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

Abstract

The invention relates to 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, in particular with natural gas, comprising a first valve (3) for connecting the gas rail (2) to a gas inlet (4), a second valve (5) for connecting the gas rail (2) to a gas return (6) and a control piston (7) for actuating the two valves (3, 5), wherein the control piston (7) defines a control chamber (8) which can be pressurized with a hydraulic pressure medium via a pressure medium inlet (9) and relieved via a pressure medium outlet (10), further comprising a sealing element (11) designed as a corrugated or bellows, which is arranged for media separation between a gas chamber (12) and a pressure medium chamber (13).The valve arrangement is characterized by a pressure differential limiting valve (14) with a reciprocating piston (15) which is acted upon on one side by a pressure (p1) prevailing in the gas chamber (12) and on the other side by a pressure (p2) prevailing in the pressure medium chamber (13), and which opens an additional gas return (16) when a predetermined pressure differential applied to the piston (15) is exceeded. The invention further relates to a fuel system with a valve arrangement (1) according to the invention for gas pressure control in a gas rail (2).

Description

[0001] The invention relates to a valve arrangement for gas pressure regulation in a gas rail of a fuel system for supplying an internal combustion engine with a gaseous fuel, in particular with natural gas, comprising the features of the preamble of claim 1. Furthermore, 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

[0002] German patent application DE 10 2016 207 743 A1 discloses a fuel system for supplying an internal combustion engine with gaseous fuel, including a device for metering the gaseous fuel to an injector. The device comprises a pressure control unit with a shut-off valve, a pressure control valve, and a control valve, forming a single assembly. When the shut-off valve is open, gaseous fuel is metered, initially entering a high-pressure storage tank or a gas rail to which at least one injector is connected. Opening the control valve allows gaseous fuel to be discharged from the gas rail, thus reducing the gas pressure within it. This ensures that the gas pressure in the gas rail does not exceed a predetermined limit.The shut-off valve and the control valve are hydraulically controlled via the control pressure in a control chamber, which can be pressurized with a hydraulic pressure medium, specifically diesel fuel. A diesel pressure control valve, connected to a separate diesel circuit, is also provided for changing the control pressure in the control chamber.

[0003] The hydraulic control of such a pressure regulating unit requires the use of at least one sealing element for media separation. A corrugated or bellows seal is particularly suitable as a sealing element, since it still allows the control piston to move when attached to it. However, its limited mechanical strength proves to be a disadvantage, especially under high pressure differentials. For example, if a malfunction of the diesel pressure control valve causes a sudden pressure drop in the control chamber, an extremely high pressure differential can briefly occur at the sealing element. This can then lead to irreparable damage to the sealing element (plastic deformation, cracking), resulting in a permanent disruption of the gas pressure regulator's function. In the worst case, gas can leak into the diesel return line, potentially forming an explosive gas-diesel mixture in the diesel tank.

[0004] The present invention is therefore based on the objective of further developing a valve arrangement for gas pressure control in a gas rail of a fuel system in such a way that a safe media separation is achieved over the lifetime of the valve arrangement.

[0005] To solve the problem, the valve arrangement with the features of claim 1 is proposed. Advantageous embodiments of the invention are described in the dependent claims. Furthermore, a fuel system with a valve arrangement according to the invention is described. Disclosure of the invention

[0006] The proposed valve arrangement serves to regulate the gas pressure in a gas rail of a fuel system for supplying an internal combustion engine with a gaseous fuel, which may in particular be natural gas. The valve arrangement comprises a first valve for connecting the gas rail to a gas inlet, a second valve for connecting the gas rail to a gas return, and a control piston for actuating the two valves. The control piston defines a control chamber that can be pressurized with a hydraulic pressure medium via a pressure medium inlet and relieved via a pressure medium outlet. Furthermore, the valve arrangement includes a sealing element designed as a corrugated or bellows, which is arranged to separate the gas chamber from the pressure medium chamber.According to the invention, the valve arrangement is characterized by a pressure differential limiting valve with a reciprocating piston which is subjected on one side to a pressure p1 prevailing in the gas space and on the other side to a pressure p2 prevailing in the pressure medium space, and which opens an additional gas return when a predetermined pressure differential applied to the piston is exceeded.

[0007] The differential pressure relief valve thus prevents high pressure differences from occurring at the sealing element intended for media separation, which could damage the sealing element. In this way, reliable media separation is achieved throughout the service life of the valve assembly.

[0008] For example, in the event of a sudden pressure drop in the control chamber, the pressure differential relief valve can connect the gas chamber to the additional gas return. This causes the pressure p1 in the gas chamber to decrease until it reaches the pressure level in the pressure medium chamber or corresponds to pressure p2. Pressure differences are thus equalized, and the stress on the sealing element used for media separation is reduced. Opening the additional gas return can also accelerate the pressure reduction in the gas chamber. This is particularly advantageous if the gas chamber is connected to the gas supply, so that high pressure normally prevails in the gas chamber. Alternatively, the gas chamber can be connected to the gas return, so that low pressure normally prevails in the gas chamber.

[0009] The differential pressure relief valve is controlled by the pressures p1 and p2 applied to the piston. Therefore, no additional actuator is required. The differential pressure relief valve is actuated solely by pressure.

[0010] Preferably, the differential pressure relief valve is designed like a pressure balance valve. The desired pressure equalization is achieved by the movement of the piston, which simultaneously opens an additional gas return. The maximum pressure difference between pressures p1 and p2 can be set via the opening pressure of the differential pressure relief valve. Preferably, the pressure difference is limited to a maximum of 30 bar, and even more preferably to a maximum of 25 bar. This reliably prevents damage to the sealing element, which is designed as a corrugated or bellows seal for media separation.

[0011] Furthermore, the piston preferably has a sealing surface that interacts with a valve seat for releasing and closing the additional gas return. The valve seat can be designed as a flat seat or a conical seat. The sealing surface formed on the piston can, in particular, be flat, conical, or spherical. Preferably, the sealing surface is formed on an end face of the piston so that a closing force can be generated via the pressure conditions acting on the piston, which holds the piston in contact with the valve seat.

[0012] In a further development of the invention, it is proposed that the piston be designed as a stepped piston. This means that the piston has sections with different diameters. The opening pressure of the differential pressure relief valve can, in turn, be influenced by the diameter ratio of the pressurized piston sections. For example, a diameter ratio can be selected that prevents the valve from opening even with slight pressure fluctuations in the gas space.

[0013] Alternatively or additionally, it is proposed that the piston be designed in multiple parts, preferably with the multiple parts being integrally joined. This is particularly advantageous when the piston is designed as a stepped piston. The multi-part design simplifies manufacturing and / or assembly.

[0014] Advantageously, the piston of the additional valve is acted upon by the spring force of at least one spring. The spring force can act in the closing direction or in the opening direction. Furthermore, at least two springs can be provided, one acting in the closing direction and the other in the opening direction. Preferably, the piston is biased against the valve seat by a spring acting in the closing direction. In this way, the required opening force can be increased to prevent the valve from opening even with the slightest pressure fluctuations. The dynamics of the piston movement can be influenced by a spring acting in the opening direction.

[0015] As a further development measure, it is proposed that a connecting channel be formed in the piston. This connecting channel allows pressure equalization between two pressure chambers located on either side of the piston, which serve as the piston's movement space. Preferably, both pressure chambers are pressurized with the gaseous fuel, so that a connection between the gas chamber and the additional gas return can be established via at least one pressure chamber when the differential pressure relief valve opens. Preferably, a throttle is incorporated in the connecting channel to dampen the piston movement.

[0016] The differential pressure relief valve preferably includes a sealing element. The sealing element serves to separate the media and, in particular, prevents the mixing of gaseous fuel and hydraulic fluid via the piston guide. Preferably, the sealing element is designed as a diaphragm, corrugated bellows, or bellows, since these sealing elements still allow reciprocating movement of the piston.

[0017] According to a preferred embodiment of the invention, the gas chamber is connected to the gas inlet, and the pressure medium chamber is connected to the control chamber. The piston of the differential pressure relief valve is thus subjected to both the control pressure (p1) and the control pressure (p2). In the event of a fault, i.e., a sudden pressure drop in the control chamber, to limit the pressure difference between the control pressure and the control pressure, the valve opens and connects the gas inlet to the additional gas return. Consequently, gas flows out of the gas inlet, so that the control pressure (p1) equals the control pressure (p2). This creates pressure equalization, which reduces the stress on the (main) seal of the valve assembly, designed as a corrugated or bellows-type seal, thus ensuring reliable media separation over the long term.

[0018] According to an alternative preferred embodiment of the invention, the gas chamber is connected to the gas return, and the hydraulic fluid chamber is connected to the hydraulic fluid inlet and / or outlet. In this case, the differential pressure relief valve is not located in the high-pressure section of the valve assembly, but rather in the low-pressure section. The operating principle of the differential pressure relief valve remains otherwise unchanged. The connection between the hydraulic fluid chamber and the hydraulic fluid inlet and / or outlet is preferably made indirectly via at least one throttle, so that the hydraulic fluid is fed into the hydraulic fluid chamber at a throttled rate and / or discharged from the hydraulic fluid chamber at a throttled rate.

[0019] A pressure relief valve is preferably arranged in the pressure medium outlet, which serves to relieve the pressure in the control chamber. The pressure relief valve allows the control pressure prevailing in the control chamber to be precisely adjusted.

[0020] Furthermore, a fuel system for supplying an internal combustion engine with a gaseous fuel, in particular with natural gas, comprising a valve arrangement according to the invention for gas pressure control in a gas rail, is proposed, since this represents a preferred application of the valve arrangement according to the invention.

[0021] Preferred embodiments of the invention are explained in more detail below with reference to the accompanying drawings. These show: Fig. 1 a schematic longitudinal section through a valve arrangement according to the invention in a first preferred embodiment, Fig. 2 a schematic longitudinal section through a valve arrangement according to the invention in a second preferred embodiment, Fig. 3 a schematic longitudinal section through a first preferred embodiment of a differential pressure relief valve for a valve arrangement according to the invention, Fig. 4 a schematic longitudinal section through a second preferred embodiment of a differential pressure relief valve for a valve arrangement according to the invention and Fig. 5 a schematic longitudinal section through a third preferred embodiment of a differential pressure relief valve for a valve arrangement according to the invention. Detailed description of the drawings

[0022] The Fig. The valve assembly 1 is 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 can be, in particular, natural gas. The illustrated valve assembly 1 has a first valve 3, through which the gas rail 2 can be connected to a gas supply 4, and a second valve 5, which serves to connect the gas rail 2 to a gas return 6. By selectively opening and closing the valves 3 and 5, the gas pressure in the gas rail 2 can be increased or decreased. The two valves 3 and 5 are arranged coaxially and are actuated by a control piston 7, which is also arranged coaxially. The control piston 7 defines a control chamber 8, which can be pressurized with a hydraulic pressure medium, for example, diesel fuel, via a pressure medium supply 9 with an integrated inlet throttle 17.The control chamber 8 can be connected to a pressure medium drain 10 via a pressure medium control valve 27.

[0023] When the control chamber 8 fills with hydraulic fluid, the pressure in the control chamber 8 increases. This causes the control piston 7 to be subjected to a hydraulic pressure force at its end face, which displaces the control piston 7 against the spring force of a spring 28 towards a valve piston 29. This leads to the closing of the second valve 5. The control piston 7 now moves the valve piston 29 along with it until it comes into contact with a valve tappet 30 and lifts it out of a valve seat 32 against the spring force of a spring 31. The first valve 3 opens. To close the first valve 3, the control pressure in the control chamber 8 is reduced so that the control piston 7 is returned to its initial position by the spring force of the spring 28. The valve piston 29 follows the movement of the control piston 7, as it is acted upon by the spring force of a spring 33.The valve piston 29 then detaches from the valve tappet 30, allowing the spring 31 to pull the valve tappet 30 into the valve seat 32. The first valve 3 closes. The movement of the valve piston 29 is limited by a stop collar 34, so that the second valve 5 subsequently opens again.

[0024] To separate the gaseous fuel and hydraulic fluid, a sealing element 11 is provided, which in this case is designed as a metallic bellows. The sealing element 11 is attached to the control piston 7 on one side and to the housing on the other, so that the sealing element 11 separates a gas chamber 12 from a pressure fluid chamber 13. The pressure p1 prevailing in the gas chamber 12 and the pressure p2 prevailing in the pressure fluid chamber 13 are thus exerted on the sealing element. Since high pressure differentials can damage the sealing element 11, measures must be taken to prevent such high pressure differentials. The measures described in the Fig. The valve arrangement 1 shown in Figure 1 has a pressure differential limiting valve 14, which is arranged in the low-pressure area of ​​the valve arrangement 1.

[0025] In the Fig. Figure 2 shows a valve arrangement 1 according to the invention for gas pressure regulation in a gas rail 2 with a pressure differential limiting valve 14, which - in contrast to the Fig. 1 - is located in the high-pressure area of ​​the valve arrangement 1. Furthermore, the second valve 5 has a sleeve-shaped valve piston 29, which is guided reciprocally on the control piston 7. The first valve 3 is actuated by means of a sleeve 35, which has an actuating element 36 at its end facing the first valve 3 for contacting the valve tappet 30 of the first valve 30. The first valve 30 is otherwise identical to the first valve 30 of the Fig. 1 valve arrangement 1 is formed.

[0026] The sealing element 11 of the in the Fig. In the valve arrangement 1 shown in Figure 2, the internal pressure corresponds to the control pressure. The external pressure is the control pressure prevailing in the control chamber. Pressure equalization can be achieved via the differential pressure relief valve 14, so that the sealing element 11 is not damaged.

[0027] The differential pressure relief valve 14 of the valve arrangement 1 of the Fig. 1 and / or the valve arrangement 1 of the Fig. 2 can be adjusted according to the in the Fig. 3, Fig. 4 to Fig. 5 illustrated embodiments.

[0028] The Fig. Figure 3 shows a differential pressure relief valve 14, designed in the manner of a pressure balance. It comprises a reciprocating piston 15, which is designed as a stepped piston and is subjected on one side to the pressure p1 prevailing in the gas chamber 12 and on the other side to the pressure p2 prevailing in the pressure medium chamber 13. The pressure force acting on the piston 15 is determined by the diameters D1 and D2. The piston 15 has a sealing surface 19 at its end, where the pressure p1 is applied, which interacts with a valve seat 18. Furthermore, the piston 15 is biased against the valve seat 18 by the spring force of a spring 20. Another spring 21 biases the piston 15 in the opposite direction, so that the piston 15 is largely force-balanced. However, since the diameter D1 is smaller than the diameter D2, a hydraulic pressure force acts on the piston 15, which pushes the piston 15 against the valve seat 18.If, in the event of a fault, the pressure p2 in the pressure medium chamber 13 suddenly drops, the pressure forces acting on the piston 15 cause the piston 15 to lift off the valve seat 18 and open the differential pressure relief valve 14. With the differential pressure relief valve 14 open, a connection is established between the gas chamber 12 and the additional gas return 16, so that the pressure p1 in the gas chamber 12 also drops until pressure equilibrium is reached. The movement of the piston 15 is dampened by a throttle 23, which is formed in a connecting channel 22 of the piston 15.

[0029] To prevent the mixing of the media gaseous fuel and hydraulic pressure medium by way of leakage via a guide of the piston 15, the pressure differential limiting valve 14 also has a sealing element 24, which in this case is designed as a diaphragm.

[0030] The Fig. Figure 4 shows a further preferred embodiment of a differential pressure relief valve 14 for a valve arrangement 1 according to the invention. This differs from that of the Fig. 1 essentially by the fact that a bellows is provided as a sealing element 24 instead of the membrane.

[0031] In the Fig. Figure 5 also shows a differential pressure relief valve 14, which has a piston 15 that is only single-stage and in turn has a diaphragm as a sealing element 24. The piston 15 is biased against the diaphragm by the spring force of a spring 21. A hydraulic pressure force is generated via the area ratio of the diameters D1 and D2, which holds the piston 15 in contact with the valve seat 18. The connection of the differential pressure relief valve 14 to the gas chamber 12 is arranged laterally, while the connection to the additional gas return 16 is arranged coaxially with the piston 15.

Claims

[1] Valve arrangement (1) for gas pressure control in a gas rail (2) of a fuel system for supplying an internal combustion engine with a gaseous fuel, comprising a first valve (3) for connecting the gas rail (2) to a gas inlet (4), a second valve (5) for connecting the gas rail (2) to a gas return (6), and a control piston (7) for actuating the two valves (3, 5), wherein the control piston (7) defines a control chamber (8) which can be pressurized with a hydraulic pressure medium via a pressure medium inlet (9) and relieved via a pressure medium outlet (10), further comprising a sealing element (11) designed as a corrugated or bellows, which is arranged for media separation between a gas chamber (12) and a pressure medium chamber (13), characterized bya pressure differential limiting valve (14) with a reciprocating piston (15) which is subjected on one side to a pressure (p1) prevailing in the gas space (12) and on the other side to a pressure (p2) prevailing in the pressure medium space (13), and which opens an additional gas return (16) when a predetermined pressure differential applied to the piston (15) is exceeded. [2] Valve arrangement (1) according to claim 1, characterized by , that the piston (15) for releasing and closing the additional gas return (16) has a sealing surface (19) which interacts with a valve seat (18) and is formed on an end face of the piston (15). [3] Valve arrangement (1) according to claim 1 or 2, characterized by that the piston (15) is designed as a stepped piston and / or multi-part. [4] Valve arrangement (1) according to one of the preceding claims, characterized by , that the piston (15) is acted upon by the spring force of at least one spring (20, 21). [5] Valve arrangement (1) according to one of the preceding claims, characterized by , that a connecting channel (22) is formed in the piston (15), wherein a throttle (23) is formed in the connecting channel (22). [6] Valve arrangement (1) according to one of the preceding claims, characterized by , that the differential pressure relief valve (14) includes a sealing element (24). [7] Valve arrangement (1) according to claim 6, characterized by , that the sealing element (24) is designed as a membrane, corrugated bellows or bellows. [8] Valve arrangement (1) according to one of the preceding claims, characterized by , that the gas space (12) is connected to the gas inlet (4) and the pressure medium space (13) is connected to the control space (8). [9] Valve arrangement (1) according to any one of claims 1 to 7, characterized by, that the gas space (12) is connected to the gas return (6) and the pressure medium space (13) is connected to the pressure medium inlet (9) and / or to the pressure medium outlet (10). [10] Valve arrangement (1) according to one of the preceding claims, characterized by , that to relieve the control chamber (8) a pressure medium relief valve (27) is arranged in the pressure medium outlet (10). [11] Fuel system for supplying an internal combustion engine with a gaseous fuel, comprising a valve arrangement (1) according to one of the preceding claims for gas pressure control in a gas rail (2).

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