybrid vehicle of FIG. 1 is operated at three different excess air ratios. [Figure 5] 3 is a flowchart of a catalyst pre-warm-up control routine executed by the control device. [Figure 6] Graphs showing the changes in target engine power (A), excess air ratio (B), NOx generation amount (C), and exhaust thermal energy (D) against driver requested power during catalyst pre-warm-up control by the control device. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of a control device for a hybrid vehicle will be described in detail below with reference to FIGS. <Hybrid vehicle drivetrain configuration> First, with reference to FIG. 1, the configuration of a drive system of a hybrid vehicle equipped with a control device of this embodiment will be described. As shown in FIG. 1, the hybrid vehicle is equipped with an engine 10. The engine 10 is a hydrogen gas engine that uses hydrogen gas as fuel. The engine 10 is connected to wheels 12 via a transmission 11. The engine 10 is also connected to a generator motor 13. The transmission 11 changes the rotational speed ratio by switching gears. The transmission 11 is provided with a clutch 14 for establishing a neutral gear in which power transmission between the engine 10 and the wheels 12 is connected and disconnected. Note that even when the clutch 14 is disconnected and the neutral gear is established, the connection between the engine 10 and the generator motor 13 is maintained.

[0010] The generator motor 13 is electrically connected to the battery 16 via an inverter 15. The generator motor 13 generates power by receiving power discharged from the battery 16. The generator motor 13 also generates power by receiving power from an external source and charges the generated power into the battery 16. The inverter 15 drives the generator motor 13 by adjusting the power exchanged between the generator motor 13 and the battery 16.

[0011] A catalytic converter 18 that purifies nitrogen oxides (NOx) in the exhaust gas is installed in an exhaust passage 17 of the engine 10. A heater 19 that generates heat in response to the supply of electric power to heat the catalytic converter 18 is installed in the catalytic converter 18. The heater 19 is electrically connected to the battery 16 via a power adjustment circuit 20. The power adjustment circuit 20 is a circuit for adjusting the electric power supplied from the battery 16 to the heater 19.

[0012] <Control device configuration> Next, the configuration of a control device for a hybrid vehicle will be described with reference to Fig. 2. As shown in Fig. 2, the control device of this embodiment includes an electronic control unit 21 for vehicle control. The electronic control unit 21 includes an arithmetic processing device 22 and a storage device 23. The storage device 23 stores programs and data for vehicle control. The arithmetic processing device 22 reads and executes programs from the storage device 23 to perform various processes for vehicle control.

[0013] The electronic control unit 21 receives detection signals from various sensors installed in the engine 10. Examples of sensors installed in the engine 10 include an air flow meter 29, an air-fuel ratio sensor 30, a water temperature sensor 31, an intake air temperature sensor 32, and a crank angle sensor 33. The air flow meter 29 detects the intake air flow rate of the engine 10. The air-fuel ratio sensor 30 detects the air-fuel ratio of the mixture burned in the engine 10. The water temperature sensor 31 detects the coolant temperature of the engine 10. The intake air temperature sensor 32 detects the intake air temperature of the engine 10. The crank angle sensor 33 detects the rotational phase of the crankshaft of the engine 10. The electronic control unit 21 calculates the engine speed, which is the rotational speed of the crankshaft of the engine 10, from the detection result of the crank angle sensor 33. The electronic control unit 21 also receives detection signals from sensors installed in parts other than the engine 10 in the hybrid vehicle. Examples of such sensors are an accelerator pedal sensor 34 and a vehicle speed sensor 35. The accelerator pedal sensor 34 is a sensor that detects the amount of accelerator pedal operation by the driver, and the vehicle speed sensor 35 is a sensor that detects the traveling speed of the hybrid vehicle. Furthermore, the electronic control unit 21 monitors the charge / discharge amount of the battery 16, and calculates the battery charge amount, which is the amount of power stored in the battery 16, from the monitoring results.

[0014] The electronic control unit 21 performs various controls of the hybrid vehicle based on the detection results of these sensors. For example, the electronic control unit 21 controls the power running / regenerative torque of the generator motor 13 through control of the inverter 15, and controls the power of the heater 19 through control of the power adjustment circuit 20. The electronic control unit 21 also controls the gear shifting of the transmission 11. Furthermore, the electronic control unit 21 controls the operation of the engine 10 through control of various actuators installed in the engine 10. The actuators of the engine 10 controlled by the electronic control unit 21 include a throttle valve 24, a hydrogen gas injector 25, an ignition device 26, a water injector 27, and an exhaust gas recirculation device 28. The throttle valve 24 is a valve for adjusting the amount of intake air used for combustion in the engine 10. The hydrogen gas injector 25 is a valve for injecting hydrogen gas into the intake air. The ignition device 26 is a device for igniting a mixture of hydrogen gas and intake air by spark discharge. The water injection valve 27 is a valve that injects water into the intake air. The exhaust gas recirculation device 28 is a device that recirculates a portion of the exhaust gas into the intake air.

[0015] <Relationship between the air-fuel ratio of the engine 10 and the exhaust / output characteristics> In engine 10, nitrogen oxides (NOx) are produced during the combustion reaction of hydrogen gas. In the hybrid vehicle of FIG. 1, a catalytic converter 18 installed in an exhaust passage 17 of engine 10 reduces and purifies the NOx produced by the combustion, thereby reducing and purifying the NOx, thereby suppressing the emission of NOx into the outside air. However, after engine 10 is started, for a period until the warm-up of catalytic converter 18 is complete, catalytic converter 18 is unable to fully demonstrate its NOx purification capability. Meanwhile, the amount of NOx produced by the combustion of hydrogen gas varies depending on the combustion state.

[0016] FIG. 3 shows the relationship between the excess air ratio λ and the amount of NOx generated. The excess air ratio λ represents the ratio of the air-fuel ratio to the stoichiometric air-fuel ratio. That is, when the excess air ratio λ is "1", the engine 10 performs stoichiometric combustion at the stoichiometric air-fuel ratio. When the excess air ratio λ exceeds "1", the engine 10 performs lean combustion at an air-fuel ratio leaner than the stoichiometric air-fuel ratio. The amount of NOx generated in the figure represents the weight ratio of NOx in the exhaust. The permissible value shown in FIG. 3 represents the allowable upper limit of the amount of NOx emitted into the outside air. The permissible value is preset so that the amount of NOx emitted into the outside air satisfies the regulations.

[0017] As shown in FIG. 3, the amount of NOx generated is maximum when the excess air ratio λ is slightly greater than 1. As the excess air ratio λ is increased from the value at which the amount of NOx generated is maximum, the amount of NOx generated gradually decreases. As shown in the same figure, when the excess air ratio λ is in the range of λL or more, the amount of NOx generated is below the allowable value. Therefore, even if the catalytic converter 18 is not yet warmed up, by performing lean combustion with the excess air ratio λ set to λL or more, the amount of NOx emitted into the outside air can be kept below the allowable value.

[0018] FIG. 4 shows the relationship between engine speed and maximum engine torque when the excess air ratio λ is "1" and when the excess air ratio is "λL." There is a limit to the amount of intake air that can be filled into the cylinders of engine 10. On the other hand, the higher the excess air ratio λ, the smaller the proportion of hydrogen gas in the intake air filled into the cylinders. Therefore, during lean combustion, the maximum output of engine 10 is smaller than during stoichiometric combustion.

[0019] <Control when catalyst is not warmed up> Next, a description will be given of the catalyst pre-warm-up control executed by the electronic control unit 21. The catalyst pre-warm-up control is a control executed to suppress NOx emissions when the catalytic converter 18 is in an unwarmed state and to promote warm-up of the catalytic converter 18.

[0020] A flowchart of the catalyst unwarmed state control routine is shown in Figure 5. The electronic control unit 21 repeatedly executes the processing of this routine at predetermined control intervals while the hybrid vehicle is in operation.

[0021] When processing of this routine starts, the electronic control unit 21 first determines in step S100 whether warming up of the catalytic converter 18 has been completed. Warming up of the catalytic converter 18 is completed when the catalytic converter 18 reaches or exceeds a predetermined temperature. The predetermined temperature here is the temperature at which the catalyst of the catalytic converter 18 becomes active. The temperature of the catalytic converter 18 during the period from cold start of the engine 10 until warming up is completed correlates with the engine 10 coolant temperature. Therefore, in this embodiment, it is determined whether the catalytic converter 18 is at or above the predetermined temperature based on the engine 10 coolant temperature. If warming up of the catalytic converter 18 has been completed (YES), the electronic control unit 21 ends processing of this routine. On the other hand, if warming up of the catalytic converter 18 has not been completed, i.e., if the catalytic converter 18 has not yet been warmed up (NO), the electronic control unit 21 proceeds to step S110.

[0022] In step S110, the electronic control unit 21 acquires the driver's requested power PU, the heater's requested power PH, the input limit WIN, and the output limit WOUT. The driver's requested power PU represents a value obtained by converting the hybrid vehicle's requested driving force, calculated based on the accelerator pedal depression amount, into the electric power of the generator motor 13 required to generate power equal to the requested driving force value. The heater's requested power PH is a requested value of electric power to be supplied to the heater 19 to heat the catalytic converter 18, and this value is calculated based on the coolant temperature of the engine 10, etc. The input limit WIN represents the upper limit of the electric power that can be charged to the battery 16, and the output limit WOUT represents the upper limit of the electric power that can be discharged from the battery 16, and these values ​​are calculated based on the battery storage amount, battery temperature, etc. The electronic control unit 21 calculates the values ​​of the driver's requested power PU, the heater's requested power PH, the input limit WIN, and the output limit WOUT in a routine separate from this routine.

[0023] Next, in step S120, the electronic control unit 21 calculates the lean-burn maximum power PLEAN. The lean-burn maximum power PLEAN represents the maximum output of the engine 10 when the excess air ratio λ is set to the above-mentioned "λL," converted into the electric power of the generator-motor 13 required to generate power equal to that value. In other words, the lean-burn maximum power PLEAN is the electric power converted value of the driving force of the hybrid vehicle generated by the engine 10 when the engine 10 is operated at the maximum output at which lean combustion is possible. The electronic control unit 21 calculates the lean-burn maximum power PLEAN based on the engine speed, etc.

[0024] Next, in step S130, the electronic control unit 21 determines whether the driver requested power PU is equal to or less than the coasting determination value PCST. The coasting determination value PCST is set to the maximum value of the range of values ​​of the driver requested power PU, which indicates that the hybrid vehicle does not require driving force, i.e., is coasting or is stopped. If the driver requested power PU is equal to or less than the coasting determination value PCST (YES), the electronic control unit 21 proceeds to step S140, and if not (NO), the electronic control unit 21 proceeds to step S160.

[0025] If the process proceeds to step S140 (S130: YES), the electronic control unit 21 disengages the clutch 14 and places the transmission 11 in neutral in step S140. Then, in the following step S150, the electronic control unit 21 sets the sum (PH+WIN) of the heater required electric power PH and the input limit WIN as the value of the target engine power PE. Also, in step S150, the electronic control unit 21 sets the value obtained by inverting the sign of "PH+WIN" as the value of the target MG power PMG. Furthermore, in step S150, the electronic control unit 21 sets the excess air factor λ of the engine 10 to "λL." After the process of step S150, the electronic control unit 21 ends the process of this routine for the current control cycle.

[0026] On the other hand, if the process proceeds to step S160 (S130: NO), the electronic control unit 21 performs the following process. That is, in step S160, the electronic control unit 21 determines whether the driver required power PU is equal to or less than "PLEAN-PH-WIN." If the driver required power PU is equal to or less than "PLEAN-PH-WIN" (YES), the electronic control unit 21 proceeds to step S170, or if the driver required power PU exceeds "PLEAN-PH-WIN" (NO), the electronic control unit 21 proceeds to step S180.

[0027] If the process proceeds to step S170 (S160: YES), the electronic control unit 21 sets the sum of the driver requested power PU, the heater requested electric power PH, and the input limit WIN as the value of the target engine power PE in step S170. The electronic control unit 21 also sets the value obtained by inverting the sign of "PH+WIN" as the value of the target MG power PMG in step S170. Furthermore, the electronic control unit 21 also sets the excess air factor λ of the engine 10 to "λL" in step S170. After the process of step S170, the electronic control unit 21 ends the process of this routine for the current control cycle.

[0028] On the other hand, if the process proceeds to step S180 (S160: NO), the electronic control unit 21 determines whether the driver requested power PU is equal to or less than "PLEAN-PH+WOUT" in step S180. If the driver requested power PU is equal to or less than "PLEAN-PH+WOUT" (YES), the electronic control unit 21 proceeds to step S190, and if the driver requested power PU exceeds "PLEAN-PH+WOUT" (NO), the electronic control unit 21 proceeds to step S200.

[0029] If the process proceeds to step S190 (S180: YES), the electronic control unit 21 sets the value of lean-burn maximum power PLEAN as the value of target engine power PE in step S190. Also in step S190, the electronic control unit 21 sets the value obtained by subtracting lean-burn maximum power PLEAN from driver-requested power PU as the value of target MG power PMG. Furthermore, in step S190, the electronic control unit 21 sets the excess air ratio λ of the engine 10 to "λL." After processing step S190, the electronic control unit 21 ends the processing of this routine for the current control cycle.

[0030] On the other hand, if the process proceeds to step S200 (S180: NO), the electronic control unit 21 sets the value obtained by subtracting the output limit WOUT from the driver requested power PU as the value of the target MG power PMG in step S200. Also, in step S200, the electronic control unit 21 sets a value equal to the output limit WOUT as the value of the target MG power PMG. Furthermore, in step S200, the electronic control unit 21 sets the excess air ratio λ of the engine 10 to "1". Then, after processing step S200, the electronic control unit 21 ends the processing of this routine for the current control cycle.

[0031] As described above, in this routine, the electronic control unit 21 sets the target engine power PE, the target MG power PMG, and the excess air factor λ of the engine 10 when the catalytic converter 18 is not yet warmed up. After completing this routine, the electronic control unit 21 controls the engine 10 to generate power equal to the power generated by the generator motor 13 using electric power equivalent to the target engine power PE under the excess air factor λ set in this routine. Specifically, the electronic control unit 21 controls the opening of the throttle valve 24 to an opening that provides the amount of intake air required to generate the power under the excess air factor λ set in this routine. The electronic control unit 21 then controls the hydrogen gas injector 25 to inject an amount of hydrogen gas that provides the set excess air factor λ for the amount of intake air. The opening of the throttle valve 24 may be feedback-controlled based on the detection result of the air flow meter 29. The injection amount of the hydrogen gas injector 25 may also be feedback-controlled based on the detection result of the air-fuel ratio sensor 30.

[0032] Furthermore, when the catalytic converter 18 is not yet warmed up, the electronic control unit 21 controls the inverter 15 so that the charge / discharge amount of the battery 16 for the generator motor 13 is equal to the value of the target MG power PMG. Furthermore, the electronic control unit 21 at this time controls the power adjustment circuit 20 so that the maximum power supplied to the heater 19 is such that the discharge amount of the battery 16 is equal to or less than the output limit WOUT and is equal to or less than the heater required power PH.

[0033] When the warm-up of the catalytic converter 18 is completed (S100: YES), the electronic control unit 21 sets the target engine power PE, the target MG power PMG, and the excess air ratio λ of the engine 10 in the following manner in the processing of another routine.

[0034] When the warm-up of the catalytic converter 18 is complete, the electronic control unit 21 controls the charge / discharge amount of the battery 16 so as to maintain the battery charge amount at a predetermined control target value. Specifically, the electronic control unit 21 sets the target charge / discharge amount of the battery 16 so as to bring the battery charge amount closer to the control target value within a range in which the charge amount of the battery 16 is equal to or less than the input limit WIN and the discharge amount of the battery 16 is equal to or less than the output limit WOUT. The electronic control unit 21 then sets a value equal to the target charge / discharge amount as the value of the target MG power PMG. In this case, the electronic control unit 21 also sets the value obtained by subtracting the target MG power PMG from the driver requested power PU as the value of the target engine power PE. In addition, in this case, the electronic control unit 21 sets the value of the excess air ratio λ of the engine 10 to "λL" if the target engine power PE is equal to or less than the lean-burn maximum power PLEAN, and to "1" otherwise.

[0035] <Effects of the embodiment> The operation and effects of this embodiment will be described. Figure 6(A) shows the change in target engine power PE relative to driver demand power PU during execution of control when the catalyst is not yet warmed up. Figure 6(B) shows the change in excess air ratio λ relative to driver demand power PU during execution of control when the catalyst is not yet warmed up. Figures 6(C) and 6(D) show the change in the amount of NOx generated by engine 10 and the change in exhaust heat energy relative to driver demand power PU during control when the catalyst is not yet warmed up, respectively.

[0036] Furthermore, sections A to E shown in FIG. 6 respectively indicate the ranges of values ​​of driver requested power PU as follows: Section A is the range of values ​​of driver requested power PU that are equal to or less than the coasting judgment value PCST; Section B is the range of values ​​of driver requested power PU that exceed the coasting judgment value PCST and are equal to or less than "PLEAN-PH-WIN"; Section C is the range of values ​​of driver requested power PU that exceed "PLEAN-PH-WIN" and are equal to or less than the lean combustion maximum power PLEAN; Section D is the range of values ​​of driver requested power PU that exceed the lean combustion maximum power PLEAN and are equal to or less than "PLEAN+WOUT". Section D is the range of values ​​of driver requested power PU that exceed "PLEAN+WOUT".

[0037] 6A to 6D also show, with dashed two-dot lines, the transitions of the target engine power PE, excess air factor λ, NOx generation amount, and exhaust heat energy relative to the driver demand power PU when catalyst warm-up control is not executed. For ease of explanation, the target charge / discharge amount of the battery 16 is set to "0." In this case, a value equal to the driver demand power PU is set as the target engine power PE. Therefore, in this case, the engine 10 performs lean combustion with the excess air factor λ set to "λL" in sections A to C where the driver demand power PU is equal to or less than the lean-burn maximum power PLEAN. Furthermore, in this case, the engine 10 performs stoichiometric combustion with the excess air factor λ set to "1" in sections D and E where the driver demand power PU exceeds the lean-burn maximum power PLEAN. Stoichiometric combustion generates NOx exceeding the allowable value. At this time, the catalytic converter 18 has not yet warmed up and is unable to sufficiently purify NOx. Therefore, when the driver required power PU exceeds the lean burn maximum power PLEAN, NOx exceeding the allowable amount is released into the outside air.

[0038] In contrast, in this embodiment, in sections D and E where driver required power PU exceeds lean-burn maximum power PLEAN, the generator motor 13 is powered within a range in which the charge amount of the battery 16 is equal to or less than the output limit WOUT. The engine output is reduced by the amount of power generated by the generator motor 13 due to this powering. As a result, the target engine power PE is equal to or less than the lean-burn maximum power PLEAN, and the range of driver required power PU within which lean combustion can be performed by the engine 10 is extended to section D. Furthermore, in this embodiment, stoichiometric combustion is performed in section E because the target engine power PE exceeds the lean-burn maximum power PLEAN. However, in section E, power equal to the value of the output limit WOUT is supplied to power the generator motor 13, and the engine output is reduced by the amount of power generated by this powering. As a result, the amount of NOx produced by the engine 10 is reduced, thereby suppressing NOx emissions into the ambient air.

[0039] In this embodiment, in sections A to C where driver required power PU is equal to or less than lean-burn maximum power PLEAN, the generator motor 13 is regeneratively driven within a range where target engine power PE does not exceed lean-burn maximum power PLEAN. In these sections A to C, lean combustion is performed in the engine 10, so NOx emissions into the outside air are kept below an allowable value. In addition, the engine output is increased by the amount required for regenerative driving of the generator motor 13, increasing the thermal energy of the exhaust, thereby facilitating warm-up of the catalytic device 18. Furthermore, in this embodiment, the catalytic device 18 is electrically heated by the heater 19 using electric power generated by the regenerative driving of the generator motor 13, which also facilitates warm-up of the catalytic device 18.

[0040] In addition, in section A where the driver required power PU is equal to or less than the coasting judgment value PCST, the electronic control unit 21 disengages the clutch 14 of the transmission 11 to separate the engine 10 and the generator motor 13 from the wheels 12. In this state, the operating point of the engine 10 can be changed to some extent freely. In section A, the electronic control unit 21 controls the engine 10 to perform lean combustion while increasing the engine speed within a range that does not cause unstable combustion. In other words, the electronic control unit 21 at this time operates the engine 10 at an operating point with poor thermal efficiency. When thermal efficiency deteriorates, the thermal energy of the exhaust gas increases. This also promotes warming up of the catalytic converter 18.

[0041] As described above, in this embodiment, when the catalytic converter 18 is not warmed up, the generator motor 13 is regeneratively driven if the driver required power PU is equal to or less than the lean-burn maximum power PLEAN. Furthermore, when the catalytic converter 18 is not warmed up, the generator motor 13 is powered if the driver required power PU exceeds the lean-burn maximum power PLEAN. As described above, the driver required power PU is the value obtained by converting the driving force required by the hybrid vehicle into electric power. Furthermore, the lean-burn maximum power PLEAN is the value obtained by converting the driving force of the hybrid vehicle generated by the engine 10 when operating at the maximum output at which lean combustion is possible, i.e., the lean-burn maximum driving force, into electric power. Therefore, in this embodiment, when the catalytic converter 18 is not warmed up, the generator motor 13 is regeneratively driven if the driving force required by the hybrid vehicle is equal to or less than the lean-burn maximum driving force. Furthermore, when the catalytic converter 18 is not warmed up, the generator motor 13 is powered if the driving force required by the hybrid vehicle exceeds the lean-burn maximum driving force.

[0042] According to the control device for a hybrid vehicle of the present embodiment described above, the following effects can be achieved. (1) When the catalytic converter 18 is below a predetermined temperature, the electronic control unit 21 regeneratively drives the generator motor 13 if the required driving force of the hybrid vehicle is equal to or less than the lean-combustion maximum driving force. Furthermore, when the catalytic converter 18 is below a predetermined temperature, the electronic control unit 21 powers the generator motor 13 if the required driving force of the hybrid vehicle exceeds the lean-combustion maximum driving force. This expands the range of required driving force for performing lean combustion in the engine 10. Furthermore, even when performing stoichiometric combustion, the powering of the generator motor 13 reduces engine output, thereby reducing the amount of NOx produced. Therefore, the control device for a hybrid vehicle according to this embodiment has the effect of suppressing NOx emissions into the outside air before the catalytic converter 18 has fully warmed up.

[0043] (2) When the required driving force before the catalyst device 18 is warmed up is equal to or less than the maximum driving force for lean combustion, the generator motor 13 is regeneratively driven to boost the engine output. This increases the thermal energy of the exhaust gas, thereby accelerating the warming up of the catalyst device 18.

[0044] (3) The catalytic converter 18 is electrically heated using the electric power generated by the regenerative driving of the generator motor 13 when the catalytic converter 18 is not yet warmed up, which also helps to promote the warming up of the catalytic converter 18. (4) When the catalytic converter 18 is not yet warmed up and the vehicle is coasting or stopped, the engine 10 and the generator motor 13 are disconnected from the wheels 12, and the engine 10 is operated under lean combustion and the generator motor 13 is operated under regenerative driving. By operating the engine 10 under lean combustion at an operating point with poor thermal efficiency, the thermal energy of the exhaust gas is further increased, which also helps to promote the warming up of the catalytic converter 18.

[0045] <Other embodiments> This embodiment can be modified as follows: This embodiment and the following modifications can be combined and implemented within the scope of technical compatibility.

[0046] When the generator-motor 13 is regeneratively driven while the catalytic converter 18 is not yet warmed up, water injection into the intake air using the water injection valve 27 and / or exhaust gas recirculation into the intake air using the exhaust gas recirculation system 28 may be performed. Water injection and exhaust gas recirculation lower the combustion temperature of the engine 10, thereby reducing the amount of NOx generated, as shown by the two-dot chain line in FIG. 3. As a result, the lower limit of the excess air ratio λ, at which the amount of NOx generated is below the allowable value, decreases. In the example shown in FIG. 3, the lower limit of the excess air ratio λ, at which the amount of NOx generated is below the allowable value, decreases from "λL" to "λL-α." As shown by the dashed line in FIG. 4, when the excess air ratio λ is "λL-α," ​​the maximum engine torque is greater than when it is "λL." As a result, the lean-burn maximum power PLEAN increases. Therefore, if water injection and exhaust gas recirculation are performed in the engine 10 in conjunction with the regenerative driving of the generator motor 13, the range of driver requested power PU in which lean combustion can be performed when the catalyst device 18 is not yet warmed up is further expanded.

[0047] In the above embodiment, during coasting or when the vehicle is stopped and the catalyst device 18 is not yet warmed up, the engine 10 and the generator motor 13 are disconnected from the wheels 12, and the engine 10 runs on lean combustion and the generator motor 13 runs on regenerative power. However, during coasting or when the vehicle is stopped, the engine 10 and the generator motor 13 may remain connected to the wheels 12 and the engine 10 runs on lean combustion and the generator motor 13 runs on regenerative power. In this case, the process of steps S130 to S150 may be omitted from the catalyst not yet warmed up control routine in FIG. 5.

[0048] In the above embodiment, an electrically heated catalytic converter 18 equipped with a heater 19 is used, but a catalytic converter other than an electrically heated catalytic converter may be used. In that case, it is preferable to set the heater power requirement PH to "0" in the catalyst pre-warm-up control routine of FIG. 5.

[0049] In section E, rich combustion may be performed by setting the air-fuel ratio to a richer side than the stoichiometric air-fuel ratio, that is, by setting the excess air ratio λ to a value less than "1." The control device of the above embodiment can also be applied to a hybrid vehicle equipped with an engine that uses a fuel other than hydrogen gas. [Explanation of symbols]

[0050] 10...Engine 11...Gearbox 12...Wheel 13... Generator motor 14...Clutch 15...Inverter 16...Battery 17...Exhaust passage 18...Catalytic device 19...Heater 20...Power adjustment circuit 21...Electronic control unit 22...Processing device 23…Storage device 24...Throttle valve 25...Hydrogen gas injection valve 26…Ignition device 27...Water injection valve 28...Exhaust gas recirculation system 29...Air flow meter 30...Air-fuel ratio sensor 31...Water temperature sensor 32...Intake air temperature sensor 33...Crank angle sensor 34...Accelerator pedal sensor 35...Vehicle speed sensor

Claims

[Claim 1] A control device for a hybrid vehicle including an engine equipped with a catalytic converter that purifies nitrogen oxides in exhaust gas, a generator motor connected to the engine, a battery that exchanges electric power with the generator motor, and a heater that generates heat in response to the supply of electric power to heat the catalytic converter, When the driving force of the hybrid vehicle generated by the engine when the engine is operated at the maximum output at which lean combustion is possible is defined as lean combustion maximum driving force, the driving force of the hybrid vehicle based on the operation amount of the accelerator pedal is defined as driver requested power, the upper limit of the electric power that can be charged to the battery is defined as input limit, and the requested value of electric power required for the heater is defined as heater requested power, When the catalytic device is below a predetermined temperature, When the driver requested power is equal to or less than a value obtained by subtracting the heater requested power and the input limit from the lean combustion maximum driving force, the sum of the driver requested power, the input limit, and the heater requested power is set as a target power of the engine, the heater requested power is supplied from the battery to the heater, and the generator motor is regeneratively driven to generate power equivalent to the sum of the input limit and the heater requested power, When the driver requested power exceeds the lean combustion maximum driving force, the lean combustion maximum driving force is set as a target power for the engine, and the generator motor is powered to output a value obtained by subtracting the lean combustion maximum driving force from the driver requested power. A control device for a hybrid vehicle.

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