JP3014447B2 - Handling of fuel vapor emissions - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the treatment of fuel vapor generated in a fuel tank that provides fuel to an internal combustion engine.

In many countries, regulations on emissions from vehicles require the treatment of such steam to eliminate or significantly reduce the amount of fuel released to the atmosphere by the steam generated in the fuel tank. During the operation of the vehicle,
The temperature of the fuel tank is on the order of 30 ° C. to 55 ° C., so that a large amount of fuel vapor is generated in the fuel tank. Such fuel vapors are harmful if released to the atmosphere without any treatment.

Accordingly, many regulations governing emissions emitted by vehicles require the provision of suitable forms of separators, which include from the vapors that escape from the fuel tank through the separators. The fuel is removed before the air is released to the atmosphere. Typically, the separator is an activated carbon type device of the type commonly referred to as a "carbon canister." Such separators operate on the principle of physical adsorption of fuel vapors on activated carbon surfaces. During operation of the engine, air released from the separator is directed to the intake system of the engine, and therefore, fuel not removed by the separator is directed to the engine and therefore not released to the atmosphere. However, when the engine is not running, especially when the temperature of the fuel tank is high immediately after the engine is stopped, the generation of fuel vapor continues and the pressure is sufficient to discharge the vapor into the separator. Thus, fuel accumulates in the separator for quite some time after the engine has stopped.

Usually, the separator is designed to have sufficient capacity to hold all the fuel passing from the fuel tank to the separator after the engine has been stopped, but this is done at the next start of the engine. Fills the filter media with fuel. This fuel in the filter media is drawn into the intake system of the engine, providing excess fuel to the engine at start-up, thus increasing the level of hydrocarbon emissions in the exhaust gas. Further, this excess fueling may cause the engine to operate at a much higher speed than determined by the throttle position and fuel metering system. This aspect of engine operation after startup is unacceptably commercially and environmentally acceptable.

One proposal to address this problem is to provide a solenoid operated valve in the steam control system that operates to isolate the separator from the air induction system during startup.

It is an object of the present invention to provide, in connection with an internal combustion engine, a system for treating fuel that accumulates in a separator during engine shutdown without adversely affecting engine operation.

To this end, according to the present invention, an air compressor for supplying air for injecting fuel for combustion in an engine, a fuel tank for storing fuel used in the engine,
An air / fuel separator that receives the vapor generated in the fuel tank and separates the fuel in the vapor from air, and at least a portion of the air drawn in by the compressor when the compressor is operating, is fuel-retained. And a passage communicating the portion of the separator where fuel is retained with the intake port of the compressor, such that fuel is removed from the portion of the separator. A multi-cylinder internal combustion engine facility is provided, wherein the passage is provided with control means for controlling the flow rate of air to the compressor through the separator.

Conveniently, a check valve is provided between the fuel tank and the separator set, such that the check valve remains closed if the pressure in the fuel tank is below a preset value, for example 7 kPa. Is set. This is because if the pressure in the fuel tank is too low, the fuel will vaporize excessively, which will increase the load on the fuel vapor acting on the system. Furthermore, conveniently, another valve is provided between the check valve and the fuel tank, or on the fuel tank itself, which opens when the pressure in the fuel tank drops below atmospheric pressure. Avoid the danger of vacuum damaging or breaking the fuel tank.

In a fuel injection system in which air is used to deliver fuel to an engine, the pressure of the air at which the fuel is delivered is usually maintained at a predetermined value lower than the normal delivery pressure of the compressor. A pressure regulator is provided upstream. The air released by the regulator is preferably redirected to the compressor intake port.

By sucking air backflow into the compressor through the separator, fuel accumulated in the separator during the period following engine shutdown is transported into the compressor and then delivered through a fuel injector to the combustion chamber. This allows the accumulated fuel to be purged from the separator without significantly changing the actual air-fuel ratio of the mixture in the combustion chamber. Therefore,
As proposed by the present invention, although the fuel is purged from the separator by the compressor every engine cycle and subsequently delivered to the engine, the amount of fuel purged does not exceed the amount of fuel per engine cycle. Calculating based on volume,
Significantly less than the amount of fuel normally purged from the separator. Thus, barging fuel from the separator in accordance with the present invention has a significant effect on the level of emissions in the exhaust gas as compared to previously used systems. This advantage is further enhanced by controlling the proportion of fuel passing from the separator to the compressor. This is most conveniently achieved by controlling the flow of air through the separator to the compressor, and thus directly controlling the proportion of fuel passing through the compressor. The control means
Preferably, for a particular or narrow range of load of the engine at a particular speed, the flow of air to the compressor is constant.

Modern engine equipment includes a programmable fuel metering means configured to determine engine fuel demand in response to input signals of engine operating conditions. These input signals include an engine speed signal and the program is configured to apply a predetermined correction to the fuel demand of the engine for the engine speed as a compensation for the flow of fuel from the separator to the compressor.

Further, the present invention can be conveniently applied to engine equipment having fuel rails that individually distribute fuel and air to multiple fuel injector units, as described in U.S. Pat. No. 4,934,329. . In such installations, fuel is circulated back to the fuel tank by the rail to prevent the formation of fuel vapor in the rail.
It will be appreciated that heat is transferred from the compressed air supplied to the rails to the fuel as compared to conventional engine equipment, thereby adding a large heat input to the fuel tank.
This places a high load on the steam to be handled in such equipment and therefore requires the regulator to purge while the engine is running.

The present invention will be readily understood from the following detailed description of one specific configuration of a fuel vapor treatment process for an internal combustion engine incorporating the present invention, and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of a steam control and compressed air system currently in use, and FIG. 2 is a schematic diagram of a steam control and compressed air system according to one embodiment of the present invention. FIG. 3 is a schematic diagram of a steam control and compressed air system according to a modification of the present invention.

Embodiments Referring now to FIG. 1, a separator 10 is a conventional device having a filter media made of activated carbon and is referred to as a carbon canister in the field of the automotive industry. Steam space 11 in fuel tank 12
Communicates with a conduit 13 following the inlet side of the separator 10. The check valve 14 disposed in the conduit 13 is opened when the vapor pressure in the fuel tank 12 is higher than the pressure in the separator 10 by 10 kPa or more so that the vapor flows from the fuel tank 12 to the separator 10. It has been set. The check valve 17 communicates with the vapor space 11 in the fuel tank via the conduit 13, and is set so as to open when the pressure in the fuel tank 12 drops below the atmospheric pressure.

The outlet side of the separator 10 communicates with the air guide passage 15 of the engine via a conventional air box 16 and a conduit 9 downstream of the throttle valve 8. During operation of the engine, air is drawn into the engine air induction system through the air box 16 and the throttle valve 8. Thus, when the engine is running and the pressure in the vapor space 11 in the fuel tank 12 is sufficiently high,
The steam passes from a fuel tank through a separator 10 that absorbs the fuel in the steam with activated carbon, and the treated air passes through an air guide passage 15. During operation of the engine, the air entering the air guide passage 15 from the separator 10 forms part of the air conveyed into the engine through the air guide system, and from the separator 10 when the engine is stopped. The air passing into the air passage 15 is released to the atmosphere.

A compressor 20 draws air from the air box 16 via a conduit 19 and delivers compressed air to an air duct of an air and fuel rail 21 having an air duct and a fuel duct (not shown). Air is supplied to a series of fuel injectors 22 that deliver fuel from the engine to the combustion chamber of the engine. A regulator 23 controls the air and the pressure of the air in the fuel rail 21, and the air released by the regulator 23 is returned to the conduit 19 on the intake side of the compressor 20.

Although the compressor 20 draws in supply air through conduit 19 from the air box 16 from which purified air from the separator 10 is being delivered, the proportion of air entering the compressor 20 from this air box 16 is the air box 16 and The amount of air passing through the passage 15 and entering the air induction system of the engine is small. When the engine stops, fuel accumulates in the separator 10 and the next time the engine is started, air flows through the separator and conduit 9 into the air guide passage 15 and the air box
Sucked into 16. Any fuel drawn into the air guide passage 15 with the air from the separator 10 immediately enters the air guide system and is conveyed into the combustion chamber of the engine without passing the fuel through the conduit 19 leading to the compressor 20. . Separator 10
Because most of this fuel from the APC is transported directly into the air induction system, an over-rich mixture is delivered to the engine, which causes excessive contaminants in the exhaust gas and / or Causes engine overspeed as mentioned.

The present invention modifies the above described system by replacing the conduit 19 shown in FIG. 1 with a conduit 25 shown in FIG. 2 which is directly connected to the conduit 13 downstream of the check valve 14 and upstream of the separator 10. Propose that. Thus, the fuel vapor discharged from the fuel tank 12 is directly sucked into the intake port of the compressor 20. Thus, when the engine is running, the compressor draws fuel vapor from the fuel tank 12 and draws the required additional air from the engine air box 16 into the conduit 28 and the separator 10.
Inhale through. This additional air is sucked back through the separator 10. If the load of fuel from the fuel tank is greater than the load that the compressor can accept, excess steam passes through the separator 10 in a conventional manner and is delivered through conduit 28 into the engine air induction system. You.

One advantage of the fuel handling system shown in FIG. 2 is that after the engine has been shut down for a predetermined period of time, fuel accumulates in the activated carbon in the separator 10 as described above, but separates from the air induction passage when the engine is started. This means that a backflow of air through the unit 10 to the compressor occurs. This backflow purges fuel from the activated carbon in the separator 10 and the fuel is subsequently delivered by the compressor 20 to the combustion chamber of the engine via air and fuel rails 21 and injectors 22. Separator
This backflow of air through 10 prevents excess fuel in the separator from being drawn directly into the engine's air induction system, but instead reduces the level of fuel in the engine's performance or emissions in the exhaust gas. In a substantially reduced amount through the injector 22 to the combustion chamber of the engine.

Further, at a predetermined time during the engine cycle in which the exhaust port of the engine is closed, fuel from the separator is injected into the injection device 22.
Another advantage is that it is delivered directly into the fuel chamber. That is, the fuel vapor delivered from the fuel tank 12
It is drawn directly into the compressor 20 through 25. In addition, air is sucked from the air guide passage 15 through the conduit 28 and the separator 10, and the fuel vapor accumulated in the separator 10 is removed by the compressor 20.
Sucked into. When a large amount of fuel vapor is present in the separator 10, some fuel vapor is discharged to the air guide passage 15 through the conduit 28. Therefore, it is avoided that the fuel is short-circuited and exits from the exhaust port in a state of unburned gas,
If fuel from the separator is delivered with the guided air, some of the raw fuel may dissipate through the open exhaust port. This is especially true for two-stroke engines.

FIG. 3 shows another embodiment of the present invention, in which a duct 30 and a separator 30 directly connect the air box 16 and the compressor 20 of the engine to each other. Communicate. A central orifice of the control orifice or venturi 31 is provided in the duct 28 at the junction with the duct 30 so that
Duct 30 is an air box through which air passes through a venturi 31
Under the influence of a partial vacuum created in the center of the venturi 31 to pass from 16 to the compressor 20. With this configuration, the pressure in duct 30 is substantially directly proportional to the flow of air along duct 28, which is proportional to engine speed. Thus, when the compressor is operating, the flow of air from separator 10 with or without fuel vapor to duct 28 is substantially proportional to engine speed. Thus, Venturi 31
Can be determined to determine the relationship between the flow rate of air from the separator to the compressor and the speed of the engine.

A conduit through which air sucked from the separator 10 to the compressor 20 passes
The entry position of the fuel-free air from the air box 16 and the entry position of the steam from the fuel tank 11 to the separator 10 with respect to 30 are determined by both the air from the air box and the air from the fuel tank. It is arranged so as to pass through the filter medium 32 inside. This arrangement equalizes the fuel content of the air passed through the compressor. The filter media acts like an accumulator for the fuel coming from the fuel tank, which is then released into the air passing through the compressor.

Therefore, the ECU for engine control having the function of determining the fuel demand of the engine as its function, that is, the electric control device 34
Adjusts the metered amount of fuel delivered through the injectors with respect to the speed of the engine in determining the amount of fuel required by the engine so that the fuel in the form of steam supplied with the compressed air It can be programmed to compensate for the quantity and to dispense a metered quantity of fuel.

It will be appreciated that for large fuel supplies, such as at high loads and speeds, the amount of fuel supplied from the separator to the compressor is small with respect to the fuel demand of the engine. Therefore, in such an operating state of the engine, the correction to the fuel supply amount for the fuel contained in the compressed air may be ignored. However, during warm-up or other low-speed, low-load conditions, such corrections are important in maintaining acceptable levels of emissions. Furthermore, EC
U can be programmed to make a single correction to the fuel supply for a range of engine speeds. This is because the actual variation of the true correction for the range is small and does not significantly affect engine performance or emission levels.

As part of the engine control system, a shut-off valve 29 is further provided in the duct 30 of the separator. This shutoff valve may be in the form of a solenoid operated valve. The solenoid valve is periodically operated to open and close the separator duct 30.
The function of the solenoid valve is to obtain a suitably stable vapor content in the air sucked from the separator 10 into the duct 28 following the compressor 20 under normal operating conditions of the engine. Thus, by repeatedly stopping the flow of air from the separator 10 to the compressor, so that steam is accumulated in the separator,
This vapor is purged from the separator the next time the solenoid is opened.

It was found that it was convenient to open and close the solenoid valve repeatedly, such as opening it for 5 seconds and closing it for 10 seconds.

When the solenoid is opened and the air containing fuel vapor passes from the canister to the compressor, the engine control ECU 34
For the metered amount of fuel that the injector delivers to the engine
The ECU is programmed to make the appropriate adjustments as described above. However, closing the solenoid valve does not provide any fuel to the air from the compressor,
The engine control ECU makes no correction to the metered amount of fuel. The solenoid can operate with no open and closed periods set,
It will be appreciated that these periods may be modulated by the engine control ECU in accordance with the operating conditions of the engine.

────────────────────────────────────────────────── ─── Continued on front page (72) Inventor Smith, Darren Andrew Western Australia, Australia, Double View, Beatrice, Street, 25 (72) Inventor Higgins, Stuart Andrew, Western Australia, Australia Embleton, Ferrady, Street, 1 (72) Inventor Thayer, Christopher Neville Francis, Western Australia, Ferndale, Vasaria, Crescent, 41 (56) References JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) F02M 25/08

Claims (14)

(57) [Claims] 1. An air compressor 20 for supplying air only to an injection device for injecting fuel for combustion in an engine, a fuel tank 12 for storing fuel used in the engine, and a fuel tank formed in the fuel tank. In a multi-cylinder internal combustion engine system having an air / fuel separator 10 that receives steam and separates fuel from air, at least a portion of the air drawn by the compressor when the compressor 20 is operating is reduced by an air induction system. The fuel of the separator 10 is retained from the parts 15 and 16 so that the fuel to be delivered to the injector together with the compressed air is removed from said part of the separator 10 through the retained part of the separator 10. And a compressor passage through the separator passage 25; 30 from the air / fuel separator 10 to communicate the separated portion with the intake port of the compressor.
Internal combustion engine equipment, provided with control means 14; 29, 34 for controlling the flow rate of air to the internal combustion engine. 2. The facility has air and fuel rails 21 with fuel ducts, and fuel is continuously supplied from the fuel tank 12 through the fuel ducts to supply fuel from the fuel ducts to respective fuel injectors 22. 2. The internal combustion engine installation according to claim 1, wherein the internal combustion engine equipment is circulated in a static manner. 3. The internal combustion engine system according to claim 2, wherein said air and fuel rails have air ducts for receiving air from a compressor to supply respective fuel injectors. 4. The apparatus of claim 1 wherein said control means maintains a substantially constant ratio between the total flow of air to the compressor and the flow of air from the air / fuel separator to the compressor. The internal combustion engine equipment according to claim 1. 5. The control means according to claim 1, wherein said control means controls said air flow from said air / fuel separator to said compressor to be substantially constant over a predetermined engine load range at a preselected engine speed. The internal combustion engine equipment according to claim 1, wherein: 6. The internal combustion engine equipment according to claim 1, wherein the control means is adapted to selectively block a flow reaching the intake port of the compressor through the separator passage. 7. Means are provided for connecting an intake port of the compressor to an air induction system 15, 16 of the engine, through which air is supplied to the combustion chamber of the engine, whereby the compressor draws air through the induction system. An internal combustion engine installation according to any one of claims 1, 2, and 3, which is receivable from 15, 16, and the separator 10. 8. The air connection system according to claim 1, wherein said connection means includes an air guiding system.
A separate passage for conveying from 5 and 16 to the suction port of the compressor 20; the separator passage 30 being connected to the another passage in the middle of its length, a venturi 31 being provided in the another passage; ,
The internal combustion engine installation according to claim 7, wherein the separator passage (30) is connected to the small diameter portion of the venturi (31) for controlling the flow of air from the separator into another passage. 9. The venturi according to claim 8, wherein the flow rate of air from the separator to the intake port of the compressor is substantially constant over a predetermined engine load range at a preselected engine speed. The internal combustion engine equipment according to claim 1. 10. The internal combustion engine installation according to claim 6, further comprising a shut-off means for selectively shutting off the air flow through the separator passage from the separator to an intake port of the compressor. 11. The internal combustion engine installation according to claim 10, wherein the shut-off means (29) is adapted to provide an intermittent cycle with respect to the connection of the separator passage (30) to another passage. 12. The internal combustion engine equipment according to claim 10, wherein said shut-off means 29 changes a cycle period according to a selected operating state of the engine. 13. A program fuel metering means 34 configured to determine engine fuel demand in response to an input signal of engine operating conditions, said input signal including an engine speed signal, and wherein said input signal includes an engine speed signal. The fuel metering means 34
The internal combustion engine according to any one of claims 6 to 11, wherein the internal combustion engine is configured to make a predetermined correction to the fuel demand of the engine relative to the engine speed as a compensation for the flow rate of fuel to the inlet of the compressor. Facility. 14. The input signal includes a signal indicating the state of the shut-off means 29, and the programmed fuel metering means 34 makes the predetermined correction to the fuel demand of the engine only when the shut-off means 29 is open. 14. The internal combustion engine equipment according to claim 13.