DE102015216703B3 - Pressure control device for a fuel volume and method for controlling a fuel pressure - Google Patents

Abstract

The invention relates to a pressure control device (9) for a fuel volume, comprising - a valve element (14) with a closing element (15), via which the pressure of the fuel volume on the output side of the pressure control device (9) is controllable; - A control line (16) for the valve element (14) in which a diverted from the fuel volume control volume is guided; - A pilot element for the valve element (14), wherein by means of the pilot element, the pressure of the control volume is controllable; wherein the control line (16) is formed such that the control volume upstream of the valve element (14) is branched off from the fuel volume and routed downstream of the valve element (14) via a throttle element (21) and again downstream of the throttle element (21) the fuel volume is merged, wherein the throttle element (21) is designed to be variable in its throttle effect.

Description

The invention relates to a pressure control device for a fuel volume, in particular in a fuel supply line of a vehicle operated with a compressed gas. It further relates to a method for controlling a fuel pressure in such a vehicle.

A compressed gas is understood here and below to mean a gaseous fuel which is stored in the vehicle in a pressure vessel. For example, it is understood to mean natural gas or hydrogen.

From the DE 10 2007 036 958 A1 a fuel supply device for a natural gas-powered vehicle is known. In this device, a pressure reducing device is provided to reduce the tank pressure of, for example, 200 bar to the lower system pressure of the fuel injector.

The publication DE 10 2006 019 404 A1 describes a pressure regulator for gaseous media. The gas pressure can be selectively changed via an actuator which acts on a valve of an overflow device and the output pressure can be set to a desired value.

The publication DE 10 2014 218 818 A1 describes a pressure reducing device for a compressed gas operated vehicle and has a housing equipped with an outside with a heating area. The heating area has an enlarged surface with heat exchange structures.

In such fuel supply devices nowadays piezo valves are frequently used as pilot valves of the pressure control device. By means of the piezo valve, a partial volume diverted from the fuel volume is regulated as a control volume. Instead of the piezo valve can also be used for example a solenoid valve.

In order to return the partial volume used as the control volume to the fuel volume, the partial volume is conducted via an outflow throttle. This throttle is designed as a conduit region with a narrow cross-section.

The problem may be in such a fuel supply device that the control of the pilot valve is not linear. At high fuel input pressures only very small strokes of the pressure control valve are needed. These strokes can be so small that due to the control of the pilot valve this begins to pulse and thus the output pressure is not sufficiently accurately adjustable.

At low inlet pressures, larger strokes of the pressure control valve are required to provide the desired gas volume or pressure. It may happen that even the largest possible stroke of the pilot valve is not sufficient to set the desired pressure ratio. The tank can therefore not be sufficiently drained.

It is an object of the present invention to provide a pressure control device for a fuel volume, with the possible in all operating conditions, a precise control of the fuel pressure to the supply pressure of the fuel supply device is possible. Furthermore, a method for such a precise regulation is to be specified.

The object is solved with the subject matter of the independent claims. Advantageous embodiments are the subject of the dependent claims.

According to one aspect of the invention, a pressure control device for a fuel volume is specified, which has a valve element with a closing element, via which the pressure of the fuel volume on the output side of the pressure regulating device can be controlled. The pressure regulating device furthermore has a control line for the valve element, in which a control volume diverted from the fuel volume is guided. Furthermore, the pressure regulating device has a pilot control element for the valve element, wherein the pressure of the control volume can be controlled by means of the pilot control element. In this case, the control line is designed such that the control volume is branched off from the fuel volume upstream of the valve element and is passed downstream of the valve element via a throttle element and is brought together again downstream of the throttle element with the fuel volume. The throttle element is designed to be variable in its throttle effect.

The pressure control device has the advantage that the throttle effect can be variably adapted to the operating state of the vehicle or the pressure control device. This leads to a better controllability of the pilot element. In particular, particularly high and very low tank pressures can be handled better, resulting in the same tank volume to a larger working range of the pressure control device.

Due to the variable throttle, a larger part of the fuel quantity can be added through the control path. As a result, z. B. in the election a weaker spring of the throttle element, a larger volume can be provided and in the case of a stronger spring, a smaller volume. This results in a variable concept in the design of the pressure control device, so that it can be easily modified in principle for different applications, especially car or truck applications.

A variable throttle effect is understood here and below to mean that the throttling effect of the throttle element can be changed. Throttling elements, which only cause opening and closing of the line, can have a variable throttling effect, if they can be actuated at intervals, for example. In particular, however, the cross section of the throttle element, through which the control volume is guided, may be designed to be variable.

According to one embodiment of the invention, the pilot element is designed as a piezoelectric actuator. In this embodiment, the inverse piezoelectric effect is exploited, in which, for example, in certain types of ceramics a deformation is generated by the application of an electric field. Stackable translators and bending transducers are customary as possible designs. Due to the deformation of the piezoelectric actuator, the closing element of a valve is displaced.

In an alternative embodiment, the pilot element has a solenoid valve.

However, other controllable valves are also possible as a pilot control element.

The throttle element may be formed as a valve with a spring-loaded closing body. In this mechanical embodiment of the throttle element, the control pressure works against a spring force. The closing body may be formed, for example, as a ball, cone or pipe, which is pressed onto a seat. As a spring, for example, spiral or leaf springs can be used. It is also conceivable to form the throttle element as a slider or diaphragm.

These mechanical embodiments of the throttle element have the advantage that they are inexpensive and robust.

In an alternative embodiment, the throttle element has a piezoelectric valve. Alternatively, it may also have a solenoid valve.

Such throttle elements have the advantage that they are technically more complex, but are designed to be adjustable. It is thus possible even more differentiated influencing the throttle effect.

In one embodiment, the throttle element has a partial passage region with a fixed cross section. In particular, this partial passage region, which is not variable, can be designed such that it is always open. This has the advantage that, irrespective of the function of the throttle element, at least the partial passage region is always open in order to pass through even very small control volumes.

According to one aspect of the invention, there is provided a fuel supply apparatus for a compressed gas fueled vehicle having the described pressure regulator for reducing a fuel pressure from a tank pressure to a fuel injection supply pressure.

Further, a compressed gas powered vehicle is provided with such a fuel supply device. The vehicle has the advantage that it can be operated efficiently even in operating conditions that are fundamentally problematic for pressure regulation, such as in the case of a relatively full or empty fuel tank or during an overrun fuel cutoff.

According to a further aspect of the invention, a method is provided for controlling a fuel pressure from a tank pressure to a supply pressure in a compressed gas powered vehicle, wherein a diverted as control volume for a pilot element from the fuel flow partial stream prior to merging with the pressure reduced fuel flow in dependence at least one parameter is throttled.

The throttling is thus carried out variably as a function of the parameter used. The method thus has the advantages described above in connection with the pressure control device.

According to one embodiment, the parameter is selected from the group consisting of a pressure in the partial flow, a setpoint for the control pressure and a requested fuel volume.

Under the control pressure is thus understood that pressure in the partial flow, which is relevant for the pilot control process.

It is conceivable to also use predictive data as a parameter. For example, if the request for a high fuel volume in near Foreseeable future, this can be taken into account in the throttling.

In particular, the method makes it possible to carry out the pressure regulation efficiently in the following potentially problematic operating states:
If a quick build-up of the control pressure is desired, the throttle effect can be selected very high or the throttle element can be closed. Once the required control pressure has been reached, the throttle can be opened slowly. As a result, the required control pressure is available very quickly.

In a fuel cut, the throttle element opens a maximum and the pilot element closes. In this way the control volume is reduced as quickly as possible and pressure peaks are avoided.

In the case of a large requested fuel volume, the throttle element can additionally open more, as this also a significant volume of fuel can flow through the control path. In addition, this would significantly improve the response of the control in the event of an unexpected fuel cut. This rule option can be adjusted to volume levels or subject to continuous adjustment.

Another aspect of the invention relates to a computer program product comprising a computer readable medium and program code stored on the computer readable medium which, when executed on a computing unit, directs the computing unit to execute the described method.

The arithmetic unit can be designed in particular as an engine control unit.

Embodiments of the invention will now be described with reference to the accompanying figures.

1 shows schematically a vehicle with a device for supplying fuel according to an embodiment of the invention,

2 shows a schematic diagram of the pressure control device according to an embodiment of the invention and

3 schematically shows a cross section through a pressure regulating device according to an embodiment of the invention.

1 shows a vehicle indicated only by dashed lines 1 , which is designed in particular as a passenger car, truck or bus. The vehicle 1 is fueled by compressed natural gas (CNG). Alternatively, hydrogen could also be used as the fuel, for example.

The vehicle 1 has an internal combustion engine 2 with a number of cylinders 3 on, in which natural gas is burned. In the embodiment shown, the internal combustion engine 2 four cylinders 3 but only one of them is shown.

The fuel passes through a fuel injector 4 in the combustion chamber of the cylinder, not shown in detail 3 , The fuel injector 4 upstream is a fuel rail 5 coming from the supply line 10 supplied fuel into the individual fuel injection devices 4 and the cylinders assigned to them 3 distributed.

The fuel injector 4 typically operates at a fuel pressure of about 5 to 20 bar. This pressure P2 also prevails in the supply line 10 , In contrast, the compressed natural gas is formed as a pressure vessel tanks 6 held under a pressure P1 of about 200 bar. This pressure P1 also prevails in the supply line 7 that from the tanks 6 over a filter 8th to the pressure control device 9 leads. The pressure regulator 9 reduces the pressure P1 to the pressure P2.

The pressure regulator 9 is via a signal line 25 from a computing unit 30 , in particular as an engine control unit of the internal combustion engine 2 can be designed, driven. The arithmetic unit 30 has a processing unit 31 and a computer readable medium 32 on. The processing unit 31 For example, it can be designed as an electronic processor, in particular as a microprocessor or microcontroller. The computer-readable medium 32 For example, it can be designed as an EEPROM, flash memory or flash EEPROM or NV-RAM. On the computer readable medium 32 is a program code stored, which, when placed on the arithmetic unit 30 is executed, the arithmetic unit 30 to carry out the above-mentioned embodiments of the method.

About the arithmetic unit 30 is one in the 1 not shown pre-control element of the pressure control device 9 and a throttle element for the control volume controllable.

2 shows a schematic diagram of the structure of the pressure control device 9 , The pressure regulator 9 has an entrance 12 on, in which the supply line 7 opens and at which the pressure P1 is applied. It also has an exit 13 on that in the supply line 10 opens and at which the pressure P2 is applied.

To regulate the fuel pressure from P1 to P2, the pressure regulator 9 a valve element 14 with a closing element 15 on. about the valve element 14 the main part of the fuel volume flows.

From the fuel volume, however, a small part is branched off as a control volume. This part is controlled by the control line 16 directed to a pre-control element 17 , which is formed in the embodiment shown as a piezoelectric element.

The pilot element 17 regulates the pressure in the control line 16 , It sets the control pressure Ps in the control line 16 available, which is required to the valve element 14 in accordance with the output pressure P2 to be set.

The control volume with the control pressure PS hits in the embodiment shown on a baffle plate 18 attached to a piston 19 is applied and transmits power to this. By the control pressure Ps is therefore the piston 19 in the direction of the arrow 20 postponed. In this case, a shift to the right causes a further closing of the valve element 14 , a shift to the left another opening.

The control volume then flows through a throttle element 21 and unites with the main volume of the fuel volume in the supply line 10 , The throttle element is variable. This is in the schematic diagram according to 2 by a spring-loaded closing body 22 indicated. Next to it, the throttle element 21 but also a non-variable partial passage area 23 with a narrow cross section. The closing body 22 is pressed by the control pressure Ps against a spring force to open the throttle cross section to the right. In this embodiment, therefore, the throttle effect of the variable throttle 21 depending on the control pressure Ps.

3 shows the pressure control device 9 in cross section. The housing 11 has an inlet 12 on which fuel enters at the pressure P1. It also has an outlet 13 on, the fuel exits at the pressure P2. Before the inlet 12 Typically, an unillustrated shut-off valve is provided. In particular, a shut-off valve directly on the tank 6 be arranged, with which the fuel supply, for example, when stopping the engine 2 or switch off when switching to another type of fuel.

In the 3 shown pressure reducing device 9 points in the control line 16 as an actuator one of the in 3 not shown motor control controlled piezoelectric actuator 17 on. The actor 17 is a valve 24 over which the flow of the control volume through an opening 26 is controllable. Output side of the valve 24 is a first chamber 27 arranged in which the piston 19 is movably mounted. In the first chamber 27 is the control pressure Ps on. A baffle plate is not shown in this illustration. The piston 19 is in a cylinder 28 arranged and against the force of a spring 29 movable.

A throttle element 21 connects the first chamber 27 with the outlet 13 the pressure control device 9 , The throttle element 21 is how based on 2 described, formed variably in its throttle effect.

For a regulation of the piezoelectric actuator 17 Typically, pressures P1 and P2 are measured by pressure sensors.

In operation, the piezoelectric actuator shifts 18 the closure piece of the valve 24 against the valve seat and thus controls the flow of the control volume through the opening 26 , A change in this flow causes a change in the first chamber 27 prevailing pressure Ps and thus a change in the force on the piston 19 , The piston 19 becomes thereby inside the cylinder 21 postponed.

The valve element 15 gets through the on the piston 19 acting control pressure Ps in the first chamber 27 opened or closed. As a result, the fuel volume flows through the opening 31 in the second chamber 30 , In the second chamber 30 the pressure P2 is applied.

LIST OF REFERENCE NUMBERS

1

vehicle

2

internal combustion engine

3

cylinder

4

Kraftstoffeinblasvorrichtung

5

Fuel rail

6

tank

7

supply line

8th

filter

9

pressure regulator

10

supply

11

casing

12

inlet

13

outlet

14

valve element

15

closing element

16

control line

17

piezo actuator

18

flapper

19

piston

20

arrow

21

throttle element

22

closing element

23

Part passage area

24

Valve

25

signal line

30

computer unit

31

processing unit

32

computer readable medium

Claims (12)

Pressure control device ( 9 ) for a fuel volume, comprising - a valve element ( 14 ) with a closing element ( 15 ), via which the pressure P2 of the fuel volume on the output side of the pressure regulating device ( 9 ) is controllable; A control line ( 16 ) for the valve element ( 14 ), in which a diverted from the fuel volume control volume is guided; A pilot element for the valve element ( 14 ), wherein by means of the pilot control element, the pressure Ps of the control volume is controllable; where the control line ( 16 ) is designed such that the control volume upstream of the valve element ( 14 ) is branched off from the fuel volume and downstream of the valve element ( 14 ) via a throttle element ( 21 ) and downstream of the throttle element ( 21 ) is merged again with the fuel volume, wherein the throttle element ( 21 ) is variably formed in its throttle effect. Pressure control device ( 9 ) according to claim 1, wherein the pilot element comprises a piezoelectric actuator ( 17 ) having. Pressure control device ( 9 ) according to claim 1, wherein the pilot element comprises a solenoid valve. Pressure control device ( 9 ) according to one of claims 1 to 3, wherein the throttle element ( 21 ) as a valve with a spring-loaded closing body ( 22 ) is trained. Pressure control device ( 9 ) according to one of claims 1 to 3, wherein the throttle element ( 21 ) has a piezo valve. Pressure control device ( 9 ) according to one of claims 1 to 3, wherein the throttle element ( 21 ) has a solenoid valve. Pressure control device ( 9 ) according to one of claims 1 to 6, wherein the throttle element ( 21 ) is designed adjustable. Pressure control device ( 9 ) according to one of claims 1 to 7, wherein the throttle element ( 21 ) a partial passage area ( 23 ) has a fixed cross-section. Device for supplying fuel to a compressed gas-powered motor vehicle ( 1 ), comprising a pressure regulating device ( 9 ) according to one of claims 1 to 8 for reducing a fuel pressure from a tank pressure to a supply pressure of a fuel injection device ( 4 ). Vehicle operated by compressed gas ( 1 ) with a device for supplying fuel according to claim 9. Method for regulating a fuel pressure from a tank pressure to a supply pressure in a compressed gas-fueled vehicle ( 1 ), wherein as a control volume for a pilot control element branched off from the fuel flow partial flow is throttled before merging with the pressure-reduced fuel flow in dependence on at least one parameter, wherein the parameter is selected from the group consisting of a pressure in the partial flow, a desired value for a control pressure and a requested fuel volume. Computer program product comprising a computer readable medium ( 32 ) and on the computer-readable medium ( 32 stored program code which, when stored on a computer unit ( 30 ) is executed, the arithmetic unit ( 30 ) to carry out a method according to claim 11.

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