WO2021044396A1

WO2021044396A1 - Improved fuel tank isolation valve with an integrated stepper motor and an improved plunger

Info

Publication number: WO2021044396A1
Application number: PCT/IB2020/058491
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: CN114502407A

Abstract

The present invention relates to an improved fuel tank isolation valve. 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 (OPR) and over vacuum relief (OVR) which is a compact design with less weight & cost and provides precise controlled flow.

Description

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

PLUNGER”

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 vapour 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 refueling.

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. The main drawback of this invention is that 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 integrated with a stepper motor for plunger movement and inline function of over pressure relief and over vacuum relief.

Another object of the present invention is to provide an improved fuel tank isolation valve integrated with stepper motor to maintain pressure within a protected pressure range, provide electric control of fuel vapors flow from tank to canister during refueling, provide over pressure relief and over vacuum relief.

Yet another object of the present invention is to provide an improved fuel tank isolation valve which is robust and compact as all the functions provided are inline to each other. Yet another object of the present invention is to provide an improved fuel tank isolation valve wherein the plunger movement is controlled in multiple steps to achieve precise controlled flow.

Still another object of the present invention is to provide a fuel tank isolation valve which is light weight and has reduced size.

SUMMARY OF THE INVENTION

The present invention provides an improved fuel tank isolation valve integrated with a stepper motor for plunger movement and inline function of over pressure relief (OPR) and over vacuum relief (OVR).

In an embodiment of the present invention, an improved fuel tank isolation valve comprises of a valve housing and a motor housing, wherein the valve housing has a canister port, a tank port and is fitted over the motor housing, the valve housing includes a compression spring fixed inside the valve housing for performing OPR function, a seal sub assembly for OPR function having a sealing surface for OPR function and refueling, a seal for OVR function, a compression spring for OVR function, a sealing surface for OVR function and a plunger; and the motor housing includes a stepper motor, a stepper motor rotor having an axial threaded cavity, a spring holder, and a plurality of ball bearings between an annular cavity between said motor housing and stepper motor rotor for reducing friction when stepper motor rotor is in working condition. The plunger at its bottom end is threaded and screwed in the threaded cavity of the stepper motor rotor to provide inline function. The improved fuel tank isolation valve integrated with stepper motor maintains pressure within a protected pressure range, provide electric control of fuel vapors flow from tank to canister during refueling, provide over pressure relief and over vacuum relief.

In another embodiment, the present invention provides an improved fuel tank isolation valve with a plunger having a top end inserted into a compression spring for OVR function followed by a cavity provided in the seal for OVR function and a bottom end which is threaded corresponding to threads provided in the axial cavity of stepper motor rotor. The plunger has an annular flange made to fit in the cover. The plunger movement is controlled in multiple steps to achieve controlled flow. Therefore, the present invention provides a light weighted improved fuel tank isolation valve having reduced size which is efficient in precisely controlling the flow in multiple steps using a stepper motor.

BRIEF DESCRIPTION OF THE DRAWING

The present invention will be described with reference to the following drawings. The drawings and the associated descriptions are provided to illustrate embodiments of the invention and not to limit the scope of the invention:

Fig. 1(a) is a perspective view of the fuel tank isolation valve in accordance with the present invention.

Fig. 1(b) is an exploded view of the fuel tank isolation valve 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.

The present invention provides an improved fuel tank isolation valve integrated with a stepper motor for precisely controlled plunger movement and inline function of over pressure relief (OPR) and over vacuum relief (OVR).

In another embodiment, the present invention provides an improved fuel tank isolation valve with a plunger having a top end inserted into a compression spring for OVR function followed by a cavity provided in the seal for OVR function and a bottom end which is threaded corresponding to threads provided in the axial cavity of stepper motor rotor. The plunger has an annular flange made to fit in the cover. The plunger movement is controlled in multiple steps to achieve controlled flow.

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 fuel tank isolation valve (10) comprises of canister port (13) fitted over compression spring (4) for OPR function which is mounted on seal sub assembly (6). A tank port (14) is positioned below the seal sub assembly (6) to connect to tank. A seal (2) for OVR function is provided and compression spring (1) is positioned under it. To hold the compression spring (1), a spring holder (8) is provided. A plunger (7) is provided that passes through the compression spring (1) and spring holder (8) and gets screwed in rotor (9) stepper motor (16).

Referring to Fig. 2(a), a sectional view of the fuel tank isolation valve (10) in accordance with the present invention is shown. In the fuel tank isolation valve (10) there is a compression spring (4) for OPR function is fitted over a seal sub assembly (6) with a sealing surface (5) for OPR function, a seal (2) for OVR function having an axial shaft at top end which gets fitted to the seal sub assembly (6) for OVR function and sealing surface (3) for inline functioning and a cavity at the bottom end, a compression spring (1) is positioned below the seal (2) for OVR function, a plunger at the top end passing through the compression spring (1) gets fitted into the axial cavity of the seal (2) for OVR function and the plunger (7) at the bottom end passing through a spring holder (8) gets fitted into a cavity provided in stepper motor rotor (9). The plunger (7) has a flange that gets fitted into the spring holder (8) and at the bottom end the plunger (7) has threads corresponding to threads provided in the cavity of the stepper motor rotor. There is an annular cavity provided between motor housing (12) and stepper motor rotor (9) for plurality of ball bearings (22) for reducing friction when stepper motor rotor (9) in working condition. The seal sub assembly (6) for OPR function is a rubber component whereas the sealing surface

(5) is the solid component on which rubber over molding is done. Sealing surface (5) forms a part of seal sub assembly (6) for OPR function.

Referring to Fig. 2(b), an enlarged sectional view of the fuel tank isolation valve in accordance with the present invention is shown. The sealing surface (5) is fitted over seal sub assembly (6) for OPR function to provide sealing for OPR function & refueling. Also, the seal sub assembly (6) for OPR function is extended to be in contact with sealing surface (3) of seal (2) to provide sealing for OVR function.

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 respectively. In the idle condition, the compression spring (1) for OVR function holds the seal (2) for OVR function, which is in contact with the sealing surface (3) and keeps the valve closed. On the other hand, the compression spring (4) keeps the seal sub assembly

(6) for OPR function downwards and attached to the sealing surface (5). Hence, both the openings for OVR and OPR are closed and canister port of the valve is not connected to the tank port of the valve. In the idle condition, the fuel vapors remain inside the fuel tank till the pressure inside the tank is within safety limit.

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 stepper motor is turned on and with stepwise rotation of stepper motor rotor, the plunger (7) screwed in the stepper motor rotor (9) move upwards making contact with the seal (2) for OVR function. Seal (2) for OVR function compresses rubber component of seal sub assembly (6) for OPR function and after a defined compression limit it makes contact with the solid component of the seal sub assembly (6) for OPR function and then with more movement of plunger (7), seal (2) for OVR function and the seal sub assembly (6) for OPR function to move upwards together with plunger (7) by compressing the compression spring (4) as depicted in Fig. 4(a). With plunger (7) moving upwards, the seal (2) for OVR function and seal sub assembly (6) for OPR function move upwards and hence the seal sub assembly (6) for OPR function detach itself from the sealing surface (5). Therefore, the tank port (14) is opened and connects to canister port (13) at the time of actuation by stepper motor (16) during refueling. In a first condition, with motor’s (16) leakage point + 2 rotations, a small linear stroke of plunger (7) 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 (16) i.e. at motor’s leakage point + 20 rotations, further stroke of plunger (7) 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 (16), the plunger (7) 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 (17) between the spring holder (8) and seal sub assembly (6) for OPR function and compression spring (4) for OPR function keeps the seal sub assembly (6) 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 (4) for OPR function and lifts the seal sub assembly (6) for OPR function upwards as depicted in Fig. 5(b). As the seal sub assembly (6) 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 (17) between the spring holder (8) and sub assembly (6) for OPR function and compression spring (1) for OVR function keeps the seal (2) for OVR function in contact with the seal sub assembly (6) 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 (2) for OVR and plunger (7) to use the full spring force for sealing without any dependency on threads provided in the bottom end of plunger (7). 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 (1) and the seal (2) for OVR function moves downwards due to stroke between seal (2) for OVR function and plunger (7) as depicted in Fig. 6(b). Here, the plunger (7) remains at its position and maximum movement of seal (2) for OVR function is equal to stroke provided between seal (2) for OVR function and plunger (7). As the seal (2) 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.

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 upwards and makes contact with seal for OVR function. Seal for OYR function compresses the rubber component of seal sub assembly for OPR function and after a certain compression limit it makes contact with the solid component i.e. sealing surface of seal sub assembly for OPR function and then with further plunger movement Seal (OVR) and Seal Sub Assy. (OPR) move upwards together with plunger by compressing the compression spring. 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.

Therefore, the present invention provides a light weighted improved fuel tank isolation valve having reduced size with a stepper motor in comparison to a solenoid valve is light and has reduced size. Further, with the use of stepper motor, the improved fuel tank isolation valve is efficient in precisely controlling the flow in multiple steps. 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

We claim:

1. An improved fuel tank isolation valve (10) with an integrated stepper motor (16) and an improved plunger (7) comprising:

(a) a valve housing (11) comprising a canister port (13) and a tank port (14) and including a compression spring (4), a seal sub assembly (6) for performing over pressure relief (OPR) function, a seal (2) and a compression spring (1) for performing over vacuum relief (OVR) function and said plunger (7);

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

(c) a spring holder (8); wherein, said sub seal assembly (6) includes a sealing surface (3) for inline functioning and a sealing surface (5) for performing over-pressure relief (OPR) function and refueling; said motor housing (12) includes said stepper motor (16), a stepper motor rotor (9) having an axial threaded cavity and plurality of ball bearings (22) positioned between said motor housing (12) and stepper motor rotor (9) for reducing friction while said stepper motor rotor (9) is in active condition; said plunger (7) having a top end (70) inserted into said compression spring (4) for over vacuum relief (OYR) function through an axial cavity provided in said seal (2) and is threaded in bottom end (71), screwed in a threaded cavity (90) in said rotor (9) to provide inline function; and said plunger (7) has an annular flange (72) made to fit in the cover (8) and movement of said plunger (7) is controlled in plurality of steps in order to achieve controlled flow.

2. The improved fuel tank isolation valve (10) with an integrated stepper motor (16) and an improved plunger (7) as claimed in claim 1, wherein said canister port (13) fitted over compression spring (4) for over-pressure relief (OPR) function that is mounted on said seal sub assembly (6) and said tank port (14) is positioned below said seal sub assembly (6).

3. The improved fuel tank isolation valve ( 10) with an integrated stepper motor (16) and an improved plunger (7) as claimed in claim 1, wherein said seal sub assembly (6) for over-pressure relief (OPR) function is extended to be in contact with said sealing surface (3) to provide sealing for over vacuum relief (OVR) function.

4. The improved fuel tank isolation valve ( 10) with an integrated stepper motor (16) and an improved plunger (7) as claimed in claim 1, wherein said seal (2) is having an axial shaft at top end assembled with a seal sub assembly (6) for performing over vacuum relief (OVR) function.

5. The improved fuel tank isolation valve ( 10) with an integrated stepper motor (16) and an improved plunger (7) as claimed in claim 1, wherein said compression spring (1) is associated with a spring holder (8).

6. The improved fuel tank isolation valve (10) with an integrated stepper motor (16) and an improved plunger (7) as claimed in claim 1 , wherein said plunger (7) passes through said compression spring (1) and spring holder (8) and gets screwed in said stepper motor rotor (9).

7. The improved fuel tank isolation valve (10) with an integrated stepper motor (16) and an improved plunger (7) as claimed in claim 1, wherein said compression spring (4) for over-pressure relief (OPR) function is fitted over said seal sub assembly (6) with said sealing surface (5).

8. The improved fuel tank isolation valve (10) with an integrated stepper motor (16) and an improved plunger (7) as claimed in claim 1, wherein the seal sub assembly (6) for OPR function is a rubber component and sealing surface (5) is a solid component over which rubber over molding is done.

9. The improved fuel tank isolation valve (10) with an integrated stepper motor (16) and an improved plunger (7) as claimed in claim 1, wherein between said motor housing (12) and stepper motor rotor (9) an annular cavity is provided for said ball bearings

(22).

10. The improved fuel tank isolation valve (10) with an integrated stepper motor (16) and an improved plunger (7) as claimed in claim 1, wherein said valve (10) in OVR condition provides a stroke between said seal (2) and said plunger (7) to use full spring force for sealing without any dependency on threads provided in the bottom end of said plunger (7).

11. The improved fuel tank isolation valve (10) with an integrated stepper motor (16) and an improved plunger (7) 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 (OYR).