Engine system for gaseous fuel

Abstract

An internal combustion engine system comprising a gaseous fuelled engine (2) comprising one or more cylinders (7); a fuel supply (21) configured to store pressurised gas; and one or more fuel injectors (16) configured to deliver pressurised gas to the cylinders of the engine. A fuel rail (17) is configured to supply pressurised gas to the one or more fuel injectors, and a compressor arrangement (22; 30) is configured to receive gas at a first pressure from the fuel supply and to deliver gas at a higher pressure to the fuel rail. The compressor arrangement (22; 30) is hydraulically driven and connected to a hydraulic pump (32) via a hydraulic fluid circuit (33).

Description

Background Technology

[0001] In the modern technology field, the need to move away from fossil fuels and replace them with renewable energy is growing. This has significantly impacted the transportation industry, where traditional gasoline or diesel vehicles are being replaced by battery electric vehicles (BEVs). However, current battery electric vehicle technology has not yet achieved energy densities comparable to conventional fuels, which compromises its driving range. This limits the appeal of battery electric vehicle technology, particularly for heavy-duty applications where the required battery size to meet range and load requirements is impractical.

[0002] The known alternative is the use of conventional internal combustion engines fueled by hydrogen. Hydrogen is a promising choice as an energy carrier and primary fuel due to its carbon-free content, wide flammability limit, and rapid flame speed. For spark-ignition internal combustion engines, direct injection of hydrogen has proven to achieve high engine power output and efficiency combined with low emissions. Extensive research supports the feasibility of this solution, but many challenges remain to be addressed for the large-scale commercialization of this technology. One challenge of using hydrogen is reliably delivering the gas at high pressure to the cylinders of the associated engine. This may require a compression system to disconnect the engine from the main gas tank, where the storage pressure varies with the gas volume. Such a compression system, driven by an engine or electric motor, introduces further parasitic losses, thus maximizing the efficiency of any such compression system is desirable. It is against this backdrop that the present invention was conceived. Summary of the Invention

[0003] This invention is defined by the features set forth in the appended independent claims, and optional features are set forth in the dependent claims.

[0004] Additional optional and advantageous features are mentioned in the detailed description and the appended claims. Attached Figure Description

[0005] To better understand the present invention, reference is now made to the following figures by way of example only, wherein: Figure 1 This is a schematic diagram of an internal combustion engine, in which examples of the present invention can be incorporated; Figure 2 This is a schematic diagram of the compressor system associated with the engine system; Figures 3 to 5 This is a flowchart illustrating an exemplary control scheme associated with a compressor system; Figure 6 This is a schematic diagram of a vehicle equipped with an example of the present invention, particularly a heavy-duty vehicle such as a truck. Detailed Implementation

[0006] This invention relates to an internal combustion engine system for delivering pressurized gas to a vehicle, which may be an automobile. The gas may be hydrogen, which is known in the art to be used as fuel for vehicles.

[0007] Gaseous fuel power units typically require the delivery of gaseous fuel, referred to below as "gas," within a narrow range of predetermined pressures. Onboard tanks receive gas from refueling stations at a pressure typically around 700 bar, but sometimes as low as 350 bar. However, as the gas is used, the pressure in the tank will decrease. Therefore, suitable devices are desired to provide intermediate pressure boosting and / or regulation to ensure a stable gas supply to the power unit throughout the entire filling capacity of the main tank.

[0008] In order to place examples of the present invention in the technical context, reference will now be made to... Figure 1 This section describes a discussion of internal combustion engines that use gaseous hydrogen as fuel.

[0009] Overall, the internal combustion engine system 1 includes an engine block 2, an intake system 3, a fuel delivery system 4, and an exhaust system 5. The engine system 1 also includes a controller or “control unit” or “ECU” 6, which is adapted to receive data input 6.1 to sense engine operating parameters and, based on driver commands, provide appropriate control output signals 6.2 to control its operation, as is customary. The terms “controller” and “control unit” are used synonymously herein.

[0010] The illustrated engine block 2 includes four combustion chambers 7 or cylinders arranged in an "inline" configuration. However, it should be noted that this is for illustrative purposes only, and as those skilled in the art will know, an engine block can include any suitable number of combustion chambers and in any suitable configuration. Common engine configurations are single-cylinder engines, twin-cylinder, three-cylinder, inline six-cylinder or V6 engines, and V8 engines. In this document, the term "combustion chamber" will be considered synonymous with "cylinder".

[0011] The intake system 3 includes an intake port 8, which delivers fresh air to the air duct network 9 via an air filter 10. An air mass flow sensor (AMF) 11 is provided to provide data on the airflow entering the engine system 1 to the control unit 6.

[0012] Air duct network 9 delivers incoming air through air compressor 12 and then to intercooler 13. The functions of air compressor 12 and intercooler 13 are known in the art and will not be discussed further. Duct network 9 leads from intercooler 13 through throttle valve 14 to intake manifold 15. As is known, intake manifold 15 directs fresh air to each combustion chamber 7 of engine block 2 via individual air passages.

[0013] The fuel delivery system 4 includes a group of one or more fuel injectors 16 (only one of which is labeled) arranged to inject combustible fuel, in this case hydrogen, into the fresh air flowing into the combustion chamber 7.

[0014] In the illustrated example, there are multiple fuel injectors 16, the number of which corresponds to the number of combustion chambers 7. Each fuel injector 16 is arranged to inject fuel directly into a corresponding cylinder 7.

[0015] Each fuel injector 16 is connected to a fuel accumulator, or “common rail” or “fuel rail” 17, these terms may be used synonymously herein. As is known, the common rail 17 provides a relatively large volume of fuel maintained at a predetermined and controllable pressure level, meaning that the fuel injectors 16 are connected to a fuel source with a pressure level that is essentially static and unaffected by its operation. However, it should be noted that the fuel pressure within the common rail 17 may change during use due to various requirements beyond the scope of this discussion.

[0016] The fuel pressure within the common rail 17 is determined by the control unit 6 using a fuel pressure sensor 18. In this example, the fuel pressure sensor 18 is shown connected to the end of the common rail 17, which has an elongated shape. However, the shape of the common rail 17 and the relative position of the pressure sensor 18 are configurational aspects and not central to the invention. The fuel-air mixture in the cylinder 7 is ignited in the usual manner by a corresponding spark plug 19.

[0017] The common rail 17 is supplied with fuel by the fuel supply system 20. The fuel supply system 20 includes a pressurized fuel source or reservoir 21, a compressor system 22, a shut-off valve (SOV) 23, and a gas supply line 24 connecting the shut-off valve 23 to the common rail 17. In some examples, the shut-off valve 23 may be directly connected to the common rail, but typically a section of gas supply line 24 may also be present to achieve the desired separation distance between the engine system 1 and the fuel supply system 20. The pressurized fuel source 21, or "fuel tank," may be suitably configured to store hydrogen at an appropriate pressure level, typically between 350 bar and 700 bar when the fuel tank 21 is full, although the gas pressure in the tank 21 may drop significantly during use. The compressor system 22 is configured to maintain the gas pressure at a pressure suitable for injection, which may be between 150 bar and 300 bar for direct injection systems. It should be noted that the configuration of the fuel supply system 20 will be explained in more detail below.

[0018] Turning to exhaust system 5, combustion gases from cylinder 7 enter exhaust pipe or "manifold" 25, which combines the exhaust gas into a single pipe leading to turbine 26. As is known, turbine 26 is connected to air compressor 12, and together turbine 26 and air compressor 12 constitute the turbocharger of engine system 1. The turbocharger provides a means to increase the charge density of the air delivered to cylinder 7, thereby providing more efficient and powerful combustion. However, its use is not essential for operation. Turbochargers are known in automotive technology, and therefore, for the sake of brevity, will not be discussed in detail here.

[0019] Those skilled in the art will understand that the engine system 1 discussed above has been simplified for the present purpose, and in practice, the engine system will be more complex. However, the illustrated engine system 2 is intended to demonstrate the principle components and subsystems relevant to the examples of the present invention.

[0020] Figure 2 An example of compressor system 22 is shown in more detail.

[0021] Overall, the compressor system 22 includes a gas compression unit 30, a hydraulic drive system / pump 32, a heat exchanger 34, a buffer volume in the form of a buffer tank 36, and an optional pressure regulator 38. The pressure regulator 38 is advantageous in providing more precise control over the gas pressure supplied to the fuel rail 17 and can be controlled by the controller 6. These components are fluidly located between the storage tank 21 and the shut-off valve 23.

[0022] The gas compression device 30 takes the form of a double-end pressure enhancer, and its working principle is that the hydraulically driven moving piston compresses the gas in a pair of working chambers.

[0023] Hydraulic drive pump 32 is connected to gas compression device 30 via hydraulic circuit 33. Hydraulic drive pump 32 can be any suitable hydraulic pump, but preferably should have variable capacity. In the illustrated example, hydraulic drive pump 32 is driven by power output from engine block 2. This is a relatively simple mechanical implementation. In this case, hydraulic drive pump 32 can be a variable displacement pump, such as a swashplate pump, whose output can be controlled by controller 6, as will be discussed further below. Other options are also possible, and preferably any such pump will be able to reach pressures in the 300-400 bar range. For example, hydraulic drive pump can be an electrically driven pump, such as by a motor (not shown) driven by the vehicle's battery system. In this case, a pump of a known type, such as a gear pump, may be suitable because its output can be controlled by changing its drive speed.

[0024] In the illustrated example, the hydraulic circuit 33 forms a closed loop between the hydraulic pump 32, the compressor control valve 52, and the input returning to the hydraulic pump 32. An oil reservoir 35 is provided to supply sufficient oil to the hydraulically driven pump 32, allowing it to operate at any desired capacity. In this respect, the hydraulic circuit 33 can be considered to include a supply line 33a for delivering hydraulic fluid from the hydraulically driven pump 32 to the gas compressor 30 via valve 52, and a return line 33b for returning hydraulic fluid from the gas compressor 30 to the hydraulically driven pump 32. The oil reservoir 35 is connected in a branch line 33c, which connects the supply line 33a and the return line 33b. Other configurations are possible to supply hydraulic fluid to the hydraulic circuit, as those skilled in the art will understand. However, this “closed-loop” approach is considered advantageous because it provides a larger hydraulic fluid capacity when needed and offers some advantages in terms of system efficiency. Further modifications to the hydraulic circuit 33 are possible. For example, when the actuation valve 52 is not required, a bypass line can be incorporated into the hydraulic circuit 33 to allow the hydraulic fluid supply to bypass valve 52. The bypass line is implemented as shown in the accompanying drawings, wherein the input line 33a and the output line 33b are connected by means of the central position of the spool valve 52, such that hydraulic fluid flows through the spool valve 52 when it is in the neutral position.

[0025] As can be seen, the gas compression device 30 includes a piston assembly 31, which includes a pair of pistons 40 and 42 connected and spaced apart by a connecting rod 44. A first compression chamber 45 is defined at the end of the first piston 40, and a second compression chamber 46 is defined at the end of the second piston 42. A corresponding pair of hydraulically driven chambers 48 and 50 are located between the pistons 40 and 42.

[0026] Valve assembly 52 is operable to control the hydraulic fluid pressure within the hydraulic drive chambers 48, 50. In the illustrated example, valve assembly 52 is a spool valve (the term may be used synonymously), the position of which is controlled by control unit 6. Valve arrangement 52 is a three-position valve and is therefore operable to direct hydraulic drive fluid from hydraulic drive pump 32 to either of the hydraulic drive chambers 48, 50 depending on the position of valve 52. The configuration of spool valve 52 is readily understood by those skilled in the art and therefore will not be discussed further. Other valve assemblies comprising one or more valves may also be used instead of spool valves.

[0027] Hydraulic fluid is supplied to the first hydraulic drive chamber 48 via hydraulic circuit 33, driving the connecting rod 44 in a first direction (to the left in the drawing), thus compressing the gas in the first compression chamber 45. Similarly, hydraulic fluid is supplied to the second hydraulic drive chamber 50 via hydraulic circuit 33, driving the connecting rod 44 in a second direction (to the right in the drawing), thus compressing the gas in the second compression chamber 46.

[0028] In the neutral position, valve 52 prevents hydraulic drive fluid from flowing to either of the hydraulic drive chambers 48 or 50, thus keeping piston assembly 31 stationary and preventing compressed gas from being pumped out of gas compression device 30. In the neutral position, hydraulic drive fluid is allowed to circulate around the hydraulic circuit.

[0029] Compression chambers 45 and 46 receive gas from gas tank 21 at any available pressure level. The gas pressure level and temperature vary significantly depending on the amount of gas in tank 21. Compression chambers 45 and 46 are connected to gas tank 21 via inlet line 53 and inlet check valve 54. Similarly, compression chambers 45 and 46 are connected to outlet line 56 via their respective outlet check valves 58.

[0030] Inlet line 53 connects to inlet check valve 54 from gas tank 21. However, a flow control valve 55 is provided at an intermediate location. Flow control valve 55 controls the flow of gas from the gas tank to inlet line 53, or alternatively to bypass line 57, which connects upstream of shut-off valve 23. Flow control valve 54 is controlled by controller 6, as will be described in more detail below.

[0031] Gas output line 56 is connected to the fuel rail via buffer tank 36. Buffer tank 36 provides a certain volume of gas that can be maintained within a predetermined pressure range, which can be selected by control unit 6. It is envisioned that buffer tank 36 will maintain a gas pressure level higher than the gas pressure level of fuel rail 17.

[0032] The heat exchanger 34 is fluidly located downstream (or upstream) of the buffer tank 36. The function of the heat exchanger 34 is to regulate the temperature of the gas flowing into the buffer tank, which will experience a temperature increase due to the compression process. The heat exchanger 34 has at least one flow passage for the gas to flow through it (in... Figure 2 (Not shown in detail), these flow channels are constructed to exchange heat energy with the fluid medium flowing through individual channels in a manner commonly found in heat exchange devices. Figure 2 Although not shown, it is implied that there is a backflow of the heat exchange fluid medium from the coolant system 57, which will affect the heat transfer with the gas flowing through the heat exchanger 34. It should be noted that the precise form of the heat exchanger is not essential to the present invention, as will be understood by those skilled in the art.

[0033] The function of heat exchanger 34 can be combined with the function of buffer tank 36. Therefore, the internal volume of heat exchanger 34 can be limited to a sufficient volume to serve as a buffer volume, which would otherwise be provided by a separate tank.

[0034] It should be understood that the size of the buffer tank 36 can be configured such that the intermittent flow delivered by the compressor unit 30 can be smoothed before reaching the regulator 38 without causing the pressure within the buffer tank 36 to drop below an acceptable level. This acceptable level should be higher than the pressure in the fuel rail 17 so that the regulator 38 can operate normally. Typically, this means that the volume of the buffer tank 36 should be larger than the volume of the fuel rail 17, for example, 2, 3, 4, or 5 times the fuel rail volume, or up to 10 times the fuel rail volume. The preferred larger volumetric capacity of the buffer tank 36 compared to the fuel rail 17 should be balanced with the requirements for encapsulating the buffer tank 36 under typical space constraints in automotive installations.

[0035] Advantageously, and as will be described in further detail below, the presence of the buffer tank 36 provides a continuous supply of pressurized gas to the fuel rail 17. Since the volume of the buffer tank 36 is larger than that of the fuel rail 17, the buffer tank 36 acts as an intermediate mechanism between the fuel rail 17 and the gas compression device 30, ensuring that the fuel required by the engine can be met by the fuel supply system 20. Furthermore, the presence of the gas compression device 30 means that the gaseous fuel within the fuel tank can be better utilized. A further advantage of this system is that the gas compression device 30 and other components of the compressor system 22 can be located away from the components of the internal combustion engine system 1. This advantage is achieved by a hydraulically driven pump 32, which provides hydraulically driven fluid to the gas compression device 30 via a hydraulic circuit 33. In principle, the hydraulic circuit 33 can be configured to any length, thus allowing the gas compression device 30 to be physically separated from the engine block 2 and associated components. This provides significant encapsulation advantages, as the gas compression device 30 does not need to be housed within the vehicle's engine compartment. (See attached image) Figure 6 This can be understood more fully. Figure 6 Heavy vehicles, such as trucks, are shown. Figure 6 In this vehicle 60, certain components of the engine system 1, such as the engine block 2, intake system 3, exhaust system 5, fuel delivery system 4, etc., are housed within the driver's cab area A1. The driver's cab area A1 may include a suitable engine compartment 61 for housing these components. The gas compressor 30 and fuel tank 21 are shown located in an area of ​​the chassis, shown as area A2, which is a different part of the vehicle. As shown here, in the illustrated example, area A2 is an external area exposed to environmental conditions, although this is not necessary. In other examples, the engine compartment 61 may be positioned forward, such that the passenger compartment is located between the engine compartment and area A2 where the gas compressor 30 is located.

[0036] Area A2 is separated from Area A1 by a partition 62. This provides a safety benefit because the physical separation provided by the hydraulically driven pump 32 means that the gas compression unit 30 and the associated fuel tank(s) 21 can be located in a less space-constrained part of the vehicle, where any gas leakage can be mitigated by an exposed location.

[0037] Back Figure 2 Control of the gas output from the compressor system 22 is achieved through the position of the control valve 52. Valve 52 is a spool valve that can move between a central neutral position (in the illustrated example) that sets the piston assembly 31 in a stationary position, preventing compressed gas from flowing out of the compressor assembly 30. Valve 52 is a computer-controlled valve and can be controlled by the controller 6 via appropriately configured control signals. As will be described below, the controller 6 is configured to control the gas output from the gas compressor 30 to the buffer tank 36 based at least in part on a predetermined gas pressure at the buffer tank 36. In this way, the gas pressure at the buffer tank 36 can be controlled to remain within a predetermined pressure range. Such a pressure range can be static or can be dynamic based on the operating conditions of the engine system 1. The benefit of this method is that the system utilizes the gas supply within the gas tank 21 more efficiently because as the gas pressure within the gas tank 21 decreases during use, the compressor system 22 increases the pressure and stores gas in the buffer tank 36, thereby providing a predictable and reliable supply to the fuel rail 17.

[0038] Control of the gas output from the compressor system 22 also benefits from controlling the output of the hydraulically driven pump 32. As will be described below, the hydraulically driven pump is controlled to control the output of the hydraulic oil driving the gas compression device 30. By controlling the hydraulic oil output, more efficient pumping can be achieved, making the entire system more efficient.

[0039] like Figure 2 As can be seen, controller 6 is configured to receive a set of data signals and output a set of control signals. In summary, the data signals include the gas pressure and temperature in the buffer tank (P_BUF, T_BUF), the gas pressure and temperature in gas tank 21 (P_TNK, T_TNK), engine torque demand, and engine speed (TQ, SPD), while the control signals include signals related to the required position (POS_VLV) of spool valve 52 and signals related to the required output (PUMP_Q) of the hydraulically driven pump. Suitable sensors can be provided to provide the data signals.

[0040] Having described the various hardware aspects of the illustrated examples of the present invention, the discussion will now turn to control schemes, approaches or methods that can be implemented by the controller 6 for the operation of the engine system 1.

[0041] exist Figure 3In this method 100, a control algorithm is described, which the controller 6 can use to control the compressor system 22 to achieve one or more of the aforementioned effects. Method 100 is intended to be implemented on the controller 6 in a suitable execution environment defined by appropriate hardware / software / firmware.

[0042] Method 100 is proposed to be executed continuously for continuous control of the compressor system 22. A suitable execution cycle can be selected as needed; for example, the method could execute once every 25 ms. However, it should be understood that this is only an example, and other execution rates are also acceptable. In principle, the system is expected to respond to changes within a time period on the order of approximately one second; therefore, a 25 ms processing cycle time should meet this requirement without placing excessive demands on processing resources.

[0043] Method 100 begins at step 102, in which controller 6 determines the gas pressure within gas tank 21. Optionally, controller 6 may also determine the gas temperature within gas tank 21. A suitable sensing device (not shown) may be provided at gas tank 21 for this purpose. In principle, direct measurement of gas pressure may be sufficient. However, it is also conceivable that the gas pressure could be determined based on a pressure value stored at the start of engine operation or at the start of tank filling operation, and then derived from the gas usage record of the engine system. Determining the gas temperature of gas tank 21 may be useful for determining the quantity / mass of gas in gas tank 21 rather than simply relying on pressure readings. However, for the present purpose, the determination of gas pressure alone will be discussed. Controller 6 receives suitable data readings P_TNK and T_TNK (optional).

[0044] In step 104, the controller 6 compares the gas pressure in tank 21 with a predetermined acceptable pressure threshold or range. This part of the process ensures that the gas compression system 22 operates only when needed, avoiding unnecessary energy consumption. When filling the hydrogen tank, depending on the application, it is typically at a pressure of 700 bar (referred to as "full pressure") or 350 bar. Therefore, if the gas is filled to 700 bar, the controller 6 can be configured to determine whether the gas pressure has dropped below 300 bar, which may indicate a significant decrease in the amount of gas in tank 21.

[0045] In the ongoing discussion, it should be noted that the determination based on pressure can also be based on the determination of the gas quantity, which can be calculated based on the ideal gas law, gas pressure, gas temperature, and the known geometry of the container.

[0046] If the gas pressure is at an acceptable level, method 100 proceeds to step 106, where the flow control valve 55 is configured to allow gas to flow from the gas tank 21 to the main supply line 24 upstream of the shut-off valve 23. Furthermore, the hydraulic pump 32 and the gas compressor 30 are configured to be deactivated. In this manner, the controller 6 sets the POS_VLV signal to null or "0", so that the piston assembly 31 is in a stationary position and no gas is supplied from the gas compressor 30. Similarly, the controller 6 sets the PMP_Q signal to zero, so that no hydraulic fluid is pumped to the gas compressor 30.

[0047] If the gas pressure is not at an acceptable level, method 100 proceeds to a set of actions to configure the operation of the gas compression device 30 and the hydraulic pump 32 with appropriate settings.

[0048] Essentially, controller 6 is configured to control the operation of gas compression device 30 so that the gas supply to fuel rail 17 is maintained at a level suitable for the operation of engine system 1. When the gas pressure in fuel tank 21 is within an acceptable range, flow control valve 55 is configured to supply fuel directly upstream of shut-off valve 23 via fuel bypass line 57. For the purposes of this discussion, shut-off valve 23 can be considered to be in the open position. However, it should be noted that shut-off valve 23 can be commanded to the closed position during engine system 1 shutdown or in emergency events requiring the disconnection of hydrogen supply to fuel rail 17.

[0049] Buffer tank 36 provides a volume of gas that can be pressurized to a pressure equal to or greater than the gas pressure in the fuel rail. In this way, buffer tank 36 can be filled with a gas pressure greater than that of gas tank 21, thereby better utilizing the remaining gas in gas tank 21 while still providing a reliable pressurized gas source for fuel rail 17. For this purpose, controller 6 is configured to control gas compression device 30 to maintain the gas pressure within buffer tank 36 within an acceptable pressure range, or at least above the minimum acceptable pressure level.

[0050] Therefore, in step 108, controller 6 measures the gas pressure P_BUF in the buffer tank. In the illustrated example, controller 6 also measures the gas pressure in the main gas tank 21, as shown in step 110.

[0051] In step 112, the controller 6 is configured to position or state the valve 52 to maintain the gas pressure in the buffer tank 36 within the desired range. To this end, the controller 6 is configured to switch the valve state between +1 and -1 positions to control the reciprocating motion of the piston device 31, thereby inducing a suitable pressurized gas mass flow rate from the gas compression device 30. For this purpose, the controller 6 can read from an internal data structure that sets the valve switching timing based on the error between the measured gas pressure in the buffer tank 36 and the desired pressure. Other possibilities will be conceived by those skilled in the art.

[0052] In step 114, the controller 6 sets the flow output of the hydraulic drive pump 32 by outputting the PMP_Q signal. This causes the hydraulic drive pump 32 to supply a suitable hydraulic fluid to the gas compression device 30 through valve 52. For this purpose, the controller 6 can read from an internal data structure that sets the threshold of the PMP_Q signal based on the gas pressure / temperature reading. Other possibilities will be conceived by those skilled in the art.

[0053] Advantageously, controlling the output of the hydraulic drive pump 32 based on the gas pressure in tank 21 provides more efficient operation of the entire system. If the gas pressure is low, the controller 6 will compensate for this by increasing the flow rate from the hydraulic drive pump 32, which in turn will drive the gas compressor 30 more powerfully. Conversely, if the gas pressure in tank 21 drops only slightly, the flow rate from the hydraulic drive pump 32 can be set at a more moderate level. This method achieves a more efficient system because it provides a variable flow rate of hydraulic drive fluid tailored to the needs of the gas compressor 30 and avoids using energy to drive the hydraulic drive pump 32 when the pressure in tank 21 is at an acceptable level. This results in a reduction of parasitic losses.

[0054] Steps 110 and 114 are shown here to be performed simultaneously. However, precise timing is not required for this invention.

[0055] After completing steps 112 and 114, the method is repeated at appropriate time intervals as discussed above. In this way, the method applies continuous and adaptive control to the outputs of the hydraulically driven pump 32 and the gas compression device 30.

[0056] Another method 200 according to the invention is shown in Figure 4 In method 200, steps 102 to 112 are the same as those described above. Figure 3 The same steps are discussed in Method 100, so for clarity, they will not be discussed again. However, the discussion will focus on the differences between Method 200 and Method 100, and the technical significance of these differences.

[0057] In method 200, step 110 involves controller 6 receiving data related to the gas pressure in main gas tank 21, as discussed above. However, method 200 includes another step (step 202) where controller 6 receives data related to engine system operating conditions. In this specific example, controller 6 receives an engine torque demand signal (TQ) and / or an engine speed signal (SPD).

[0058] Upon receiving data relating to the gas pressure (and optionally temperature) of the gas in tank 21 and engine operating conditions (TQ, SPD), controller 6 is operable to calculate the required hydraulic fluid output from hydraulically driven pump 32 and control hydraulically driven pump 32 to produce the required flow rate based on the gas pressure data and engine operating condition data (step 204). For this purpose, controller 6 can access a multidimensional mapping, which can be stored in memory, and create a lookup list of pump output PMP_Q relative to engine torque and / or engine speed (TQ; SPD) and tank pressure / temperature (P_TNK, T_TNK).

[0059] The advantage of this method is that the controller 6 can more accurately manage the output from the hydraulically driven pump 32 based on a wider range of operating conditions, thereby providing a more accurate gas mass flow rate from the gas compression unit 30. Furthermore, it is believed that method 200 will reduce the activation / deactivation of the slide valve 52, which improves the reliability of this component.

[0060] Another method 300 according to the invention is shown in Figure 5 In method 300, steps 102 to 112 are the same as those mentioned above. Figure 3 and Figure 4 Methods 100 and 200 are the same, so for clarity, the same steps will not be discussed again. However, the discussion will focus on the differences in method 300 and the technical significance of these differences.

[0061] In method 300, step 110 involves controller 6 receiving data related to the gas pressure in main gas tank 21, as discussed above. However, method 300 includes another step (step 302) where controller 6 receives data related to engine system operating conditions and data related to the gas pressure P_BUF in buffer tank 36. Note that the pressure in buffer tank 36 could also be the gas pressure in heat exchanger 34, where heat exchanger 34 provides the buffer volume of buffer tank 36.

[0062] Therefore, in this specific example, controller 6 receives the engine torque demand signal (TQ) and / or the engine speed signal SPD, as well as the pressure P_BUF within the buffer tank 36.

[0063] Upon receiving data relating to the gas pressure (and optionally temperature) of the gas in tank 21, data relating to engine operating conditions (TQ, SPD), and data relating to the buffer tank pressure P_BUF, the controller 6 is operable to calculate the required hydraulic fluid output from the hydraulically driven pump 32 based on the gas pressure data, engine operating condition data, and buffer tank pressure data (step 304), and controls the hydraulically driven pump 32 to produce the required flow rate. For this purpose, the controller 6 can access a multidimensional mapping, which can be stored in memory, and create a lookup list of the pump output PMP_Q relative to engine torque and / or engine speed (TQ; SPD), tank pressure (P_TNK), and buffer tank pressure (P_BUF). When calculating the required hydraulic fluid output from the hydraulically driven pump 32, any suitable control algorithm can be used, such as a PID (proportional / integral / derivative) control structure or a similar algorithm, as will be apparent to those skilled in the art.

[0064] Method 300 offers the advantage of further improved efficiency in controlling the hydraulically driven pump 32 to provide a suitable hydraulic fluid flow rate to drive the gas compression device, thereby providing the required mass flow rate to the buffer tank to set the desired pressure level. In methods 100, 200, and 300, it should be noted that suitable control algorithms can be implemented to ensure proper control of the actual / measured buffer tank pressure to minimize the error compared to the target buffer tank pressure, which may be within a suitable range, for example, between 300 and 350 bar, depending on the conditions. Suitable control algorithms would include appropriately adjusted proportional-integral-derivative closed-loop control algorithms, as will be understood by those skilled in the art.

[0065] As a further aspect of the control methods detailed above in methods 100, 200, and 300, it should be noted that in step 112, the controller 6 controls the slide valve 52 to maintain the buffer tank pressure within a specified pressure range. The controller 6 has the authority to set the slide valve position to one of three different positions: -1, 0, and +1, to drive the piston device 31 to the left and right in the figures. In one example, the controller 6 is configured to select a specific timing for when to control the slide valve 52 to the "0" position to stop the gas compression device 30. Specifically, in one example, the controller 6 is configured to determine the equilibrium point of the gas compression device 30 when the controller 6 determines that the buffer tank pressure is within an acceptable range and therefore operation can be stopped. The equilibrium point of the gas compression device 30 is a position where the gas pressure in each compression chamber 45, 46 is substantially equal or at least within a small range relative to each other, for example, within 2-8%. The advantage of this method is that when the piston assembly 31 is stationary, the hydraulic fluid trapped in the drive chambers 48 and 50 is not significantly compressed. This means that when the control valve 52 resumes the movement of the piston assembly 31, the movement will resume smoothly rather than abruptly, providing smoother and quieter operation of the gas compression device 30. Furthermore, when the engine system 1 is shut down with the valve 52 in the "closed" position, there is no significant pressure residue, which reduces wear on the valve 52.

Claims

1. An internal combustion engine system, comprising: A gas-fueled engine (2) includes one or more cylinders (7); a fuel supply device (21) configured to store pressurized gas; one or more fuel injectors (16) configured to deliver the pressurized gas to the cylinders of the engine; and a fuel rail (17) configured to supply the pressurized gas to the one or more fuel injectors. A compressor unit (22; 30) configured to receive gas at a first pressure from the fuel supply device and deliver gas at a higher pressure to the fuel rail. The compressor unit (22; 30) is hydraulically driven and connected to the hydraulic pump (32) via a hydraulic fluid circuit (33).

2. The engine system according to claim 1, characterized in that, The hydraulic pump is directly driven by the gas-fueled engine.

3. The engine system according to claim 1 or 2, characterized in that, The hydraulic pump is located away from the gas fuel engine.

4. The engine system according to any one of the preceding claims, characterized in that, It also includes a buffer volume (36), wherein the buffer volume is located between the compressor unit (30) and the fuel rail (17).

5. The engine system according to any one of the preceding claims, characterized in that, It also includes a heat exchanger (34) located between the compressor unit (30) and the fuel rail (17).

6. The engine system according to claim 5, which is dependent on claim 5, is characterized in that, The heat exchanger (34) provides the buffer volume (36).

7. The engine system according to any one of the preceding claims, characterized in that, The hydraulic circuit (33) includes a hydraulic supply line (33a) and a hydraulic return line (33b), the hydraulic supply line (33a) being used to deliver hydraulic fluid from the hydraulic pump to the compressor unit, and the hydraulic return line (33b) being used to deliver the hydraulic fluid away from the compressor unit (30).

8. The engine system according to claim 7, characterized in that, The hydraulic fluid reservoir (35) is connected in a branch line (33c) located between the hydraulic supply line (33a) and the hydraulic return line (33b).

9. The engine system according to any one of the preceding claims, characterized in that, The hydraulic circuit includes a bypass system configured to bypass hydraulic fluid when hydraulic drive to the compressor is not required.

10. The engine system according to any one of the preceding claims, characterized in that, The hydraulic circuit (33) includes a valve device (52) to selectively control the output of the compressor device (30).

11. A vehicle (60) comprising the internal combustion engine system (1) as described in claims 1 to 10.

12. The vehicle according to claim 11, characterized in that, It includes an engine compartment (61) and a chassis area (A2) separate from the engine compartment (61), wherein the gas fuel engine is located in the engine compartment and wherein the compressor unit (30) is located in the chassis area (A2).

13. The vehicle according to claim 12, characterized in that, The hydraulic drive pump (32) is located in the engine compartment (61).

14. The vehicle according to claim 11 or 12, characterized in that, The passenger compartment (A1) is located between the engine compartment and the chassis area (A2) where the compressor unit is located.

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