WO2021044395A1

WO2021044395A1 - An improved fuel tank isolation valve with an integrated stepper motor

Info

Publication number: WO2021044395A1
Application number: PCT/IB2020/058490
Authority: WO
Inventors: Kabir BHANDARI; Amardip KUMAR; Varun Kumar; Sahil Singla
Original assignee: Padmini Vna Mechatronics Pvt. Ltd.
Priority date: 2019-09-04
Filing date: 2020-09-12
Publication date: 2021-03-11
Also published as: JP7476300B2; JP2022546737A; CN114502406A

Abstract

The present invention relates to an improved fuel tank isolation valve (FTIV) assembly. The present invention relates to a stepper motor driven valve having application in EVAP system & is used to maintain pressure inside the fuel tank in a protected pressure range in both over pressure & over vacuum condition along with controlled flow of fuel vapors from fuel tank to canister at the time of refueling.

Description

“AN IMPROVED FUEL TANK ISOLATION VALVE WITH AN INTEGRATED STEPPER MOTOR”

FIELD OF THE INVENTION

The present invention relates to an improved fuel tank isolation valve. More particularly, the present invention relates to an improved fuel tank isolation valve integrated with a stepper motor for plunger movement and inline function of over pressure relief and over vacuum relief which is a compact design with less weight and cost and provides precise controlled flow.

BACKGROUND OF THE INVENTION

Hybrid cars run most of the times with the electrical power and the combustion engine is idle. Since fuel tank is a closed system, thus in general due to evaporation of stored fuel it results in positive pressure inside the fuel tank. Moreover, it is necessary for vehicles to maintain an elevated pressure in the fuel tank to suppress the rate of fuel vapor generation and to minimize hydrocarbon emissions to the atmosphere. The most obvious solution, to overcome the problem is to provide a fuel tank isolation valve (FTIV) coupled to fuel tank to control fuel tank venting. The fuel tank isolation valve (FTIV) may be located in a conduit between a fuel tank and a fuel vapor canister in an evaporative emission control system. It opens automatically when the pressure exceeds protection limits and valve is electrically actuated at the time of re-fueled.

The fuel tank isolation valve (FTIV) also enables fuel vapor containment in the fuel tank until conditions are inappropriate for the engine to process the excess vapor. Generally, the fuel tank isolation valve includes an electrically controlled solenoid valve to open and close the inlet and outlet port with either less precise control on opening of intermediate positions or no control of opening on intermediate positions. Thus, have no precise control of flow of fuel vapors from fuel tank to canister at the time of refueling.

In US20020112702A1, discloses a method for operating a fuel tank isolation valve and a canister vent valve. The fuel tank isolation valve has a first port, a second port, an electric actuator and a valve body. The first port is in fluid communication with a fuel vapor collection canister and the second port is in fluid communication with a fuel tank. The electric actuator moves the valve body to control fluid communication between the first and second ports. And the canister vent valve controls ambient fluid flow with respect to the fuel vapor collection canister. The method includes supplying a first electric signal to the electric actuator such that the valve body permits substantially unrestricted fuel vapor flow between the first and second ports, supplying a second electric signal to the electric actuator such that the valve body substantially prevents fuel vapor flow between the first and second ports, supplying a third electric signal to the electric actuator such that the valve body provides restricted fuel vapor flow between the first and second ports, and supplying a fourth electric signal to the canister vent valve to permit ambient fluid flow into the fuel vapor collection canister. In this system the fuel tank isolation valve is controlled by an electrical actuator such as solenoid valve, which is a typical component and it provides predefined open and close settings as well as costly. Also controlling the solenoid valve is difficult. In US20020088441A1, discloses a system and method for controlling evaporative emissions of a volatile fuel. The system preferably has a fuel vapor collection canister, a purge valve, an isolation valve and a fuel tank. The isolation valve includes housing, a valve body, and a seal. The housing has a first port in fluid communication with the supply port of the fuel vapor collection canister, a second port, and a fuel vapor flow path that extends between the first and second ports. The valve body is movable with respect to the housing along an axis between a first configuration and a second configuration. The first configuration permits substantially unrestricted fuel vapor flow between the first and second ports, and the second configuration substantially prevents fuel vapor flow between the first and second ports. The fuel tank is in fluid communication with the second port of the isolation valve. In this system the fuel tank isolation valve is controlled by an electrical actuator such as solenoid valve, which is a typical component and it provides predefined open and close settings as well as costly. Also controlling the solenoid valve is difficult.

Therefore, the present invention overcomes the drawbacks of the cited art and provides an improved fuel tank isolation valve with integration of a stepper motor working as an actuator. This will lead to compact design, precise functional control, cost effective, less weight and reduced number of components in the overall assembly. OBJECT OF THE INVENTION

The main object of the present invention is to provide an improved fuel tank isolation valve assembly that allows precise controlled flow and is a low-cost compact design.

Another main object of the present invention is to provide an assembly to incorporate a nozzle, a threaded plunger and a stepper motor to control the opening and closing of the fuel tank isolation valve.

Yet another main object of the present invention is to provide an assembly for controlling the opening and closing of the valve by the linear movement of the threaded plunger.

Still another object of the present invention is to provide an assembly that allows automatic opening and closing of the valve with the help of compression springs when the pressure or vacuum inside the fuel tank exceeds beyond the limit.

SUMMARY OF THE INVENTION

The present invention relates to an improved fuel tank isolation valve (FTIV) assembly. More particularly, the present invention relates to a stepper motor driven valve having application in EVAP system and is used to maintain pressure inside the fuel tank in a protected pressure range in both over pressure and over vacuum condition along with controlled flow of fuel vapors from fuel tank to canister at the time of refueling.

In a main embodiment, the present invention provides an assembly of FTIV. The assembly comprises of nozzle with integrated tank port for connecting the valve to the fuel tank, a canister port for connecting the valve to the canister and a stepper motor used for the electrical opening and closing of the valve. The stepper motor comprises of a motor housing, a rotor with internal threads, a ball bearing and a moving plunger with threads on its outer diameter. The sub assembly further includes a seal sub assembly for over pressure relief (OPR) with a compression spring fixed above it and in contact with a sealing surface to perform the over pressure relief function, a seal sub assembly for over vacuum relief (OVR) with a compression spring fixed below it and in contact with a sealing surface to perform the over vacuum function. The motor housing has a rotor with internal threads and a ball bearing to reduce friction while rotation. The threaded plunger secured to the cavity is fastened to the threaded rotor of the motor thus completing the assembly of FTIV. The linear movement of the threaded plunger in the motor housing leads to the opening and closing of the valve.

In yet another embodiment, the present invention provides an improved FTIV assembly in idle condition. The idle condition allows the seal sub assembly for OVR and the seal sub assembly for OPR to close thus not connecting the tank port to the canister port. The compression spring for OVR holds the seal sub assembly (OVR) and at the same time the compression spring for OPR holds the seal sub assembly (OPR) and keeps the valve closed.

In yet another embodiment, the present invention provides an improved FTIV assembly in ON condition or refueling condition. The refueling condition allows the energizing of motor that leads to opening of valve. With the rotation of rotor of motor, plunger moves upwards and downwards depending upon the direction of rotation of motor for opening and closing of the valve during refueling.

In yet another embodiment, the present invention provides an improved FTIV assembly in OPR condition. The OPR condition allows compressing of the compression spring for OPR and lifting the seal sub assembly (OPR) upwards that make the flow of fuel vapors from tank port to canister port when the pressure exceeds the predefined limit.

Still another embodiment, the present invention provides an improved FTIV assembly in OVR condition. The OVR condition allows compressing of the compression spring for OVR and moving the seal sub assembly (OVR) downwards that makes the flow of fuel vapors from canister port to tank port when the vacuum exceeds the predefined limit.

BRIEF DESCRIPTION OF THE DRAWING

Fig. 1(a) and Fig. 1(b) are perspective view and an exploded view of the fuel tank isolation valve respectively in accordance with the present invention.

Fig. 2(a) is a sectional view of the fuel tank isolation valve in accordance with the present invention.

Fig. 2(b) is an enlarged sectional view of the fuel tank isolation valve in accordance with the present invention. Fig. 3(a) and Fig. 3(b) is a sectional and enlarged sectional view of the fuel tank isolation valve in idle condition respectively in accordance with the present invention.

Fig. 4(a) is a sectional view of the fuel tank isolation valve during refueling in accordance with the present invention.

Figs. 4(b), 4(c), 4(d) and 4(e) are enlarged sectional views of the fuel tank isolation valve during refueling in accordance with the present invention.

Fig. 5(a) is a sectional view of the fuel tank isolation valve working in OPR condition in accordance with the present invention.

Figs. 5(b) and 5(c) are enlarged sectional views of the fuel tank isolation valve working in OPR condition in accordance with the present invention.

Fig. 6(a) is a sectional view of the fuel tank isolation valve working in OVR condition in accordance with the present invention.

Figs. 6(b) and 6(c) are enlarged sectional views of the fuel tank isolation valve working in OVR condition in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Many aspects of the invention can be better understood with references made to the drawings below. The components in the drawings are not necessarily drawn to scale. Instead, emphasis is placed upon clearly illustrating the components of the present invention. Moreover, like reference numerals designate corresponding parts through the several views in the drawings. Before explaining at least one embodiment of the invention, it is to be understood that the embodiments of the invention are not limited in their application to the details of construction and to the arrangement of the components set forth in the following description or illustrated in the drawings. The embodiments of the invention are capable of being practiced and carried out in various ways. In addition, the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting.

Referring to Fig. 1(a), a perspective view of the fuel tank isolation valve (10) in accordance with the present invention is shown. The fuel tank isolation valve comprises of a valve housing (11) fitted over a motor housing (12), wherein the valve housing (11) comprises of a canister port (13) and a tank port (14) and the motor housing (12) has an electrical connection port (15).

Referring to Fig. 1(b), an exploded view of the fuel tank isolation valve (10) in accordance with the present invention is shown. The assembly comprises of nozzle with integrated tank port (14) for connecting the valve to the fuel tank, a canister port (13) for connecting the valve to the canister and a stepper motor (17) used for the electrical opening and closing of the valve. The sub assembly further includes a seal sub assembly (4) for over pressure relief (OPR) with a compression spring (3) fixed above it and in contact with a sealing surface to perform the over pressure relief function, a seal sub assembly (7) for over vacuum relief (OVR) with a compression spring (6) fixed below it and in contact with a sealing surface to perform the over vacuum function. The motor housing (12) has a rotor (20) with internal threads and a ball bearing to reduce friction while rotation. The threaded plunger (16) secured to the cavity is fastened to the threaded rotor of the motor thus completing the assembly of FTIV (10).

Now referring to Fig. 2(a), the present invention provides the sectional view of FTIV assembly. The assembly (10) comprises of nozzle with integrated tank port (14) for connecting the valve to the fuel tank, a canister port (13) for connecting the valve to the canister and a stepper motor (17) used for the electrical opening and closing of the valve. The stepper motor (17) comprises of a motor housing (12), a rotor (20) with internal threads, a ball bearing (9) and a moving plunger (16) with threads on its outer diameter. The sub assembly further includes a seal sub assembly (4) for over pressure relief (OPR) with a compression spring (3) fixed above it and in contact with a sealing surface (5) to perform the over pressure relief function, a seal sub assembly (7) for over vacuum relief (OVR) with a compression spring (6) fixed below it and in contact with a sealing surface (8) to perform the over vacuum function. The motor housing (12) has a rotor (20) with internal threads and a ball bearing (9) to reduce friction while rotation. The threaded plunger (16) secured to the cavity is fastened to the threaded rotor (20) of the motor thus completing the assembly of FTIV. The linear movement of the threaded plunger (16) in the motor housing leads to the opening and closing of the valve (10).

Referring to Fig. 2(b), an enlarged sectional view of the fuel tank isolation valve in accordance with the present invention is shown. The seal sub assembly (4) is fitted over sealing surface (5) for OPR function to provide sealing for OPR function. Also, the seal sub assembly (7) is fitted under sealing surface (8) for OVR function to provide sealing for OVR function and refueling function.

Now referring to Figs. 3(a) and 3(b), a sectional and enlarged sectional view of the fuel tank isolation valve in idle condition in accordance with the present invention is shown. The compression spring (6) for OVR keeps the seal sub assembly (7) for OVR in contact with the sealing surface (8) and at the same time the compression spring (3) for OPR keeps the seal sub assembly (4) for OPR in contact with the sealing surface (5) thus not connecting the tank port (14) to the canister port (13) and keeping the fuel vapors inside fuel tank. Said threaded plunger (16) has an annular flange (22) at the top end to fit in the seal sub assembly (7) and at the bottom end it is secured in a threaded cavity (21) in said rotor (20) to provide inline function

Referring to Figs. 4(a) - 4(e), sectional and enlarged sectional view of the fuel tank isolation valve during refueling in accordance with the present invention is shown. During refueling, the motor (17) gets energized and rotor (20) along with shaft starts rotating that moves the threaded plunger (16) downwards causing the seal sub assembly (7) for OVR to move downwards by compressing the compression spring (6) and allowing the flow condition from tank port (14) to canister port (13) as depicted in Fig. 4(a).

In a first condition, with motor’s (17) leakage point + 2 rotations, a small linear stroke of plunger (16) takes place and a small opening path opens and fulfills the first condition of flow rate as depicted in Fig. 4(b). With further rotation of motor (17) i.e. at motor’s leakage point + 20 rotations, further stroke of plunger (16) takes place and opening path area increases that fulfils the second condition of flow rate as depicted in Fig. 4(c). With the complete rotation of motor (17), the plunger (16) take its full stroke and there is full opening of the valve (10) and a flow resistance condition is fulfilled as depicted in Fig. 4(d). Flow path in refueling condition is as shown in Fig. 4(e).

Referring to Figs. 5(a) - 5(c), sectional and enlarged sectional view of the fuel tank isolation valve (10) working in OPR condition in accordance with the present invention is shown. When the fuel tank isolation valve (10) is in OPR condition, there is a pressure built up inside the valve (10) in the area (18) between the spring holder (19) and seal sub assembly (4) for OPR function and compression spring (3) for OPR function keeps the seal sub assembly (4) in contact with the sealing surface (5) keeping the fuel tank isolation valve (10) in closed condition as depicted in Fig. 5(a). When the pressure increases beyond a predefined protection point limit, the pressure exerts a force to compress the compression spring (3) for OPR function and lifts the seal sub assembly (4) for OPR function upwards as depicted in Fig. 5(b). As the seal sub assembly (4) for OPR function lifts up, valve opens, and flow starts from tank port (14) to canister port (13). The excess fuel vapors go to canister and the pressure starts dropping as depicted in Fig. 5(c). As soon as the pressure drop reaches to protection point limit i.e. safety limit, valve closes again.

Referring to Figs. 6(a) - 6(c), sectional and enlarged sectional view of the fuel tank isolation valve (10) working in OVR condition in accordance with the present invention is shown. When the fuel tank isolation valve (10) is in OVR condition, there is a vacuum built up inside the valve (10) in the area (18) between the spring holder (19) and seal sub assembly (7) for OVR function and compression spring (6) for OVR function keeps the seal sub assembly (7) for OVR function in contact with the sealing surface (8) to keep the fuel tank isolation valve (10) in closed condition as depicted in Fig. 6(a). There is a stroke provided between the seal sub assembly (7) for OVR and plunger (16) to use the full spring force for sealing without any dependency on threads provided in the bottom end of plunger (16). In addition, the same stroke is utilized for the OVR function as it is controlled in line with flow resistance function. When the vacuum increases beyond the protection point limit, vacuum exerts a force to compress the compression spring (6) and the seal sub assembly (7) for OVR function moves downwards due to stroke between seal sub assembly (7) for OVR function and plunger (16) as depicted in Fig. 6(b). Here, the plunger remains at its position and maximum movement of seal sub assembly (6) for OVR function is equal to stroke provided between seal sub assembly (7) for OVR function and plunger (16). As the seal sub assembly (7) for OVR moves downwards, valve opens, and flow starts from canister port (13) to tank port (14) as depicted in Fig. 6(c). The vacuum starts to release from tank and as soon as the vacuum reaches the protection point limit i.e. safety limit the valve closes again.

Therefore, the FTIV assembly allows opening and closing of valves by the linear movement of the plunger.

EXAMPLE 1

REFUELING DURING ON CONDITION

During refueling, stepper motor gets turned ON. Due to the rotation of stepper motor, the plunger with lead screw moves downwards causing seal assembly for OVR function to move downwards by compressing the compression spring for OVR function. In first condition, with motor’s leakage point + 2 rotations a small linear stroke of plunger takes place and a small opening path gets opened which fulfilled the condition of 11.4 L/min max. at 16 kPa. With further rotation of motor i.e. at motor’s leakage point + 20 rotations further stroke of plunger took place and opening path area increased which fulfilled the condition of 155 L/min. max. at 16 kPa. With the complete rotation of motor (416 steps), plunger takes its full stroke and full opening of the valve happens and flow resistance condition of 78 L/min. at a pressure difference of 0.35 kPa max. is fulfilled.

The foregoing description of embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiments were chosen and described in order to explain the principals of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated.

Claims

CLAIMS We claim:

1. An improved fuel tank isolation valve (10) with an integrated stepper motor (17) comprising:

(a) a valve housing (11) comprising a canister port (13) and a tank port (14) and including a compression spring (3), a seal sub assembly (4) for performing over pressure relief (OPR) function, a seal subassembly (7) and a compression spring (6) for performing over vacuum relief (OVR) function;

(b) a motor housing (12) having an electrical connection port (15);

(c) a threaded plunger (16); and

(d) a spring holder (19); wherein, said stepper motor (17) includes said motor housing (12), a threaded rotor (20) and plurality of ball bearings (9) positioned between said motor housing (12) and said rotor (20) for reducing friction while said rotor (20) is in active condition; said threaded plunger (16) has an annular flange (22) at the top end to fit in the seal sub assembly (7) and at the bottom end it is secured in a threaded cavity (21) in said rotor (20) to provide inline function; and said valve (10) allows opening and closing of valve through linear motion of threaded plunger (16).

2. The improved fuel tank isolation valve (10) with an integrated stepper motor (17) as claimed in claim 1, wherein said spring holder (19) secures the compression spring (6) and said plunger (16) passes through said spring holder (19).

3. The improved fuel tank isolation valve (10) with an integrated stepper motor (17) as claimed in claim 1, wherein said seal subassembly (4) with said compression spring

1 (3) fixed above it gets in contact with a sealing surface (5) for over pressure relief (OPR) function.

4. The improved fuel tank isolation valve (10) with an integrated stepper motor (17) as claimed in claim 1, wherein said seal sub assembly (7) with said compression spring

(6) fixed below it gets in contact with a sealing surface (8) to perform the over vacuum relief (OVR) function.

5. The improved fuel tank isolation valve (10) with an integrated stepper motor (17) as claimed in claim 1, wherein between said motor housing (12) and said threaded rotor (20) an annular cavity is provided for said ball bearings (9).

6. The improved fuel tank isolation valve (10) with an integrated stepper motor (17) as claimed in claim 1, wherein said stepper motor (16) maintains pressure within a protected pressure range, provide electric control of fuel vapors flow from tank to canister during refueling, provide over pressure relief (OPR) and over vacuum relief (OVR).

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