WO2023007530A1

WO2023007530A1 - Catalyst warm-up control method and device for internal combustion engine

Info

Publication number: WO2023007530A1
Application number: PCT/JP2021/027469
Authority: WO
Inventors: 容康木村
Original assignee: 日産自動車株式会社
Priority date: 2021-07-26
Filing date: 2021-07-26
Publication date: 2023-02-02

Abstract

An internal combustion engine (2) which drives a motor generator (1) for generating electricity in a series hybrid vehicle includes a catalyst device (31) upstream of a turbine (12b) of a turbocharger (12). Catalyst warm-up operation occurs prior to effective full power generation operation at the start of a vehicle trip. An engine controller (8) fully closes a wastegate valve (34) during catalyst warm-up operation. This increases the resistance to the flow of exhaust, increasing the pressure and temperature of the exhaust on the upstream side of the turbine (12b). This promotes warm-up of the catalyst device (31). An opening degree of a throttle valve (22) is reduced, for example, to limit output.

Description

METHOD AND APPARATUS FOR INTERNAL COMBUSTION ENGINE CATALYST WARM-UP CONTROL

This invention relates to catalyst warm-up control in an internal combustion engine having a catalyst upstream of the turbine of a turbocharger.

In an internal combustion engine with a turbocharger, the catalyst provided in the exhaust system for purifying exhaust gas is often arranged downstream of the turbine of the turbocharger. In such a configuration, it is common to fully open the wastegate valve of the turbine during catalyst warm-up operation that is performed after a cold start. That is, early activation of the catalyst is attempted by guiding the exhaust gas to the catalyst downstream of the turbine without passing through the turbine.

On the other hand, depending on the specifications of the internal combustion engine, the catalyst may be placed upstream of the turbine of the turbocharger. In such a configuration, even if the waste gate valve is fully opened during the catalyst warm-up operation, it is not effective for heating the catalyst.

Patent document 1 discloses reducing the opening of the waste gate valve during catalyst warm-up operation in a configuration in which the catalyst is arranged downstream of the turbine. This is to keep water from hitting the A/F sensor and has nothing to do with early catalyst warm up.

JP 2014-005779 A

The present invention relates to catalyst warm-up control for an internal combustion engine in which at least one catalyst is arranged upstream of a turbine of a turbocharger, wherein during catalyst warm-up operation, the opening of a waste gate valve of the turbine is reduced or the opening of the turbine is reduced. By reducing the opening of the variable nozzle, the temperature of the exhaust gas upstream of the turbine is increased.

As the temperature of the exhaust gas upstream of the turbine rises in this way, the temperature of the catalyst positioned upstream of the turbine rises quickly, and the exhaust gas purification action can be obtained quickly.

FIG. 2 is a configuration explanatory diagram of a series hybrid vehicle; FIG. 1 is a configuration explanatory diagram of an internal combustion engine to which catalyst warm-up control of one embodiment is applied; Explanatory drawing of a variable nozzle.

FIG. 1 schematically shows the configuration of a series hybrid vehicle as an example of a vehicle to which the present invention is applied. The series hybrid vehicle includes a motor generator 1 for power generation that mainly operates as a power generator, an internal combustion engine 2 that is used as an internal combustion engine for power generation that drives the motor generator 1 for power generation according to electric power demand, and an internal combustion engine 2 that mainly operates as a motor. It is composed of a traveling motor generator 4 that drives the drive wheels 3 as a driving force, and a battery 5 that temporarily stores the generated electric power. Electric power obtained by the internal combustion engine 2 driving the motor generator 1 is stored in the battery 5 via an inverter device (not shown). The driving motor generator 4 is driven and controlled using the electric power of the battery 5 . Electric power generated during regeneration by the motor generator 4 for traveling is stored in the battery 5 via an inverter device (not shown).

FIG. 2 shows the system configuration of the internal combustion engine 2. The internal combustion engine 2 is a four-stroke cycle spark ignition internal combustion engine equipped with a turbocharger 12. A pair of intake valves 14 and a pair of exhaust valves 15 are arranged on the ceiling wall surface of each cylinder 13. , and an ignition plug 16 is arranged in a central portion surrounded by the intake valve 14 and the exhaust valve 15 . A fuel injection valve 17 that supplies fuel into the cylinder 13 is provided below the intake valve 14 . The engine controller 8 controls the ignition timing of the ignition plug 16 and the injection timing and injection amount of fuel by the fuel injection valve 17 .

In addition, the intake valve 14 and the exhaust valve 15 are provided with variable

valve timing mechanisms

18 and 19 that can change their opening timing and closing timing. Although the variable

valve timing mechanisms

18 and 19 may be of any type, for example, a type of mechanism that retards the phase of the camshaft with respect to the phase of the crankshaft can be used.

The intake passage 21 has an intake collector 21a, and an electronically controlled throttle valve 22 whose opening is controlled by a control signal from the engine controller 8 is provided upstream of the intake collector 21a. A compressor 12a of the turbocharger 12 is positioned upstream of the throttle valve 22, and an air flow meter 24 and an air cleaner 25 for detecting the amount of intake air are disposed upstream of the compressor 12a. A water-cooled intercooler 26, for example, is provided between the compressor 12a and the throttle valve 22 to cool the high temperature and high pressure intake air. A recirculation valve 27 is provided to communicate the discharge side and the suction side of the compressor 12a. The recirculation valve 27 is basically for suppressing a phenomenon in which the pressure rises transiently upstream of the throttle valve 22 when the throttle valve 22 suddenly closes and decelerates rapidly. is open, the pressure downstream of the compressor 12a is released to the low pressure side upstream of the compressor 12a.

A turbine 12 b of the turbocharger 12 is positioned in the exhaust passage 30 , and a catalyst device 31 is arranged upstream of this turbine 12 b , that is, between the turbine 12 b and the exhaust valve 15 . In this embodiment, the catalyst device 31 has a shape in which a three-way catalyst 31A, a particulate filter (so-called GPF) 31B for collecting exhaust particulates, and an oxidation catalyst 31C are arranged in series from the upstream side. It has a configuration that is combined with A selective catalytic reduction device, that is, an SCR device 32 is arranged downstream of the turbine 12b to reduce NOx using urea water as a second catalyst. The upstream catalytic device 31 is mounted, for example, adjacent to the cylinder head of the internal combustion engine 2, and the SCR device 32 is arranged, for example, under the floor of the vehicle.

An air-fuel ratio sensor 33 that detects the air-fuel ratio is arranged upstream of the catalyst device 31 in the exhaust passage 30 . Turbine 12b includes a wastegate valve 34 that bypasses a portion of the exhaust in response to boost pressure to control boost pressure. The wastegate valve 34 is of an electric type whose opening is controlled by the engine controller 8 .

Further, an exhaust gas recirculation passage 35 for recirculating part of the exhaust gas from the exhaust passage 30 to the intake passage 21 is provided. It is

In addition to the air flow meter 24 and the air-fuel ratio sensor 33, the engine controller 8 includes a crank angle sensor 41 for detecting the engine rotation speed, a water temperature sensor 42 for detecting the cooling water temperature, and a catalyst temperature of the catalyst device 31 (for example,

catalyst temperature sensors

43 and 44 for detecting the catalyst temperature of the three-way catalyst 31A) and the catalyst temperature of the SCR device 32, respectively; an atmospheric pressure sensor 45 for detecting atmospheric pressure; Detection signals from sensors such as the supercharging pressure sensor 47 are input. Based on these detection signals, the engine controller 8 controls the fuel injection amount, injection timing, ignition timing, opening of the throttle valve 22, opening of the recirculation valve 27, opening of the waste gate valve 34, intake valve 14 and The opening/closing timing of the exhaust valve 15, etc. are optimally controlled. Instead of directly detecting the carrier temperature of the catalyst, the

catalyst temperature sensors

43 and 44 may indirectly determine the catalyst temperature from the temperature of the gas before and after the catalyst.

The internal combustion engine 2 is basically started when the SOC of the battery 5 drops to a predetermined starting SOC value, and stops when the SOC recovers to a predetermined level. When the internal combustion engine 2 drives the electric power generating motor generator 1 to generate electric power, the internal combustion engine 2 is basically operated near the best fuel consumption point. and lean operation is performed. A portion of the unburned HC generated during such lean operation is purified by the three-way catalyst 31A and further purified by the downstream oxidation catalyst 31C. Exhaust particulates are also collected by the particulate filter 31B. Further, NOx generated by lean operation is partially purified by the three-way catalyst 31A, but is mainly reduced by the SCR device 32. In lean operation, the exhaust gas temperature is relatively low, but since the catalyst device 31 is positioned upstream of the turbine 12b, the exhaust gas before the temperature is lowered by the turbine 12b is guided to the catalyst device 31, and sufficient catalytic action is obtained. maintained.

On the other hand, when the vehicle starts to trip, except for the case where the internal combustion engine 2 is already warmed up, the catalytic converter 31 is warmed up before the actual start of power generation in order to quickly secure the exhaust purification performance by warming up the catalytic converter 31 . A warm-up operation is performed. In this embodiment, during catalyst warm-up operation, air-fuel ratio control is executed with the stoichiometric air-fuel ratio as the target air-fuel ratio, and retarded combustion is performed in which the ignition timing is retarded due to an increase in exhaust temperature.

During such catalyst warm-up operation, in this embodiment, the waste gate valve 34 in the turbine 12b of the turbocharger 12 is controlled to be fully closed. This increases the resistance to the exhaust flow, increasing the pressure and temperature of the exhaust from the exhaust valve 15 to the turbine 12b. As a result, the catalyst device 31 located upstream of the turbine 12b is effectively warmed, and the three-way catalyst 31A and the oxidation catalyst 31C quickly reach their activation temperatures. When at least the most upstream three-way catalyst 31A reaches the activation temperature, the exhaust purification action during the catalyst warm-up operation can be obtained.

In this catalyst warm-up operation, a large output of the internal combustion engine 2 is not required, and it is desirable that the exhaust gas amount is small from the viewpoint of emission control of unburned HC. By fully closing the waste gate valve 34, the supercharging effect of the turbocharger 12 tends to be increased. The output is suppressed in accordance with the reduction of the opening of the waste gate valve 34 . A first method for suppressing the output is correction for decreasing the opening of the throttle valve 22. By controlling the opening of the throttle valve 22 to the closing side, the output of the internal combustion engine 2 and the amount of exhaust gas are suppressed. The second means is to appropriately open the recirculation valve 27, which is generally opened during deceleration (when the throttle valve 22 is closed), to reduce the supercharging pressure. A third means is to use the variable

valve timing mechanisms

18 and 19 to control the opening/closing timings of the intake valve 14 and the exhaust valve 15 in the direction in which the volumetric efficiency decreases. Any one of these output suppression means may be used alone, or may be used in combination as appropriate.

Also, if the waste gate valve 34 is fully closed during the catalyst warm-up operation, catalyst warm-up of the SCR device 32 located downstream of the turbine 12b tends to be delayed. Therefore, in a preferred embodiment, the temperature of the SCR device 32 is monitored when the upstream catalyst warm-up progresses to some extent, and if the temperature of the SCR device 32 is below the threshold, the opening of the waste gate valve 34 is increased. to correct. As a result, part of the exhaust gas is introduced into the SCR device 32 without passing through the turbine 12b, thereby promoting the warm-up of the SCR device 32.

Next, a second embodiment in which the turbine 12b of the turbocharger 12 has a variable nozzle will be described. FIG. 3 is an explanatory diagram of an example of the variable nozzle 51. As shown in FIG. The turbocharger 12 equipped with the variable nozzle 51 is adapted to correspond to the magnitude of the exhaust flow rate by varying the nozzle area of the exhaust inlet in the scroll of the turbine 12b. 52 operates to change the nozzle area of the variable nozzle 51 .

In this embodiment, the variable nozzle 51 is controlled to the minimum opening degree during the catalyst warm-up operation. This increases the resistance to the flow of the exhaust, again increasing the pressure and temperature of the exhaust from the exhaust valve 15 to the turbine 12b. Therefore, the catalyst device 31 located upstream of the turbine 12b is effectively warmed.

Controlling the variable nozzle 51 to the minimum opening also increases the supercharging effect of the turbocharger 12, so it is desirable to perform output suppression by means of the first to third means described above as well.

Warming up of the SCR device 32 on the downstream side is also the same as in the above embodiment. If there is, the opening degree of the variable nozzle 51 is corrected to increase.

It should be noted that the control that minimizes the opening of the variable nozzle 51 during the catalyst warm-up operation can be used in combination with the above-described control that fully closes the waste gate valve 34 . That is, the variable nozzle 51 can be set to the minimum opening degree, and in addition, the waste gate valve 34 can be fully closed. Alternatively, instead of controlling the waste gate valve 34 to be fully closed, the variable nozzle 51 may be set to the minimum opening.

As described above, the control that fully closes the waste gate valve 34 or minimizes the opening of the variable nozzle 51 during catalyst warm-up operation also improves the transient response when transitioning from catalyst warm-up operation to power generation operation. contribute. That is, since the turbine 12b is maintained in a state of rotating at a relatively high speed, the output can be immediately increased to the vicinity of the best fuel consumption point.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible. For example, the present invention is not limited to the internal combustion engine of a series hybrid vehicle, and can be widely applied to other types of hybrid vehicles and internal combustion engines of general vehicles using only an internal combustion engine as a drive source. Further, the catalyst arranged upstream of the turbine is not limited to the catalyst device having the combined structure as in the above embodiment, and may be any catalyst such as a three-way catalyst or an oxidation catalyst depending on the specifications of the internal combustion engine. . Of course, the present invention is not limited to internal combustion engines that perform lean combustion.

Further, in the above embodiment, the waste gate valve 34 is fully closed or the variable nozzle 51 is set to the minimum opening during catalyst warm-up, but it may be set to an appropriate intermediate opening.

Claims

A catalyst warm-up control method for an internal combustion engine in which at least one catalyst is arranged upstream of a turbine of a turbocharger,
During catalyst warm-up operation, the exhaust temperature upstream of the turbine is increased by reducing the opening of the waste gate valve of the turbine or reducing the opening of the variable nozzle of the turbine.
A catalyst warm-up control method for an internal combustion engine.
At the time of the above catalyst warm-up operation, the reduction correction of the throttle valve opening is also performed.
2. The catalyst warm-up control method for an internal combustion engine according to claim 1.
At the time of the above catalyst warm-up operation, supercharging pressure reduction control using a recirculation valve in the compressor of the turbocharger is also performed.
3. The catalyst warm-up control method for an internal combustion engine according to claim 1 or 2.
At least one of the intake valve and exhaust valve is equipped with a variable valve timing mechanism,
controlling the variable valve timing mechanism in a direction in which the volumetric efficiency decreases during the catalyst warm-up operation;
A catalyst warm-up control method for an internal combustion engine according to any one of claims 1 to 3.
Fully closing the waste gate valve during the catalyst warm-up operation,
2. The catalyst warm-up control method for an internal combustion engine according to claim 1.
setting the opening of the variable nozzle to be the minimum opening during the catalyst warm-up operation;
2. The catalyst warm-up control method for an internal combustion engine according to claim 1.
comprising a second catalyst downstream of the turbine;
If the temperature of the second catalyst is equal to or lower than the threshold value, the opening of the waste gate valve is corrected to increase.
6. The catalyst warm-up control method for an internal combustion engine according to claim 5.
comprising a second catalyst downstream of the turbine;
If the temperature of the second catalyst is equal to or lower than the threshold value, the opening degree of the variable nozzle is corrected to increase.
7. The catalyst warm-up control method for an internal combustion engine according to claim 6.
A catalyst warm-up control device for an internal combustion engine, comprising: a turbocharger having at least one of a wastegate valve and a variable nozzle; at least one catalyst arranged upstream of the turbine of the turbocharger; and a controller,
The controller reduces the opening of the waste gate valve of the turbine or the opening of the variable nozzle of the turbine in order to increase the exhaust temperature upstream of the turbine during catalyst warm-up operation.
Catalyst warm-up controller for internal combustion engine