Device and method for actively recovering fuel vapors from a tank of an internal combustion vehicle

Abstract

This method of recovering gasoline vapors from a fuel tank (4) of an internal combustion vehicle and conveying the gasoline vapors to an air intake line (5) of the vehicle's combustion engine (3) via a purge pump (10) having multiple possible flow rates and a solenoid valve (11) controlling the opening and / or closing of a recirculation circuit (14) of air laden with gasoline vapors from downstream of the purge pump (10) to upstream of the pump (10). The opening and closing of the recirculation circuit (14) correspond respectively to the closing and opening of a main circuit (12) leading from the solenoid valve (11) to the air intake line (5) of the engine (3). The method alternates the following steps: - Recovery and storage of the gasoline vapors from the fuel tank (4) in a trap activated carbon (9) placed upstream of the pump (10);- Purging of the activated carbon trap (9) up to the air intake line (5) of the engine (3); the gasoline vapor recovery and storage stage corresponding to the operation of the purge pump (10) at a relatively low non-zero flow rate and the opening of the recirculation circuit (14), and the purging stage, triggered when the quantity of gasoline vapors stored in the trap (9) exceeds a predetermined threshold, corresponding to the operation of the purge pump (10) at a relatively high flow rate and the closing of the recirculation circuit (14). Figure for the abbreviation: Fig 2;

Description

Title of the invention: Device and method for actively recovering fuel vapors from a tank of an internal combustion vehicle technical field

[0001] The invention relates, in general, to internal combustion and / or hybrid vehicle engines.

[0002] In particular, the invention relates to devices for recovering fuel vapors, generally gasoline vapors, in order to prevent their emission into the atmosphere. Prior art

[0003] For internal combustion vehicles, the regulatory context requires that fuel vapors, generally from gasoline, but also sometimes from ethanol, be recovered rather than emitted into the atmosphere.

[0004] For this purpose, vehicles are sometimes equipped with a fuel vapor recovery system fitted with an activated carbon trap located between the fuel tank and its atmospheric pressure relief valve. This trap stores the fuel vapors and needs to be purged to prevent the carbon from becoming saturated. This purging is done by drawing air through the trap and adding filtered air to the engine's air intake.

[0005] On the one hand, recent vehicles and an increasing number of systems are adopting hybrid powertrains combining an internal combustion engine and an electric motor.

[0006] On the other hand, the performance of internal combustion engines is constantly being improved, and requires air compressors or turbochargers increasing the air boost.

[0007] The phases during which the engine has the capacity to draw in fuel vapors to purge the trap therefore tend to be shorter and shorter, while regulations in terms of pollutant emissions tend to become stricter.

[0008] The present invention therefore aims to overcome the aforementioned drawbacks and to propose a device for recovering gasoline vapors and a method for recovering these gasoline vapors.

[0009] The invention therefore relates to a method for recovering gasoline vapors from a fuel tank of an internal combustion vehicle and conveying the gasoline vapors to an air intake line of the vehicle's combustion engine via a purge pump having a plurality of flow rates possible and a solenoid valve controlling the opening and / or closing of a recirculation circuit for air laden with gasoline vapors from downstream of the purge pump to upstream of the purge pump, the opening and closing of the recirculation circuit corresponding respectively to the closing and opening of a main circuit leading from the solenoid valve to the engine air intake line, the process alternating the following steps:

[0010] - Recovery and storage of gasoline vapors from the fuel tank in a activated carbon trap placed upstream of the purge pump;

[0011] - Purge of the activated carbon trap up to the engine air intake line;

[0012] the gasoline vapor recovery and storage step corresponding to the operation of the purge pump at a relatively low non-zero flow rate and the opening of the recirculation circuit, and the purging step, triggered when the quantity of gasoline vapors stored in the trap exceeds a predetermined threshold, corresponding to the operation of the purge pump at a relatively high flow rate and the closing of the recirculation circuit.

[0013] The invention thus proposes an active fuel vapor purging device that allows fuel vapors to be recovered efficiently with short purging periods while consuming little energy.

[0014] The invention also relates to a device for recovering gasoline vapors from a fuel tank of an internal combustion vehicle and for conveying the gasoline vapors to an air intake line of the combustion engine of the vehicle comprising successively an activated carbon trap, a purge pump and a solenoid valve controlling the opening and / or closing of a recirculation circuit of air charged with gasoline vapors from downstream of the purge pump to upstream of the purge pump, the opening and closing of the recirculation circuit corresponding respectively to the closing and opening of the main circuit leading from the solenoid valve to the air intake line, the purge pump having a plurality of possible flow rates, the device being capable of implementing the process according to the invention.

[0015] Advantageously, the device includes a control unit for the engine and / or the solenoid valve and / or the purge pump.

[0016] This calculator implements the process according to the invention.

[0017] Advantageously, the purge pump is a closed-impeller centrifugal pump of low inertia.

[0018] In one embodiment, the solenoid valve has a relatively low resistance to the aerodynamic pressure loss.

[0019] In one embodiment, the device includes ducts optimized for aerodynamic pressure losses.

[0020] The invention also relates to an internal combustion vehicle equipped with a device according to the invention.

[0021] Advantageously, the bleed pump is at zero flow only when the vehicle is at a complete stop, with the ignition not having been switched on. Brief description of the drawings

[0022] Other objects, features and advantages of the invention will become apparent from the following description, given solely by way of non-limiting example, and made with reference to the accompanying drawings in which:

[0023] [Fig-1] illustrates a fuel vapor recovery device depending on the state of the technique;

[0024] [Fig.2] illustrates a fuel vapor recovery device according to the invention; and

[0025] [Fig. 3] illustrates a method for recovering fuel vapors according to the invention. Detailed description of at least one embodiment

[0026] Figure [1] shows a fuel supply system 1 comprising a fuel vapor recovery device 2 according to the state of the art.

[0027] The fuel supply system 1 is mounted on a vehicle equipped with an internal combustion engine 3. This engine can be an engine from a land, sea or aeronautical motor vehicle.

[0028] The fuel is stored in a fuel tank 4. The engine 3 includes an inlet supplied by an intake line 5, itself connected to a first air filter 6.

[0029] The fuel supply system 1 includes a fuel supply circuit 7 and the fuel vapor recovery device 2, the supply circuit and the recovery device linking the fuel tank 4 and the intake line 5.

[0030] The fuel can be a liquid fuel, usually gasoline, or in other cases ethanol or a mixture of the two, depending on the engine 3 used.

[0031] During normal operation of the engine 3, gasoline is transferred from the tank 4 to the intake line 5 of the engine 3 via the fuel supply circuit 7.

[0032] The fuel emits fuel vapors within the tank 4. These vapors are recovered and enter the recovery device 2, being mixed with filtered air from a second air filter 8.

[0033] The fuel vapor recovery device 2 comprises successively an activated carbon trap 9, a purge pump 10 and a solenoid valve 11.

[0034] The activated carbon trap 9 is also called a "canister" according to its English name or a gasoline vapor trap. Fuel vapors from the tank 4 are sucked in, mixed with filtered air and stored in the activated carbon trap 9. The trap 9 thus prevents the tank from being over-pressurized on the one hand, and fuel vapors from escaping into the atmosphere on the other.

[0035] The fuel vapors stored in the activated carbon trap 9 must be purged to prevent saturation of the carbon. This purging is carried out by suction through the trap 9 with the addition of filtered air from a second air filter 8.

[0036] This suction is achieved by the purge pump 10 positioned downstream of the trap 9. The purge pump 10 is an active pump which directs the flow of air laden with fuel vapors to the intake line 5 of the engine 3. Alternatively, it is possible in the prior art to do without the pump and to use the vacuum of the air intake of the engine 3.

[0037] A solenoid valve 11 controls the opening of the circuit 12 positioned between the solenoid valve 11 and the intake line 5, and thus connecting the pump 10 to the intake line 5 of the engine 3. This solenoid valve 11 is thus able to open or close access to the intake line 5 of the engine 3 for the air laden with fuel vapors drawn in by the pump 10.

[0038] The purge pump 10, the solenoid valve 11 and the inlet 3a of the engine 3 are controlled by a computer 13. The computer 13 thus manages the purge phases and the controlled combustion of volatile compounds, gasoline or ethanol, in the combustion chamber of the engine 3. The computer 13 receives the degree of saturation of the trap 9 from one or more sensors observing the trap 9, determines when it is time to purge the trap, and implements the purge by activating the pump 10 and opening via the solenoid valve 11 the access 12 to the intake line 5 and to the engine 3.

[0039] Figure 2 describes a fuel supply system 1 for an internal combustion engine or hybrid motor vehicle, comprising a fuel vapor recovery device 2 according to the invention. The same elements are designated by the same reference numerals in both Figures 1 and 2. The system 1 of Figure 2 includes the motor 3, the tank 4, the first air filter 6 and the second air filter 8, the activated carbon trap 9, the purge pump 10, the solenoid valve 11, the control unit 13, as well as conduits such as the intake line 5, the circuit 12, and the fuel supply circuit 7.

[0040] The fuel vapor recovery device 2 according to the invention comprises a recirculation duct 14 of air laden with fuel vapors from downstream to upstream of the pump 10. This recirculation duct 14 is controlled by the solenoid valve 11.

[0041] More specifically, the solenoid valve 11 allows the recirculation duct 14 to be opened and closed, in addition to allowing the circuit leading from the pump 10 to the inlet line 5 to be opened and closed. In this way, a single component, The solenoid valve 11 is used to perform the two functions of opening and closing the respective conduits 12 and 14, which improves the compactness of device 2.

[0042] More specifically, the closing of the recirculation duct 14 by the solenoid valve 11 and the opening of the circuit connecting the pump 10 and the inlet line 5 are simultaneous. Similarly, the opening of the recirculation duct 14 by the solenoid valve 11 and the closing of the circuit connecting the pump 10 and the inlet line 5 are simultaneous.

[0043] The purge pump 10 is a low-inertia, closed-impeller centrifugal pump. The solenoid valve 11 preferably has less resistance to aerodynamic pressure loss when open, so as to allow maximum airflow. To achieve this, the solenoid valve 1 may have an optimized valve, adapted flow cross-sections, etc. Similarly, the piping of the device 2 is also optimized to reduce aerodynamic pressure losses, for example with larger diameters and shorter circuits, and the connections are chosen to minimize disturbance to the gas flow. All these components are therefore low-power, in order to reduce the energy consumption of the device 2.

[0044] Due to its low power rating, the pump 10 requires several seconds after starting to reach its maximum flow rate, which conflicts with the duration of the purging phases, which can last only a few seconds. Therefore, the pump 10 is designed with several possible flow rates, including at least a first, relatively low but non-zero flow rate, corresponding to a speed of approximately 10,000 revolutions per minute, and a second, relatively high flow rate, corresponding to a speed between 30,000 and 50,000 revolutions per minute. Thus, the pump 10 starts at its relatively low flow rate as soon as the vehicle ignition is switched on, and operates continuously at at least this minimum flow rate.

[0045] The pump 10 is therefore never completely stopped, including during phases without purging, its relatively low flow rate allowing the pump to deliver efficiently by reaching its nominal speed immediately upon opening by the solenoid valve 11 of the circuit leading to the inlet line 5. The latency delays due to the low power of the pump 10 therefore do not impact the quality of the purging or the energy savings.

[0046] Fig. 3 illustrates the steps of a process for recovering fuel vapors from tank 4 and conveying these fuel vapors to the intake line 5 of engine 3, via the fuel vapor recovery device 2.

[0047] When the vehicle is completely stopped, before the ignition is switched on, all the elements of device 2 are at a standstill. This is the only time when the purge pump 10 has a speed and therefore a flow rate.

[0048] When the ignition is switched on in the vehicle, the pump 10 is started by the control unit 13 and brought to its relatively low speed, on the order of ten thousand revolutions per minute. This low speed corresponds to a low flow rate, which is not sufficient to purge the trap 9.

[0049] During this phase 15 without purging, the pump 10 remains at this low speed, and the solenoid valve keeps the circuit leading from the pump 10 to the intake line 5 of the engine 3 closed, and opens the recirculation line 14. The air trapped by the solenoid valve 11 can thus circulate in the recirculation line 14 connecting the solenoid valve to the inlet of the pump 10. In this way, the flow circulates without a pressure increase in this short loop, limiting friction and temperature rise. This step 14 is maintained as long as a need to purge fuel vapors from the trap 9 is not identified during the operation of the engine 3. Indeed, during this step 14, the trap 9 collects and stores fuel vapors from the tank 4 and gradually fills until saturated.

[0050] At a step 16, trap 9 saturation is detected by the control unit 13, or at least trap 9 saturation exceeds a predetermined threshold to trigger trap 9 purging. When the control unit 13 detects a need to purge trap 9, it commands the solenoid valve 11 to open the circuit 12 leading from downstream of the pump 10 to the intake line of the engine 3, thus closing the recirculation line 14. The control unit 13 also opens the inlet 3a of the engine 3. Finally, the control unit 13 commands the purge pump to increase its speed, corresponding to the relatively low flow rate, up to a speed of thirty to fifty thousand revolutions per minute, corresponding to the relatively high flow rate. Having the pump 10 constantly running at low speed prevents a strong pressure wave from being generated towards the engine by restarting it regularly.This also allows for increased efficiency in achieving a high flow rate, enabling faster and more effective purging, thus improving the pump's responsiveness by 10.

[0051] Thus, in this purging step 16, the flow rate corresponding to the relatively high speed of the pump 10 is applied in the device 2 between the trap 9 and the air intake line 5 of the engine 3. During this purging phase, the flow rate in the recirculation duct 14 is zero. The trap 9 is thus purged of its fuel vapors by suction with the addition of filtered air from the second air filter 8, and the air laden with fuel vapors is conveyed by the device 2 to the intake line 5 via the circuit 12 and then to the inlet 3a of the engine 3.

[0052] When the control unit 13 decides to stop purging, either because the trap 9 is empty or because a sufficient quantity of fuel vapors has already been purged, the control unit 13 commands the solenoid valve 11 to close the conduit 12 leading to the intake line 5 and to open the recirculation conduit 14. The airflow in the device 2 is then redirected into the recirculation duct 14 without experiencing an increase in pressure or temperature, thus returning to step 14. The pump 10 can therefore slowly reduce its speed, using its inertia, to the relatively low speed of ten thousand revolutions per minute corresponding to the relatively low flow rate. In this way, if the purging process needs to resume only a few moments after the last purge has stopped, the inertia retained by the pump 10 and by the recirculation of the airflow will allow the purge flow to resume more quickly while limiting the energy required by the pump 10.

Claims

Demands

1. A method for recovering gasoline vapors from a fuel tank (4) of an internal combustion vehicle and conveying the gasoline vapors to an air intake line (5) of the combustion engine (3) of the vehicle via a purge pump (10) having a plurality of possible flow rates and a solenoid valve (11) controlling the opening and / or closing of a recirculation circuit (14) of air laden with gasoline vapors from downstream of the purge pump (10) to upstream of the purge pump (10), the opening and closing of the recirculation circuit (14) corresponding respectively to the closing and opening of a main circuit (12) leading from the solenoid valve (11) to the air intake line (5) of the engine (3), the method alternating the following steps: - Recovery and storage (step 15) of gasoline vapors from the fuel tank (4) in an activated carbon trap (9) placed upstream of the purge pump (10); - Purge (step 16) of the activated carbon trap (9) to the air intake line (5) of the engine (3); the recovery and storage step (15) of gasoline vapors corresponding to the operation of the purge pump (10) at a relatively low non-zero flow rate and the opening of the recirculation circuit (14), and the purging step (16), triggered when the quantity of gasoline vapors stored in the trap (9) exceeds a predetermined threshold, corresponding to the operation of the purge pump (10) at a relatively high flow rate and the closing of the recirculation circuit (14).

2. A device (2) for recovering gasoline vapors from a fuel tank (4) of an internal combustion vehicle and for conveying the gasoline vapors to an air intake line (5) of the vehicle's internal combustion engine (3), comprising successively an activated carbon trap (9), a purge pump (10), and a solenoid valve (11) controlling the opening and / or closing of a recirculation circuit (14) of air laden with gasoline vapors from downstream of the purge pump (10) to upstream of the purge pump (10), the opening and closing of the recirculation circuit (14) corresponding respectively to the closing and

3.

4.

5.

6.

7.

8. the opening of a main circuit (12) leading from the solenoid valve (11) to the air intake line (5) of the engine (3), the purge pump (10) having a plurality of possible flow rates, the device (2) being able to implement the method of claim 1. Device (2) according to claim 2, comprising a control computer (13) for the motor (3) and / or the solenoid valve (11) and / or the purge pump (10). Device (2) according to any one of claims 2 or 3, wherein the purge pump (10) is a low inertia closed impeller centrifugal pump. Device (2) according to any one of claims 2 to 4, wherein the solenoid valve (11) comprises a valve and / or passage sections configured to reduce the aerodynamic pressure loss in the open position. Device (2) according to any one of claims 2 to 5, comprising pipes having a diameter and length configured to reduce aerodynamic pressure losses. Internal combustion vehicle equipped with a device (2) according to any one of claims 2 to 6. Vehicle according to claim 7, in which the purge pump (10) is at zero flow only when the vehicle is at a complete stop, the ignition not having been switched on.

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