JP2005048618A - Control device for hybrid vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrict increase of NOx in a high-load side range to achieve large NOx reducing effect as a whole by using torque assist using a driving force control motor of a hybrid vehicle while sufficiently reducing NOx in a low-load side operation range of an engine by using premixed combustion. <P>SOLUTION: This device is provided with an engine control means 43 to change a premixed combustion mode with a large EGR ratio and a diffusion combustion mode with a small EGR ratio from each other in accordance with operation states of an engine 3, the driving force control motor 1 changeable between a power generating state and a torque assist state, and a motor control means 44. In an operation range for the premixed combustion mode, power generation only is executed, while in an operation range for the diffusion combustion mode, torque assist only is executed. The driving force control motor is thus controlled with relation to engine control. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for a hybrid vehicle provided with a driving force control motor capable of generating power by an engine and assisting torque to the engine.
[0002]
[Prior art]
In recent years, hybrid vehicles have been developed in which an engine and a motor are combined, and the motor generates electricity by the engine as needed, or auxiliary driving force is applied (hereinafter referred to as torque assist or simply assist). (For example, refer to Patent Document 1). In this hybrid vehicle, in an area where the engine output corresponding to the traveling load (hereinafter referred to as target engine output) is low, the engine output is set higher than the target engine output, and the motor generates power with the surplus output and the energy is supplied to the battery. Store. On the other hand, in a region where the target engine output is high, torque assist is performed by setting the engine output lower than the target engine output and supplementing the insufficient output with the motor output (driving the motor with the energy stored in the battery).
[0003]
That is, since the actual engine output fluctuation range can be set narrower than the target engine output fluctuation range, the engine can be easily operated in a high-efficiency region, and fuel consumption and exhaust gas purification performance can be improved.
[0004]
Also, in order to suppress the formation of nitrogen carbide (NOx) and soot in direct injection engines (engines provided with fuel injection means in the combustion chamber) such as diesel engines, in recent years, premixed compression ignition combustion (hereinafter referred to as premixing) A new combustion mode called “combustion” has been proposed (for example, Patent Document 2). In this combustion mode, in order to prevent premature ignition and to suppress generation of NOx and the like, a large amount of exhaust gas is recirculated to the intake air (hereinafter, the exhaust gas recirculated to the intake air is referred to as EGR gas), and the compression top dead center of the cylinder. The fuel and the fuel are sufficiently mixed by injecting the fuel in the middle of the compression stroke much earlier, and then the mixture is self-ignited and burned at the end of the compression stroke.
[0005]
However, if the intake air at the time of combustion contains a lot of EGR gas, the amount of air contained in the intake air is reduced accordingly, so that it is difficult to realize such a combustion mode on the high speed rotation and high load side of the engine. It is. For this reason, conventionally, premixed combustion is performed as described above mainly in the operating region on the low speed rotation and low load side, and at this time, the ratio of the EGR gas contained in the intake air (hereinafter referred to as the EGR rate) is compared. Control over the first set value that is higher than the upper limit, mainly in the operating region on the high speed rotation or high load side, the fuel injection mode is switched to perform fuel injection near the top dead center of the compression stroke, and Combustion is performed in a state where the EGR rate is controlled to be equal to or lower than a second set value lower than the first set value (hereinafter referred to as diffusion combustion).
[0006]
[Patent Document 1]
JP 2002-242721 A
[Patent Document 2]
JP 2000-110669 A
[0007]
[Problems to be solved by the invention]
In the engine described in Patent Document 2, generation of NOx and soot can be sufficiently suppressed in the operation region on the low load side where the premixed combustion is performed, but on the high load side where diffusion combustion is performed. In the operation region, the amount of NOx generated tends to increase. That is, during diffusion combustion, there is no time for sufficient mixing of fuel and air, resulting in non-uniformity in the air-fuel mixture concentration, and combustion temperature rises and NOx is generated at a portion where the air-fuel mixture concentration is close to the theoretical air-fuel ratio. The Moreover, in the high load side operation region, the fuel injection amount is large and the heat generation amount is large, and diffusion combustion is performed under such circumstances, so that the NOx generation amount tends to increase.
[0008]
For this reason, it is desired to suppress an increase in NOx in a region where diffusion combustion is performed.
[0009]
In addition, the control of the hybrid vehicle that switches the motor as shown in Patent Document 1 between the power generation state and the torque assist state, and the engine control that switches between the premixed combustion state and the diffusion combustion state as shown in Patent Document 2. However, there has been no conventional technique for controlling them by associating them with a special relationship.
[0010]
In view of such circumstances, the present invention makes it possible to sufficiently reduce NOx in the operating region on the engine low load side where the combustion mode with a large EGR rate can be set, while the combustion mode with a large EGR rate. The hybrid vehicle can suppress the increase of NOx by using torque assist using the driving force control motor of the hybrid vehicle in the driving region where the load cannot be increased, and can exhibit a significant NOx reduction effect as a whole. A control apparatus is provided.
[0011]
[Means for Solving the Problems]
In order to solve the above-described problems, a control apparatus for a hybrid vehicle according to the present invention includes an operation state detection unit that detects an operation state of an engine, a temperature detection unit that detects a temperature related to the engine temperature, and a detection by the temperature detection unit. Engine control means for switching between a first combustion mode with a high EGR rate and a second combustion mode with a low EGR rate when the temperature to be operated is equal to or higher than a predetermined temperature, A driving force control motor capable of switching between a state of generating power by rotation and a state of performing torque assist to the engine, and a motor control means for controlling the driving force control motor according to the operating state of the engine, The motor control means performs only power generation in the first combustion mode and performs only torque assist in the second combustion mode. And controls the power control motor.
[0012]
According to this configuration, since the torque assist is performed within the operation region in which the second combustion mode is set, the generated torque of the engine itself becomes lower than the torque to be transmitted to the drive wheels by the amount of the torque assist. NOx is reduced compared to the case where torque assist is not performed. On the other hand, in order to compensate for the power consumption by the torque assist, power generation is performed in the operation region set to the first combustion mode. In this power generation state, the generated torque of the engine itself is higher than the torque to be transmitted to the drive wheels. However, NOx is suppressed sufficiently low by combustion in the first combustion mode with a large EGR rate. Therefore, NOx is effectively reduced as a whole.
[0013]
In this invention, the engine control means is configured to prohibit the execution of the first combustion mode when the temperature detected by the temperature detection means is lower than a predetermined temperature, and the motor control means When the temperature is lower than the temperature, power is generated in the low load area, torque assist is performed in the high load area, and the driving power is reduced so that the power generation amount and torque assist amount are reduced compared to when the temperature is equal to or higher than the predetermined temperature. It is preferable to control the control motor.
[0014]
In this way, when the temperature related to the engine temperature is low, the combustion stability of the engine is impaired by a large amount of EGR, or the activation of the catalyst provided in the exhaust passage is delayed due to the low exhaust temperature. In order to avoid such a situation, the execution of the first combustion mode is prohibited. Even if the execution of the first combustion mode is prohibited in this way, the motor is changed between the power generation state and the torque assist state in accordance with the driving state, thereby obtaining an effect such as fuel efficiency improvement as a hybrid vehicle. It is done. However, since the NOx reduction action by the first combustion mode cannot be obtained, the amount of power generation is less than that when the temperature related to the engine temperature is high in order to avoid an increase in NOx when the motor is in a power generation state. Accordingly, the torque assist amount is reduced.
[0015]
The battery control unit further includes a storage amount detection unit that detects a parameter related to a storage amount of a battery that is electrically connected to the driving force control motor, and the motor control unit is configured to detect when the storage amount is equal to or greater than a predetermined increase determination reference value. It is preferable that power generation by the driving force control motor in the first combustion mode is suppressed or torque assist in the second combustion mode is increased.
[0016]
In this way, excessive charging of the battery by power generation is avoided, and the battery is protected.
[0017]
The battery control unit further includes a storage amount detection unit that detects a parameter related to a storage amount of a battery that is electrically connected to the driving force control motor, and the motor control unit is configured to detect when the storage amount is equal to or less than a predetermined decrease determination reference value. It is preferable that torque assist by the driving force control motor in the second combustion mode is suppressed or power generation in the first combustion mode is increased.
[0018]
In this way, overdischarge of the battery is prevented.
[0019]
As the torque assist suppression control when the charged amount is equal to or less than a predetermined decrease determination reference value, for example, torque assist is performed only in a region where the NOx emission amount is relatively large in the operation region set to the second combustion mode. The driving force control motor is controlled as described above.
[0020]
In this way, while NOx suppression action by torque assist is obtained in a region where the amount of NOx emission is relatively large, over-discharge of the battery is prevented because torque assist is not performed in other regions.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0022]
FIG. 1 is a schematic system block diagram in the present embodiment. The engine 3 is a diesel engine, and a motor 1 (driving force control motor) is connected to a main shaft (crankshaft) via a motor connecting shaft 2. The motor 1 can apply a rotational driving force to the engine 3 (torque assist) using electricity as a power source, and can also generate electricity by being reversely driven by the engine 3. A transmission 4, a propeller shaft 5, a drive shaft 6 and a drive wheel 7 are connected to the engine 3 in this order, and the driving force of the motor 1 and the engine 3 is shifted to an appropriate rotational speed and transmitted to the drive wheel 7.
[0023]
The engine 3 is provided with an intake passage 11 for sucking air for combustion and an exhaust passage 12 for discharging exhaust gas after combustion. Further, an EGR passage 13 that communicates the intake passage 11 and the exhaust passage 12 is provided, and an EGR valve 14 is provided in the passage. By opening the EGR valve 14, a part of the exhaust is recirculated to the intake air (EGR). Further, an intake throttle valve 15 is provided upstream of the connection portion of the EGR passage 13 in the intake passage 11.
[0024]
The EGR rate can be controlled by adjusting the opening of the EGR valve 14 and adjusting the opening of the intake throttle valve 15. That is, the EGR amount increases as the opening degree of the EGR valve 14 increases, and the EGR rate increases as the intake fresh air amount decreases and the EGR amount increases as the opening degree of the intake throttle valve 15 decreases. Here, the EGR rate refers to the ratio of the EGR amount to the amount of gas flowing into the cylinder (new air amount + EGR amount).
[0025]
The exhaust passage 12 is provided with an oxidation catalyst 21, a NOx purification catalyst 22, and a particulate filter (hereinafter abbreviated as DPF) 23 downstream from the branch point with the EGR passage 13.
[0026]
The oxidation catalyst 21 oxidizes and purifies HC, CO, etc. contained in the exhaust. A temperature sensor 36 that detects the temperature of the exhaust gas flowing into the oxidation catalyst 21 is provided immediately upstream of the oxidation catalyst 21.
[0027]
The NOx purification catalyst 22 occludes NOx in the exhaust gas when the exhaust gas has a lean air-fuel ratio, and releases and reduces NOx when the exhaust gas becomes a rich air-fuel ratio. A temperature sensor 37 that detects the temperature of the exhaust gas flowing into the NOx purification catalyst 22 is provided immediately upstream of the NOx purification catalyst 22.
[0028]
The DPF 23 collects and purifies particulate matter (particulate matter such as soot, hereinafter referred to as PM) contained in the exhaust gas. A pressure sensor 38 is provided immediately upstream of the DPF 23, and a pressure sensor 39 is provided immediately downstream of the DPF 23 to detect the exhaust pressure.
[0029]
A battery 32 is connected to the motor 1 via an inverter 31. At the time of torque assist, electric power is supplied from the battery 32 via the inverter 31 so that the motor 1 can obtain a predetermined output. At the time of power generation, the power generated by the motor 1 is charged to the battery 32 via the inverter 31.
[0030]
Further, an accelerator opening sensor 33 that detects the accelerator opening by the driver's operation is provided.
[0031]
The detection signals from the temperature sensors 36 and 37, the pressure sensors 38 and 39, and the accelerator opening sensor 33 are input to the ECU 40, and a signal indicating the engine speed is also input to the ECU 40.
[0032]
The ECU 40 is a control unit that controls the motor 1 and the engine 3. The ECU 40 functionally includes an operation state detection unit 41, a storage amount detection unit 42, an engine control unit 43, and a motor control unit 44.
[0033]
The operating state detecting means 41 detects the operating state of the engine based on the value corresponding to the engine load and the engine speed. For example, the driving state is checked based on the accelerator opening detected by the accelerator opening sensor 33 and the engine rotation speed, or the target torque of the driving wheel is obtained from the accelerator opening, and the target torque and the engine rotation speed are used. Check the driving condition. In addition, the charged amount detecting means 42 detects a parameter related to the charged amount of the battery 32 and, for example, obtains the SOC from the current value and the voltage value as will be described in detail later.
[0034]
The engine control means 43 performs premixing with a large EGR rate when the exhaust temperature (temperature related to the engine temperature) detected by the temperature sensor 36 (temperature detection means) immediately upstream of the oxidation catalyst 21 is equal to or higher than a predetermined temperature. The combustion mode (first combustion mode) and the diffusion combustion mode (second combustion mode) with a low EGR rate are switched according to the operating state of the engine. For this purpose, a premixed combustion region (H) that is an operation region in which the premixed combustion mode is executed and a diffusion combustion region (D) that is an operation region in which the diffusion combustion mode is executed are set in advance in a map. As shown in FIG. 2, the low load region (except for the high speed region) where the accelerator opening (target torque of the drive wheels) is equal to or less than a predetermined value is set as the premixed combustion region (H), and the accelerator opening is larger than the predetermined value. The high load region and the high speed region are the diffusion combustion region (D).
[0035]
Here, the premixed combustion mode means that fuel and air are injected by injecting fuel during the compression stroke considerably before the compression top dead center while increasing the EGR rate to a predetermined value or more in order to prevent premature ignition. Refers to a combustion mode in which combustion by self-ignition is started in the vicinity of compression top dead center after sufficient mixing, and diffusion combustion mode refers to compression top dead while reducing the EGR rate below a predetermined value. Combustion mode in which fuel is injected near the point so that part of the fuel self-ignites immediately after the start of injection, and that part becomes the core and combustion spreads while entraining surrounding fuel spray and air Say.
[0036]
In the case of the premixed combustion mode, in order to improve the mixing of fuel and air, the injection starts as the fuel injection amount increases so that the end of injection becomes a fixed time before compression top dead center (for example, BTDC 30 ° CA). It is preferable to advance the timing and perform the fuel injection divided into a plurality of times according to the increase in the fuel injection amount.
[0037]
When the exhaust gas temperature is lower than a predetermined temperature, the premixed combustion mode is prohibited and the diffusion combustion mode is executed in the entire operation region of the engine.
[0038]
The motor control means 44 controls the motor 1 by issuing a motor torque command to the inverter 31. If the torque value of the motor torque command is positive, the torque assist state is entered, and if it is negative, the power generation state is entered. When it is zero, it becomes a neutral state (N) that is neither. Hereinafter, such control of the motor 1 is referred to as ISG control.
[0039]
In particular, the motor control means 44 controls the motor 1 so that only power generation is performed in the premixed combustion mode and only torque assist is performed in the diffusion combustion mode. That is, when the exhaust temperature is equal to or higher than a predetermined temperature, control is performed such that power generation is performed in the premixed combustion region (H) and torque assist is performed in the diffusion combustion region (D). When the exhaust temperature is lower than the predetermined temperature and premix combustion is prohibited, power generation is performed in a low load side region where the accelerator opening or target torque is low, and a high load side region where the accelerator opening or target torque is high. Torque assist is performed, and the amount of torque assist is reduced compared to when the exhaust temperature is equal to or higher than a predetermined temperature. Further, when the value detected by the charged amount detection means 42 is equal to or greater than a predetermined increase determination reference value, power generation by the driving force control motor in the premixed combustion mode is suppressed, or torque assist in the diffusion combustion mode is performed. In addition, the torque assist by the driving force control motor in the diffusion combustion mode is suppressed or the power generation by the driving force control motor in the premixed combustion mode is suppressed when the value is equal to or less than a predetermined decrease determination reference value. Try to increase.
[0040]
The control by this control device will be specifically described.
[0041]
3 and 4 are flowcharts of engine control and ISG control according to the operating state. When the processing of this flowchart is started, signals from various sensors and the like are input in step S1, and in step S2, the exhaust temperature Tc detected by the temperature sensor 36 immediately upstream of the oxidation catalyst 21 is set to a predetermined temperature Tc0. It is determined whether the temperature is higher than (eg, 200 ° C.).
[0042]
When the determination in step S2 is YES, the target torque of the drive wheels is set according to the accelerator opening detected by the accelerator opening sensor 33 (step S3). Then, the operating state is examined based on the target torque (or accelerator opening) and the engine speed, and it is determined whether or not the operating state is in the premixed combustion region (H) (step S4).
[0043]
When the determination in step S4 is YES, that is, in the premixed combustion region (H), fuel injection and EGR control in the premixed combustion mode is performed in step S5. That is, the EGR valve 14 and the intake air are controlled so that the fuel injection is performed at a relatively early timing (for example, the timing at which the injection is terminated in the vicinity of BTDC 30 ° CA), and the EGR rate becomes larger than a predetermined value. The throttle valve 15 is controlled.
[0044]
When the determination in step S4 is NO (when in the diffusion combustion region), fuel injection and EGR control in the diffusion combustion mode are performed in step S6. That is, the fuel injection is controlled to start near the compression top dead center, and the EGR valve 14 and the intake throttle valve 15 are controlled so that the EGR rate becomes smaller than a predetermined value.
[0045]
Following the process of step S5 or S6, an increase determination reference value SOC in which SOC (battery storage amount) is preset. _H It is determined whether or not it is larger (step S7). If the determination is NO, the SOC is a preset decrease determination reference value SOC. _L It is determined whether it is smaller (step S8).
[0046]
The SOC is obtained from the current-voltage-SOC characteristics as shown in FIG. 5 based on the current value and voltage value between the battery 32 and the inverter 31. As shown in this figure, if the current value is the same, the higher the voltage value, the larger the SOC.
[0047]
Based on the determinations in steps S7 and S8, an appropriate characteristic is selected from the three types of motor torque characteristics A to C for ISG control shown in FIG.
[0048]
That is, FIG. 6 shows the motor torque characteristic for ISG control with the accelerator opening (target torque of the drive wheel) on the horizontal axis and the motor torque on the vertical axis. In this figure, the motor torque is positive. In this case, torque assist in which driving force is applied from the motor 1 to the engine 3 is performed (assist region). Conversely, when the motor torque is negative, power generation in which driving force is applied to the motor 1 from the engine 3 is performed. (Power generation area).
[0049]
In each of the three types of motor torque characteristics A to C shown in the figure, the low load side region where the accelerator opening is small is the power generation region, and the high load side region where the accelerator opening is large is the assist region. Further, between the power generation region and the assist region, a motor torque = 0, that is, a neutral N region in which neither power generation nor torque assist is performed is provided. As for the relationship with the region in engine control, the power generation region is in the premixed combustion region, the assist region is in the diffusion combustion region, and the N region is the boundary between the premixed combustion region and the diffusion combustion region. It is set to exist in the vicinity.
[0050]
Among the three types of motor torque characteristics A to C shown in the figure, the motor torque characteristic A suppresses the power generation amount in the power generation region, while increasing the torque assist amount in the assist region. In the motor torque characteristic C, the power generation amount in the power generation region is increased, while the torque assist amount in the assist region is suppressed small. In the motor torque characteristic B, the power generation amount in the power generation region and the torque assist amount in the assist region are values approximately between the motor torque characteristics A and C.
[0051]
Based on the determinations in steps S7 and S8, when the SOC is high (determination in step S7 is YES), the motor torque characteristics A, and when the SOC is low (determination in step S8 is YES), the motor torque When the characteristics C and SOC are medium (the determinations at steps S7 and S8 are both NO), the motor torque characteristic B is selected. In each case, the motor torque corresponding to the accelerator opening is determined by the selected torque special setting. Torque control corresponding to this is performed (steps S9, S10, S11).
[0052]
In the example shown in FIG. 6, three types of motor torque characteristics A to C having different power generation amounts in the power generation region and torque assist amounts in the assist region can be selected according to the SOC. In addition to this, as shown in FIG. 7, the power generation area and the assist area may be enlarged or reduced according to the SOC. That is, in FIG. 7, when the SOC is large, the assist region is wider than the power generation region, when the SOC is small, the power generation region is wider than the assist region, and when the SOC is medium, the power generation region and the assist region are approximately the same. It is set to do.
[0053]
When the determination result in step S2 is NO, that is, when the exhaust gas temperature Tc is lower than the predetermined temperature Tc0, execution of the premixed combustion mode is prohibited and control in the diffusion combustion mode is executed in the entire operation region. (Step S12). Further, an increase determination reference value SOC in which SOC is set in advance _H It is determined whether or not it is larger (step S13). If the determination is NO, the SOC is a preset decrease determination reference value SOC. _L It is determined whether it is smaller (step S14).
[0054]
Based on the determinations of steps S13 and S14, an appropriate characteristic is selected from the three types of motor torque characteristics A ′ to C ′ shown in FIG. Also in this case, the motor torque characteristics A ′ to C ′ are set so that the low load side region is the power generation region, the high load side region is the assist region, and the space between them is the N region. The power generation amount in the power generation region is small, the torque assist amount in the assist region is relatively large, and the motor torque characteristic C ′ is relatively large in the power generation region and the torque assist amount in the assist region is small. Further, the motor torque characteristic B ′ is a value approximately between the characteristics A ′ and C ′. Based on the determinations in steps S13 and S14, when the SOC is high (determination in step S13 is YES), the motor torque characteristic A ′ is small. When the SOC is low (determination in step S14 is YES), the motor torque When the characteristics C ′ and SOC are medium (the determinations at steps S13 and S14 are both NO), the motor torque characteristic B ′ is selected, and in each case, the motor corresponding to the accelerator opening degree by the selected torque special setting. Torque is obtained and torque control is performed accordingly (steps S15, S16, S17).
[0055]
In this case, the torque characteristics A ′ to C ′ (FIG. 8) are smaller in both the power generation amount in the power generation region and the torque assist amount in the assist region than the torque characteristics A to C (FIG. 6) when the exhaust temperature is high. ing.
[0056]
In addition to or in addition to changing the power generation amount in the power generation region and the torque assist amount in the assist region (selection of torque characteristics A ′ to C ′) according to the SOC as shown in FIG. Accordingly, the power generation area and the assist area may be enlarged or reduced (see FIG. 7). However, when the exhaust temperature is low, the power generation region and the assist region are made smaller than when the exhaust temperature is high.
[0057]
According to the ISG control as described above, when the target torque is low, the motor torque is negative (power generation state) and the engine output is increased. When the target torque is high, torque assist is performed and the engine output is decreased. As a result, the overall engine output approaches the engine output at which the fuel consumption becomes optimum, and the energy stored in the battery 32 is taken out during the torque assist, so that the energy is used without waste and the fuel consumption is improved.
[0058]
As engine control, as shown in FIG. 9, in the premixed combustion region (H) where the accelerator opening (target torque of the drive wheels) is equal to or less than a predetermined value, the EGR valve opening is increased and the intake throttle valve is increased. By reducing the opening degree, the EGR rate is increased. In this state, fuel injection is performed at a relatively early timing, whereby premixed combustion is performed. In addition, since it is difficult to achieve premixed combustion in order to secure the air amount at high loads, it is difficult to achieve premixed combustion, so that the accelerator opening (target torque of the drive wheels) is higher than a predetermined value in a diffusion combustion region ( In D), the EGR valve opening is reduced and the intake throttle valve opening is increased to reduce the EGR rate. In this state, fuel is injected near the top dead center, and diffusion combustion is performed.
[0059]
When the premixed combustion is performed, a uniform and lean air-fuel mixture can be formed, so that both NOx and PM can be reduced, and NOx can also be reduced by performing a larger amount of EGR. The On the other hand, at the time of diffusion combustion, since there is no time for fuel and air to sufficiently mix, the concentration of the mixture becomes uneven, and the combustion temperature becomes high and NOx is generated when the mixture concentration is close to the theoretical air-fuel ratio. Also, NOx is likely to increase due to a low EGR. In this diffusion combustion state, NOx increases rapidly as the load increases.
[0060]
In contrast to this tendency, in the control device of the present embodiment, power generation is performed in the premixed combustion region, while torque assist is performed in the diffusion combustion region, so that an effect of reducing NOx can be obtained. That is, on the high load side of the diffusion combustion region, torque assist by the motor is performed, so that the generated torque of the engine itself becomes lower than the target torque by the amount of torque assist, so NOx is greatly reduced. In addition, power generation is performed on the low load side in the premixed combustion region in order to supplement the power consumption by the torque assist. In this power generation state, the generated torque of the engine torque itself is higher than the target torque, but the premixed combustion This keeps NOx low enough. Therefore, the NOx reduction effect can be effectively obtained as a whole.
[0061]
As shown in the figure, the PM emission amount does not increase suddenly when switching from premixed combustion to diffusion combustion, but gradually increases as the engine torque increases. Therefore, lowering the actual torque of the engine itself by torque assist at high load is also effective for suppressing increase in PM emission at high load.
[0062]
Furthermore, in the present embodiment, the motor torque characteristics are changed according to the amount of charge (SOC) of the battery (see Steps S7 to S11, S13 to S17, and FIGS. 6 to 8), and thus the above effects are exhibited. However, it is possible to prevent an excess or deficiency in the amount of electricity stored in the battery. That is, when the SOC is large, the power generation amount in the premixed combustion region is reduced or the power generation region is reduced, so that overcharging of the battery is prevented, and when the SOC is small. The torque assist amount in the diffusion combustion region is reduced or the assist region is reduced, so that overdischarge of the battery is prevented.
[0063]
Further, when the exhaust gas temperature is low, if a large amount of EGR is performed, the combustion of the engine becomes unstable and the combustion temperature in the cylinder becomes low. As the temperature rises, the emission will deteriorate. In order to avoid such a situation, premixed combustion is prohibited when the exhaust gas temperature is low, but in this case as well, power generation is performed in the region on the low load side of the engine and torque assist is performed in the region on the high load side. As a result, the fuel efficiency improvement effect and the effect of suppressing the increase in NOx on the high load side can be obtained. However, in this case, since the NOx suppression action due to premixed combustion cannot be obtained in the low load side region, the power generation amount in the low load side region is reduced compared with when the exhaust gas temperature is high, and accordingly the high load is increased. The torque assist amount in the side region is reduced.
[0064]
Next, processing for regenerating the DPF 23 provided in the exhaust passage 12 when the PM accumulation amount increases and processing for regenerating the NOx purification catalyst 22 when the NOx adsorption amount increases will be described.
[0065]
FIG. 10 is a flowchart showing determination of the regeneration condition of the DPF 23 and regeneration processing corresponding to the determination. When this process starts, first, in step S21, the PM discharge amount at each time point is calculated from the map of the PM discharge amount characteristic shown in FIG. This map of PM emission characteristics shows the relationship between the accelerator opening, the engine rotation speed, and the PM emission. As this relationship, the PM emission increases as the accelerator opening increases, and the engine The PM emission increases as the rotational speed increases.
[0066]
Subsequently, the PM accumulation amount Q1 is estimated by integrating the PM discharge amount (step S22). On the other hand, the exhaust pressure before and after the DPF 23 detected by the pressure sensors 38 and 39 is input, and the differential pressure ΔP before and after the DPF is calculated (step S23). Then, the PM accumulation amount Q2 with respect to the DPF front-rear differential pressure ΔP at the present time is separately estimated from the DPF front-rear differential pressure characteristics shown in FIG. 12 (step S24). The DPF front-rear differential pressure characteristic indicates the relationship between the PM deposition amount and the DPF front-rear differential pressure, and the DPF front-rear differential pressure increases as the PM deposition amount increases.
[0067]
Next, it is determined whether or not the DPF front-rear differential pressure ΔP is larger than a preset threshold value ΔP0 (step S25). If the determination in step S25 is YES, it is determined that the PM deposition amount Q2 is more accurate than the PM deposition amount Q1, and Q2 is set as the final PM deposition amount Q (step S26). On the other hand, if NO is determined in step S25, it is determined that the PM accumulation amount Q1 is more accurate than the PM accumulation amount Q2, and Q1 is set as the final PM accumulation amount Q (step S27).
[0068]
Subsequently, in step S28, it is determined whether or not the PM accumulation amount Q exceeds the regeneration determination reference value Qa. If NO is determined in step S28, the process returns because the PM accumulation amount is sufficiently small and the PF regeneration process is not yet required.
[0069]
If the determination in step S28 is YES, a DPF regeneration command is issued (step S29), the intake throttle valve 15 is throttled and post-injection is performed (step S30). As a result, the exhaust temperature rises to about 600 ° C., and PM burns. Next, it is determined whether or not the PM accumulation amount Q estimated from the regeneration time or the differential pressure before and after the DPF is smaller than a regeneration completion determination reference value Q0 (a value close to 0). If this determination is NO, the process returns to step S30 to continue the PF regeneration process. If YES, the PF regeneration process is terminated (step S32) and the process returns.
[0070]
According to the DPF regeneration process as described above, when the PM accumulation amount Q increases, the PF regeneration process (step S32) is performed, whereby the PM deposited on the DPF 23 is burned and the DPF 23 is regenerated. Therefore, the PM purification performance by the DPF 23 is kept good.
[0071]
FIG. 13 is a flowchart showing the determination of the regeneration condition of the NOx purification catalyst 22 and the regeneration process corresponding thereto. When this process starts, first, in step S41, the NOx emission amount at each time point is estimated from the NOx emission amount characteristic map shown in FIG. This NOx emission characteristic map shows the relationship between the accelerator opening, the engine speed, and the PM emission, and this relationship includes diffusion combustion from the premixed combustion region (H) as the accelerator opening increases. When shifting to the region (D), the NOx emission amount increases rapidly. Further, in the diffusion combustion region (D), the NOx emission amount increases as the accelerator opening increases, and the NOx emission amount increases as the engine speed increases. To increase.
[0072]
Subsequently, the NOx accumulation amount of the NOx purification catalyst (LNT) 22 is estimated by integrating the NOx emission amount (step S42), and it is determined whether or not the NOx accumulation amount exceeds a predetermined value (step S42). Step S43). If NO is determined in step S43, the process returns because the NOx accumulation amount is sufficiently small and the regeneration process is not yet required.
[0073]
If the determination in step S43 is yes, an LNT regeneration command is issued (step S44), and a regeneration process is executed (step S45). The regeneration process performed here is a process (so-called rich spike) in which the fuel injection amount is increased and corrected so that the air-fuel ratio becomes richer than the stoichiometric air-fuel ratio for a predetermined time (about 1 second).
[0074]
According to the NOx purification catalyst regeneration process as described above, when the NOx accumulation amount of the NOx purification catalyst 22 increases, the regeneration process (step S45) by so-called rich spike is performed, so that the NOx deposited on the NOx purification catalyst 22 is performed. Is released and reduced, and the NOx purification catalyst 22 is regenerated. Therefore, the NOx purification performance by the NOx purification catalyst 22 is kept good.
[0075]
As mentioned above, although embodiment of this invention was described, the specific structure of the apparatus of this invention is not limited to the said embodiment, A various change is possible.
[0076]
For example, in the above embodiment, the engine 3 is a diesel engine. However, the engine 3 may be applied to a control device for a hybrid vehicle equipped with a gasoline engine that performs compression self-ignition by a direct injection method.
[0077]
In this embodiment, the oxidation catalyst 21, the NOx purification catalyst 22, and the DPF 23 are provided in the exhaust passage 12, but the oxidation catalyst 21 is not provided and the DPF 22 also has an oxidation catalytic action (oxidation catalyst supporting DPF). It is also good.
[0078]
【The invention's effect】
As described above, the hybrid vehicle control device of the present invention includes the engine control means for switching between the first combustion mode with a large EGR rate and the second combustion mode with a small EGR rate according to the operating state of the engine, and the driving force control. And the motor control means, and the driving force control motor is controlled so that only power generation is performed in the first combustion mode and only torque assist is performed in the second combustion mode. NOx is reduced by the torque assist in the operation region set to the combustion mode, while power generation is performed in the operation region set to the first combustion mode. At this time, in the first combustion mode in which the EGR rate is large. Combustion keeps NOx sufficiently low. Thus, NOx can be greatly reduced as a whole by effectively relating the control of the driving force control motor in the hybrid vehicle and the engine control for switching the first and second combustion modes. .
[Brief description of the drawings]
FIG. 1 is a schematic system block diagram of a control apparatus for a hybrid vehicle according to an embodiment of the present invention.
FIG. 2 is a diagram showing a control map for switching the combustion mode of the engine.
FIG. 3 is a flowchart of engine control and ISG control.
4 is a flowchart of engine control and ISG control, which is a part following the flowchart of FIG. 3;
FIG. 5 is a characteristic diagram illustrating a relationship between a current value and a voltage value of a battery and a storage amount (SOC).
FIG. 6 is a characteristic diagram showing ISG control characteristics when the exhaust gas temperature is high.
FIG. 7 is a region setting diagram when the power generation region and the assist region are enlarged or reduced.
FIG. 8 is a characteristic diagram showing ISG control characteristics when the exhaust gas temperature is high.
FIG. 9 is a diagram showing changes in a combustion mode, an EGR rate, an EGR valve opening, an intake throttle valve opening, a NOx emission amount, and a PM emission amount according to the accelerator opening degree.
FIG. 10 is a flowchart of DPF regeneration condition determination and regeneration processing in accordance therewith.
FIG. 11 is a characteristic diagram showing the relationship between the accelerator opening, the engine speed, and the PM emission amount.
FIG. 12 is a characteristic diagram showing the relationship between the PM deposition amount and the differential pressure before and after the DPF.
FIG. 13 is a flowchart of determination of regeneration conditions for the NOx purification catalyst and regeneration processing corresponding thereto.
FIG. 14 is a characteristic diagram showing the relationship between the accelerator opening, the engine rotation speed, and the NOx emission amount.
[Explanation of symbols]
1 Motor
3 Engine
13 EGR passage
14 EGR valve
15 Inlet throttle valve
32 battery
33 Accelerator position sensor
36 Temperature sensor
40 ECU
41 Operating state detection means
42 Storage amount detection means
43 Engine control means
44 Motor control means

Claims (5)

An operating state detecting means for detecting the operating state of the engine;
Temperature detecting means for detecting a temperature related to the engine temperature;
Engine control means for switching between a first combustion mode with a high EGR rate and a second combustion mode with a low EGR rate according to the operating state of the engine when the temperature detected by the temperature detection means is equal to or higher than a predetermined temperature;
A driving force control motor that is power-coupled to the engine and can be switched between a state in which power is generated by engine rotation and a state in which torque assist to the engine is performed;
Motor control means for controlling the driving force control motor according to the operating state of the engine,
The control apparatus for a hybrid vehicle, wherein the motor control means controls the driving force control motor so as to perform only power generation in the first combustion mode and perform only torque assist in the second combustion mode. The engine control unit is configured to prohibit execution of the first combustion mode when the temperature detected by the temperature detection unit is lower than a predetermined temperature, and the motor control unit is configured to prevent the motor control unit from executing the first combustion mode. The driving force control motor is set so that power generation is performed in the low-load region, torque assist is performed in the high-load region, and the power generation amount and torque assist amount are reduced as compared to when the temperature is equal to or higher than the predetermined temperature. 2. The control apparatus for a hybrid vehicle according to claim 1, wherein the control apparatus controls the hybrid vehicle. A power storage amount detecting unit configured to detect a parameter relating to a power storage amount of a battery electrically connected to the driving force control motor, wherein the motor control unit is configured to perform the first operation when the power storage amount is equal to or greater than a predetermined increase determination reference value; The hybrid vehicle control device according to claim 1, wherein power generation by the driving force control motor in the first combustion mode is suppressed, or torque assist in the second combustion mode is increased. A power storage amount detecting unit configured to detect a parameter related to a power storage amount of a battery electrically connected to the driving force control motor, wherein the motor control unit is configured to perform the first operation when the power storage amount is equal to or less than a predetermined decrease determination reference value; 4. The hybrid vehicle control device according to claim 1, wherein torque assist by the driving force control motor in the second combustion mode is suppressed, or power generation in the first combustion mode is increased. 5. The motor control means performs torque only in a region where the NOx emission amount is relatively large in the operation region set to the second combustion mode as control of torque assist suppression when the charged amount is equal to or less than a predetermined decrease determination reference value. 5. The control apparatus for a hybrid vehicle according to claim 4, wherein the driving force control motor is controlled so as to perform assist.

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