Fuel vapor switches and ventilation valves for internal combustion engines

Abstract

The invention relates to a fuel vapor switch and ventilation valve (10) for an internal combustion engine (26), the fuel vapor switch and ventilation valve having an electromagnet (28), a first connection part (12) and a second connection part (16), a valve body (62), the valve body being coupled to an armature (36) of the electromagnet (28) and comprising a first bearing surface (84) and a second bearing surface (90), the valve body (62) being able to be lowered onto a first valve seat (82) arranged between the first connection part (12) and the second connection part (16) and being able to be lifted from the first valve seat (82) by means of the first bearing surface, and the valve body (62) being able to be moved relative to a second valve seat (92) by means of the second bearing surface, the second valve seat being able to be axially moved and being loaded in the direction of the valve body (62) by means of a spring (122). In addition, in order to be able to limit the flow to the activated carbon filter, according to the invention, the second valve seat (92) is arranged on a flow restriction element (94).

Description

Technical Field

[0001] The present invention relates to a fuel vapor switch and ventilation valve for an internal combustion engine, which includes an electromagnet, a first connecting part, a second connecting part, and a valve body. The valve body is connected to the armature of the electromagnet and includes a first supporting surface. The valve body can be lowered to a first valve seat arranged between the first connecting part and the second connecting part and lifted from the first valve seat by means of the first supporting surface. The valve body also includes a second supporting surface. The valve body can be moved relative to a second valve seat by means of the second supporting surface. The second valve seat can be axially displaced and is loaded in the direction of the valve body by a spring. Background Art

[0002] The fuel vapor switch and ventilation valve acts as a shut-off valve and pressure relief valve and is arranged fluidically between the vehicle's fuel tank and an activated carbon filter for absorbing fuel vapors, compensating for pressure fluctuations in the fuel tank with fuel vapors. In the event of overpressure or underpressure in the fuel tank, the pressure is reduced by venting the activated carbon filter in the event of overpressure via a mechanical bypass function, and in the event of underpressure, the underpressure in the fuel tank is limited or compensated by ventilation.

[0003] Furthermore, for safety reasons, it is necessary to allow the valve to be actively actuated so that in the event of a failure in the fuel tank pressure control, the passage between the fuel tank and the activated carbon canister can be opened to avoid an implosion or explosion.

[0004] For example, the fuel vapor switch and the ventilation valve must be opened before refueling and directly during refueling to ensure that, on the one hand, fuel vapor does not reach the user due to overpressure when the fuel tank cap is opened, and on the other hand, the pressure in the fuel tank does not increase during refueling.

[0005] Various valves are known that combine one or more of these functions. For example, DE 10 2010 044336 A1 describes a valve device in which a switching valve can be actuated by an electromagnet to establish a connection between a fuel tank and an activated carbon filter. The valve body of the valve comprises a second bearing surface with which the valve body abuts against a pressure relief valve. The pressure reducing valve bears against the valve body under spring load, thus closing the central channel in the valve body if there is no overpressure in the fuel tank. In addition, if there is underpressure in the fuel tank, the valve body can be moved from the valve seat against the spring element, thus venting the fuel tank. Thus, with just one valve, an active switching device for a fluid connection between the fuel tank and the activated carbon filter can be established, and in addition, ventilation or venting can be established in the event of overpressure or underpressure via defined switching points.

[0006] However, it has been found that it is also necessary to limit the total flow through the valve, since the activated carbon filter has only a limited absorption capacity per unit time. Thus, by reducing the maximum flow through the valve, the size of the activated carbon filter can also be reduced. Summary of the invention

[0007] The technical problem to be solved by the present invention is therefore to provide a fuel vapor switch and ventilation valve which, in addition to active and passive ventilation of the fuel tank, can also reliably limit the total flow into the activated carbon filter without requiring additional valves or increasing the installation space. Therefore, a flow rate that depends on the applied pressure difference must be ensured.

[0008] The flow limitation is ensured without the use of additional components in that a second valve seat is arranged on the flow limiting element, which provides a reduced flow cross section when the overpressure at the first connection increases. Conversely, the control body also ensures a passive overpressure function. It is also used to limit the flow rate, so there is neither an increased installation space requirement nor a greater number of components. The overpressure function is achieved by applying pressure from the fuel tank to the surface of the flow restriction element in the second valve seat, and once the force generated by the pressure difference exceeds the force of the spring, the flow restriction element will rise from the second valve seat accordingly. In addition to active opening and closing, the valve body also ensures a passive underpressure function, because when underpressure occurs in the fuel tank, the pressure difference on the valve body has an opening effect, so that when the force generated by the pressure difference exceeds the spring force of the spring element acting on the valve body, the valve body is lifted from the first valve seat, so that the fuel tank is ventilated.

[0009] Preferably, the flow restriction element comprises a control body which can be moved into a nozzle arranged in the housing part of the second connection, wherein the spring loads the flow restriction element in the direction outward from the nozzle. By using a nozzle, the area available for flow can be changed depending on the applied pressure difference, so that a smaller flow area can be obtained at a greater pressure difference, so that the volume flow to the activated carbon filter can be limited even at high pressure differences.

[0010] If the flow restriction element comprises a spherical or conical flow-around surface arranged opposite to the nozzle inner surface, the equalizing effect of the throughflow to the activated carbon filter can be further increased. In this way, a nearly constant throughflow can be achieved at different pressure differences.

[0011] Furthermore, it is advantageous that a radially outer ring is provided on the flow restriction element, the spring abutting against the ring, wherein one or more flow openings are formed radially between the ring and the second valve seat and / or the spherical or conical flow surface, through which the fuel vapor can flow from one end of the flow restriction element to the other end of the flow restriction element. The ring also serves as a bearing surface for the spring, so that the flow restriction element is uniformly stressed in the circumferential direction in the direction of the electromagnet.

[0012] In another embodiment, a stopper is provided on the flow housing portion of the second connection, against which the flow restriction element rests in a state in which the gap between the spherical or conical flow surface of the flow restriction element and the inner surface of the nozzle is minimized. In this position, the fuel vapor can still flow through the flow opening and then through the gap between the flow restriction element and the nozzle, because there is still a gap there, through which a defined flow can flow from the fuel tank to the activated carbon filter, thereby preventing overloading of the activated carbon filter.

[0013] In order to prevent radial displacement of the flow restriction element, an axial groove is designed on the ring, and the end of the spring abutting on the ring extends into the axial groove, so that the flow restriction element is maintained in its radial position.

[0014] Preferably, a through-flow opening is designed on the valve body, which leads to the inside of the second valve seat in radial direction. Through the through-flow opening, when the internal pressure of the fuel tank increases, the pressure from the fuel tank to the flow restriction element opening can act on the inner surface of the flow restriction element.

[0015] It is also advantageous if the valve body is cardanically fastened to a valve rod which is fastened to the armature. This type of connection allows the valve body to be tilted slightly toward the armature, thus ensuring a circumferential and therefore tight support of the valve body on the first valve seat, even in the event of inaccurate assembly or slight deposits.

[0016] Preferably, the valve body comprises a carrier element connected to the valve stem and made of solid material, and a sealing element with which the valve body can be lowered onto the two valve seats, the sealing element being made of elastic material. The carrier element ensures sufficient rigidity in the area of ​​the connection between the valve body and the valve stem, while on the other hand, the elasticity of the sealing element ensures a high degree of sealing when the sealing element is placed on the two valve seats.

[0017] In a preferred further development of the present invention, the spring element is clamped between the armature and the magnetic core of the electromagnet. Thus, the spring element is not arranged in a direct flow region and the spring can be well guided in the magnetic core, thus reliably avoiding bending.

[0018] In another alternative design of the present invention, the spring element is sandwiched between the electromagnet and the valve body and surrounds the valve stem, which prevents bending. In this embodiment, the assembly of the electromagnet is simplified.

[0019] In another embodiment, the spring element abuts against a radial extension of a sliding bushing of the electromagnet, in which the armature is guided and by which the electromagnet is sealed relative to the connection. In this way, a large diameter helical spring can be used, which abuts against a non-magnetizable element so that no magnetic force is transmitted. Since it is arranged between the extension of the sliding bushing and the armature, the movement of the spring element in the radial direction is limited, thereby preventing the occurrence of lateral sliding. On the one hand, the sliding bushing ensures low-friction movement of the armature, and on the other hand, it protects the coil of the electromagnet from being penetrated by fuel vapor. For this purpose, a seal is preferably also arranged between the sliding bushing and the outer cover of the electromagnet, and in addition, the sliding bushing is configured as a bowl-shaped closing part at its end away from the valve body.

[0020] Advantageously, the spring is clamped between the ring and the support surface of the flow housing of the second connection. The support surface can also include an inner annular projection, which forms a nozzle inside, whereby the spring is also radially restricted in its freedom of movement at its end resting against the flow housing.

[0021] Preferably, the armature of the electromagnet, the valve body and the flow restriction element are arranged axially one behind the other and can move along a common axis, thereby reducing the required radial space. In addition, all functions of the valve are realized by displacement along this axis.

[0022] Thus, a fuel vapor switch and a ventilation valve are provided, with which a connection between the activated carbon filter and the fuel tank can be actively established or closed, wherein the connection is established by the pressure difference that exists at certain operating points, i.e. at an excessively high pressure relative to the atmosphere in the fuel tank or at an excessively low pressure relative to the atmosphere in the fuel tank. Furthermore, a flow control element according to the invention can prevent fuel vapor from flowing out of the fuel tank too quickly and into the activated carbon filter, by limiting the flow at all pressures to a maximum flow corresponding to the flow of fuel vapor that the activated carbon filter can absorb or store, respectively. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] An exemplary embodiment of a fuel vapor switch and ventilation valve according to the invention for an internal combustion engine, in particular for a hybrid drive, is shown in the drawing and described below.

[0024] Figure 1 A side view of a fuel vapor switch and ventilation valve according to the present invention is shown, wherein the connected components are schematically illustrated.

[0025] Figure 2The cross-sectional view shows Figure 1 FIG. 1 is a side view of a fuel vapor switch and a ventilation valve according to the present invention. DETAILED DESCRIPTION

[0026] like Figure 1 As shown, the fuel vapor switch and ventilation valve 10 according to the present invention comprises a first connection portion 12 and an axial second connection portion 16 extending transversely from a housing 14 of the fuel vapor switch and ventilation valve 10. The transverse first connection portion 12 is connected to a fuel tank 18, while the axial second connection portion 16 is connected to an activated carbon filter 20. From the activated carbon filter 20, a conduit leads to the atmosphere through a fuel vapor outlet valve 22, or to an internal combustion engine 26 through a second conduit in which a purge valve 24 is arranged, where fuel vapor can be supplied for combustion.

[0027] Figure 2The structure of the fuel vapor switch and ventilation valve 10 can be seen in FIG. The fuel vapor switch and ventilation valve includes an electromagnet 28, which serves as an actuator and includes a coil 32 wound on a coil frame 30, an internal magnetic core 34, an axially movable armature 36, a yoke 38 radially surrounding the coil 32, and a rear cover plate 40 arranged at both axial ends of the coil frame 30, which constitute an electromagnetic circuit. The electromagnet 28, especially the yoke 38, is coated with a plastic material to form an actuator accommodating portion 42 of the housing 14, which also includes a plug 44 and a fastening eye 46, and at the end opposite to the magnetic core, includes an axial opening 48, and a sliding bushing 50 guiding the armature 36 is inserted into the opening. The sliding bushing 50 is made of non-magnetic material and is designed in the shape of a bowl, wherein the bottom 52 abuts against the magnetic core 34. The main guide area of ​​the sliding bushing 50 is surrounded by a soft magnetic bushing 54, which is pressed into the rear cover plate 40 and the coil frame 30. The sliding bushing 50 comprises a radial extension 55, from which an extension region 56 extends at its open end, which is arranged opposite to the wall of the actuator receiving part 42 defining the opening 48, wherein a sealing ring 58 is arranged between the extension region 56 of the sliding bushing 50 and the wall defining the opening 48, by which the fuel vapor is prevented from penetrating in the direction of the coil 32. A first receiving part 60 is designed on the actuator receiving part 42, which forms the first connection part 12 and in which a valve body 62 can move, and the valve body 62 is coupled to the armature 36 by connecting a valve stem 64 to the armature 36, and the valve body 62 is fixed to the valve stem in a cardanic manner. The valve stem 64 is fixed to the armature 36 by pushing the valve stem 64 through the through hole 66 on the armature 36 until the valve stem with the extension 68 axially abuts against the end of the armature 36 facing the valve body 62. In this state, the valve stem 64 projects from the armature 36 at the opposite end and can be deformed there so that a type of rivet head 70 is located in a circular recess 72 on the side of the armature 36 facing the magnetic core 34. On the opposite side, the valve stem 64 also comprises a type of rivet head 74, which projects into the valve body 62 so that the valve body 62 abuts against the flat end of the rivet head 74 on the armature side, for which purpose an opening 76 is provided in the valve body 62, the diameter of which substantially corresponds to the diameter of the valve stem 64. The round side of the rivet head 74 is arranged opposite a projection 78 which projects radially into the interior of the valve body 62, so that the valve body 62 can only be moved slightly axially relative to the valve stem 64.

[0028] On the one hand, the spring element 80 pre-tensions the valve body 62 on the flat side of the rivet head 74, and on the other hand, by clamping the spring element 80 between the valve body 62 and the extension 55 of the sliding bushing 50, the valve body 62 together with the armature 36 is pre-tensioned on the first valve seat 82, which is arranged on the first flow accommodating component 60.

[0029] In the closed state, the valve body 62 abuts against the first valve seat 82 around the throughflow opening 87 with a radially outer first bearing surface 84, which is designed as a sealing lip of a sealing element 86. The sealing element 86 consists of an elastic material, in particular an elastomer, and is fixed to a carrier element 88, through which the connection to the valve rod 64 is also produced, so that the projection 78 and the opening 76 are formed on the carrier element 88. The carrier element 88 covers the sealing element 86 as much as possible in the direction of the armature 36 and surrounds it at least partially in the radial direction. In addition to the first bearing surface 84, the sealing element 86 also includes a further second bearing surface 90, which is located radially inside the first bearing surface 84, which is also designed as a sealing lip and is axially closer to the armature 36 than the first bearing surface 84, and the sealing element 86 can be lowered onto the second valve seat 92 with this second bearing surface.

[0030] The second valve seat 92 is axially movable and is formed according to the invention on a flow restriction element 94 which, when resting on the second bearing surface 90 , closes a flow opening 96 formed radially within the second bearing surface 90 on the sealing element 86 and the valve body 62 .

[0031] The flow restriction element 94 is designed in two parts and comprises a valve seat portion 98 on which the second valve seat 92 is formed, and a control body 100, into which a pin-shaped portion of the valve seat portion 98 extends for fixing the control body 100 on the valve seat portion 98. The control body 100 comprises a spherical flow-around surface 102 corresponding to a nozzle 104 formed on an inner surface 106 of a second flow accommodating member 108, which is connected to the first flow accommodating member 60 and forms the second axial connection portion 16.

[0032] The flow restriction element 94 comprises webs 110 which extend radially outward from the control body 100 and connect the flow surface 102 to a radially outer ring 112. Thus, a plurality of flow openings 114 are formed between the webs 110 and between the flow surface 102 and the ring 112.

[0033] The second flow accommodating member 108 comprises a radially inner annular projection 116, on the inner side of which the nozzle 104 is formed and whose axial end serves as a stopper 118 for the movement of the flow restriction element 94, and when the ring 112 abuts against the stopper 118, it can only open a narrow gap 120 between the flow-around surface 102 and the nozzle 104. A spring 122 sandwiched between an axial groove 124 of the ring 112 and a bearing surface 126 on the second flow accommodating member 108 loads the flow restriction element 94 in the direction of the valve body 62 and away from the stopper 118, so that the spring 122 presses the second valve seat 92 toward the valve body 62 and loads the control body 100 starting from the smallest cross section of the nozzle 104.

[0034] The function of the valve is now such that the valve body 62 rests in the normal state against the first valve seat 82 and the second valve seat 92 , so that no flow occurs between the connections 12 , 16 .

[0035] If, for example, due to heating, the pressure in the fuel tank 18 and therefore in the first connection 12 rises to, for example, more than 0.3 bar above atmospheric pressure, the second valve seat 92 is lifted off the second bearing surface 90 of the valve body 62, because at this pressure, the force acting on the flow restriction element 94 due to the pressure difference is greater than the elastic force of the spring 122. As a result, fuel vapor flows from the first connection 12 through the flow opening 96 in the valve body 62 and the flow opening 87 in the first valve seat 82 and through the flow opening 114 between the web 110 and the gap 120 to the second connection 16 and thus in the direction of the activated carbon filter 20, thereby reducing the pressure in the fuel tank 18. At very high pressures, which may result in a volume flow that can no longer be absorbed by the activated carbon filter 20, the function of the flow restriction element 94 begins to take effect. At very high pressure differences, the flow restriction element is displaced until it abuts against the stop 118. In this position, only a minimum gap 120 is opened between the control body 100 and the nozzle 104, which allows a maximum flow rate corresponding to the maximum permissible flow rate of the activated carbon filter 20 (e.g., about 220 l / min). In other states, the flow rate through the gap changes depending on the applied pressure difference, i.e., as the pressure decreases, a larger flow cross section is available.

[0036] If, for example, the pressure in the fuel tank 18 and therefore the pressure at the first connection 12 drops to an underpressure of, for example, less than -0.1 bar compared to the atmosphere due to the fuel tank being emptied, the valve body 62 is lifted off the first valve seat 82, since at this pressure the force acting on the valve body 62 due to the pressure difference is greater than the spring force of the spring element 80. As a result, air flows from the second connection 16 through the gap 120 between the control body 100 and the nozzle 104 and through the throughflow opening 87 and radially between the valve body 62 and the first valve seat 82 to the first connection 12, so that a pressure balance is formed in the fuel tank. In this state, the flow restriction element 94 continues to abut against the second bearing surface 90 of the valve body 62 and is thus moved together in the direction of the electromagnet 28 under the action of the spring 122.

[0037] Furthermore, the fuel vapor switch and ventilation valve 10 can be actively activated by energizing the electromagnet 28. This can be done, for example, before starting a refueling process to ensure that there is no overpressure or underpressure in the fuel tank 18 at this time. In this case, the state of the valve 10 produced by the lift is the same as a high underpressure situation in the fuel tank 18. Air can flow from the second connection 16 to the first connection 12 and fuel vapor can flow in the opposite direction, wherein the function of the flow restriction element 94 is maintained.

[0038] Thus, a fuel vapor switch and ventilation valve 10 is provided which can reliably eliminate underpressure and overpressure in the fuel tank 18 and additionally limit the flow of fuel vapor to a maximum permissible value. Active switching is also possible. All these functions are realized in a small-sized valve with a minimum number of parts.

[0039] It is obvious that various modifications are possible compared to the exemplary embodiment without departing from the scope of protection of the independent claims. In addition to different designs of the housing separation, the flow restriction element 94, the electromagnet 28 or the valve body 62 can also have different designs. The switching point can be adjusted individually depending on the application using the existing spring. The same applies to the maximum permissible flow, which can be adjusted by constructively modifying the nozzle 104 and / or the flow restriction element 94.

Claims

1. A fuel vapor switch and ventilation valve (10) for an internal combustion engine (26), the fuel vapor switch and ventilation valve comprising: an electromagnet (28), a first connection portion (12), the first connection portion (12) being connected to a fuel tank (18) of an internal combustion engine, A second connecting portion (16), A valve body (62) is coupled to the armature (36) of the electromagnet (28) and has a first bearing surface (84) and a second bearing surface (90), the valve body (62) can be lowered onto a first valve seat (82) arranged between the first connection part (12) and the second connection part (16) with the first bearing surface and lifted from the first valve seat (82), and the valve body (62) can be moved relative to the second valve seat (92) with the second bearing surface, the second valve seat can be axially moved and is loaded in the direction of the valve body (62) by a spring (122), It is characterized in that The second valve seat (92) is arranged on a flow restriction element (94) which provides a reduced flow cross section when the overpressure at the first connection (12) increases.

2. A fuel vapor switch and ventilation valve (10) for an internal combustion engine (26) according to claim 1, It is characterized in that The flow restriction element (94) comprises a control body (100) which is movable into a nozzle (104) arranged in a flow housing portion (108) of the second connection portion (16), the spring (122) loading the flow restriction element (94) in a direction outward from the nozzle (104).

3. A fuel vapor switch and ventilation valve (10) for an internal combustion engine (26) according to claim 2, It is characterized in that The flow restriction element (94) includes a spherical or conical flow-around surface (102) disposed opposite to an inner surface (106) of the nozzle (104).

4. A fuel vapor switch and ventilation valve (10) for an internal combustion engine (26) according to claim 3, It is characterized in that A radially outer ring (112) is formed on the flow restriction element (94), and the spring (122) abuts against the ring, wherein one or more flow openings (114) are formed radially between the ring (112) and the second valve seat (92) and / or between the spherical or conical flow surface (102).

5. A fuel vapor switch and ventilation valve (10) for an internal combustion engine (26) according to claim 3 or 4, It is characterized in that A stopper (118) is formed on the flow housing portion (108) of the second connecting portion (16), and the flow restriction element (94) abuts against the stopper so that a gap (120) between the spherical or conical flow-around surface (102) of the flow restriction element (94) and the inner surface (106) of the nozzle (104) is minimized.

6. A fuel vapor switch and ventilation valve (10) for an internal combustion engine (26) according to claim 4, It is characterized in that An axial groove (124) is formed on the ring (112), and one end of the spring (122) abutting against the ring (112) extends into the axial groove.

7. A fuel vapor switch and ventilation valve (10) for an internal combustion engine (26) according to claim 1, It is characterized in that A through-flow opening (96) is formed on the valve body (62), and the through-flow opening leads to the radial inside of the second valve seat (92).

8. A fuel vapor switch and ventilation valve (10) for an internal combustion engine (26) according to claim 1, It is characterized in that The valve body (62) is fastened in a cardanic manner to a valve rod (64), which is fastened to the armature (36).

9. A fuel vapor switch and ventilation valve (10) for an internal combustion engine (26) according to claim 8, It is characterized in that The valve body (62) comprises a carrier element (88) fixed to the valve stem (64), the carrier element being made of a solid material and comprising a sealing element (86), the valve body (62) being able to be lowered onto the first valve seat (82) and the second valve seat (92) with the sealing element, the sealing element being made of an elastic material.

10. A fuel vapor switch and ventilation valve (10) for an internal combustion engine (26) according to claim 1, It is characterized in that A spring element (80) is sandwiched between the armature (36) and the core (34) of the electromagnet (28).

11. A fuel vapor switch and ventilation valve (10) for an internal combustion engine (26) according to claim 8 or 9, It is characterized in that A spring element (80) is sandwiched between the electromagnet (28) and the valve body (62) and surrounds the valve stem (64).

12. A fuel vapor switch and ventilation valve (10) for an internal combustion engine (26) according to claim 11, It is characterized in that The spring element (80) abuts against a radial extension (55) of a sliding bushing (50) of the electromagnet (28), in which the armature (36) is guided and by which the electromagnet (28) is sealed relative to the first connection (12) and the second connection (16).

13. A fuel vapor switch and ventilation valve (10) for an internal combustion engine (26) according to claim 4, It is characterized in that The spring (122) is clamped between the ring (112) and a bearing surface (126) of the flow housing portion (108) of the second connecting portion (16).

14. A fuel vapor switch and ventilation valve (10) for an internal combustion engine (26) according to claim 1, Features The armature (36) of the electromagnet (28), the valve body (62) and the flow restriction element (94) are arranged axially one behind the other and are movable along a common axis.

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