阅读说明：本技术 用于燃料截止阀的限流装置 (Flow-limiting device for fuel shut-off valve ) 是由 朱瑞·瓦格纳 蒂姆·万采克 杰西卡·塔玛希 于 2019-02-20 设计创作，主要内容包括：本发明涉及一种用于燃料截止阀(18)的限流装置(20),包括：限流元件(36),所述限流元件被布置在流道(34)中；弹簧(38),所述弹簧在限流元件(36)上施加力,所述力与由流体压力产生的力方向相反,其中,限流元件(36)在第一极限位置处比在第二极限位置处开放出更大的通流横截面,在所述第一极限位置处,弹簧(38)作用在限流元件(36)上的力大于由流体压力产生的力,在所述第二极限位置处,作用在限流元件(36)上的由流体压力产生的力大于弹簧(38)的力。为了保护下游的阀免于过载,根据本发明建议,通流横截面通过限流元件(36)和环绕的流机壳体(32)之间的圆周间隙(80)被布置在两个极限位置之间。其中,限流元件(36)和环绕的流机壳体(32)之间的开放横截面沿轴向持续减小直至最窄的开放横截面,且从所述最窄的开放横截面起沿轴向持续增大。(The invention relates to a flow-limiting device (20) for a fuel shut-off valve (18), comprising: a flow restriction element (36) disposed in the flow passage (34); a spring (38) exerting a force on the flow-limiting element (36) which is in the opposite direction to the force generated by the fluid pressure, wherein the flow-limiting element (36) opens up a larger flow cross section in a first extreme position in which the force exerted by the spring (38) on the flow-limiting element (36) is greater than the force generated by the fluid pressure, than in a second extreme position in which the force generated by the fluid pressure exerted on the flow-limiting element (36) is greater than the force of the spring (38). In order to protect the downstream valve from overloading, it is proposed according to the invention that the flow cross section is arranged between the two limit positions by means of a circumferential gap (80) between the flow-limiting element (36) and the surrounding flow housing (32). Wherein the open cross section between the flow-limiting element (36) and the surrounding flow housing (32) decreases continuously in the axial direction up to a narrowest open cross section and increases continuously in the axial direction from said narrowest open cross section.)

1. A flow restricting device (20) for a fuel shut-off valve (18), comprising:

a fluid housing (32) forming a flow passage (34);

a flow restriction element (36) disposed in the flow passage (34);

a spring (38) exerting a force on the flow restriction element (36) in an opening direction of the flow restriction element (36) opposite to a force generated by fluid pressure acting on the flow restriction element (36) in a closing direction,

wherein the flow-limiting element (36) opens up a larger flow cross section in a first extreme position in which the force of the spring (38) acting on the flow-limiting element (36) is greater than the force generated by the fluid pressure, than in a second extreme position in which the force generated by the fluid pressure acting on the flow-limiting element (36) is greater than the force of the spring (38),

it is characterized in that the preparation method is characterized in that,

the flow cross section is arranged in two extreme positions by means of a circumferential gap (80) between the flow limiting element (36) and the surrounding flow housing (32), wherein the open cross section between the flow limiting element (36) and the surrounding flow housing (32) decreases continuously in the axial direction to a narrowest open cross section and increases continuously in the axial direction from said narrowest open cross section.

2. Flow-limiting device for a fuel shut-off valve according to claim 1, characterized in that the function of the opening cross-section with respect to the length of the flow-limiting element (36) is differentiable from the inflow edge (64) to the outflow edge (78) of the flow-limiting element (36).

3. Flow-limiting device for fuel shut-off valves according to one of the preceding claims, characterized in that the flow housing (32) has the shape of a venturi nozzle (60), wherein the flow-limiting element (36) projects out of the narrowest cross section of the venturi nozzle (60) into the adjoining diffuser (62).

4. Flow-limiting device for a fuel shut-off valve according to one of the preceding claims, characterized in that the radially outer wall (70) of the flow-limiting element (36) is designed to taper off.

5. The flow-limiting device for a fuel shut-off valve according to claim 4, characterized in that the circulating outer wall (70) of the flow-limiting element (36) is configured from the inflow edge (64) to the outflow edge (78) as a flow body (68) having a first convex portion (72), a second concave portion (74) adjoining the first convex portion, and a third convex portion (76) adjoining the second concave portion.

6. Flow-limiting device for fuel shut-off valves according to claim 5, characterized in that the flow body (68) is rotationally symmetrical.

7. The flow restriction device for a fuel shut-off valve according to any one of the preceding claims, characterized in that the second concave portion (74) of the flow body (68) of the flow restriction element (36) is arranged in the narrowest cross section of the venturi nozzle (60) of the flow housing (32) in both of the extreme positions.

8. The flow-limiting device for fuel shut-off valves according to one of the preceding claims, characterized in that at least three webs (46) are designed on the flow-limiting element (36), which webs project radially outward through radial gaps (44) extending to the circumference onto the inner wall (40) of the flow housing (32) and on which the force of the spring (38) acts.

9. The flow-limiting device for fuel shut-off valves according to one of the preceding claims, characterized in that the spring (38) is arranged in a preloaded manner between an inner wall (40) of the flow housing (32) and an outer wall (42) of the flow housing (32).

10. Flow-restricting device for a fuel shut-off valve according to any one of claims 2 to 9, characterized in that the flow-restricting element (36) has a rotationally symmetrical recess (66) extending from the inflow edge (64) to a radially inner portion of the flow-restricting element (36).

Technical Field

The invention relates to a flow-limiting device for a fuel shut-off valve, comprising: a flow housing forming a flow passage; a flow restriction element disposed in a flow passage; a spring exerting a force on the flow-limiting element in an opening direction of the flow-limiting element, which force is opposite to a force, which is generated by a fluid pressure, acting on the flow-limiting element in a closing direction, wherein the flow-limiting element is in a first extreme position in which the spring force acting on the flow-limiting element is greater than the force generated by the fluid pressure, opening a larger flow cross section than in a second extreme position in which the force generated by the fluid pressure acting on the flow-limiting element is greater than the spring force.

Such a flow restriction device is used in a tank venting system to ensure that the pressure does not become too high due to evaporation of fuel in the tank. For this purpose, the fuel vapors are conveyed via the tank vent valve into an activated carbon filter container, by means of which the hydrocarbons contained in the vapors are stored in order to prevent the hydrocarbons contained in the vapors from escaping into the environment. The activated carbon filter is regenerated by the engine air drawn in from the intake pipe, or by a separate secondary air blower. By means of the flow restriction it is ensured that the downstream valve is not subjected to excessive pressures which could lead to malfunctions.

In order to achieve this, mechanical systems for throttling the volume flow are known, in which a spring is used as the force application element, the spring determining the minimum actuating force resulting from the existing volume flow. The actuating force is thereby generated by the inflow of the end face of the flow-limiting element as a force which counteracts the spring force at the stagnation point.

Correspondingly, known flow-limiting devices have a switching point at which the available flow cross section is reduced by displacing the flow-limiting element when the pressure rises too quickly, in order to reduce the volume flow through. However, in most known embodiments, very high pressure losses occur at low flow rates compared to before the switching point of the flow restriction.

A fuel shut-off valve with a flow restrictor is known, for example, from EP 2665913B 1, in which the pressure losses are reduced at low volumetric flows. When the shut-off valve is open, fuel vapor can flow through the inner small nozzle of the flow restrictor and an additional cross section, which is controlled by an axially movable closing element. If the pressure difference between the inlet and the outlet is too great, the force acting on the closure element exceeds the force of the counter-spring and the closure element is pressed against its valve seat, so that only the inner cross-section of the nozzle can still flow through, whereby the maximum flow is reliably limited.

However, this embodiment has the problem that the switching point of the restrictor is very difficult to set, since in the open state of the restrictor, when a flow passes through the outside of the too small inner cross section, high pressure losses occur as a result of the increase in the eddy currents, which can result in the unambiguous opening time point not being able to be determined from the existing stagnation pressure.

Disclosure of Invention

The object of the present invention is therefore to provide a flow restriction device, in particular for a fuel shut-off valve, in which, on the one hand, the total pressure loss is low and, on the other hand, the switching point and the maximum volume flow can be unambiguously determined. Furthermore, switching should be possible even at relatively low flow rates without the spring force of the spring element having to be reduced too much.

The object is achieved by a current limiting device having the features of claim 1.

Since the circumferential gap between the flow restriction element and the surrounding flow housing forms a flow cross section within two limit positions, wherein the opening cross section between the flow restriction element and the surrounding flow housing decreases in the axial direction to the narrowest opening cross section and increases in the axial direction from the narrowest opening cross section, a pure nozzle flow is established at the two limit positions, wherein no pressure loss step occurs when opening or closing the flow restriction element, whereby a clear switching point can be determined. Therefore, first of all, an acceleration of the low pressure loss is achieved between the two surfaces, by which means a low pressure region is created to increase the pressure difference and thus delay the opening time point until only a lower absolute pressure is present at the inflow edge. By means of a subsequent gradual pressure release, the total pressure loss is kept very low. By this design, the switching behavior can be adjusted very precisely.

The function of the open cross-section with respect to the length of the flow-limiting element is preferably differentiable from the inflow edge to the outflow edge of the flow-limiting element, which means that no cross-sectional steps occur which lead to the formation of vortices. Accordingly, the total pressure loss that occurs will be significantly reduced.

Furthermore, it is advantageous if the flow housing has the shape of a venturi nozzle, wherein the flow restriction element projects out of the narrowest cross section of the venturi nozzle into the adjoining diffuser. This also results in a flow rate reduction with low pressure loss. The pressure difference between the front side and the rear side of the flow restriction is increased again by the venturi nozzle, so that the opening force can be reduced with the same spring characteristic, since the stagnation pressure area and the spring characteristic are no longer the only variables for determining the opening pressure. Accordingly, the flow restriction can be made smaller, since a higher opening force is applied at the same diameter.

The radially outer wall of the flow restriction is preferably designed to taper off, thereby reducing the flow resistance. The rotational speed of the pump can therefore be reduced without switching the flow-limiting element (i.e. with a larger opening cross section when delivering gas through the pump) at the same volume flow rate, and the current consumption of the pump is therefore reduced.

In a preferred embodiment of the invention, the radially outer wall of the flow-limiting element, from the inflow edge to the outflow edge, forms a flow body with a first convex section, a second concave section adjoining the first convex section, and a third convex section adjoining the second concave section. This allows a reduced switching pressure to be achieved with low pressure losses and simple production.

It is particularly advantageous if the flow body is rotationally symmetrical so that it is suitable for conventional round pipes, without a different flow occurring in the cross section.

In a preferred embodiment, the second concave section of the flow body of the flow restriction is arranged in both extreme positions within the narrowest cross section of the venturi nozzle of the fluid housing. This design also results in a preferred swirl-free flow in both switching states.

Furthermore, at least three webs are advantageously provided on the flow restriction element, which webs project radially outward through a radial gap extending to the circumference onto the inner wall of the flow housing and the spring force acts on the webs. Accordingly, the flow-limiting element is fixed and clamped outside the flow-through region, which further reduces the pressure losses. Furthermore, the flow restriction element is securely fixed in the flow channel.

It is furthermore advantageous for the spring to be arranged in a preloaded manner between the inner wall of the flow housing and the outer wall of the flow housing, since in this embodiment on the one hand a reliable guidance of the spring is achieved and on the other hand the spring is also arranged outside the through-flow region. In this way, the assembly of the spring is also simplified.

In order to establish a centrally designed stagnation point, the flow-limiting element has a rotationally symmetrical recess extending from the inflow edge into a radially inner portion of the flow-limiting element.

A current limiting device is thus achieved, by means of which the switching point can be set precisely and the pressure loss minimized and the opening pressure reduced, so that the size of the current limiting element can also be reduced.

Drawings

Embodiments of the flow-limiting device according to the invention are shown in the drawings and an example of the use of the flow restrictor as a fuel shut-off valve will be described below, wherein other uses are of course possible.

Fig. 1 schematically shows a fuel tank venting system of an internal combustion engine in an exploded perspective view.

Fig. 2 shows a section through a flow-limiting device according to the invention in a first switching state in a side sectional view.

Fig. 3 is a cross-section in a side sectional view of the current limiting device of the present invention shown in fig. 2 in a second switching state.

Detailed Description

The fuel tank venting system shown in fig. 1 comprises a fuel tank 10 in which fuel is stored and which can be filled through a filler pipe 12. In the fuel tank is a fuel pump 14 by means of which the internal combustion engine (not shown) can be supplied with fuel. An exhaust line 16 branches off from the filler pipe 12, in which a fuel shut-off valve 18 and a downstream flow restriction 20 form a unit as a tank pressure valve 22. The exhaust pipe 16 opens into an activated carbon filter container 24, wherein fuel vapors generated in the tank 10 are stored in the activated carbon filter container 24 together with hydrocarbons contained therein. Due to the limited storage capacity of the activated carbon filter vessel, the activated carbon filter vessel must be periodically flushed. For this purpose, the activated carbon filter vessel is connected to an inlet line 28 via a regeneration line 26, wherein a regeneration valve 30 is arranged in the regeneration line 26, which can be opened or closed by the regeneration valve 30. Upon opening of the valve 30, the stored fuel vapor is supplied to the intake pipe 28 and is thereby delivered to the engine for combustion, thereby reliably preventing the overflow of the fuel vapor. The driving pressure drop for delivery of fuel vapor from the carbon filter cartridge 24 to the inlet duct 28 is either provided by the inlet duct pressure itself or generated by an additional regeneration blower.

Depending on the selected fuel tank and the connected electric motor, different vapor pressures are allowed in the fuel tank 10. If the pressure exceeds a predetermined threshold, the fuel shut-off valve 18 is first opened so that fuel vapor can flow through the flow restriction 20 to the activated carbon filter cartridge 24.

The flow restriction 20 serves to prevent excessive flow which could result in damage to the downstream valve or sudden overloading of the carbon filter before it can be regenerated.

Fig. 2 and 3 show such a current limiting device 20 according to the invention. The flow-limiting device comprises a surrounding flow housing 32, in which a flow channel 34 is formed, through which fuel vapor flows when the fuel shut-off valve 18 is opened, and a flow-limiting element 36 arranged therein and having a substantially rotationally symmetrical design.

The flow restriction element 36 is preloaded by a spring 38 in a direction against the flow direction of the fuel vapor. The spring 38 is arranged in a substantially non-flow-through region between an inner wall 40 of the flow housing 32 and an outer wall 42 of the flow housing 32, which is in fluid communication with the flow channel 34 defined by the inner wall 40 only via a circumferential radial gap 44 on the inner wall 40. Three webs 46 project through the radial gap 44, which webs extend radially outward from the flow restriction element 36 and form a ring 48 at their radially outer ends, against which ring 48 the spring 38 bears.

The radial gap 44 is produced by the joining of two housing parts 50, 52 which are connected to one another by a flange connection 54, wherein one housing part 50 has only the inner wall 40, while on the opposite second housing part 52 an annular groove 56 extending in the axial direction is formed between the inner wall 40 and the outer wall 42, the rear wall 58 of which serves as a stop for the spring 38 and in which the spring 38 is received.

The inner wall 40 of the second housing portion 52 is shaped as a venturi nozzle 60 having an adjacent diffuser 62 that receives the flow restriction element 36 therein.

The web 46 extends from an inlet edge 64 of the flow restriction 36, at which a rotationally symmetrical, approximately hemispherical recess 66 is formed, which extends into the interior of a flow body 68 of the flow restriction 36.

The flow body 68 forms an annular or incident flow region of the flow restriction element 36 and has a rotationally symmetrical outer wall 70, the diameter of which wall 70 decreases progressively and a first portion 72 of which extends convexly from the inflow edge 64, which means that a tangent at each point of the first portion 72 is arranged in a region which is radially outside with respect to the portion 72 of the flow body 68.

The second portion 74 of the flow body 68 adjoins the convex first portion 72, however, the second portion 74 is shaped concave, which accordingly means that the tangent at each point of the concave second portion 74 is arranged in a region which is radially inside with respect to the concave second portion 74 of the flow body 68.

Next, a third, again convex section 76 is adjoined, the end of which finally converges into a point-like shape as an outflow edge of the flow body 68. The respective transitions between the convex first portion 72, the convex third portion 76 and the concave second portion 74 are each continuously differentiable, i.e. without any cross-sectional steps. If the edge of the outer wall 70 is correspondingly represented as a function from the inflow edge 64 to the outflow edge 78, the derivative of this function will also be a continuous, step-less function.

The flow body 68 of the flow restriction 36 is arranged radially inside the narrowest cross section of the venturi nozzle 60 in both the first extreme position and the second extreme position with its concave second section 74.

Accordingly, when the upstream fuel cut valve is opened, the flow body 68 is completely circulated. In the first extreme position shown in fig. 2, the flow cross-section formed between the inner wall 40 of the flow housing 32 and the flow body 68 is larger than in the second extreme position shown in fig. 3.

This means that when the upstream fuel shut-off valve 18 is closed, the pressure from the flow restriction 36 is deactivated, so that the flow restriction is pressed into its first extreme position by the force of the spring 38. However, no fuel vapor flows. When the fuel cut valve 18 is opened, the fuel vapor flows to the flow restriction element 36, thereby exerting a force on the flow restriction element 36 in the closing direction. If the pressure exceeds the set threshold pressure, the flow-limiting element 36 is moved into its second extreme position, in which the flow cross section is reduced. This results in a reduction in the volume flow that can flow to the activated carbon container 24, i.e. the flow is restricted. The critical pressure is therefore dependent on the force of the spring, the shape and size of the inlet lip 64 and the shape of the flow body 68.

The pressure losses generated by the flow restriction 20 are kept very small by the special shape of the inner wall 40 of the flow housing 32 and of the flow body 68 and the gap 80 surrounding the flow body 68, which gap first decreases continuously and then widens gradually in the flow direction, and the diffuser 62 connected downstream of the venturi nozzle 60, in which the flow slowly decelerates again to the previous speed level. Conversely, the fuel vapor first undergoes an acceleration of low pressure loss, thereby establishing a low pressure zone that increases the pressure differential and thereby increases the force required to move the restriction element 36 from the first extreme position to the second extreme position. Thus, the switching point in time can be moved to a lower pressure without changing the robustness of the system, e.g. smaller springs have to be used. Accordingly, additional design variables are created whereby the switching behavior can be designed more precisely and the valve can be made smaller if necessary since the size of the spring and the stagnation pressure area are no longer the only variables. When the flow restriction is active, the speed of rotation of the pump or the size of the connected pump can be reduced by low pressure losses. This also reliably protects the downstream valve from overloading.

It should be clear that the invention is not limited to the described embodiments, but that various modifications of the shape of the flow body and the surrounding housing structure are possible. The flow restriction device according to the invention can also be integrated directly into the upstream fuel shut-off valve. Furthermore, such a flow-limiting device can of course also be used for other applications.