JP2006220046A - Diesel hybrid vehicle exhaust purification system - Google Patents

Abstract

An object of the present invention is to minimize deterioration of response during transient operation while ensuring fuel consumption and emission.
An exhaust emission control device for a diesel hybrid vehicle (10) that can be driven by at least one of a diesel engine (11) having a turbocharger (26) and a motor generator (17). The diesel engine (11) is a turbine of the turbocharger (26). A pre-catalyst 40 upstream of 26b and having oxidation ability in the exhaust manifold 30a, a bypass passage 44 branched from the upstream of the pre-catalyst 40 to bypass the pre-catalyst 40 and communicate with the upstream of the turbine 26b, and the bypass passage And a bypass valve 46 for controlling the amount of exhaust gas passing through 44. When the bypass valve 46 is fully closed and the exhaust gas passes through the pre-catalyst 40 during vehicle acceleration, the motor generator 17 torques the diesel engine 11 Assist and accelerate response while ensuring fuel economy and emissions Worse was configured so as to minimize the.
[Selection] Figure 1

Description

  The present invention relates to an exhaust gas purification device for a diesel hybrid vehicle, and more particularly to an exhaust gas purification device for a diesel hybrid vehicle that can minimize deterioration of response during transient operation while ensuring fuel efficiency and emission.

  Conventionally, exhaust purification has been performed with an exhaust purification catalyst provided in the middle of an exhaust pipe. As this type of exhaust purification device, for example, the following technique has been proposed (see, for example, Patent Document 1). That is, the NOx occlusion reduction catalyst provided in the middle of the exhaust pipe downstream of the turbocharger turbine, the fuel addition means for adding fuel into the exhaust pipe upstream of this, and the upstream of the turbine of the turbocharger Port oxidation catalyst provided at the exhaust port, manifold oxidation catalyst provided at the exhaust manifold outlet, low load determination means for determining that the operating state is in the low load operation region, and fuel injection to each cylinder A fuel injection device that performs pilot injection prior to main injection of fuel when determining a low-load operation region, and a control device that outputs to the fuel injection device a fuel injection command for performing main injection at a timing slightly later than the normal injection timing; It is equipped with. This exhaust purification device increases the exhaust temperature by performing main injection at the above timing, and activates the NOx storage reduction catalyst to ensure emission.

  In addition, a three-way catalyst is provided upstream of the turbine of the turbocharger, a NOx absorption reduction catalyst is provided downstream of the turbine, and a bypass passage and a bypass control valve for bypassing the three-way catalyst are provided, and exhaust gas is provided. There has been proposed an exhaust gas purification device for a gasoline engine that opens the bypass control valve when hydrocarbon (HC) or carbon monoxide (CO) therein increases (see, for example, Patent Document 2).

  In this exhaust purification device, the bypass control valve is opened when hydrocarbons (HC) and carbon monoxide (CO) in the exhaust gas increase, so that a part of the exhaust bypasses the three-way catalyst. It is introduced upstream of the turbocharger through a passage. Therefore, pressure loss due to passage of the three-way catalyst can be avoided and reduction of supercharging efficiency is suppressed, and hydrocarbon (HC) and carbon monoxide (CO) necessary for NOx reduction contained in the exhaust are oxidized in the three-way catalyst. As a result, a reduction in the NOx purification action of the NOx absorption reduction catalyst is suppressed.

JP 2004-204699 A JP 9-209742 A

  In the first prior art, since the catalyst is disposed on the turbine upstream side of the turbocharger, the exhaust gas temperature is raised by the oxidation reaction heat in the catalyst, and the catalyst is disposed downstream of the turbine. Further, it is possible to ensure the front end surface bed temperature of the catalyst and to achieve a predetermined emission. However, since the exhaust gas is throttled by the catalyst upstream of the turbocharger to cause pressure loss, there is a problem that the response may be deteriorated during transient operation (acceleration operation) due to a supercharging delay.

  In the second prior art, the bypass control valve is opened during transient operation to suppress a decrease in supercharging efficiency (deterioration of acceleration response) and perform combustion giving priority to emission. For this reason, there has been a problem that the fuel consumption is deteriorated.

  In recent years, diesel hybrid vehicles have been developed from the viewpoint of conservation of the global environment and resource saving, and an exhaust emission control device is indispensable for ensuring the emission of such diesel hybrid vehicles. If the conventional exhaust emission control device is applied to a diesel hybrid vehicle as it is, the same problems as described above may occur, and therefore, provision of means for minimizing deterioration of response during transient operation while ensuring fuel efficiency and emission Was requested.

  The present invention has been made in view of the above, and an object of the present invention is to provide an exhaust emission control device for a diesel hybrid vehicle that can minimize deterioration of response during transient operation while ensuring fuel consumption and emission. To do.

  In order to solve the above-described problems and achieve the object, an exhaust emission control device for a diesel hybrid vehicle according to the present invention is an exhaust gas for a diesel hybrid vehicle that can be driven by at least one of a diesel engine having a turbocharger and a motor. The diesel engine is a purification device upstream of the turbine of the turbocharger and having an oxidizing ability in an exhaust collecting pipe, and is branched from the upstream of the catalyst to bypass the catalyst and to the upstream of the turbine. A bypass passage that communicates with the bypass valve that controls an amount of exhaust gas that passes through the bypass passage, and the motor is used when the bypass valve is fully closed and the exhaust gas passes through the catalyst during vehicle acceleration. The diesel engine is configured to be torque-assisted.

  When the vehicle is accelerated, the bypass valve is closed and exhaust gas is passed through the catalyst. At this time, on the engine side, combustion is performed with the highest priority on fuel consumption and emission by known techniques. Since the exhaust gas temperature rises due to the oxidation reaction heat in the catalyst, the front end surface bed temperature of the catalyst disposed downstream of the turbocharger can be secured, and predetermined emission can be achieved. However, since the flow of exhaust gas is restricted by the catalyst upstream of the turbocharger, a pressure loss occurs, and the acceleration response may deteriorate due to a delay in supercharging. Therefore, torque reduction that occurs during acceleration is assisted by the motor generator to minimize deterioration in acceleration response.

  According to the exhaust gas purification apparatus for a diesel hybrid vehicle according to the present invention, there is a possibility that the response during transient operation (acceleration operation) may deteriorate due to the catalyst disposed upstream of the turbocharger turbine. By assisting the engine with torque, it is possible to minimize deterioration of response during transient operation while ensuring fuel consumption and emissions.

  Embodiments of an exhaust emission control device for a diesel hybrid vehicle according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

  FIG. 1 is a schematic diagram illustrating an exhaust emission control device according to an embodiment of the present invention, FIG. 2 is a schematic diagram illustrating a schematic configuration of a diesel hybrid vehicle, and FIG. 3 is a flowchart illustrating a control operation. First, a schematic configuration of a diesel hybrid vehicle will be described with reference to FIG. As shown in FIG. 2, the diesel hybrid vehicle 10 is provided with a diesel engine (hereinafter simply referred to as an engine) 11 as a travel drive source.

  The driving force generated by the engine 11 is transmitted to the drive wheels 13 through a stepped transmission (hereinafter referred to as MMT (multi-mode manual transmission)) 12, a differential gear 15 and a drive shaft 14 that can be automatically shifted. It is like that.

  The MMT 12 electrically and automatically controls a gear shift operation by an actuator in accordance with a traveling state. Between the engine 11 and the MMT 12, there is provided a clutch 12a that performs contact and separation of power transmission, and the contact and separation operation is electrically and automatically controlled by an actuator according to the running state.

  A motor generator (motor) 17 in which a drive system gear unit (gear train) is integrated is connected to a battery 20 that is a rechargeable secondary battery via an inverter 19 and functions as a motor that is a travel drive source. The power running mode and the regenerative operation mode that functions as a generator are configured to take two operating states.

  The motor generator 17 receives power supplied from the battery 20 in the power running mode and generates power for driving the drive shaft 14. Thereby, the shift assist can be performed at the time of shifting, and the acceleration assist can be performed at the time of acceleration. In the regenerative operation mode, the motor generator 17 converts the driving force transmitted from the engine 11 or the drive shaft 14 into electric power and charges the battery 20.

  Whether motor generator 17 is operated in the power running mode or the regenerative operation mode is determined in consideration of the state of charge (SOC) of battery 20. The battery charge state amount SOC is calculated by a predetermined battery state monitor computer.

  Next, a schematic configuration of the engine 11 and an exhaust purification device according to the present embodiment will be described with reference to FIG. As shown in FIG. 1, in an intake passage 21 of an engine 11 having a common rail fuel injection system 11a, an air flow meter (not shown) for detecting the intake air amount and a throttle valve 24 for adjusting the intake air amount are provided. It has.

  The engine 11 also includes a turbocharger 26 that assists engine torque by driving the coaxial compressor 26a by rotating the turbine 26b using exhaust gas pressure to increase the intake air amount.

  An intercooler 28 is provided in the intake passage 21 between the turbocharger 26 and the intake manifold 21a for cooling the intake air that has been supercharged and heated. The fresh air that has passed through the intercooler 28 and the throttle valve 24 is introduced into the intake manifold 21a.

  A pre-catalyst having oxidizing ability is provided in the exhaust manifold (exhaust collecting pipe) 30a upstream of the turbocharger 26 and in the exhaust manifold (exhaust collecting pipe) 30a in order to secure the front end surface bed temperature of the front catalyst 33a downstream of the turbocharger 26. (Catalyst) 40 is provided.

  The pre-catalyst 40 captures, for example, an oxidation catalytic converter (CCO) that oxidizes and purifies carbon monoxide (CO) and hydrocarbons (HC) in the exhaust gas and particulate matter (PM) in the exhaust gas. A diesel particulate filter (DPF) that collects and purifies can be used.

  Further, the exhaust manifold (exhaust collecting pipe) 30a branches from the upstream side of the pre-catalyst 40, bypasses the pre-catalyst 40, and communicates with the upstream side of the turbine 26b, and passes through the bypass passage 44. A bypass valve 46 for controlling the amount of exhaust gas is provided.

  The bypass valve 46 is controlled by an electronic control unit (hereinafter referred to as ECU) (not shown) together with other components such as various sensors. A fuel addition valve 42 is provided in the exhaust manifold 30a and upstream of the pre-catalyst 40 to add fuel based on a detection value of an air-fuel ratio sensor 48 described later.

  The exhaust passage 30 of the engine 11 is provided with a particulate filter 33 carrying an NOx storage reduction catalyst and a pre-stage catalyst 33a for purifying particulate matter and nitrogen oxides (NOx) in the exhaust gas. It has been. Further, an air-fuel ratio sensor 48 that detects the air-fuel ratio of the air-fuel mixture burned in the engine 11 based on the oxygen concentration of the exhaust gas flowing into the front-stage catalyst 33 a is provided upstream of the front-stage catalyst 33 a.

The engine 11 includes an EGR device 35 that recirculates a part of the exhaust gas to the intake system. The EGR passage 36 of the EGR device 35 is provided with an EGR cooler 37 that cools the EGR gas and an EGR valve 38 that adjusts the flow rate of the EGR gas. That is, a part of the exhaust gas discharged from the exhaust manifold 30a of the engine 11 is recirculated to the intake manifold 21a through the EGR cooler 37 and the EGR valve 38 of the EGR passage 36.

  The diesel hybrid vehicle 10 configured as described above is basically controlled as described below by the ECU based on output information from various sensors such as a vehicle speed sensor and an accelerator opening sensor (not shown), and travels in various states. can do.

  When the diesel hybrid vehicle 10 is in a low-speed steady traveling state where the traveling load is small, the motor 11 travels (EV traveling) by powering the motor generator 17 while the engine 11 is stopped. When the diesel hybrid vehicle 10 reaches a predetermined speed or load after the start of traveling, the engine 11 is cranked and started using a starter (not shown) provided separately from the motor generator 17. Shift to operation using.

  Further, during an operation with a large traveling load such as acceleration, the engine 11 is normally operated so as to generate an output substantially equal to the required power of the drive shaft 14. At this time, almost all of the output of the engine 11 is transmitted to the drive shaft 14. The control by the motor generator 17 during the acceleration operation will be described later.

  When the state of charge SOC of the battery has decreased below a predetermined reference value, the engine 11 is operated at an output higher than the required output of the drive shaft 14, and a part of the surplus power is supplied by the motor generator 17. And is used for charging the battery 20. When the output torque of the engine 11 is insufficient, the motor generator 17 assists the insufficient torque according to the battery charge state amount SOC, and the necessary torque is ensured.

  The diesel hybrid vehicle 10 is also subjected to so-called eco-run (economy & ecology running) control in order to save fuel and reduce emissions. For example, when the diesel hybrid vehicle 10 stops due to a signal waiting at an intersection or the like, the engine 11 is automatically stopped under a predetermined stop condition, and thereafter, under a predetermined restart condition (for example, when an accelerator pedal is depressed). Control for restarting the engine 11 is also performed.

  The above is the basic configuration and basic control operation of the diesel hybrid vehicle 10 according to the present invention.

  Next, the control operation according to this embodiment will be described with reference to FIGS. 1 and 2 based on FIG. Here, FIG. 3 is a flowchart showing the control operation. When the motor generator 17 is driven to assist the torque of the engine 11 in step S13 of FIG. 3 to be described later, since the battery 20 consumes a predetermined amount of power, it is necessary to grasp the current state of charge of the battery SOC.

  Therefore, the current battery charge state amount SOC is detected or estimated, and the data is read to determine whether or not the battery charge state amount SOC exceeds a predetermined value (step S10). The predetermined value is a threshold value of the battery charge state amount SOC for determining whether or not torque assist by the motor generator 17 should be performed, and an optimal value (for example, 50%) is set in advance through experiments or the like.

  If the current state of charge SOC of the battery is greater than the predetermined value (Yes at Step S10), torque assist by the motor generator 17 can be performed, so that the diesel hybrid vehicle 10 running the engine accelerates (transient operation). It is determined whether it is in the middle (step S11). This may be determined based on an accelerator opening signal or the like by an accelerator opening sensor (not shown). If it is not accelerating (No at Step S11), the control is terminated because it is out of this control.

  If the engine is accelerating (Yes at Step S11), all the bypass valves 46 in the exhaust manifold 30a are closed and the exhaust gas is passed through the pre-catalyst 40 (Step S12). At this time, since the exhaust gas temperature rises due to the heat of oxidation reaction in the pre-catalyst 40, the front end surface bed temperature of the front catalyst 33a disposed downstream of the turbocharger 26 can be secured, and a predetermined emission is achieved. Can be achieved. However, since the flow of exhaust gas is restricted by the pre-catalyst 40, pressure loss occurs, and the acceleration response may deteriorate due to a delay in supercharging.

  Therefore, on the engine 11 side, the motor generator 17 assists the torque reduction that occurs during acceleration while performing combustion with the highest priority on fuel consumption and emission by a known technique (step S13). As a result, it is possible to minimize deterioration of acceleration response while ensuring fuel consumption and emission. It should be noted that the optimum value of the torque assist amount is set in advance by a map or the like through experiments or the like.

  On the other hand, when the current state of charge of the battery SOC is smaller than the predetermined value (No in step S10) and the state of charge of the battery SOC has decreased, the torque generated by the motor generator 17 regardless of whether the operation is transient or not. Assistance cannot be implemented.

  Therefore, only in such a case, the bypass valve 46 is opened to allow the exhaust gas to pass through the bypass passage 44 (step S14), and this control is finished. At this time, since the exhaust gas bypasses the pre-catalyst 40, no pressure loss due to the pre-catalyst 40 occurs upstream of the turbocharger 26. Thereby, a response does not deteriorate at the time of transient operation (acceleration operation).

  In the above embodiment, the present invention is applied to the diesel hybrid vehicle 10 having the MMT 12, but the present invention is not limited to this, and the continuous continuously variable transmission (CVT), automatic transmission (AT), manual You may apply to the hybrid vehicle provided with the transmission (MT).

  As described above, the exhaust gas purification apparatus for a diesel hybrid vehicle according to the present invention is useful for a diesel hybrid vehicle equipped with a turbocharger. It is suitable for diesel hybrid vehicles that can minimize the above.

1 is a schematic diagram showing an exhaust emission control device according to an embodiment of the present invention. It is a mimetic diagram showing a schematic structure of a diesel hybrid vehicle. It is a flowchart which shows control operation.

Explanation of symbols

10 Diesel Hybrid Vehicle 11 Diesel Engine 17 Motor Generator (Motor)
26 Turbocharger 26b Turbine 30a Exhaust manifold (exhaust collecting pipe)
40 Pre-catalyst (catalyst)
44 Bypass passage 46 Bypass valve

Claims (1)

An exhaust purification device for a diesel hybrid vehicle that can be driven by at least one of a diesel engine having a turbocharger and a motor,
The diesel engine is a catalyst upstream of the turbocharger turbine and having an oxidizing ability in an exhaust collecting pipe, a bypass passage branched from the catalyst upstream to bypass the catalyst and communicate with the turbine upstream; A bypass valve for controlling the amount of exhaust gas passing through the bypass passage,
An exhaust emission control device for a diesel hybrid vehicle, wherein the diesel engine is torque-assisted by the motor when the bypass valve is fully closed and the exhaust gas passes through the catalyst during vehicle acceleration. .

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