Exhaust purifier

Abstract

The present invention provides an exhaust gas purification system equipped with an electrically heated catalyst that can reduce the power consumption of the electrically heated catalyst and prevent the exhaust pipe from becoming blocked due to the freezing of the on / off valve. [Solution] When the vehicle is stopped and the engine 10 is stopped, the ECU 81 of the exhaust gas purification device 1 drives the first motor generator 11 to motorize the engine 10 when closing the first on-off valve 141 and the second on-off valve 142, to discharge the combustion gases remaining in the engine 10 and the exhaust pipe 118 and replace them with fresh air. Then, it closes the second on-off valve 142 located upstream of the electric heated catalyst 140 to raise the electric heated catalyst 140 to a first target temperature. After that, when the temperature of the electric heated catalyst 140 reaches the first target temperature, it stops the power supply to the electric heated catalyst 140 and closes the first on-off valve 141 located downstream of the electric heated catalyst 140.

Description

Technical Field

[0005]

[0001] The present invention relates to an exhaust gas purification device for purifying the exhaust gas of an engine, and particularly to an exhaust gas purification device provided with an electrically heated catalyst.

Background Art

[0002] In recent years, in exhaust gas regulations, reduction of emissions during cold start (low temperature start) has been required. For example, regulations such as the North American Cold FTP (Federal Test Procedure) test and the European -10°C RDE (Real Driving Emissions) have been strengthened.

[0003] In order to cope with such strengthened regulations, the use of an electrically heated catalyst that can be electrically heated (for example, see Patent Document 1) has been proposed. Here, an electrically heated catalyst (EHC) can raise the temperature to a temperature at which the catalyst becomes active (for example, about 300 to 500°C) in a short time (about several seconds to several tens of seconds). On the other hand, since a large amount of power (large current) is required to raise the temperature of the electrically heated catalyst, if the power consumed by raising the temperature of the electrically heated catalyst is replenished (charged) by power generation by the engine, the fuel consumption may deteriorate.

[0004] Therefore, for example, covering the electrically heated catalyst with a double exhaust pipe in which a vacuum chamber is formed between an inner pipe and an outer pipe (for example, see Patent Document 2), sealing it with a plug and insulating it during parking to suppress (keep warm) the temperature drop of the electrically heated catalyst, thereby reducing the power required to raise the temperature of the electrically heated catalyst at the next engine start can be considered.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

[0006] However, even if the electrically heated catalytic converter is sealed and insulated with a double exhaust pipe and a plug, if the vehicle is left parked (unattended) for a long period of time in extremely low temperatures, for example, the plug may freeze, making it impossible to open the plug when starting the engine again. As a result, the exhaust pipe may become blocked.

[0007] The present invention was made to solve the above problems, and aims to provide an exhaust gas purification device equipped with an electrically heated catalyst that can reduce the power consumption of the electrically heated catalyst and prevent the exhaust pipe from becoming blocked due to the freezing of the plug (on-off valve). [Means for solving the problem]

[0008] The exhaust gas purification device according to the present invention is an exhaust gas purification device mounted on a vehicle comprising an engine and an electric motor capable of transmitting power between the engine and the crankshaft, and comprises an electrically heated catalyst configured to be heated up by the supply of electricity and purifying the exhaust gas of the engine at a predetermined activation temperature or higher, an exhaust pipe having a vacuum layer formed to cover at least the entire side surface of the electrically heated catalyst, a first on-off valve disposed on the upstream side of the electrically heated catalyst in the exhaust pipe and opening and closing the exhaust pipe, a second on-off valve disposed on the downstream side of the electrically heated catalyst in the exhaust pipe and opening and closing the exhaust pipe, and power supply to the electrically heated catalyst, and the first The system includes a control unit that controls the operation of an on-off valve and a second on-off valve, wherein, after the vehicle is stopped and the engine is stopped, the control unit drives an electric motor to motorize the engine when closing the first on-off valve and the second on-off valve, exhausts the combustion gases remaining in the engine and exhaust pipe and replaces them with fresh air, then closes the second on-off valve to raise the temperature of the electric heated catalyst to a first target temperature, and then, when the temperature of the electric heated catalyst reaches the first target temperature, stops the power supply to the electric heated catalyst and closes the first on-off valve.

[0009] According to the exhaust gas purification device of the present invention, first, after the vehicle is stopped and the engine is stopped, before the first and second on-off valves are closed, an electric motor is driven to motorize the engine, and combustion gases remaining in the engine and exhaust pipe are discharged and replaced with fresh air. As a result, combustion gases containing a large amount of water vapor are discharged and replaced with fresh air with a low water vapor content, which reduces the amount of water vapor inside that can cause freezing, and thus prevents freezing of the first and second on-off valves, etc.

[0010] Next, the second valve is closed, the electrically heated catalyst is heated to the first target temperature, and then, once the temperature of the electrically heated catalyst reaches the first target temperature, the power supply to the electrically heated catalyst is stopped and the first valve is closed. In this way, after the electrically heated catalyst is heated to the first target temperature, the first and second valves are closed (the electrically heated catalyst is sealed), so as the temperature gradually decreases thereafter, the internal pressure decreases (depressurization), heat conduction through the air decreases, and heat retention improves, thereby reducing the power consumption of the electrically heated catalyst. In particular, because the second valve is closed at that time (when the electrically heated catalyst is heated), condensate that tends to accumulate on the rear side of the exhaust pipe (muffler, etc.) is prevented from evaporating again due to the heat from heating and entering the second valve, etc., thus preventing freezing.

[0011] In this state, that is, when the internal pressure is reduced, heat conduction decreases (improving heat retention), and the amount of water vapor inside is reduced, the electric heating catalyst is sealed, insulated, and kept warm by the exhaust pipe with a vacuum layer formed on it, and by the first and second on-off valves (i.e., it is a so-called thermos bottle structure). As a result, the power consumption of the electric heating catalyst can be reduced, and even if left for a long period of time at extremely low temperatures, the first and second on-off valves will not freeze and become unable to open. [Effects of the Invention]

[0012] According to the present invention, in an exhaust gas purification device equipped with an electrically heated catalyst, it is possible to reduce the power consumption of the electrically heated catalyst and prevent the exhaust pipe from becoming blocked due to the freezing of the on / off valve (plug). [Brief explanation of the drawing]

[0013] [Figure 1] This diagram shows a skeleton diagram of the power unit configuration of a hybrid vehicle equipped with an exhaust gas purification device according to an embodiment, and a block diagram showing the configuration of its control system. [Figure 2] This figure shows the configuration of an exhaust gas purification device according to an embodiment and an engine to which the exhaust gas purification device is applied. [Figure 3] This is a diagram showing the configuration of an exhaust gas purification device according to an embodiment. [Figure 4] This is a diagram (timing chart) illustrating the power consumption reduction and freeze prevention treatment performed by the exhaust gas purification device according to the embodiment. [Figure 5] This flowchart shows the processing procedure for reducing power consumption and preventing freezing using the exhaust gas purification device according to the embodiment. [Modes for carrying out the invention]

[0014] Preferred embodiments of the present invention will be described in detail below with reference to the drawings. In the drawings, the same or corresponding parts will be denoted by the same reference numerals. In addition, in each drawing, the same elements will be denoted by the same reference numerals, and redundant explanations will be omitted.

[0015] First, the configuration of the exhaust purification device 1 according to this embodiment will be explained using Figures 1 to 3 together. Figure 1 is a skeleton diagram showing the configuration of the power unit of a hybrid vehicle equipped with the exhaust purification device 1, and a block diagram showing the configuration of its control system. Figure 2 is a diagram showing the configuration of the exhaust purification device 1 and the engine 10 to which the exhaust purification device 1 is applied. Figure 3 is a diagram showing the configuration of the exhaust purification device 1. Here, the case in which the exhaust purification device 1 is installed in a series-parallel hybrid vehicle (HEV) will be explained as an example.

[0016] First, with reference to Figure 1, the configuration of the hybrid vehicle's power unit and other components will be explained. The crankshaft 10a of the engine 10 (details will be described later) is connected to a power split mechanism 30 via a flywheel damper 20 and a pair of gears 21 that absorb rotational fluctuations of the engine 10. The power split mechanism 30 is connected to a drivetrain 15, which consists of multiple gears and shafts and transmits torque to the drive wheels, and a first motor-generator (MG) 11 (corresponding to the electric motor described in the claims). The power split mechanism 30 has a planetary gear mechanism consisting of, for example, a sun gear 30a, a ring gear 30b, a pinion gear 30c, and a planetary carrier 30d, and transmits the drive torque generated from the engine 10 to the drivetrain 15 and the first motor-generator 11 in a split manner.

[0017] More specifically, the carrier 30d is connected to the crankshaft 10a of the engine 10 via a flywheel damper 20 and a pair of gears 21. The sun gear 30a is connected to the first motor-generator 11. Meanwhile, the ring gear 30b is connected to the propeller shaft (rear wheel output shaft) 50 that constitutes the drivetrain 15 via a pair of gears (counter gears) 31, and is further connected to the front drive shaft (front wheel output shaft) 60 via a drive reduction gear 43.

[0018] When the first motor-generator 11 functions as a generator, the power distribution mechanism 30 distributes the torque (driving force) from the engine 10 input from the planetary carrier 30d to both the sun gear 30a and the ring gear 30b according to their respective gear ratios. On the other hand, when the first motor-generator 11 functions as a motor, the power distribution mechanism 30 integrates the torque from the engine 10 input from the planetary carrier 30d and the torque from the first motor-generator 11 input from the sun gear 30a and outputs the integrated torque to the ring gear 30b. The torque output to the ring gear 30b is output to the propeller shaft 50 constituting the drive train 15 via a pair of gears (counter gears) 31, and is further output to the front drive shaft 60 via the drive reduction gear 43.

[0019] On the other hand, a second motor-generator (MG) 12 (corresponding to the electric motor described in the claims) is also connected to the drive train 15. More specifically, the second motor-generator 12 is connected to the propeller shaft 50 via a motor reduction gear 41. The second motor-generator 12 is also connected to the front drive shaft 60 via a drive reduction gear mechanism 40 composed of the motor reduction gear 41 and the drive reduction gear 43. The front drive shaft 60 transmits torque to the front wheels. The propeller shaft 50 transmits torque to the rear wheels.

[0020] The first motor-generator 11 and the second motor-generator 12 are configured as synchronous motor-generators having both the function of a motor that converts the supplied electric power into mechanical power and the function of a generator that converts the input mechanical power into electric power. That is, each of the first motor-generator 11 and the second motor-generator 12 operates as a motor that generates driving torque during vehicle driving and operates as a generator during regeneration. The first motor-generator 11 mainly operates as a generator, and the second motor-generator 12 mainly operates as a motor.

[0021] The drive reduction gear mechanism 40 is composed of a motor reduction gear 41 and a drive reduction gear 43. The motor reduction gear 41 is composed of planetary gears, and the reduction gear 43 is composed of, for example, spur gears (or helical gears).

[0022] More specifically, the motor reduction gear 41 has, for example, a planetary gear mechanism composed of a sun gear 41a, a ring gear 41b, a pinion gear 41c, and a planetary carrier 41d. When the second motor generator 12 functions as a motor, the motor reduction gear 41 reduces the rotation transmitted from the second motor generator 12 (increases the torque) and outputs it from the planetary carrier 41d. On the other hand, the motor reduction gear 41 accelerates the rotation caused by the torque (driving force) input to the planetary carrier 41d (reduces the torque) and outputs it from the sun gear 41a, thereby making the second motor generator 12 function as a generator.

[0023] The front drive shaft 60 transmits torque between the drive reduction gear mechanism 40 and the drive wheels (front wheels in the example of FIG. 1). More specifically, the torque of the second motor generator 12 etc. transmitted to the front drive shaft 60 is transmitted to the front differential (hereinafter also referred to as "front diff") 62. The front diff 62 is, for example, a bevel gear type differential device. The torque from the front diff 62 is transmitted to the left front wheel (not shown) via the left front wheel drive shaft and to the right front wheel (not shown) via the right front wheel drive shaft.

[0024] Meanwhile, the propeller shaft 50 transmits torque to the rear wheels. The propeller shaft 50 is equipped with a transfer clutch 51 that adjusts the torque transmitted to the rear wheels. The transfer clutch 51 controls the clamping force (i.e., the torque distribution rate to the rear wheels) according to the driving state of the four wheels (e.g., the slip state of the front wheels) and engine torque. Therefore, the torque from the second motor / generator 12 transmitted to the propeller shaft 50 is distributed according to the clamping force of the transfer clutch 51 and transmitted to the rear wheels.

[0025] More specifically, the torque transmitted to the propeller shaft 50 and regulated (distributed) by the transfer clutch 51 is transmitted to the rear differential (hereinafter also referred to as "rear differential") 52. The left rear drive shaft and the right rear drive shaft (not shown) are connected to the rear differential 52. The driving force from the rear differential 52 is transmitted to the left rear wheel (not shown) via the left rear drive shaft and to the right rear wheel (not shown) via the right rear drive shaft.

[0026] With this configuration, the vehicle according to this embodiment (an AWD HEV vehicle) can drive the front and rear wheels (vehicle) with two power sources: the engine 10 and the second motor-generator 12. Furthermore, depending on the driving conditions, it is possible to switch between driving using only the second motor-generator 12 (EV driving) and driving using both the engine 10 and the second motor-generator 12. In addition, it is possible to generate electricity with the second motor-generator 12, etc. Also, the engine 10 can be motorized with the first motor-generator 11, etc. (i.e., the engine 10 can be rotated with fuel injection and ignition stopped).

[0027] The engine 10, which is the driving force source of the vehicle, and the second motor-generator 12 and the first motor-generator 11 are comprehensively controlled by a hybrid vehicle control unit (hereinafter referred to as "HEV-CU") 80.

[0028] The HEV-CU80 consists of a microprocessor that performs calculations, an EEPROM that stores programs for the microprocessor to execute various processes, a RAM that stores various data such as calculation results, a backup RAM that holds the contents of the RAM, and an input / output interface.

[0029] The HEV-CU80 is connected to various sensors, including, for example, an accelerator pedal sensor 91 that detects the amount the accelerator pedal is pressed, a throttle position sensor 92 that detects the opening degree of the throttle valve, a G sensor (accelerometer) 93 that detects the acceleration of the vehicle in the front-rear and left-right directions, a vehicle speed sensor 94 that detects the speed of the wheels, a rotation speed sensor 95 that detects the rotation speed of the front drive shaft 60, a resolver 97 that detects the rotation speed (rotational velocity) of the first motor-generator 11, and a resolver 98 that detects the rotation speed (rotational velocity) of the second motor-generator 12.

[0030] Furthermore, the HEV-CU80 is connected via CAN (Controller Area Network) 70 to communicate with the engine control unit (hereinafter referred to as "ECU") 81, which controls the engine 10, and the vehicle dynamic control unit (hereinafter referred to as "VDCU") 85, which suppresses vehicle skidding and improves driving stability. The HEV-CU80 receives various information from the ECU81 and VDCU85 via CAN 70, such as engine speed and brake operation amount. On the other hand, the HEV-CU80 transmits various information such as the rotation speed (rotational velocity) of the first motor-generator 11 and the rotation speed (rotational velocity) of the second motor-generator 12 to the ECU81 via CAN 70.

[0031] Based on the various information acquired, the HEV-CU80 comprehensively controls the operation of the engine 10, the second motor-generator 12, and the first motor-generator 11. For example, based on the accelerator pedal opening (driver's requested driving force), the vehicle's operating state, and the charge state (SOC) of the high-voltage battery (hereinafter also simply referred to as "battery") 90, the HEV-CU80 determines and outputs the requested output of the engine 10 and the torque command values ​​of the second motor-generator 12 and the first motor-generator 11.

[0032] The power control unit (hereinafter referred to as "PCU") 82 drives the second motor-generator 12 and the first motor-generator 11 via the inverter 82a based on the torque command value. The PCU 82 has an inverter 82a that converts the DC power of the high-voltage battery 90 into three-phase AC power and supplies it to the second motor-generator 12 and the first motor-generator 11. As described above, the PCU 82 drives the second motor-generator 12 and the first motor-generator 11 via the inverter 82a based on the torque command value received from the HEV-CU 80. On the other hand, during regeneration, the inverter 82a converts the AC voltage generated by the second motor-generator 12 into a DC voltage to charge the high-voltage battery 90.

[0033] Furthermore, based on the above request output, the ECU 81 adjusts, for example, the opening degree of the electronically controlled throttle valve 113. Next, with reference to Figure 2, the configuration of the exhaust gas purification device 1 and the engine 10 to which the exhaust gas purification device 1 is applied will be described in detail.

[0034] Engine 10 can be of any type, but for example, it is a horizontally opposed 4-cylinder gasoline engine. Engine 10 is also an in-cylinder injection engine that directly injects fuel into the cylinders. In engine 10, air drawn in from the air cleaner 116 is restricted by an electronically controlled throttle valve (hereinafter also simply called "throttle valve") 113 provided in the intake manifold 115, passes through the intake manifold 111, and is drawn into each cylinder formed in engine 10. Here, the amount of air drawn in from the air cleaner 116 is detected by an airflow meter 114 placed between the air cleaner 116 and the throttle valve 113. In addition, a vacuum sensor 130 that detects the pressure inside the intake manifold 111 (intake manifold pressure) is provided inside the collector section (surge tank) that makes up the intake manifold 111. Furthermore, the throttle valve 113 is equipped with a throttle opening sensor 92 that detects the degree of opening of the throttle valve 113.

[0035] The cylinder head has an intake port 122 and an exhaust port 123 for each cylinder (only one bank is shown in Figure 2). Each intake port 122 and exhaust port 123 is provided with an intake valve 124 and an exhaust valve 125 that open and close the intake port 122 and exhaust port 123, respectively. Between the intake camshaft and the intake cam pulley that drives the intake valve 124, a variable valve timing mechanism 126 is provided to advance or retard the valve timing (opening / closing timing) of the intake valve 124 by rotating the intake cam pulley and the intake camshaft relative to each other, thereby continuously changing the rotational phase (displacement angle) of the intake camshaft with respect to the crankshaft 10a. This variable valve timing mechanism 126 allows the opening and closing timing of the intake valve 124 to be variably set according to the engine operating conditions.

[0036] Similarly, a variable valve timing mechanism 127 is provided between the exhaust camshaft and the exhaust cam pulley. This mechanism rotates the exhaust cam pulley and the exhaust camshaft relative to each other, continuously changing the rotational phase (displacement angle) of the exhaust camshaft with respect to the crankshaft 10a, thereby advancing or retarding the valve timing (opening / closing timing) of the exhaust valve 125. This variable valve timing mechanism 127 allows the opening and closing timing of the exhaust valve 125 to be variably set according to the engine operating conditions.

[0037] Each cylinder of the engine 10 is fitted with an injector 112 that injects fuel into the cylinder. The injector 112 directly injects fuel pressurized by a high-pressure fuel pump (not shown) into the combustion chamber of each cylinder.

[0038] Furthermore, each cylinder head is fitted with a spark plug 117 for igniting the fuel-air mixture, and an igniter-integrated coil 121 for applying a high voltage to the spark plug 117. In each cylinder of the engine 10, the fuel-air mixture, consisting of the intake air and the fuel injected by the injector 112, is ignited by the spark plug 117 and combusted. The exhaust gas after combustion is discharged through the exhaust pipe 118.

[0039] In this embodiment, to prevent exhaust interference, the exhaust pipe 118 employs a 4-2-1 layout in which the exhausts from cylinders #1 and #2, and cylinders #3 and #4 are first merged (combined) before being combined into a single pipe. Alternatively, a 4-1 layout or similar configuration may be used instead of the 4-2-1 layout.

[0040] An air-fuel ratio sensor 119 is installed downstream of the manifold of the exhaust pipe 118 and upstream of the exhaust gas purification catalyst 120, which will be described later. The air-fuel ratio sensor 119 is a linear air-fuel ratio sensor (LAF sensor) that can output signals corresponding to the oxygen concentration and unburned gas concentration in the exhaust gas (i.e., signals corresponding to the air-fuel ratio of the mixture) and can linearly detect the air-fuel ratio.

[0041] A catalytic converter 120 is installed downstream of the LAF sensor 119. The catalytic converter 120 is a three-way catalytic converter (TWC) that simultaneously oxidizes hydrocarbons (HC) and carbon monoxide (CO) in the exhaust gas and reduces nitrogen oxides (NOx), thereby purifying the harmful gas components in the exhaust gas into harmless carbon dioxide (CO2), water vapor (H2O), and nitrogen (N2).

[0042] An electrically heated catalyst (EHC) 140 is installed downstream of the exhaust gas purification catalyst 120. By positioning the electrically heated catalyst 140 behind the exhaust gas purification catalyst 120, damage due to high heat during high-load driving, for example, can be prevented.

[0043] The electrically heated catalyst 140 is configured to be able to be heated up by a heating element (heater) that generates heat when electricity is supplied through a pair of electrodes 140a. The electrically heated catalyst 140 is accelerated to reach a predetermined activation temperature (for example, around 300-500°C) by heating due to the supply of electricity, thereby activating quickly and being effective in reducing emissions (purifying exhaust gases) immediately after starting and during warm-up (especially during cold starts).

[0044] The electrically heated catalyst 140 is formed in a substantially cylindrical shape and is supported (held) by a plurality of insulating support members, such as rod-shaped ones, provided between it and the exhaust pipe 118 (inner circumferential surface) so as not to come into direct contact (surface contact) with the exhaust pipe 118.

[0045] The power supply to the electrically heated catalyst 140 (i.e., the temperature of the electrically heated catalyst 140) is controlled by the ECU 81. Further details will be described later.

[0046] In the exhaust pipe 118, a vacuum layer (hollow structure) 118a is formed in a region that covers at least the entire side surface of the electric heated catalyst 140, with the interior kept in a vacuum state. In this embodiment, in order to cover a wider area of ​​the electric heated catalyst 140 and improve heat retention performance, vacuum layers 118a are also formed on the upstream and downstream sides of the electric heated catalyst 140. In this embodiment (Figure 3), the vacuum layer 118a on the side surface of the electric heated catalyst 140, the upstream vacuum layer 118a, and the downstream vacuum layer 118a are separable, but they may also be continuous (connected) without being separated.

[0047] The inner and outer tubes of the exhaust pipe 118, and the vacuum layer 118a formed between them, each have an annular radial cross-section, and the radial thickness of the vacuum layer 118a is set according to requirements such as thermal insulation performance (heat retention performance).

[0048] The exhaust pipe 118 having a vacuum layer 118a can be manufactured, for example, by connecting the inner and outer pipes by welding or the like in a manufacturing apparatus under vacuum conditions, and then removing them. However, the air inside (vacuum layer 118a) may be removed after connecting the inner and outer pipes in the atmosphere.

[0049] A first on-off valve 141 is located upstream of the electrically heated catalyst 140 in the exhaust pipe 118. The first on-off valve 141 opens and closes the exhaust pipe 118 upstream of the electrically heated catalyst 140. The first on-off valve 141 is mainly an electromagnetic solenoid valve comprising, for example, a valve body having a frustoconical end face (sealing surface) and being movably disposed in the axial direction of the exhaust pipe 118, and an electromagnetic solenoid that drives the valve body in the axial direction. The first on-off valve 141 is opened when energized and closed when de-energized. The operation (opening and closing) of the first on-off valve 141 is controlled by the ECU 81. Further details will be described later.

[0050] Furthermore, it is preferable that the valve body of the first on-off valve 141 be hollow. Also, the clearance (stroke amount of the valve body) of the first on-off valve 141 (seal portion) is set considering the pressure loss in the exhaust pipe 118, etc.

[0051] A second on-off valve 142 is located downstream of the electrically heated catalyst 140 in the exhaust pipe 118. The second on-off valve 142 opens and closes the exhaust pipe 118 downstream of the electrically heated catalyst 140. Similar to the first on-off valve 141 described above, the second on-off valve 142 mainly consists of a valve body having, for example, a frustoconical end face (sealing surface) and arranged to be movable in the axial direction of the exhaust pipe 118, and an electromagnetic solenoid that drives the valve body in the axial direction. The second on-off valve 142 is opened when energized and closed when de-energized. The second on-off valve 142 is driven (opened and closed) by the ECU 81. Further details will be described later.

[0052] Furthermore, it is preferable that the valve body of the second on-off valve 142 be hollow. Also, the clearance (stroke amount of the valve body) of the second on-off valve 142 (seal portion) is set taking into consideration the pressure loss in the exhaust pipe 118, etc.

[0053] A muffler (silencer) is connected to the rear end of the exhaust pipe 118 (i.e., downstream of the electrically heated catalyst 140) to reduce exhaust noise. The muffler has, for example, multiple partitions arranged inside a housing formed in the shape of a rectangular parallelepiped, cylindrical, or elliptical tube, and reduces exhaust noise by lowering the pressure and temperature of the exhaust by gradually expanding the exhaust or by repeatedly causing pressure waves to interfere. Alternatively, a pre-muffler that mainly reduces high-frequency noise may be provided upstream of the muffler (main muffler).

[0054] In addition to the airflow meter 114, LAF sensor 119, vacuum sensor 130, and throttle position sensor 92 mentioned above, a cam angle sensor 132 for cylinder identification of the engine 10 is mounted near the camshaft of the engine 10. Furthermore, a crank angle sensor 133 is mounted near the crankshaft 10a of the engine 10 to detect the rotational position of the crankshaft 10a (the rotational angular velocity and rotational speed determined from the change in rotational position over time). Here, a timing rotor 133a is mounted on the end of the crankshaft 10a, for example, with 34 teeth, each missing two teeth, formed at 10° intervals. The crank angle sensor 133 detects the rotational position of the crankshaft 10a by detecting the presence or absence of the protrusions on the timing rotor 133a. For example, electromagnetic pickup type sensors are used for the cam angle sensor 132 and the crank angle sensor 133.

[0055] These sensors are connected to the ECU81. In addition, the ECU81 is also connected to various other sensors, such as a water temperature sensor 134 that detects the temperature of the engine 10's coolant and an EHC temperature sensor 135 that detects the temperature of the electrically heated catalytic converter 140. The ECU81 also receives information from the HEV-CU80 via CAN70, including the requested output, the rotational speed of the first motor-generator 11, the rotational speed of the second motor-generator 12, and the accelerator pedal opening.

[0056] The ECU81 comprises a microprocessor for performing calculations, an EEPROM for storing programs for executing various processes on the microprocessor, a RAM for storing various data such as calculation results, a backup RAM whose contents are maintained by a battery, and input / output interfaces. The ECU81 also includes an injector driver for driving the injector 112, an output circuit for outputting an ignition signal, and a motor driver for driving an electric motor 113a that opens and closes the electronically controlled throttle valve 113. Furthermore, the ECU81 includes a driver (circuit) for turning the power supply to the electrically heated catalytic converter 140 on and off, and a driver for driving (opening and closing) the first on-off valve 141 and the second on-off valve 142.

[0057] In the ECU81, the cylinder is identified from the output of the camshaft angle sensor 132, and the rotational angular velocity and engine speed are determined from the output of the crankshaft angle sensor 133. In addition, the ECU81 acquires various information such as intake air volume, intake manifold negative pressure, air-fuel ratio of the air-fuel mixture, and engine 10 water temperature based on the detection signals input from the various sensors mentioned above. The ECU81 then controls the engine 10 by controlling the fuel injection amount, ignition timing, and various devices such as the throttle valve 113 based on the requested output from the HEV-CU80 and the acquired information. The ECU81 also controls the power supply to the electrically heated catalytic converter 140 (temperature of the electrically heated catalytic converter 140), and the driving (opening and closing operation) of the first on-off valve 141 and the second on-off valve 142.

[0058] In particular, the ECU 81 has the function of reducing the power consumption of the electrically heated catalyst 140 and preventing the exhaust pipe 118 from becoming blocked due to the freezing of the first on-off valve 141 and the second on-off valve 142. In the ECU 81, these functions are realized by the execution of a program stored in an EEPROM or the like by a microprocessor.

[0059] When the vehicle is stopped and the engine 10 is shut down, the ECU 81 first drives the first motor-generator 11, etc. (outputting a drive request to the HEV-CU 80) to motorize the engine 10, thereby expelling the combustion gases remaining in the engine 10 and exhaust pipe 118 and replacing them with fresh air. It is preferable to open the throttle valve 113 when motorizing the engine 10.

[0060] As a result, combustion gas containing a large amount of water vapor is discharged and replaced with fresh air with a lower water vapor content, which reduces the amount of water vapor inside that can cause freezing, and prevents freezing of the first and second on-off valves 141, 142, etc.

[0061] Subsequently, the ECU 81 closes the second on-off valve 142 to raise the temperature of the electric heating catalyst 140 to a first target temperature (for example, 600°C). Then, when the temperature of the electric heating catalyst 140 reaches the first target temperature, the ECU 81 stops supplying power to the electric heating catalyst 140 and closes the first on-off valve 141.

[0062] In this way, after the electric heating catalyst 140 is heated to the first target temperature, the first and second on-off valves 142 are closed (sealing the electric heating catalyst 140). As the temperature then gradually decreases (natural cooling), the internal pressure decreases (depressurization), reducing heat conduction through the air and improving heat retention, thereby reducing the power consumption of the electric heating catalyst 140. In particular, because the second on-off valve 142 is closed at that time (when the electric heating catalyst 140 is heated), condensate accumulated on the rear side of the exhaust pipe 118 (muffler, etc.), where condensate tends to accumulate, is prevented from evaporating again due to the heat from heating and entering the second on-off valve 142, etc., thus preventing freezing.

[0063] In this state, that is, when the internal pressure is reduced and heat conduction decreases (improving heat retention), and the amount of water vapor inside is reduced, the electric heating catalyst 140 is sealed, insulated, and kept warm by the exhaust pipe 118 with a vacuum layer 118a formed thereon, and the first on-off valve 141 and the second on-off valve 142 (i.e., it is a so-called thermos structure). As a result, the power consumption of the electric heating catalyst 140 is reduced, and even if it is left for a long period of time at extremely low temperatures, the first on-off valve 141 and the second on-off valve 142 are prevented from freezing and becoming unable to open.

[0064] Furthermore, as described above, the ECU 81 controls the power supply to the electrically heated catalyst 140 to maintain the second target temperature (for example, around 350°C) if the temperature of the electrically heated catalyst 140 drops from the first target temperature to a second target temperature (for example, around 350°C) (natural cooling) after the temperature of the electrically heated catalyst 140 has reached the first target temperature and the power supply to the electrically heated catalyst 140 has been stopped.

[0065] The ECU 81 then controls the power supply to the electrically heated catalyst 140 so that its temperature remains at the second target temperature until the engine 10 is started again (while the vehicle is stopped). This eliminates the need for a sudden surge of power supply (heating output) in a short time when the engine is started again; in other words, it eliminates the need to raise the temperature (heat) by several hundred degrees in a few seconds, for example.

[0066] However, if the charge level (SOC) of the battery 90 drops below a predetermined value (i.e., to the point where it becomes difficult to start the engine the next time) while the electric heated catalyst 140 is being maintained at the second target temperature, the ECU 81 stops supplying power (maintaining temperature) to the electric heated catalyst 140 and opens the first on-off valve 141 and the second on-off valve 142.

[0067] On the other hand, after closing the first on-off valve 141 and the second on-off valve 142, the ECU 81 opens the first on-off valve 141 and the second on-off valve 142 when starting the engine 10 again, that is, at or just before starting the engine, more specifically, for example, simultaneously with the start of cranking (simultaneously with the push switch being pressed). Furthermore, if the electrically heated catalyst 140 is maintained at the second target temperature, the ECU 81 stops supplying power to the electrically heated catalyst 140 when the engine 10 is started.

[0068] Next, the operation of the exhaust gas purification device 1 will be explained with reference to Figures 4 and 5. Figure 4 is a diagram (timing chart) for explaining the power consumption reduction and freeze prevention treatment by the exhaust gas purification device 1. Here, the horizontal axis of Figure 4 is time (time), and the vertical axis, from top to bottom, is the state of the vehicle / engine 10 (driving, operating / stopped), the energized state of the electric heated catalyst 140, the state of the first on-off valve 141 (open / closed), the state of the second on-off valve 142 (open / closed), the temperature of the electric heated catalyst 140 (°C), and the power supplied to the electric heated catalyst 140 (W). Figure 5 is a flowchart showing the processing procedure for the power consumption reduction and freeze prevention treatment by the exhaust gas purification device 1. This process is mainly performed repeatedly at predetermined timings in the ECU 81.

[0069] First, in step S100, a determination is made as to whether the vehicle has stopped and the engine 10 has stopped. If the vehicle has not stopped and / or the engine 10 has not stopped (see time t0~t1 in Figure 4), the process is temporarily exited. On the other hand, if the vehicle has stopped and the engine 10 has stopped (see time t1 in Figure 4), the process proceeds to step S102.

[0070] In step S102, the first motor-generator 11, etc., is driven for a predetermined time to motorize the engine 10, and the combustion gases remaining in the engine 10 and exhaust pipe 118 are discharged and replaced with fresh air (see times t1 to t2 in Figure 4).

[0071] Next, in step S104, the second on-off valve 142 is closed (see time t2 in Figure 4). The first on-off valve 141 remains open.

[0072] Next, in step S106, power is supplied to the electrically heated catalyst 140, and the electrically heated catalyst 140 is heated up to the first target temperature (see time t2~t3 in Figure 4).

[0073] Next, in step S108, a determination is made as to whether the electrically heated catalyst 140 has been heated to the first target temperature. If the temperature of the electrically heated catalyst 140 has not reached the first target temperature, the process proceeds to step S106, where the electrically heated catalyst 140 is heated until its temperature reaches the first target temperature. On the other hand, when the temperature of the electrically heated catalyst 140 reaches the first target temperature (see time t3 in Figure 4), the process proceeds to step S110.

[0074] In step S110, the power supply to the electrically heated catalyst 140 is stopped (see time t3 in Figure 4). Subsequently, in step S112, the first on-off valve 141 is closed (see time t3 in Figure 4).

[0075] Next, in step S114, a determination is made as to whether the temperature of the electrically heated catalyst 140 has decreased to the second target temperature. If the temperature of the electrically heated catalyst 140 has not decreased to the second target temperature, this step is repeated until the temperature of the electrically heated catalyst 140 decreases to the second target temperature. On the other hand, when the temperature of the electrically heated catalyst 140 decreases to the second target temperature (see time t4 in Figure 4), the process moves to step S116.

[0076] In step S116, the power supplied to the electrically heated catalyst 140 is adjusted (controlled) so that the temperature of the electrically heated catalyst 140 is maintained at a second target temperature.

[0077] Next, in step S118, a determination is made as to whether the State of Charge (SOC) of the battery 90 has fallen below a predetermined value (to the point where it would be difficult to start the engine the next time). If the SOC of the battery 90 has fallen below the predetermined value, in step S120, the power supply (temperature maintenance) to the electrically heated catalyst 140 is stopped, and the first on-off valve 141 and the second on-off valve 142 are closed. After that, the process is exited. On the other hand, if the SOC of the battery 90 has not fallen below the predetermined value, the process proceeds to step S122.

[0078] In step S122, a decision is made as to whether or not the engine 10 will be started (whether it is time to start the engine or just before starting it). If the engine 10 is not started, the process is exited. On the other hand, if the engine 10 is started (see time t5 in Figure 4), the process proceeds to step S124.

[0079] In step S124, the first on-off valve 141 is opened, and the second on-off valve 142 is also opened (see time t5 in Figure 4). After that, the process is exited.

[0080] As described in detail above, according to this embodiment, first, after the vehicle is stopped and the engine 10 is stopped, the first motor-generator 11 etc. is driven to motorize the engine 10 before the first on-off valve 141 and the second on-off valve 142 are closed, and the combustion gas remaining in the engine 10 and exhaust pipe 118 is discharged and replaced with fresh air. As a result, the combustion gas containing a large amount of water vapor is discharged and replaced with fresh air with a low amount of water vapor, which reduces the amount of water vapor inside that can cause freezing, and prevents the first and second on-off valves 141, 142 etc. from freezing.

[0081] Next, the second on-off valve 142 is closed, and the electrically heated catalyst 140 is heated up to the first target temperature. After that, when the temperature of the electrically heated catalyst 140 reaches the first target temperature, the power supply to the electrically heated catalyst 140 is stopped, and the first on-off valve 141 is closed. In this way, after the electrically heated catalyst 140 has been heated up to the first target temperature, the first and second on-off valves 141 and 142 are closed (the electrically heated catalyst 140 is sealed). As a result, the temperature gradually decreases, the internal pressure decreases (depressurization), heat conduction through the air decreases, and heat retention improves, thereby reducing the power consumption of the electrically heated catalyst 140. In particular, when the electrically heated catalyst 140 is heated, the second on-off valve 142 is closed, which prevents condensed water that has accumulated on the rear side of the exhaust pipe 118 (muffler, etc.), where the exhaust gas is cooled and condensed water tends to accumulate, from evaporating again due to the heat from heating and entering the second on-off valve 142, etc., thus preventing freezing.

[0082] In this state, that is, when the internal pressure is reduced and heat conduction decreases (improving heat retention), and the amount of water vapor inside is reduced, the electric heating catalyst 140 is sealed, insulated, and kept warm by the exhaust pipe 118 with a vacuum layer 118a formed thereon, and the first on-off valve 141 and the second on-off valve 142 (i.e., it is a so-called thermos bottle structure). As a result, the power consumption of the electric heating catalyst 140 can be reduced, and even if it is left for a long period of time at extremely low temperatures, the first on-off valve 141 and the second on-off valve 142 will not freeze and become unable to open.

[0083] As a result, the power consumption of the electrically heated catalyst 140 can be reduced, and the exhaust pipe 118 will not become blocked due to the first on-off valve 141 and the second on-off valve 142 freezing (and the engine 10 (especially the exhaust system) will not be damaged).

[0084] According to this embodiment, after the temperature of the electrically heated catalyst 140 reaches a first target temperature and the power supply to the electrically heated catalyst 140 is stopped, if the temperature of the electrically heated catalyst 140 drops from the first target temperature to a second target temperature (for example, around 350°C), the power supply to the electrically heated catalyst 140 is controlled to maintain the second target temperature. Furthermore, the power supply to the electrically heated catalyst 140 is controlled to maintain the temperature of the electrically heated catalyst 140 at the time the engine 10 is started again. As a result, a sudden surge of power supply (heating output) in a short time when the engine is started again is not required; that is, it is not necessary to raise the temperature (heat) by several hundred degrees in a few seconds, for example.

[0085] According to this embodiment, after the first on-off valve 141 and the second on-off valve 142 are closed, when the engine 10 is started again, the first on-off valve 141 and the second on-off valve 142 are opened, thereby preventing the exhaust pipe 118 from becoming blocked during engine operation.

[0086] According to this embodiment, when the power supply to the electrically heated catalyst 140 is controlled so that the temperature of the electrically heated catalyst 140 is maintained at a second target temperature, if the state of charge (SOC) of the battery 90 that supplies power to the electrically heated catalyst 140 and the first motor-generator 11 etc. falls below a predetermined value, the power supply to the electrically heated catalyst 140 is stopped, and the first on-off valve 141 and the second on-off valve 142 are opened. This makes it possible to prevent the engine 10 from becoming unable to start and the exhaust pipe 118 from remaining blocked.

[0087] Although embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and can be modified in various ways. For example, in the above embodiments, the case in which the exhaust purification device 1 according to the present invention is applied to a series-parallel hybrid vehicle (HEV) was described as an example, but as long as the engine 10 can be motorized (rotated by an electric motor), it can also be applied to different types of hybrid vehicles (e.g., parallel hybrid vehicles) or plug-in hybrid vehicles (PHEVs) that can be charged from an external source. Similarly, in the above embodiments, there were two electric motors (first motor-generator 11 and second motor-generator 12), but the number of electric motors is not limited to two (2 motors), but may be one (1 motor), or three (3 motors) or more. Furthermore, it can also be applied to so-called mild hybrids equipped with an ISG: Integrated Starter-Generator (starter and generator).

[0088] Furthermore, the system configuration of controllers such as HEV-CU80 and ECU81, and the division of functions among the controllers, are not limited to the above embodiment. For example, in the above embodiment, the power supply (temperature) of the electrically heated catalyst 140 was controlled by ECU81, but it may also be configured to be performed (controlled) by HEV-CU80.

[0089] Furthermore, the above-mentioned power consumption reduction and freeze prevention treatment may be implemented (controlled) in consideration of the ambient temperature, that is, for example, in a configuration that is implemented only at extremely low temperatures.

[0090] In the above embodiments, the present invention was described using the application of a 4-cylinder engine as an example, but the present invention is not limited to 4-cylinder engines and can be applied to other engines as well. Furthermore, the present invention is not limited to horizontally opposed engines, but can also be applied to inline engines, V-type engines, and the like. In addition, in the above embodiments, the present invention was described using the application of an AWD vehicle (all-wheel drive vehicle) as an example, but the present invention can also be applied to 2WD vehicles (FF vehicles and FR vehicles). [Explanation of Symbols]

[0091] 1. Exhaust purifying device 10 Engines 11. First Motor Generator 12. Second Motor Generator 20 Flywheel damper 30. Drive force splitting mechanism 40. Drive reduction gear mechanism 41 Motor Reduction Gear 43. Drive reduction gear 50 Propeller Shaft 51 Transfer Clutch 52 Rear Differential 60 Front drive shaft 62 Front Differential 70 CAN 80 HEV-CU 81 ECU (Control Unit) 82 PCU 91 Accelerator pedal sensor 92 Throttle position sensor 93 G sensor (accelerometer) 94. Vehicle speed sensor (wheel speed sensor) 95 Rotation speed sensor 97,98 resolvers 112 Injectors 113 Electronically controlled throttle valve 114 Airflow Meter 117 Spark plug 118 Exhaust pipe 118a Vacuum layer 119 Air-fuel ratio sensor (LAF sensor) 132 Cam angle sensor 133 Crank Angle Sensor 133a Timing rotor 134 Water temperature sensor 135 EHC temperature sensor 140 Electrically heated catalysts (EHC) 140a Electrode (Heater) 141 First shut-off valve 142 Second shut-off valve

Claims

1. An exhaust gas purification device mounted on a vehicle comprising an engine and an electric motor capable of transmitting power between the engine and the crankshaft, An electrically heated catalyst, configured to be able to be heated by the supply of electricity, purifies engine exhaust at a predetermined activation temperature or higher, An exhaust pipe having a vacuum layer formed that covers at least the entire side surface of the electric heating catalyst, A first on-off valve is positioned upstream of the electrically heated catalyst in the exhaust pipe and opens and closes the exhaust pipe, A second on-off valve is positioned downstream of the electrically heated catalyst in the exhaust pipe and opens and closes the exhaust pipe, The system includes a control unit that supplies power to the electrically heated catalyst and controls the operation of the first and second on-off valves, The aforementioned control unit is When the vehicle is stopped and the engine is shut off, and the first and second on-off valves are closed, The electric motor is driven to motorize the engine, and the combustion gases remaining in the engine and the exhaust pipe are discharged and replaced with fresh air. Subsequently, the second valve is closed to raise the temperature of the electrically heated catalyst to the first target temperature. Subsequently, when the temperature of the electrically heated catalyst reaches the first target temperature, the power supply to the electrically heated catalyst is stopped and the first on-off valve is closed. An exhaust gas purification device characterized by the following features.

2. The aforementioned control unit is If the temperature of the electrically heated catalyst reaches the first target temperature and the power supply to the electrically heated catalyst is stopped, and then the temperature of the electrically heated catalyst drops from the first target temperature to the second target temperature, the power supply to the electrically heated catalyst is controlled to maintain the second target temperature. The exhaust gas purification device according to feature 1.

3. The aforementioned control unit is Next, until the engine is started, the power supply to the electric heated catalyst is controlled so that the temperature of the electric heated catalyst maintains the second target temperature. The exhaust gas purification device according to feature 2.

4. The aforementioned control unit is After closing the first and second on-off valves, the first and second on-off valves are opened when starting the engine again. The exhaust gas purification device according to feature 3.

5. The aforementioned control unit is When the power supply to the electric heating catalyst is controlled so that the temperature of the electric heating catalyst maintains the second target temperature, if the charge level of the battery supplying power to the electric heating catalyst and the electric motor falls below a predetermined value, the power supply to the electric heating catalyst is stopped and the first and second on-off valves are opened. The exhaust gas purification device according to feature 4.

Images