JP2022082956A - Internal combustion engine - Google Patents

Abstract

To introduce secondary air to an exhaust passage by adding minimal change to an existing internal combustion engine.SOLUTION: An internal combustion engine includes a fuel vaporization gas discharge suppression device 6 including: a connection passage 62 connected to a fuel tank 7; a canister 61 trapping fuel vapor generated in the fuel tank 7 and flowing in the connection passage 62; an introduction passage 64 connected to the canister 61 and capable of introducing air; and a purge gas flow passage 63 communicating the canister 61 with an intake passage 3 of the internal combustion engine and discharging the fuel vapor trapped by the canister 61 to the intake passage 3 continuing to a cylinder 1 of the internal combustion engine. In the internal combustion engine, a branch passage 66 branched from the purge gas flow passage 63 is provided, and the branch passage 66 is connected to an exhaust passage 4 continuing to the cylinder 1 of the internal combustion engine. A control valve 67 opening/closing the branch passage 66 is installed thereon, and air is caused to flow into the exhaust passage 4 via the introduction passage 64, the purge gas flow passage 63 and the branch passage 66.SELECTED DRAWING: Figure 1

Description

The present invention relates to an internal combustion engine mounted on a vehicle or the like as a power source.

Hydrocarbon HC (total hydrocarbon THC to be measured is the sum of methane CH ₄ and non-methane hydrocarbon NMHC) and carbon monoxide CO, which are harmful substances, are contained in the exhaust gas discharged from the cylinder of the internal combustion engine. It is included. HC and CO can be oxidized to make them harmless.

Regulations on emissions of internal combustion engines will be tightened more and more. That is, there is a demand for measures to further reduce the amount of harmful substances emitted.

As a means for promoting the oxidation of HC and CO, it is conceivable to introduce secondary air containing a sufficient amount of oxygen other than the combustion gas into the exhaust passage of the internal combustion engine. For example, as disclosed in the following patent document, a flow path serving as a bypass for communicating the air cleaner located at the uppermost stream of the intake passage of the internal combustion engine and the exhaust passage is laid, and the flow path is laid through the air cleaner and the flow path. Let air flow into the exhaust passage. A reed valve is installed on the flow path. The reed valve opens and closes due to the pulsation of the exhaust gas flowing through the exhaust passage that accompanies the opening and closing of the exhaust valve of each cylinder. That is, the reed valve opens when the exhaust pressure falls below the atmospheric pressure and closes when the exhaust pressure exceeds the atmospheric pressure. The structure of such a device is easy to adopt in a motorcycle in which the internal combustion engine is exposed.

However, in four-wheeled vehicles, especially light vehicles and small passenger vehicles, the volume of the engine room that houses the internal combustion engine is limited. Moreover, the engine room is already occupied by various devices. Therefore, it is not easy to route and dispose of a hose, a tube, or a pipe which is an air flow path from the air cleaner to the exhaust passage, and it is difficult to adopt the above-mentioned structure.

Japanese Unexamined Patent Publication No. 05-059943

An object of the present invention is to allow secondary air to be introduced into an exhaust passage with minimal modifications to an existing internal combustion engine.

In the present invention, a connection path connected to the fuel tank, a canister that captures fuel vapor generated in the fuel tank and flowing through the connection path, an introduction path connected to the canister and capable of introducing air, a canister and an internal combustion engine. An internal combustion engine equipped with a fuel evaporative emission control device having a purge gas flow path that communicates with the intake passage of the engine and discharges the fuel vapor captured in the canister to the intake passage connected to the cylinder of the internal combustion engine. A branch path branching from the path is provided, the branch path is connected to an exhaust passage connected to the cylinder of the internal combustion engine, a control valve for opening and closing the branch path is installed on the branch path, and the introduction path, the purge gas flow path, and the branch are provided. An internal combustion engine was configured that allowed air to flow into the exhaust passage through the path.

According to the present invention, it becomes possible to introduce secondary air into the exhaust passage with minimal modification to the existing internal combustion engine.

The figure which shows the schematic structure of the internal combustion engine for a vehicle and the control device in one Embodiment of this invention. The flow diagram which shows the procedure example of the process which the control device of the same embodiment executes according to a program.

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of an internal combustion engine for a vehicle according to the present embodiment. The internal combustion engine in the present embodiment is a spark-ignition 4-stroke gasoline engine, and includes a plurality of cylinders 1 (one of which is illustrated in FIG. 1). An injector 11 for injecting fuel is provided in the vicinity of the intake port of each cylinder 1. Further, a spark plug 12 is attached to the ceiling of the combustion chamber of each cylinder 1. The spark plug 12 induces a spark discharge between the center electrode and the ground electrode in response to the application of the induced voltage generated by the ignition coil.

The intake passage 3 reaches the intake port of each cylinder 1, and the air taken in from the outside is circulated toward each cylinder 1 and supplied to the cylinder 1. An air cleaner 31, an electronic throttle valve 32, a surge tank 33, and an intake manifold 34 are arranged on the intake passage 3 in this order from the upstream.

The internal combustion engine is accompanied by a fuel evaporative emission control device 6. The fuel evaporative emission control device 6 adsorbs and captures the vapor of the fuel evaporated in the fuel tank 7 by the charcoal canister 61 filled with activated charcoal, and at the same time, sends the fuel vapor to the intake passage 3 and mixes it with the intake air. , Combustion processing is performed in the cylinder 1.

The fuel tank 7 and the canister 61 are connected via a connecting path 62. The fuel vapor generated in the fuel tank 7 flows into the canister 61 through the connecting path 62. The canister 61 and the intake passage 3 (particularly, the surge tank 33, the intake manifold 34 or the intake port) are connected via a purge gas flow path 63. The fuel vapor captured by the canister 61 flows into the intake passage 3 through the purge gas flow path 63. In addition, the canister 61 is provided with an air introduction path 64 open to the atmosphere.

On the purge gas flow path 63, there is a purge VSV (Vacuum Switching Valve) 65, which is a control valve for opening and closing the flow path 63. While the VSV 65 is open, the canister 61 and the intake passage 3 communicate with each other via the purge gas flow path 63. Then, the fuel vapor in the canister 61 is drawn into the intake passage 3 by the intake negative pressure generated downstream of the throttle valve 32 in the intake passage 3. At this time, air, that is, outside air is taken into the canister 61 through the introduction path 64.

Further, in the present embodiment, a branch path 66 branching from the purge gas flow path 63 is provided. The branch path 66 is connected to an exhaust passage 4 (particularly, an exhaust manifold 41 or an exhaust port) connected to the cylinder 1 of the internal combustion engine. On the branch path 66, there is a VSV 67 which is a control valve for opening and closing the branch path 66. These branch paths 66 and VSV67 will be described later.

The exhaust passage 4 starts from the exhaust port of each cylinder 1 and circulates the combustion gas generated as a result of burning the fuel in each cylinder 1 and guides it to the outside. An exhaust manifold 42 and a three-way catalyst 41 for purifying exhaust gas are arranged on the exhaust passage 4. The catalyst 41 induces an oxidation / reduction reaction of harmful substances HC, CO and nitrogen oxide NO _x to detoxify them.

The exhaust gas recirculation device 2 opens and closes the external EGR passage 21 connecting the exhaust passage 4 and the intake passage 3, the EGR cooler 22 provided on the EGR passage 21, and the EGR passage 21 to open and close the EGR passage 21. The element is an EGR valve 23 that controls the flow rate of EGR gas flowing through the passage 21. The inlet of the EGR passage 21 is connected to a portion downstream of the catalyst 41 in the exhaust passage 4. The outlet of the EGR passage 21 is connected to a portion downstream of the throttle valve 32 in the intake passage 3.

The variable valve timing 5 is known to change the rotational phase of the camshaft that drives the intake valve of each cylinder 1 with respect to the crankshaft by the hydraulic pressure (lubricating hydraulic pressure) or the electric motor. The camshaft receives engine torque from the crankshaft of an internal combustion engine and rotates in accordance with the crankshaft. A winding transmission device for transmitting engine torque is interposed between the crankshaft and the camshaft. The winding transmission device includes a crank sprocket (or pulley) provided on the crankshaft side, a cam sprocket (or pulley) provided on the camshaft side, and a timing chain (or pulley) to be wound around these sprockets (or pulleys). , Timing belt) and as an element. The VVT mechanism 5 changes the rotation phase of the camshaft with respect to the crankshaft by rotating the camshaft relative to the camsprocket, thereby advancing or retarding the opening / closing timing of the intake valve of each cylinder 1. Let me.

The specific embodiment of the VVT mechanism 5 is arbitrary and is not uniquely limited. In addition to the one that advances / retards the rotation phase of the camshaft with respect to the crankshaft, the one that prepares multiple cams that open and drive the intake valve and uses those cams appropriately, and the lever ratio of the rocker arm is set via the electric motor. It is known that the intake valve is an electromagnetic solenoid valve, etc., and it is permitted to select and adopt it from these various mechanisms.

The control device (Electronic Control Unit) 0 that controls the operation of the internal combustion engine is a microcomputer system having a processor, a memory, an input interface, an output interface, and the like. The ECU 0 may be a plurality of ECUs or controllers connected to each other so as to be communicable with each other via a telecommunication line such as CAN (Control Area Network).

The input interface of ECU 0 has a vehicle speed signal a output from a vehicle speed sensor that detects the actual vehicle speed of the vehicle, a crank angle signal b output from a crank angle sensor that detects the rotation angle of the crank shaft of the internal combustion engine and the engine rotation speed. , The accelerator opening output from the sensor that detects the amount of depression of the accelerator pedal by the driver or the opening of the throttle valve 32 as the accelerator opening (so to speak, the engine torque or engine load factor or engine torque required for the internal combustion engine). Signal c, intake temperature / intake pressure signal d output from a temperature / pressure sensor that detects the intake temperature and intake pressure downstream of the throttle valve 32 in the intake passage 3 (particularly in the surge tank 33 or the intake manifold 34), internal combustion. From the cooling water temperature signal e output from the water temperature sensor that detects the cooling water temperature of the engine, or from the sensor (brake switch, master cylinder pressure sensor, etc.) that detects that the brake pedal is being depressed by the driver or the amount of depression of the brake pedal. The output brake signal f, the cam angle signal g output from the cam angle sensor at a plurality of cam angles of the intake cam shaft, the atmospheric pressure signal h output from the atmospheric pressure sensor for detecting the atmospheric pressure, and the like are input. ..

From the output interface of ECU 0, the ignition signal i for the igniter 13 of the ignition plug 12, the fuel injection signal j for the injector 11, the opening operation signal k for the throttle valve 32, and the opening for the EGR valve 23. The operation signal l, the intake valve timing control signal m for the VVT mechanism 5, the open / close control signal n for the VSV65, the open / close control signal o for the VSV66, and the like are output.

The processor of ECU 0 interprets and executes a program stored in the memory in advance, calculates an operation parameter, and controls the operation of the internal combustion engine. The ECU 0 acquires various information a, b, c, d, e, f, g, h necessary for the operation control of the internal combustion engine via the input interface, obtains the engine speed, and is sucked into the cylinder 1. Estimate the amount of air (fresh air). Then, based on those engine rotation speeds, intake air amount, etc., required fuel injection amount, fuel injection timing (including the number of fuel injections for one combustion), fuel injection pressure, required EGR rate (or EGR gas amount), Various operating parameters such as ignition timing (including the number of spark ignitions for one combustion), opening / closing timing of the intake valve, etc. are determined. The ECU 0 applies various control signals i, j, k, l, m, n, and o corresponding to the operation parameters via the output interface.

Therefore, the branch passage 66 that branches from the purge gas flow path 63 of the fuel evaporative emission control device 6 and connects to the exhaust passage 4 plays a role of introducing secondary air other than the combustion gas into the exhaust passage 4.

The exhaust gas discharged from the cylinder 1 and flowing through the exhaust passage 4 contains HC and CO, which are harmful substances. In order to reduce the emission of HC and CO, it is necessary to promote the oxidation of HC and CO in the exhaust gas. Therefore, in the present embodiment, the fuel evaporative emission control device 6 is used to join the secondary air containing a sufficient amount of oxygen into the exhaust passage 4. If the VSV 65 on the purge gas flow path 63 is closed and the VSV 67 on the branch path 66 is opened, the exhaust passage 4 communicates with the atmosphere via the introduction path 64, the canister 61, the purge gas flow path 63 and the branch path 66. do. Then, the air in the canister 61 is drawn into the exhaust passage 4 due to the exhaust pulsation in the exhaust passage 4. At this time, air is taken into the canister 61 through the introduction path 64.

However, if the VSV 67 is opened while the fuel vapor is accumulated in the canister 61, the purge gas containing the fuel vapor will flow into the exhaust passage 4, and there is a concern that the unburned fuel component will be released to the outside. Therefore, the VSV 67 is opened after the purging process of sending the fuel vapor captured by the canister 61 to the intake passage 3 is executed. The VSV 67 is closed before or during the execution of the purge process.

As shown in FIG. 2, the ECU 0 starts the stopped internal combustion engine (particularly, cold start), then opens the VSV65 (step S2), and accumulates in the canister 61 while the internal combustion engine is stopped. Perform the purging process of the fuel vapor. The VSV 67 is closed before or during the purging process of the canister 61 (step S3). When the purging process of the canister 61 is completed (step S1), the VSV65 is closed (step S4).

In step S1, for example, the air sucked into the cylinder 1 from the start of the internal combustion engine or the start of the purge process when the time elapsed from the start of the internal combustion engine or the start of the purge process (that is, the opening of the VSV65) has reached a predetermined value. It is determined that the purge process is completed when the cumulative amount of the crankshaft exceeds the predetermined value, the cumulative number of rotations of the crankshaft from the start of the internal combustion engine or the start of the purge process exceeds the predetermined value, and the like. The above-mentioned predetermined value may be adjusted according to the temperature of the outside air temperature when the internal combustion engine is stopped or started. When the outside air temperature is high while the internal combustion engine is stopped, more fuel vapor is generated in the fuel tank 7, and it is considered that it is collected by the canister 61. Therefore, when the internal combustion engine is stopped or started. It is preferable to set the above predetermined value higher as the outside air temperature is higher and extend the period of the purging process.

After the completion of the purge process, when the condition for allowing the secondary air to flow into the exhaust passage 4 is satisfied (step S5), the VSV 67 is opened (step S6). While the VSV65 is closed and the VSV67 is open, secondary air flows into the exhaust passage 4 via the introduction path 64, the canister 61, the purge gas flow path 63, and the branch path 66. If the condition for allowing the secondary air to flow into the exhaust passage 4 is not satisfied, the VSV 67 is closed (step S7).

In step S5, for example, the current operating region of the internal combustion engine [engine speed, accelerator opening (engine torque or engine load factor, or intake pressure, intake air amount or fuel injection amount)] is within a predetermined range. In particular, it is determined that the condition for allowing the secondary air to flow into the exhaust passage 4 is satisfied when the accelerator opening degree is larger than the threshold value and the required load is high (the engine speed may be low). In the high load operating region, the fuel injection amount is often increased and corrected, and the air-fuel ratio filled in the cylinder 1 tends to be richer than the theoretical air-fuel ratio. Exhaust gas rich in air-fuel ratio has an atmosphere of oxygen deficiency, which is disadvantageous for the oxidation treatment of HC and CO. At that time, by inflowing the secondary air into the exhaust passage 4, it is possible to supplement the insufficient oxygen, promote the oxidation of HC and CO, and suppress the emission of HC and CO.

In step S6, when the VSV 67 is opened and the branch passage 66 is opened, the secondary air is transferred to the canister 61 when the pressure in the exhaust passage 4 is lower than the pressure (or atmospheric pressure) in the canister 61 due to the exhaust pulsation. Flows into the exhaust passage 4 from. On the other hand, when the pressure in the exhaust passage 4 is higher than the pressure in the canister 61, there is a concern that the exhaust gas in the exhaust passage 4 flows into the canister 61 and is discharged to the outside from the introduction path 64. In order to prevent the exhaust gas from bypassing the catalyst 41 and being discharged to the outside, the VSV 67 is opened or its opening is expanded at the timing when the pressure in the exhaust passage 4 falls below the pressure in the canister 61. In addition, the VSV 67 is operated so as to close the valve or reduce its opening in accordance with the timing when the pressure in the exhaust passage 4 falls below the pressure in the canister 61. Alternatively, it is also an idea to install a reed valve, a check valve, or the like on the branch path 6 to prevent the backflow of exhaust gas from the exhaust passage 4 side to the canister 61 side.

In the present embodiment, the connection path 62 connected to the fuel tank 7, the canister 61 that captures the fuel vapor generated in the fuel tank 7 and flowing through the connection path 62, and the canister 61 connected to the canister 61 can introduce air. Fuel evaporation gas discharge having an introduction path 64 and a purge gas flow path 63 that communicates the canister 61 and the intake passage 3 of the internal combustion engine and discharges the fuel vapor captured in the canister 61 to the intake passage 3 connected to the cylinder 1 of the internal combustion engine. An internal combustion engine to which a suppression device 6 is attached, a branch path 66 branching from the purge gas flow path 63 is provided, the branch path 66 is connected to an exhaust passage 4 connected to the cylinder 1 of the internal combustion engine, and the branch path 66 is on the branch path 66. An internal combustion engine capable of allowing air to flow into the exhaust passage 4 through the introduction path 64, the purge gas flow path 63, and the branch path 66 is configured by installing a control valve 67 that opens and closes the control valve 67.

According to the present embodiment, the combustion gas is supplied to the exhaust passage 4 with only a minimum change of adding a branch path 66 and a control valve 67 to the purge gas flow path 63 of the fuel evaporative emission control device 6 of the existing internal combustion engine. It will be possible to introduce secondary air that does not contain it. Then, it becomes possible to promote the oxidation of HC and CO, which are harmful substances, and further reduce the emission amount of HC and CO.

If HC and CO are oxidized (or burned) in the catalyst 41 while introducing secondary air into the exhaust passage 4 immediately after the cold start of the internal combustion engine, the reaction heat causes the catalyst 41 to rise early. It warms up and becomes active. This leads to higher purification efficiency by oxidation / reduction of harmful substances in the catalyst 41.

In the operating region of low rotation and high load or medium rotation and high load, the valve opening timing of the intake valve is advanced via the VVT mechanism 5 in order to increase the amount of air sucked into the cylinder 1 and increase the engine torque. Let me. However, along with this, valve overlap occurs in which both the intake valve and the exhaust valve of the cylinder 1 open. In a port injection type internal combustion engine, a part of the air-fuel mixture injected with fuel into the intake air may blow out from the intake passage 3 to the exhaust passage 4 without staying in the combustion chamber of the cylinder 1 during the valve overlap. .. This event can be a factor in increasing HC emissions.

In the conventional control of the internal combustion engine, the amount of advance of the valve opening timing of the intake valve is suppressed in order to avoid an increase in HC emission. However, by adopting the structure of the present embodiment, even if valve overlap occurs, secondary air can flow into the exhaust passage 4 to sufficiently oxidize HC, and the intake valve can be opened. It is permissible to advance the timing more than before. Therefore, the output torque of the internal combustion engine at the time of high demand load can be further increased.

The present invention is not limited to the embodiment described in detail above. The specific configuration of each part, the processing procedure, and the like can be variously modified without departing from the spirit of the present invention.

The present invention can be applied to an internal combustion engine mounted on a vehicle or the like.

0 ... Control unit (ECU)
1 ... Cylinder 11 ... Injector 12 ... Ignition plug 3 ... Intake passage 32 ... Throttle valve 4 ... Exhaust passage 41 ... Catalyst 5 ... Variable valve timing (VVT) mechanism 6 ... Fuel evaporative emission control device 61 ... Canister 62 ... Connection path 63 … Purge gas flow path 64… Introduction path 66… Branch path 67… Control valve (VSV)
7 ... Fuel tank b ... Crank angle signal c ... Accelerator opening signal o ... Control valve open / close control signal

Claims (1)

A connection path that connects to the fuel tank, a canister that captures fuel vapor generated in the fuel tank and flows through the connection path, an introduction path that is connected to the canister and can introduce air, and an intake passage between the canister and the internal combustion engine. An internal combustion engine equipped with a fuel evaporative emission control device having a purge gas flow path for discharging fuel vapor captured by a canister into an intake passage connected to a cylinder of the internal combustion engine.
A branch path branching from the purge gas flow path is provided, the branch path is connected to an exhaust passage connected to the cylinder of the internal combustion engine, and a control valve for opening and closing the branch path is installed on the branch path.
An internal combustion engine capable of allowing air to flow into the exhaust passage through the introduction passage, the purge gas passage, and the branch passage.

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