WO2019162224A1

WO2019162224A1 - Valve assembly for controlling the gas pressure, fuel system comprising a valve assembly for controlling the gas pressure

Info

Publication number: WO2019162224A1
Application number: PCT/EP2019/053945
Authority: WO
Inventors: Benedikt Leibssle; Dirk Vahle
Original assignee: Robert Bosch Gmbh
Priority date: 2018-02-23
Filing date: 2019-02-18
Publication date: 2019-08-29
Also published as: DE102018202807A1

Abstract

The invention relates to a valve assembly (1) for controlling the gas pressure in a gas rail (2) of a fuel system for supplying an internal combustion engine with a gaseous fuel, in particular with natural gas, comprising two coaxially arranged valves (3, 4) for connecting the gas rail (2) to a gas feed (5) or to a gas return (6), and a control piston (7) for actuating the two valves (3, 4), wherein the control piston (7) delimits a control chamber (8), to which a hydraulic pressure medium can be applied by a pressure medium feed (9) and which can be depressurised via a pressure medium discharge (10), and wherein a sealing element (11) for media separation is provided. According to the invention, in addition to a controllable pressure medium pressure control valve (18), means (12) for blocking or throttling the pressure medium flow from the control chamber (8) are provided. The invention further relates to a fuel system comprising a valve assembly (1) according to the invention for controlling the gas pressure in a gas rail (2).

Description

description

Title:

Valve arrangement for gas pressure control, fuel system with valve arrangement for gas pressure control

The invention relates to a valve arrangement for controlling the gas pressure in a gas rail of a fuel system for supplying an internal combustion engine with a gaseous fuel gene, in particular natural gas, with the features of the preamble of claim 1. Further, the invention relates to a fuel system for supplying an internal combustion engine with a gaseous fuel, in particular with natural gas, comprising such a valve arrangement.

State of the art

The published patent application DE 10 2016 207 743 A1 discloses a fuel system for supplying an internal combustion engine with a gaseous fuel with a device for metering the gaseous fuel to an injector. The A device comprises a pressure control unit with a shut-off valve, a pressure control valve and a shut-off valve, which form a structural unit. With the shut-off valve open gaseous fuel is metered, the gaseous fuel passes to the next in a high-pressure accumulator or in a gas rail to which at least one injector is connected. By opening the Absteuerventils gaseous fuel can be removed from the gas rail, so that the gas pressure in the gas rail is lowered ge. In this way it is ensured that the gas pressure in the gas rail does not rise above a predetermined limit. The control of the shut-off valve and the shut-off valve is carried out hydraulically via the control pressure in a control chamber, which can be acted upon by a hydraulic pressure medium, namely with diesel fuel. To change the control pressure in the control chamber, a diesel pressure control valve is also provided, which is connected to a separate diesel cycle. The hydraulic control of such a pressure control unit requires the use min least one sealing element for media separation. As a sealing element is suitable for example a diaphragm seal. In addition, a corrugated or folding bellows seal can be used for media separation. Such sealing elements have in common that they continue to allow a lifting movement of the control piston when they are attached to the control piston. However, its limited mechanical strength proves to be disadvantageous, in particular when high pressure differences are applied. If, for example, in the case of a malfunction of the diesel pressure control valve, a sudden pressure drop in the control chamber, an extremely high pressure difference on the sealing element can occur for a short time. This can then lead to irreparable damage to the sealing element (plastic deformation, cracking), so that the function of the gas pressure regulator is permanently disturbed. In the worst case, it may lead to a gas leak in the area of the diesel return, so that can form an explosive gas-diesel mixture in the diesel tank.

The present invention is therefore based on the object weiterzuentwi crawl a valve assembly for gas pressure regulation in a gas rail of a fuel system such that a secure media separation over the life of the valve assembly is achieved.

To solve the problem, the valve assembly is proposed with the features of claim 1. Advantageous developments of the invention can be found in the dependent claims. Furthermore, a fuel system is provided with a Ventila invention arrangement.

Disclosure of the invention

The proposed valve arrangement is used for gas pressure control in a gas rail of a fuel system for supplying an internal combustion engine with a gasförmi conditions fuel, which may be in particular natural gas. The Ventilanord tion includes two coaxially arranged valves for connecting the gas rails with egg nem gas inlet or with a gas return and a control piston for Actuate supply of the two valves. The control piston is this preferably at least partially hollow cylinder-shaped. The control piston limits a control chamber, which can be acted upon via a pressure medium inlet with a hydraulic pressure medium and can be relieved via a Druckmitel process. Further, a sealing element for medi separation is provided, wherein preferably the sealing element is connected to the control piston. According to the invention, in addition to a controllable Druckmitel- pressure control valve Mitel for blocking or throttling of Druckmitelabflusses are provided from the control room. The additional Mitel ensure that there is no unwanted Druckab construction in the control room in case of malfunction of Druckmitel- pressure control valve. They thus prevent the sealing element occurring high pressure differences, which could lead to damage to the sealing element. In the se way a secure media separation over the life of the Ventilanord voltage is achieved.

The additional Mitel for blocking or throttling the Druckmitelabflusses are preferably self-regulating and require no further technical hedging tion. In this way, the design and manufacturing implementation can be simplified ver.

The means for blocking or throttling the Druckmitelabflusses from the control room may be in particular hydraulically effective elements that limit the pressure reduction in the control room to an allowable pressure gradient. For this purpose, the hydraulically active elements are preferably arranged between the control chamber and the pressure medium pressure control valve.

According to a first preferred embodiment of the invention, the Mitel for blocking or throttling of Druckmitelabflusses from the control chamber comprise a sealing seat for the control piston. If the control piston at the sealing seat, it blocks the Druckmitelabfluss, preferably in the direction of Druckmitel-drain. The sealing seat can be designed as a flat seat or conical seat. Furthermore, the sealing seat can cooperate with a sealing geometry formed on the control piston.

For example, an annular upper stroke stop of the control piston can be performed as a sealing seat. Falls in case of failure of the Druckmitel- pressure control valve, the pressure in the control room, the voltage applied to the control piston behave proportions to the fact that the control piston moves in the direction of the stroke stop and comes to rest on the sealing seat. In this position, the control piston prevents further pressure fluid drainage. The pressure conditions applied to the control piston are lost other from the sealing seat diameter. On the seat diameter can thus be influenced when the spool comes to rest on the sealing seat and blocks the pressure fluid drain.

According to a second preferred embodiment of the invention, the means for blocking or throttling of the pressure medium discharge from the control chamber from a flow restrictor, which is integrated in the pressure medium flow. The pressure reduction in the control chamber can be limited to a permissible pressure reduction gradient via the outlet throttle.

Alternatively or additionally, it is proposed that the means for blocking or Dros selung the pressure fluid flow include a check valve, which is integrated into the pressure medium inlet. This ensures that under unfavorable pressure ratio sen no hydraulic pressure medium flows through the pressure medium inlet. For example, the pressure could drop in the area of the pressure medium supply, so that for a short time the pressure in the control chamber is higher than in the pressure medium inlet. In this case, the check valve prevents hydraulic pressure fluid from flowing out via the pressure medium inlet.

Preferably, an inlet throttle is integrated in the pressure medium inlet. About the Dros selquerschnitt the inlet throttle, the inflow of hydraulic pressure medium can be adjusted in the control room. If an outflow throttle is arranged in the pressure medium sequence, the two throttle cross-sections must be matched to each other who the. If a check valve for blocking the pressure medium discharge from the control chamber is provided in the pressure medium inlet in addition to the inlet throttle, an arrangement can be selected in which the inlet throttle is combined with the check valve kom. For example, in the pressure medium inlet a valve with check and throttle function can be integrated.

Advantageously, the pressure medium pressure control valve inte grated in the pressure medium sequence. Normally, thus controls the pressure fluid pressure control valve Druckmittelab flow from the control room. However, since the controllable valve can fail, he is inventively additional means for blocking or throttling of the Druckmittelab flow provided that engage automatically in case of failure of the pressure medium pressure control valve. Preferably, the pressure medium pressure control valve downstream of the Mit- tel for blocking or throttling the Druckmitelabflusses from the control room ordered. This facilitates assembly.

The media separation serving sealing element is preferably a metallic corrugated or bellows, on the one hand on the control piston, on the other hand, the housing side be strengthened. Thus, a reliable media separation is achieved. At the same time, the movement of the control piston is not restricted by the sealing element. Be limited mechanical load capacity of the sealing element is thereby taken into account that in addition to the Druckmitel- pressure control valve additional Mitel for blocking or throttling the Druckmitelabflusses are provided from the control room. The se make sure that there is no pressure drop in the control room in case of failure of Druckmitel- pressure control valve. Dangerously high pressure differences, which could lead to damage of the sealing element, are therefore not to be feared.

The valve, which serves to connect the gas rail to the gas inlet, has before given to a back and forth in the axial direction of the valve lifter, which is axially biased by the spring force of a spring against a valve seat. Preferably, the valve tappet opens into the gas inlet, so that the gas pressure in the gas inlet exerts an additional closing force on the valve tappet.

The valve, which serves to connect the gas rail to the gas return, preferably has a reciprocating valve piston, which is axially biased by the spring force of a spring against a valve seat. The valve piston is arranged coaxially with respect to the valve stem of the first valve. Preferably, the valve piston is accommodated in the control piston, so that the control piston can be used for actuation in the valves. Further preferably, the spring is supported on the one hand on the valve piston on the other hand on the control piston. The bias of the valve piston in Rich tion of the valve seat and the bias of the control piston against the control pressure in the control room can therefore be effected with a spring.

In addition, a fuel system for supplying an internal combustion engine with a gaseous fuel, in particular with natural gas, comprising a fiction, contemporary valve arrangement for gas pressure regulation in a gas rail proposed as herein a preferred application of the valve arrangement according to the invention can be seen. Preferred embodiments of the invention are explained below with reference to the accompanying drawings. These show:

1 is a schematic longitudinal section through an inventive Ventilanord voltage according to a first preferred embodiment,

2 is a schematic longitudinal section through an inventive Ventilanord voltage according to a second preferred embodiment,

3 is a schematic longitudinal section through an inventive Ventilanord voltage according to a third preferred embodiment,

Fig. 4 is a schematic longitudinal section through an inventive Ventilanord voltage according to a fourth preferred embodiment, and

Fig. 5 is a diagram for the graphic representation of the pressure reduction in the control chamber compared to the pressure reduction in the gas reflux.

Detailed description of the drawings

FIG. 1 shows a valve arrangement 1 for gas pressure regulation in a gas rail 2 of a fuel system for supplying an internal combustion engine with a gaseous fuel. The gaseous fuel may be, in particular, natural gas. For this purpose, the illustrated valve arrangement 1 has a first valve 3, via which the gas rail 2 can be connected to a gas inlet 5, and a second valve 4, which serves to connect the gas rail 2 to a gas return 6. By selectively opening and closing the valves 3, 4, the gas pressure in the gas rail 2 can be raised or lowered. The two valves 3, 4 are arranged coaxially and are actuated via a common control piston 7. The control piston 7 is formed here to at least partially hollow cylindrical.

The first valve 3 has a reciprocating valve tappet 19, which is biased by a spring 20 against a valve seat 21. The second valve 4 has a valve piston 22 which is received in the control piston 7 and by means of a spring 23 is biased against a valve seat 24. The spring 23 is on the one hand on the valve piston 22, on the other hand supported on the control piston 7. The control piston 7, the valve piston 22 and the valve stem 19 have a common longitudinal axis A, along which they reciprocate.

The control piston 7 defines a control chamber 8, which is acted upon via a pressure medium inlet 9 with a hydraulic pressure medium. The feed takes place via an inlet throttle 17. The hydraulic pressure medium can be, for example, a liquid fuel, in particular diesel fuel.

If the control chamber 8 is filled with hydraulic pressure medium, the pressure in the control chamber 8 increases. The control piston 7 is characterized acted on the front side by a hydraulic pressure force, which causes a displacement of the control piston 7 against the spring force of the spring 23 in the direction of the valve piston 22. The arranged between the control piston 7 and the valve piston 22 spring 23 pushes the valve piston 22 in the valve seat 24, so that it can not follow the movement of the control piston 7. The control piston 7 continues its motion alone and comes to rest on a force transmission element 28, which serves to actuate the valve stem 19 of the valve 3. The valve 3 opens and connects the gas inlet 5 with the gas rail 2. The end position of the control piston 7 is determined by a valve piston 22 formed on the impact surface 27.

To close the valve 3, the pressure in the control chamber 8 is lowered. For this purpose, a pressure medium pressure control valve 18 is opened, which is arranged in a pressure fluid outlet 10 at. The pressure reduction has the consequence that the spring force of the spring 23 now moves the control piston 7 in the opposite direction. In this case, the control piston 7 loses contact with the force transmission element 28, so that the Fe 20 is able to pull the valve stem 19 in the valve seat 21. Furthermore, a formed on the control piston 7 paragraph 26 comes into contact with a collar 25 of the valve piston 22, so that the control piston 7 carries the valve piston 22 and lifts out of his valve seat 24. Now, the valve 4 opens, so that the gas rail 2 is connected to the gas return line 6. Thus, both valves 3, 4 can be controlled via the pressure in the control chamber 8. In order to separate the media gaseous fuel and hydraulic pressure medium, a sealing element 11 is provided, which in the present case is designed as a metallic bellows. The sealing element 11 is on the one hand on the control piston 7, on the other hand fixed to the housing side. Since high pressure differences can damage the sealing element 11, it is necessary to prevent unwanted pressure reduction in the control chamber 8. The risk, for example, in case of failure of the pressure medium pressure control valve 18. In order to prevent un unwanted pressure reduction, therefore means 12 for blocking or Drosse development of a pressure medium discharge from the control chamber 8 are provided.

In the embodiment of FIG. 1, these means 12 include a Ablaufdros sel 15, which is integrated into the pressure medium flow 10. In the event of failure of the pressure medium pressure control valve 18, the outlet throttle 15 limits the pressure reduction in the control chamber 8 to a permissible pressure reduction gradient.

2, another embodiment of a Ventilan Regulation 1 according to the invention is shown, in which the means 12 for blocking or throttling the pressure medium outflow from the control chamber 8 a sealing seat 13 for the control piston 7 to take. The sealing seat 13 separates from the control chamber 8 from an annular space 30, in which the pressure medium inlet 9 opens. If the pressure in the control chamber 8 breaks, the pressure conditions applied to the control piston 7 cause it to be placed in the sealing seat 13. The annular space 30 is further filled via the pressure medium inlet 9 with hydrau lic pressure medium, so that builds up a back pressure, which also rests on an annular surface 30 which is defined by the diameters Di and D ₂ . On the STEU erkolben 7 thus also acts a hydraulic opening force, which causes the connection of the annular space 30 to the control chamber 8 is not completely interrupted, but allows a certain pressure reduction in the annular space 30. Thus, the pressure in the annular space 30 is undulated (see FIG. 5, curve 3).

The embodiment of FIG. 2 also has a modified control piston 7 and a modified valve piston 22. The valve piston 22 is executed from a sectionally hollow cylindrical and guided over a guide pin 31 of the control piston 7. The driver function is presently realized by a ring collar 25 'on the guide pin 31 and a shoulder 26' on the valve piston 22. 3 is another embodiment of an inventive Ventilanord statement 1 can be seen. The embodiment corresponds essentially to that of FIG. 1 with the difference that the means 12 for blocking or throttling the Druckmittelab flow from the control chamber 8 - analogous to the embodiment of FIG. 2 - comprise a sealing seat 13 for the control piston 7. In contrast to the Ausführungsbei game of Fig. 2 here is the sealing seat 13 is not out as a flat seat, but as a conical seat leads. On the control piston 7 also cooperating with the sealing seat 13 sealing geometry 14 is formed. Furthermore, the sealing seat diameter is significantly reduced compared to the diameter Di of the control piston 7. The on the control piston 7 ver remaining annular surface 29 is correspondingly larger. In this way, a Druckab construction wave can be realized with only a small pressure wave difference to the gas pressure, which zen an approximately uniform pressure reduction behavior with very small pressure differentials on the sealing element 11 result (see Fig. 5, curve 4).

In order to prevent an undesirable pressure drop in the control chamber 8 at a pressure drop in the pressure medium inlet 9, may - alternatively or in addition to the vorste initially described measures - the means 12 for blocking or throttling the pressure fluid flow from the control chamber 8 in the pressure medium inlet. 9 integrated check valve 16 include. This embodiment is shown by way of example in FIG. 4. As indicated by the dashed frame, the check valve 16 and the inlet throttle 17 can be summarized. It is irrelevant whether the inlet throttle 17 is arranged upstream or downstream of the check valve 16 in the pressure medium inlet 9.

In the diagram of Fig. 5, the pressure reduction over time at a failure of the pressure medium pressure control valve 18 is shown. Curve 1 shows the pressure reduction in STEU erraum 8 in case of failure of the pressure medium pressure control valve 18 against the also applied to the sealing element gas pressure (curve 2). Since the curve 1 is significantly steeper than the curve 2, resulting over time high pressure differences, which can lead to damage to the sealing element 11. The curve 3 shows the pressure reduction in the control chamber 8, when means 12 are provided analogously to the embodiment of FIG. The pressure reduction in the control chamber 8 is wavy to the straight-line Ver run of the curve 2, that is, for gas pressure reduction. There are thus no high pressure differences. The curve 4, which refers to the embodiment of FIG. 3, even shows a nearly uniform pressure reduction behavior with very small Druckdiffe differences to the gas pressure.

Claims

claims

1. Valve arrangement (1) for gas pressure regulation in a gas rail (2) of a fuel system for supplying an internal combustion engine with a gaseous fuel, in particular with natural gas, comprising two coaxially arranged valves (3, 4) for connecting the gas rail ( 2) with a gas inlet (5) or with a gas return (6) and a control piston (7) for actuating the two valves (3, 4), wherein the control piston (7) defines a control chamber (8), the via a pressure medium inlet (9) acted upon by a hydraulic pressure medium and a pressure medium-discharge (10) is relieved, and wherein a sealing element (11) is provided for media separation,

characterized in that in addition to a controllable pressure medium pressure control valve (18) means (12) for blocking or throttling the Druckmittelabflus ses from the control chamber (8) are provided.

2. Valve arrangement (1) according to claim 1,

characterized in that the means (12) comprise a sealing seat (13) for the Steuerkol ben (7), wherein preferably the sealing seat (13) is designed as a flat seat or conical seat and / or with a on the control piston (7) formed Dichtgeomet theory ( 14) cooperates.

3. Valve arrangement (1) according to claim 1,

characterized in that the means (12) comprise an outlet throttle (15) which is integrated in the pressure medium outlet (10).

4. Valve arrangement (1) according to one of the preceding claims,

characterized in that the means (12) comprise a check valve (16) which is integrated in the pressure medium inlet (9).

5. Valve arrangement (1) according to one of the preceding claims,

characterized in that in the pressure medium inlet (9) an inlet throttle (17) is integrated, wherein preferably the inlet throttle (17) with the check valve (16) is combined.

6. Valve arrangement (1) according to one of the preceding claims,

characterized in that the pressure medium pressure control valve (18) in the pressure medium-discharge (10) is integrated, and preferably downstream of the means (12) for blocking or throttling of the pressure medium discharge from the control chamber (8).

7. Valve arrangement (1) according to one of the preceding claims,

characterized in that the sealing element (11) is a metallic corrugated or Fal tenbalg, on the one hand on the control piston (7), on the other hand, the housing side is fixed.

8. Valve arrangement (1) according to one of the preceding claims,

characterized in that the valve (3) for connecting the gas rail (2) with the gas inlet (5) has a back and forth in the axial direction and valve lifter (19), by the spring force of a spring (20) against a valve seat (21) is axially biased.

9. Valve arrangement (1) according to one of the preceding claims,

characterized in that the valve (4) for connecting the gas rail (2) with the gas return (6) has a reciprocating valve piston (22) which by the spring force of a spring (23) against a valve seat ( 24) is axially biased, wherein preferably the valve piston (22) in the control piston (7) is received and the spring (23) on the one hand on the valve piston (22) on the other hand on the control piston (7) is supported abge.

10. Fuel system for supplying an internal combustion engine with a gasförmi conditions fuel, in particular with natural gas, comprising a valve assembly (1) according to egg nem of the preceding claims for gas pressure regulation in a gas rail (2).