JP7019463B2 - Engine system - Google Patents

Description

The present invention relates to an engine system, specifically an engine system capable of purifying exhaust gas emitted from a gasoline engine.

Exhaust gas emitted from gasoline engines and diesel engines contains harmful components such as hydrocarbons (THC), carbon monoxide (CO), and nitrogen oxides (NOx), and particulate matter (PM: Particulate Matter). It has been.

Therefore, the engine system is provided with exhaust gas purification means such as an exhaust gas purification catalyst (three-way catalyst) and a plasma reactor.

The exhaust gas purification means is usually interposed in the exhaust gas flow path. Specifically, for example, a plasma reactor for removing PM from the exhaust gas discharged from the engine of a vehicle is installed in the middle of an exhaust pipe such as an exhaust pipe. It has been proposed to mediated the portion to oxidize and remove PM in the exhaust gas (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2018-17217

On the other hand, in removing PM by a plasma reactor, it is required to electrostatically adsorb PM in the reactor and to oxidize the electrostatically adsorbed PM. In such removal of PM, oxygen is required for the latter oxidation of PM.

In this regard, when the above engine is a gasoline engine, the oxygen concentration in the exhaust gas may be lower than when it is a diesel engine, and even if the plasma reactor is operated in such a state, PM is efficient. It cannot be oxidized well and may cause waste of electricity.

Therefore, in a plasma reactor, it is required to save power while exhibiting an excellent exhaust gas purification rate.

The present invention is an engine system having excellent exhaust gas purification performance and capable of saving electric power.

The present invention [1] includes a gasoline engine in which power and exhaust gas are generated by gasoline and cooled by cooling water, an exhaust pipe through which the exhaust gas generated in the gasoline engine can pass, and a plasma reactor interposed in the exhaust pipe. A power supply that applies power to the plasma reactor, a temperature sensor that detects the temperature of the cooling water of the gasoline engine, and a control unit that controls the output of the power supply are provided, and the control unit is detected by the temperature sensor. When the temperature is equal to or higher than a predetermined value, the application of power to the plasma reactor is stopped when gasoline is supplied to the gasoline engine, and when gasoline is not supplied to the gasoline engine. Includes an engine system that controls the power source to apply power to the plasma reactor.

That is, in a gasoline engine, the amount of PM generated is usually relatively large in a specific state such as when the engine is started, and the amount of PM generated is relatively small when the engine is in steady operation.

In other words, when the temperature of the cooling water detected by the temperature sensor is less than a predetermined value (for example, when the engine is started), the amount of PM generated is relatively large, and the cooling detected by the temperature sensor is also performed. When the temperature of water is equal to or higher than a predetermined value (for example, during steady operation after warming up), the amount of PM generated is relatively small.

Therefore, in the gasoline engine of the present invention, when the temperature of the cooling water detected by the temperature sensor is equal to or higher than a predetermined value (for example, during steady operation after warming up), the amount of PM generated is relatively small, so that the amount of PM generated is always relatively small. Instead of operating the plasma reactor, operate the plasma reactor only at specific timings.

Specifically, when gasoline is supplied to the gasoline engine, the application of electric power to the plasma reactor is stopped, and when gasoline is not supplied to the gasoline engine, electric power is applied to the plasma reactor.

That is, when gasoline is not supplied to the gasoline engine (when the fuel is cut), the oxygen concentration in the exhaust gas becomes relatively high. Therefore, by operating the plasma reactor at this time, the inside of the reactor is electrostatically charged. The adsorbed PM can be efficiently oxidized (removed).

In addition, when gasoline is supplied to the gasoline engine, the oxygen concentration in the exhaust gas becomes relatively low (that is, the PM oxidation efficiency decreases), so that power is wasted by stopping the operation of the plasma reactor. Can be suppressed and power saving can be achieved.

Further, in the present invention [2], when the temperature detected by the temperature sensor of the control unit is less than a predetermined value, when gasoline is supplied to the gasoline engine and to the gasoline engine. It includes the engine system according to [1] above, which controls the power source so as to apply power to the plasma reactor both when gasoline is not supplied.

That is, when the temperature of the cooling water detected by the temperature sensor is less than a predetermined value (for example, when the engine is started), the amount of PM generated is relatively large, so that gasoline is supplied to the gasoline engine. The plasma reactor is operated both when and when the gasoline engine is not supplied with gasoline. As a result, PM can be electrostatically adsorbed in the reactor even when the oxygen concentration is relatively low.

According to the engine system of the present invention, excellent exhaust gas purification performance can be obtained, and power saving can be achieved.

FIG. 1 is a schematic view showing an embodiment of the exhaust gas purification system of the present invention. FIG. 2 is a flow chart showing a control process executed in the control unit of FIG.

1. 1. Overall Configuration of Engine System In FIG. 1, the engine system 1 is an engine system mounted on, for example, a gasoline vehicle, and includes a gasoline engine 2 and a purification system that purifies the exhaust gas emitted from the gasoline engine 2. More specifically, the engine system 1 is composed of a gasoline engine 2, an exhaust pipe 3 through which exhaust gas generated in the gasoline engine 2 can pass, a catalyst unit 4 interposed in the exhaust pipe 3, and a catalyst unit 4. Also has a plasma reactor 5 interposed in the exhaust pipe 3 on the downstream side and a power source 6 for applying (supplying) power to the plasma reactor 5.

The gasoline engine 2 is a known internal combustion engine driven by using gasoline as fuel, and includes an engine main body 15, a fuel supply device 20 for supplying fuel to the engine main body 15, and a cooling device 25 for cooling the engine main body 15. I have.

The engine body 15 is a known gasoline engine, and examples thereof include a single-cylinder gasoline engine and a multi-cylinder gasoline engine.

In the gasoline main body 15, gasoline is sucked by an intake unit (not shown), and gasoline is supplied by a fuel supply device 20 described later. Then, by repeating the ascending / descending motion of the piston in the cylinder, the mixed gas of gasoline and air is burned to generate power and exhaust gas.

The fuel supply device 20 includes a fuel tank 21 and a fuel supply pipe 22.

The fuel tank 21 is a tank in which gasoline as fuel supplied to the engine main body 15 is stored, and is formed of a heat-resistant pressure-resistant container or the like.

The fuel supply pipe 22 is provided to supply fuel from the fuel tank 21 to the engine body 15, and its upstream end is connected to the fuel tank 21, and the downstream end is the fuel injection valve 23. It is connected to the.

The fuel injection valve 23 is a valve for adjusting the amount of fuel supplied from the fuel tank 21 to the engine body 15 and injecting the fuel to the engine body 15, and is a downstream end of the fuel supply pipe 22. It is provided in the section. The fuel injection valve 23 is not particularly limited, and a known injection valve can be used.

Such a fuel injection valve 23 is electrically connected to a control unit 8 described later (see the broken line in FIG. 1), and its opening and closing is controlled by the control unit 8.

That is, by electrically connecting the fuel injection valve 23 to the control unit 8 described later, the control signal from the control unit 8 can be input to the fuel injection valve 23.

As a result, the control unit 8 can control the opening and closing of the fuel injection valve 23, that is, the supply of fuel by the fuel injection valve 23, according to the operating state of the engine body 15.

The cooling device 25 includes a radiator hose 26 for circulating cooling water in the engine body 15, and a radiator 27 for cooling the cooling water.

The radiator hose 26 is connected to a water jacket (not shown) of the engine body 15. Thereby, the cooling water circulates in the closed line formed by the radiator hose 16 and the water jacket (not shown).

The radiator 27 is interposed in the middle of the radiator hose 26 and forms a part of the closed line. As the radiator 27, for example, a known radiator having a large number of fins formed on the surface can be applied.

The exhaust pipe 3 is a pipe (for example, an exhaust manifold, an exhaust pipe, etc.) provided for exhausting exhaust gas from the cylinder of the gasoline engine 2, and constitutes an exhaust path for the exhaust gas generated in the gasoline engine 2.

The catalyst unit 4 is provided to purify harmful components (excluding PM) contained in the exhaust gas in the middle portion of the exhaust pipe 3 in the flow direction of the exhaust gas.

Examples of harmful components emitted from the gasoline engine 2 include hydrocarbons (HC), nitrogen oxides (NOx), carbon monoxide (CO) and the like.

Such a catalyst unit 4 is provided with an exhaust gas purification catalyst inside. More specifically, the catalyst unit 4 includes, for example, a catalyst carrier and an exhaust gas purification catalyst coated on the carrier.

The exhaust gas purification catalyst is appropriately selected according to the type of the above-mentioned harmful component, and examples thereof include known three-way catalysts (precious metal catalysts and the like).

The plasma reactor 5 is provided on the downstream side in the flow direction of the exhaust gas from the catalyst unit 4 in order to purify the harmful components (PM) remaining without being purified by the catalyst unit 4.

More specifically, the plasma reactor 5 has a rectangular tubular housing portion 11 integrally formed with the exhaust pipe 3, and a plurality of electrode panels arranged inside the housing portion so as to face each other at a distance from each other. It is equipped with twelve. The electrode panel 12 is a plate-shaped member including a dielectric plate and electrodes, and is connected to a power supply 6 described later. Then, in the plasma reactor 5, electric power is applied (supplied) to the electrode panel 12 (electrode), so that plasma is generated at an output corresponding to the electric power.

The power supply 6 is provided for applying electric power to the plasma reactor 5, and is electrically connected to the electrode panel 12 (electrode) of the plasma reactor 5 (see the broken line in FIG. 1). Then, when electric power is applied (supplied) from the power source 6 to the electrode panel 12 (electrode) of the plasma reactor 5, plasma is generated in the plasma reactor 5.

Examples of such a power source 6 include a DC power source, an AC power source, a pulse power source, and the like, and a pulse power source is preferable.

Further, as will be described in detail later, the power supply 6 is electrically connected to the control unit 8 (described later), and as will be described later, the detection of the temperature sensor 7 (described later) and the operating state of the fuel supply device 20 The operation is controlled based on.

Further, such an engine system 1 includes a temperature sensor 7 that detects the temperature of the cooling water of a gasoline engine, and a control unit 8 that controls the output of the power supply 6.

The temperature sensor 7 is a known temperature detector that detects the temperature of the cooling water in the radiator 27 described above, and examples thereof include known temperature detectors such as a thermistor and a thermocouple.

Such a temperature sensor 7 is electrically connected to a control unit 8 described later (see the broken line in FIG. 1), and the detection result by the temperature sensor 7 can be input to the control unit 8.

The control unit 8 is a unit (for example, an ECU: Electronic Control Unit) that executes electrical control in the engine system 1, and is composed of a microcomputer including a CPU, a ROM, a RAM, and the like.

The control unit 8 controls the fuel supply amount based on the operating state of the engine body 15 (for example, the rotation speed of the engine body 15 detected by a tachometer (not shown)).

Further, the control unit 8 is electrically connected to the temperature sensor 7 and the power supply 6 (see the broken line in FIG. 1), and its operation is based on the detection of the temperature sensor 7 and the operating state of the fuel supply device 20. Be controlled.

2. 2. Purification of exhaust gas In the engine system 1 shown in FIG. 1, for example, fuel (gasoline) is supplied from the fuel supply device 20 (fuel injection valve 23) to the gasoline engine 20 by the control of the control unit 8, and the gasoline engine 2 is driven. Once started, power and exhaust gas are generated from the gasoline engine 2 (see arrow in FIG. 1).

In the gasoline engine 2, the exhaust gas passes through the exhaust pipe 3 and is supplied to the catalyst unit 4. In the catalyst unit 4, at least a part of harmful components in the exhaust gas is purified (removed) by the exhaust gas purification catalyst. After that, the exhaust gas is discharged from the catalyst unit 4.

At this time, the exhaust gas that has passed through the catalyst unit 4 contains unpurified harmful components (PM) that remain without being purified by the exhaust gas purification catalyst.

In such a case, in the above engine system 1, the unpurified harmful component (PM) is purified by driving the plasma reactor 5 on the downstream side of the catalyst unit 4.

More specifically, the exhaust gas that has passed through the catalyst unit 4 is supplied to the plasma reactor 5 via the exhaust pipe 3.

At this time, plasma is generated in the plasma reactor 5 by supplying a predetermined electric power from the power source 6 to the electrode panel 12 (electrode) of the plasma reactor 5. As a result, harmful components (PM) in the exhaust gas passing through the plasma reactor 5 are plasma-treated (electrostatic adsorption and oxidation removal).

After that, the exhaust gas is discharged from the plasma reactor 5 and released to the atmosphere from the downstream end of the exhaust pipe 3.

As described above, in this engine system 1, harmful components in the exhaust gas are purified by the catalyst unit 4 and the plasma reactor 5.

If necessary, the catalyst unit 4 can be omitted and the harmful components can be removed only in the plasma reactor 5.

3. 3. Purification efficiency On the other hand, in the removal of PM by the plasma reactor 5, it is required to electrostatically adsorb PM in the reactor and to oxidize the electrostatically adsorbed PM. In such removal of PM, oxygen is required for the latter oxidation of PM.

In this respect, the above-mentioned gasoline engine 2 may have a lower oxygen concentration in the exhaust gas than the diesel engine, and even if the plasma reactor 5 is operated in such a state, PM cannot be efficiently oxidized and the power can be increased. May cause waste.

Therefore, in the plasma reactor 5, it is required to save power while exhibiting an excellent exhaust gas purification rate.

Therefore, in this engine system 1, the output of the plasma reactor 5 is controlled as shown below.

FIG. 2 is a flow chart showing a control process executed in the control unit 8 of the engine system 1 shown in FIG.

The control process shown in FIG. 2 is stored in the ROM of the control unit 8, and the control process is executed by the central processing unit (CPU) of the control unit 8.

Hereinafter, the control process executed by the control unit 8 will be described in detail with reference to FIG.

This control process is started with the start of driving of the gasoline engine 2 as a trigger, as shown as a start in FIG.

When the driving of the gasoline engine 2 is started, power and exhaust gas are generated from the gasoline engine 2 as described above. Further, with the start of driving the gasoline engine 2, the cooling device 25 is also started to be driven to cool the gasoline engine 2. As a result, the temperature of the cooling water rises.

Then, the exhaust gas passes through the catalyst unit 4 and the plasma reactor 5 in sequence, and harmful components in the exhaust gas are purified.

In such purification of exhaust gas, in the above engine system 1, the exhaust gas is purified as described above, and the temperature of the cooling water is detected by the temperature sensor 7 (step S1).

At this time, the temperature detected by the temperature sensor 7 is input to the control unit 8 as an electric signal.

Then, in this control process, the control unit 8 determines whether or not the temperature of the cooling water is equal to or higher than a preset predetermined threshold value (step S2).

As will be described in detail later, the threshold value of the cooling water temperature is a temperature that is an index for determining whether the amount of PM generated is large or small, and is appropriately set according to the purpose and application.

Specifically, for example, the temperature is 40 ° C. or higher, preferably 50 ° C. or higher, more preferably 60 ° C. or higher, and for example, 90 ° C. or lower, preferably 80 ° C. or lower, more preferably 70 ° C. or lower. In the range, one point is defined as the threshold value of the temperature of the cooling water.

If the temperature of the cooling water is equal to or higher than the above threshold value, it is determined that the gasoline engine 2 is in a steady state after warming up (step S2: YES).

Normally, when the gasoline engine 2 is in such a state, the PM emitted from the gasoline engine 2 is relatively small. Therefore, in this case, the fuel supply state by the fuel supply device 20 (fuel injection valve 23) is confirmed (step S3).

More specifically, the fuel supply is controlled by the control unit 8. Specifically, for example, when an improvement in the output of the gasoline engine 2 is required (such as when acceleration of a gasoline vehicle is required), the amount of fuel supplied increases. On the other hand, for example, when the output of the gasoline engine 2 is not required (such as when the deceleration of the gasoline vehicle is required), the fuel supply amount is reduced or the fuel supply is stopped.

Therefore, in this control process, the control unit 8 determines whether or not the fuel supply is stopped (step S4).

Then, when the fuel supply is stopped (step S4: YES), the output of the power supply 6 is controlled so that a predetermined electric power is applied to the plasma reactor 5.

As a result, the plasma reactor 5 operates, and the electrostatically adsorbed PM is oxidized and removed in the plasma reactor 5.

On the other hand, when the fuel supply is not stopped (step S4: NO), the temperature of the cooling water is detected again without applying electric power to the plasma reactor 5 (step S1).

That is, in the above engine system 1, when the temperature of the cooling water detected by the temperature sensor 7 is equal to or higher than a predetermined value, the control unit 8 controls the power source 6 to supply gasoline to the gasoline engine 2. At that time, the application of electric power to the plasma reactor 2 is stopped, and the electric power is applied to the plasma reactor 2 only when gasoline is not supplied to the gasoline engine 2.

On the other hand, when the temperature of the cooling water detected by the temperature sensor 7 is less than a predetermined value, it is determined that the gasoline engine 2 is before warming up or during warming up (that is, at the time of starting) (step S2). : NO).

Normally, when the gasoline engine 2 is in such a state, the PM emitted from the gasoline engine 2 is relatively large. Therefore, in this case, the output of the power supply 6 is controlled so that a predetermined electric power is applied to the plasma reactor 5 regardless of the fuel supply state by the fuel supply device 20 (fuel injection valve 23).

As a result, the plasma reactor 5 operates, and PM is electrostatically adsorbed in the plasma reactor 5.

In this way, in the above engine system 1, it is possible to reduce harmful components in the exhaust gas released to the atmosphere from the exhaust pipe 3.

The above control process is repeated until the gasoline engine 2 is stopped (return).

4. Action / Effect As described above, in the gasoline engine 2, the amount of PM generated is usually relatively large in a specific state such as when the engine is started, and the amount of PM generated is compared during steady operation of the engine. It will be less targeted.

In other words, when the temperature of the cooling water detected by the temperature sensor 7 is less than a predetermined value (for example, when the engine is started), the amount of PM generated becomes relatively large, and it is detected by the temperature sensor 7. When the temperature of the cooling water is equal to or higher than a predetermined value (for example, during steady operation after warming up), the amount of PM generated is relatively small.

Therefore, in the above gasoline engine 2, when the temperature of the cooling water detected by the temperature sensor 7 is equal to or higher than a predetermined value (for example, during steady operation after warming up), the amount of PM generated is relatively small. Instead of operating the plasma reactor 5 all the time, the plasma reactor 5 is operated only at a specific timing.

Specifically, when gasoline is supplied to the gasoline engine 2, the application of electric power to the plasma reactor 5 is stopped, and when gasoline is not supplied to the gasoline engine 2, electric power is applied to the plasma reactor 5. do.

That is, when gasoline is not supplied to the gasoline engine 2 (when the fuel is cut), the oxygen concentration in the exhaust gas becomes relatively high. PM adsorbed can be efficiently oxidized (removed).

Further, when gasoline is supplied to the gasoline engine 2, the oxygen concentration in the exhaust gas becomes relatively low (that is, the PM oxidation efficiency decreases), so that the operation of the plasma reactor 5 is stopped to generate electric power. It is possible to reduce waste and save power.

Further, in the above engine system 1, when the temperature of the cooling water detected by the temperature sensor 7 is less than a predetermined value (for example, when the engine is started), the amount of PM generated is relatively large, so that gasoline is used. The plasma reactor 5 is operated both when gasoline is supplied to the engine 2 and when gasoline is not supplied to the gasoline engine 2. As a result, PM can be electrostatically adsorbed in the reactor even when the oxygen concentration is relatively low.

In the above engine system 1, even when the temperature of the cooling water detected by the temperature sensor 7 is less than a predetermined value (for example, when the engine is started), in the above engine system 1, the temperature sensor 7 is used. As in the case where the temperature of the detected cooling water is equal to or higher than a predetermined value (for example, during steady operation of the engine), the plasma reactor 5 may be operated only when the gasoline engine 2 is not supplied with gasoline. can.

1 Exhaust gas purification system 2 Internal combustion engine 3 Exhaust pipe 4 Catalyst unit 5 Plasma reactor 6 Power supply 7 Temperature sensor 8 Control unit

Claims (2)

A gasoline engine that produces power and exhaust gas from gasoline and is cooled by cooling water,
An exhaust pipe through which the exhaust gas generated in the gasoline engine can pass, and
The plasma reactor interposed in the exhaust pipe and
A power source that applies electric power to the plasma reactor and
A temperature sensor that detects the temperature of the cooling water of the gasoline engine, and
It is equipped with a control unit that controls the output of the power supply.
The control unit
When the temperature detected by the temperature sensor is equal to or higher than a predetermined value,
When gasoline is being supplied to the gasoline engine, the application of electric power to the plasma reactor is stopped.
An engine system comprising controlling the power source so as to apply electric power to the plasma reactor when gasoline is not supplied to the gasoline engine. The control unit
When the temperature detected by the temperature sensor is less than a predetermined value,
It is characterized in that the power source is controlled so as to apply electric power to the plasma reactor both when gasoline is supplied to the gasoline engine and when gasoline is not supplied to the gasoline engine. The engine system according to claim 1.

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