Pressure tapping device and motor vehicle having a pressure tapping device, and pressure tapping method

Methods and systems are provided for a pressure tapping device for a motor vehicle where a portion of the pressure energy generated at the fuel storage reservoir is transmitted to a working medium, physically separate from the fuel via the pressure tapping device. The pressure tapping device is fluidically coupled to a pressure actuator and enables the pressure operation via transmission of the pressure energy and adjustment of valves diverting flow from the fuel storage reservoir to the engine intake through the pressure tapping device.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to German Patent Application No. 102016220037.2, filed Oct. 14, 2016. The entire contents of the above-referenced application are hereby incorporated by reference in its entirety for all purposes.

FIELD

The disclosure relates to a pressure tapping device for operating vacuum-actuated devices.

Vacuum may be generated during throttled engine operation but the operation of turbochargers may, however, reduce the amount of vacuum delivered to the intake manifold of the engine. Thus systems that may generate vacuum for other vehicle applications that rely on low pressure actuation without compromising the efficiency of the engine are desirable. DE 102014222714 A1 discloses the possibility of vehicle systems comprising various vacuum consumer devices which are actuated by means of a vacuum. This includes a brake booster, for example. The vacuum used by these devices may be provided by a special vacuum pump. In further embodiments one or more aspiration devices may be incorporated into the engine system which are capable of utilizing the air flow in the engine and using it to generate a vacuum.

The inventors herein have recognized potential issues with such systems. In one example, vacuum pumps may be parasitic and result in energy waste. As another example, vacuum pumps may increase the packaging space of the engine and increase the cost and complexity of the vehicle.

Accordingly, the inventors herein propose an approach to at least partly address the above issues. In one example, a pressure tapping device may include a fluid-carrying connection to a fuel line and may be configured to transmit a proportion of pressure energy of the fuel to a working medium, physically separate from the fuel. The pressure tapping device, according to the disclosure, may be used in a motor vehicle which comprises an internal combustion engine and a fuel storage reservoir connected to the internal combustion engine by a fuel line, wherein the fuel may be stored in the fuel storage reservoir at a storage pressure greater than an ambient pressure and thereby possesses pressure energy. According to the disclosure the pressure tapping device has a fluid-carrying connection to the fuel line and is configured to transmit a proportion of the pressure energy of the fuel to a working medium, physically separate from the fuel. The pressure tapping device advantageously allows use to be made of the pressure energy inherent in fuel that is stored under pressure, such as compressed natural gas (CNG), for example.

In one example of the pressure tapping device according to the disclosure, the device may comprise an admission line with an admission line pressure control valve and a discharge line with a discharge line valve. This makes it possible to feed fuel through the pressure tapping device and to limit the minimum and maximum working pressure. In another example of the pressure tapping device, the device comprises a pressure transmitter, including a first cylinder with a first piston and a second cylinder with a second piston having a fluid-carrying connection to the first cylinder. A transmission fluid is located between the first piston and the second piston. The admission line and the discharge line have a fluid-carrying connection to the first cylinder.

The pressure tapping device according to the disclosure may be integrated into a motor vehicle. The motor vehicle comprises an internal combustion engine and a fuel storage reservoir connected to the internal combustion engine by a fuel line. The fuel may be stored in the fuel storage reservoir at a storage pressure greater than an ambient pressure and thereby possesses pressure energy. Here the pressure tapping device has a fluid-carrying connection to the fuel line. The motor vehicle may be operated more efficiently with the pressure tapping device since conventional devices, such as pressure pumps and their drive, can be eliminated.

In another example of the motor vehicle, according to the present disclosure, the pressure tapping device is connected to a pressure-operated actuator of the motor vehicle. The actuator can therefore be operated by the pressure energy obtained from the fuel. The pressure-operated actuator may be, in this example, a brake booster. A greater pressure differential can be generated in the brake booster by the pressure tapping device than by a vacuum pump. This allows a greater boost for the same brake booster design size.

In another example, a method for operating a vehicle with a pressure tapping device includes supplying fuel to an engine from a fuel storage reservoir via a fuel line and transferring pressure energy from the fuel storage reservoir to a brake booster by the pressure tapping device. In one example, the method may further include opening an admission line pressure valve. By opening the admission line pressure valve in the admission line, fuel is diverted to the pressure tapping device, thereby transmitting a portion of the pressure energy to the brake booster via a working fluid housed within the pressure tapping device. The working fluid is then depressurized by opening the discharge line valve disposed in the discharge line which then flows fuel from the pressure tapping device to the fuel line. Use is thereby made of pressure energy derived from the fuel pressure.

In an example of the pressure tapping method according to this disclosure, an actuator of the motor vehicle is operated by the pressure energy of the working medium. In particular, a brake booster is operated. In this way, the actuator is operated by the pressure energy obtained from the fuel. In brake-boosting, greater brake power assistance can be achieved than in conventional vacuum methods.

DETAILED DESCRIPTION

In the global effort to reduce carbon dioxide emissions, spark ignited engines running on compressed natural gas (CNG), as an alternative to conventional gasoline, are expected to contribute significantly to this endeavor. The concept of a CNG-fueled engine coupled with a turbocharger and relying on direct injection of the fuel is an attractive configuration for consumers. For a CNG tank of appropriate dimensions for onboard vehicle use, the tank may be pressurized to 300 bar to provide a reasonable driving range per tank of gas. This pressure may be reduced to around 30 bar for subsequent injection into the cylinders which, as a result, may represent wasted potential energy. Ideally, this energy, henceforth referred to as pressure energy, may be captured and directed toward another energy-consuming application for engine operation.

Applications which may benefit from the capture of the pressure energy may include systems that utilize differences in pressure. As such, the pressure differentials involved in the CNG/fuel injection system may be used for a vacuum-actuated process. The following description relates to systems and methods for a pressure tapping device in arranged in the drive unit of a motor vehicle. An example of a motor vehicle with a drive unit and engine is given inFIG. 1. The motor vehicle includes a fuel storage reservoir that may store a gas, such as natural gas, at a pressure higher than an ambient pressure. A detailed depiction of the arrangement of the pressure tapping device within the drive unit of the motor vehicle is shown inFIG. 2. The elements involved in transmitting pressures and generating pressure differentials are given in relation to gas flow from the CNG tank to the engine. A flowchart describing the steps involved in the operation of the pressure tapping device and the thresholds enabling actuation of a brake booster is given inFIGS. 3A-3B.

Turning now toFIG. 1, a schematic representation of an exemplary motor vehicle10is shown. The motor vehicle10comprises a drive unit11with an internal combustion engine12utilizing fuel. The fuel may be a gas, such as natural gas (CNG) or methane or the like. For storing the fuel, the motor vehicle10comprises a fuel storage reservoir13, which is configured to store fuel at a storage pressure P1greater than an ambient pressure P5. The storage pressure P1is between 50 bar and 300 bar, for example. The pressure differential relative to ambient pressure gives the stored fuel a specific pressure energy. For delivering the fuel to the internal combustion engine12, the fuel storage reservoir13has a fluid-carrying connection to the internal combustion engine12via a fuel line23. The motor vehicle10according to the disclosure comprises a pressure tapping device40, which is coupled to the fuel line23.

FIG. 2shows the pressure tapping device40in more detail in a first embodiment together with a drive unit11. The drive unit11comprises an inlet air tract26, at the start of which an air filter17is arranged, for supplying the internal combustion engine12with inlet air. A mass air flow sensor18is arranged downstream of the air filter17. The internal combustion engine12may be fluidically coupled to a compressor16for compressing the inlet air. The compressor16is, in particular, part of a turbocharger14, which furthermore comprises an exhaust-gas turbine15arranged in an exhaust tract27of the motor vehicle10and having a torque-transmitting connection (e.g., shaft) to the compressor16. Downstream of the compressor16, a charge-air cooler19is arranged in the inlet air tract26for cooling the compressed inlet air. The inlet air tract26is moreover provided with a throttle valve22arranged downstream of the charge-air cooler19for controlling the mass air flow of inlet air.

For supplying the internal combustion engine12with fuel, the exemplary internal combustion engine12includes an injector21for each of a plurality of working chambers25(also referred to as combustion chambers or cylinders). The internal combustion engine12shown thereby has direct fuel injection. The injector21receives the fuel from a fuel rail20, which is formed at the end of a fuel line23. In the fuel rail20, the fuel has a fuel rail pressure P4which is less than a storage pressure P1of a fuel storage reservoir13. The pressure differential between the storage pressure P1and the fuel rail pressure P4is useful because, on the one hand, the fuel rail pressure P4is set so that an optimum injection operation is achieved. On the other hand, the storage pressure P1is greater than the fuel rail pressure P4and here is accounted for by the mass of fuel that may be stored. The pressure differential between the storage pressure P1and the fuel rail pressure P4gives the fuel at the storage pressure P1its pressure energy. For controlling the fuel rail pressure P4, a fuel line pressure control valve24is arranged in the fuel line23upstream of the fuel rail20.

The pressure tapping device40is arranged downstream of the fuel storage reservoir13and upstream of the fuel rail20and is coupled to the fuel line23at a set of branch points28and29. At a first branch point28, at least a portion of the fuel may be led out of the fuel line23into the pressure tapping device40and at a second branch point29, the fuel may be led out of the pressure tapping device40into the fuel line23. Thus the pressure tapping device40comprises an admission line45for connection to the first branch point28, and a discharge line43for connection to the second branch point29. In the motor vehicle10, the admission line45is formed together with the discharge line43as a tract running parallel to the fuel line23and forms a bypass around a fuel line pressure control valve24. Thus the first branch point28is situated in the fuel line23upstream of the fuel line pressure control valve24and the second branch point29is situated in the fuel line23downstream of the fuel line pressure control valve24. An admission line pressure control valve41, which is formed in the same way as the fuel line pressure control valve24, is arranged in the admission line45. A discharge line valve44, which in one example may be an On-/Off switch, is arranged in the discharge line43.

The pressure tapping device40, according to this disclosure, comprises a pressure transmitter42, which comprises a set of two interconnected cylinders46and47. A first piston51is arranged in the first cylinder46and a second piston52is arranged in the second cylinder47. A transmission fluid49, which couples first and second pistons51and52hydraulically together, is located between the first piston51and the second piston52. The first piston51may have a smaller cross sectional area and a smaller piston surface than the second piston52, as shown inFIG. 2. The pressure transmitter42is thereby embodied as a hydraulic booster.

The pressure transmitter42is configured so that pressure energy of the fuel can be transmitted to the first piston51. For this purpose the first cylinder46has a fluid-carrying connection to the admission line45and to the discharge line43. The introduction of fuel into the first cylinder46generates an intermediate pressure P2, which may be transmitted from the first piston51to the second piston52. The admission line pressure control valve41and the discharge line valve44may be actuated in order to adjust the intermediate pressure P2. The second piston52acts on a working medium50. The pressure tapping device40is configured to transmit pressure energy originating from the fuel to the working medium50, so that the working medium50has a desired working pressure P3which is greater than an ambient pressure P5. The working pressure P3may be 1 bar greater than the ambient pressure P5in one example. The pressure transmitter42is configured in the way shown so as to keep the fuel physically separate from the working medium50.

For measuring the working pressure P3, the pressure tapping device40is provided with a manometer48. The manometer48may be connected to the admission line pressure control valve41via a control line, allowing the position of the admission line pressure control valve41to be adjusted as a function of the current working pressure P3. The position of the discharge line valve44may also be adjusted as a function of the current working pressure P3. In one example, a controller54may be provided for controlling the valves41and44.

Controller54may be a conventional microcomputer including: microprocessor unit58, input/outports64, read-only memory56, random access memory60, keep alive memory62, and a conventional data bus. Controller54is shown receiving a signal the manometer48for sensing the working pressure P3. Upon receiving the signal from manometer48, controller54send signals to the admission line pressure control valve41and the discharge line valve44to actuate opening or closing of the valves. As described above, opening admission line pressure control valve41allows transfer of pressure across the pressure transmitter42, resulting in a working pressure P3generated at the working medium50.

The working medium50may be liquid or gaseous. The pressure tapping device40is configured to supply the pressure energy of the working medium50to at least one pressure-operated actuator30of the motor vehicle10. For this purpose, the pressure tapping device40has a pressure-transmitting (e.g., a fluid-carrying) connection to the actuator30. In one such example, the actuator30may be a brake booster which is configured to use pressure energy in order to boost a brake pedal force. The actuator30, as a brake booster, may therefore include a diaphragm66that divides the chamber of the brake booster into smaller chambers which may hold different pressures relative to one another.

The motor vehicle10according to this disclosure is configured to perform the pressure tapping method in which a proportion of the pressure energy of the fuel is transmitted to the working medium50. The pressure tapping method may be initiated by the pressing of a brake pedal68which may be detected by a brake sensor70that is in electronic communication with the controller54. The controller54sends signals to the admission line pressure valve41and the fuel line pressure control valve24. Through at least a partial opening of the admission line pressure valve41and/or at least a partial closure of the fuel line pressure control valve24, a proportion of the fuel may be led into the first cylinder46of the pressure transmitter42. A desired intermediate pressure P2may thereby be generated in the first cylinder46. The intermediate pressure P2bears on the first piston51and is transmitted to the second piston52in the second cylinder47. If the intermediate pressure P2is to be reduced, the discharge line valve44may be opened and the fuel fed through the discharge line43back to the fuel line23downstream of the fuel line pressure control valve24. At the same time the admission line pressure valve41may be at least partially closed. In this way, the intermediate pressure P2may be adjusted by opening and closing of the discharge line valve44, the fuel line pressure control valve24, and the admission line pressure valve41.

The working medium50is used, in particular, for controlling the actuator30of the motor vehicle10by generating a pressure differential. An actuator30embodied as a brake booster may be operated by the working medium50. Here, as in conventional brake boosters, a higher pressure is generated in a pedal chamber than in a brake cylinder chamber (not shown). In contrast to the conventional method, however, a pressure lower than the ambient pressure is not generated in the brake cylinder chamber, a pressure in excess of the ambient pressure P5instead being generated in the pedal chamber. In particular, the excess pressure is 1 bar greater than the ambient pressure P5. To return the actuator30to a resting mode, the working pressure P3is reduced by at least partially opening the discharge line valve44and feeding the fuel into the fuel line23. In this way, the brake booster is activated by transmitting the intermediate pressure P2obtained from the pressure P1at the fuel storage tank13via the fluidly connected set of cylinders46and47, generating a pressure differential that actuates the brake booster without an artificially created vacuum.

FIGS. 3A-3Bis a flow chart illustrating a method for using a pressure tapping device positioned within the drive unit of a motor vehicle, such as pressure tapping device40ofFIGS. 1-2, to activate a brake booster. Instructions for carrying out method300and the rest of the methods included herein may be executed by a controller (such as controller54ofFIG. 2) based on instructions stored on a memory of the controller and in conjunction with signals received from sensors of the engine system, such as the sensors described above with reference toFIG. 2. The controller may employ engine actuators (e.g. pressure tapping device40) of the engine system to adjust engine operation, according to the methods described below.

At302, method300includes delivering gaseous fuel to the engine for direct injection at the engine cylinders via a fuel line and fuel rail, such as engine12via fuel rail20and fuel line23. At304, the method includes checking for a signal from the brake sensor (e.g., sensor70) indicative of actuation of the vehicle brake. Then, at306, the brake signal is compared to a threshold at the controller and a determination whether the signal exceeds the threshold is made. For example, the threshold may be an amount of pressure exerted on the brake pedal (e.g., brake pedal68inFIG. 2) by the operator that indicates boost from the brake booster is requested. In one example, the threshold may be zero, such that any actuation of the brake triggers boost from the brake booster. In another example, the threshold may be greater than zero, such that relatively small amounts of braking may be performed manually by the operator without boost. If the sensor detects less pressure exerted on the brake pedal than a threshold amount of pressure, the method continues to328and gas continues flowing through the fuel line with the admission line pressure control valve closed. If, however, the detected pressure on the brake pedal is greater than the threshold amount of pressure, the method proceeds to308.

At308, the admission line pressure control valve (e.g., valve41) is at least partially opened, allowing some of the fuel flowing through the fuel line to enter the admission line of the pressure tapping device. At the same time, the fuel line pressure valve (e.g., valve24) is partially closed and the discharge line valve (e.g., valve44) is shut. The partial closing of the fuel line pressure valve may have the effect of reducing the fuel flow through the valve by an amount that results in the flow being less than 100% of the flow through the fuel line pressure valve when it is open. By partially closing the fuel line pressure valve, the fuel supply may be throttled, increasing the back-pressure upstream of the fuel line pressure valve and allowing the fuel to flow into the first cylinder of the pressure tapping device. The fuel line pressure valve may be closed by a suitable amount, such as 10% or more, but left open enough to maintain commanded pressure at the fuel rail. An intermediate pressure that is lower than the pressure of the fuel storage reservoir but higher than the ambient pressure is generated at the first cylinder of the pressure tapping device in308and transmitted to the second cylinder of the pressure tapping device at310via a transmission fluid. The intermediate pressure is transmitted yet again, at312, from the second cylinder to a working medium. Then, at314, the pressure of the working medium is measured by a manometer (e.g., manometer48inFIG. 2) and sent to the controller. The method, at316, then determines if the working pressure is equal to or greater than 1 bar above the ambient pressure.

If the pressure is not equal to or greater than 1 bar above ambient pressure, the method proceeds to330where the admission line pressure control valve remains at least partially open to continue transferring fuel to the first cylinder and continues to320where the working pressure is transferred from the working medium to the brake booster. In some examples, if the pressure does not reach 1 bar above ambient, the fuel line pressure valve may be adjusted to a more closed position. Movement of a brake diaphragm (e.g., the brake diaphragm66inFIG. 2) is actuated, generating a pressure differential across the brake diaphragm and generating boost for brake operation. If, however, the pressure in the working medium is at least 1 bar above ambient pressure, the method follows318instead. If the pressure is more than 1 bar above ambient, the discharge line valve is opened and the admission line pressure valve is at least partially closed to allow some of the pressure to bleed out through the discharge line valve into the fuel line and lower the pressure in the working medium before continuing to actuating the brake booster at320. However, if the pressure is equal to 1 bar above ambient, the discharge line valve is closed and the admission line pressure valve is closed.

The method300then proceeds to322where the controller checks the brake signal sent from the brake sensor and determines if the brake signal is below a threshold. This threshold, as described above, may be, for example, a predetermined amount of pressure exerted on the brake pedal by the operator. If the signal is not below the threshold, the method cycles back to306to continue to transfer pressure from the fuel system to the brake booster via the pressure tapping device. If the signal is determined to be below the threshold, the method continues to326where the discharge line valve and fuel line pressure control valve are both opened and fuel is flowed to the engine via the fuel line and fuel rail.