Engine braking method for operating vehicle having turbocharged internal combustion engine and related vehicle

Abstract

The present disclosure relates to an engine braking method for operating a vehicle having a turbocharged internal combustion engine (12) and a related vehicle. The engine braking method is used for operating a vehicle (10) having a turbocharged internal combustion engine (12). The engine includes: a boost pressure adjusting device (42) configured to adjust boost pressure (P2) in an intake manifold (20); and an exhaust restriction device (40) located downstream of a turbine (34) of the turbocharger (30) and configured to regulate the exhaust pressure (P3) in the exhaust manifold (22). The engine braking method comprises a dual phase during which a boost pressure regulating device (42) regulates the exhaust pressure (P3) in the exhaust manifold (22) in a closed-loop manner and an exhaust limiting device (40) controls the boost pressure (P2) in a closed-loop manner, simultaneously, during which the boost pressure regulating device (42) regulates the exhaust pressure (P3) in the exhaust manifold (22) in a closed-loop manner and the exhaust limiting device (40) controls the boost pressure (P2) in a closed-loop manner.

Description

Technical Field

[0001] The present disclosure generally relates to engine braking for turbocharged engine vehicles. In particular aspects, the present disclosure relates to an engine braking method for operating a vehicle with a turbocharged internal combustion engine and a vehicle configured to implement such an engine braking method. The present disclosure may be applied to heavy vehicles such as trucks, buses, and construction equipment, among other vehicle types. Although the present disclosure may be described with respect to a particular vehicle, the present disclosure is not limited to any particular vehicle. Background Art

[0002] Engine braking is a critical function for commercial vehicles, as it enables the vehicle to maintain a constant speed downhill for a long time without using foundation brakes, which is beneficial for safety and drivability. Engine braking is usually achieved by using a compression release system (such as the so-called Jacobs bleeder brake) and an exhaust restriction device (such as a proportional damper), which is installed after the turbocharger's turbine and is used to control the target air pressure in the exhaust manifold. Unfortunately, this control strategy has limited results in terms of braking power, because closing the damper also leads to a reduction in air flow through the engine. This has several secondary negative effects, such as overheating of the fuel injector nozzle tips due to the lack of air to cool them, increased oil discharge at the turbocharger compressor outlet due to the lack of air pressure in the compressor housing to maintain the seal, etc.

[0003] Attempts have been made to address these issues using alternative approaches. For example, on engines that include a turbocharger with a movable element (also known as a VGT) that adjusts the turbocharger's output, an alternative to using an exhaust baffle is to use a VGT to control exhaust back pressure: this is called "VGT braking." Increasing exhaust back pressure using a VGT also increases air flow, which benefits the efficiency of the compression release system. However, since this also results in a reduction in the difference between intake and exhaust pressures, VGT braking does not actually provide much of a braking power increase. Another disadvantage of this strategy is that it reacts slowly and sluggishly, which can take up to several seconds, due to the time required to pressurize the entire intake system.

[0004] The present invention aims to solve the above mentioned problems by providing an engine braking method which achieves high braking power output while keeping operating parameters such as injector cooling within their specified ranges. Summary of the invention

[0005] According to a first aspect of the invention, the invention relates to an engine braking method for operating a vehicle having a turbocharged internal combustion engine. The engine comprises: - a plurality of cylinders connected to an intake manifold collecting fresh air and to an exhaust manifold collecting exhaust gas from said cylinders, - a turbocharger having a compressor driven by a turbine, the compressor being configured to increase boost pressure in the intake manifold, and the turbine being configured to be driven by the exhaust gas flowing out of the exhaust manifold; - a boost pressure regulating device configured to adjust the boost pressure in the intake manifold, and - an exhaust restriction located downstream of the turbine and configured to adjust the exhaust pressure in the exhaust manifold.

[0006] The engine braking method comprises two phases, during which the following are performed simultaneously: - the boost pressure regulating device regulates the exhaust pressure in the exhaust manifold in a closed loop manner so as to regulate the exhaust pressure to a predetermined first threshold value, and - The exhaust gas restriction device controls the boost pressure in a closed-loop manner in order to adjust the boost pressure to a predetermined second threshold value.

[0007] Technical benefits may include increasing boost pressure and exhaust pressure simultaneously, resulting in a higher engine braking effect. At the same time, the air flow through the cylinder is kept at a high level, thereby facilitating cooling of the injector tip. Furthermore, the pressure difference between boost pressure and exhaust pressure remains positive, thereby preventing oil leakage through the compressor seal. Thus, on a steep downhill road, it is possible to increase the load of the vehicle, and / or drive the vehicle on a steeper road, while regulating the speed of the wheels based solely on engine braking, i.e. without using foundation brakes. The overall safety of the vehicle is thus improved.

[0008] Optionally, in some examples, including at least one preferred example, the engine includes an intake throttle valve disposed between the turbocharger and the intake manifold and configured to control the boost pressure, and during the two-stage, the intake throttle valve forms the boost pressure regulating device and regulates the exhaust pressure in the exhaust manifold in a closed loop. Technical benefits may include implementing the two-stage using common equipment.

[0009] Optionally, in some examples, including at least one preferred example, the turbocharger is a variable geometry turbocharger including a movable element to adjust the output of the turbocharger, and during the two-stage, the variable geometry turbocharger forms the boost pressure regulating device and regulates the exhaust pressure in the exhaust manifold in a closed loop. Technical benefits may include implementing two-stage using common equipment.

[0010] Optionally, in some examples, including at least one preferred example, the engine braking method further comprises an initial phase prior to the dual phase. The initial phase comprises a first phase and a second phase, during which the exhaust pressure is controlled by the restriction device and the turbocharger is in an open loop state so as to increase the exhaust pressure to the first threshold; the second phase is after the first phase and during which, once the exhaust pressure reaches the first threshold, the restriction device is locked in position and the turbocharger controls the exhaust pressure in the exhaust manifold in a closed loop manner so as to increase the boost pressure to the second threshold. If during the second phase, the boost pressure reaches the second threshold before a predetermined period of time, the initial phase ends and the dual phase begins. Technical benefits may include ensuring a smooth, stable and rapid transition from a driving mode of the engine to an engine braking mode.

[0011] Optionally, in some examples, including at least one preferred example, the engine further comprises a purge valve, each purge valve being associated with a corresponding cylinder and configured to cause compressed air to leak from the cylinder through an opening of the purge valve when activated, and the engine braking method comprises adjusting the opening of the purge valve to maximize the braking effect of the engine during the dual phase. Technical benefits may include further improving the engine braking performance of the vehicle.

[0012] Optionally, in some examples, including at least one preferred example, the dual phase is engaged when the engine speed (expressed in revolutions per minute) is above a predetermined third threshold. Technical benefits may include ensuring a higher engine braking effect compared to prior art methods.

[0013] According to a second aspect of the invention, the invention relates to a vehicle comprising a turbocharged internal combustion engine. The vehicle is configured to implement an engine braking method according to any one of the preceding claims. The engine comprises: - a plurality of cylinders connected to an intake manifold configured to collect fresh air and to an exhaust manifold configured to collect exhaust gas from the cylinders, - a turbocharger having a compressor driven by a turbine, the compressor being configured to increase boost pressure in the intake manifold, and the turbine being configured to be driven by the exhaust gas flowing out of the exhaust manifold; - a boost pressure regulating device configured to adjust the boost pressure in the intake manifold, and - An exhaust restriction located downstream of the turbine and configured to increase exhaust pressure in the exhaust manifold.

[0014] A second aspect of the disclosure may seek to provide a vehicle, such as a truck, having improved engine braking capability. Technical benefits may include allowing higher loads on downhill grades and / or allowing speed regulation on steeper downhill grades.

[0015] The disclosed aspects, examples and / or appended claims may be appropriately combined with each other, which is obvious to any person skilled in the art. Additional features and advantages are disclosed in the following description, claims and drawings, and in part will be obvious to those skilled in the art or recognized by practicing the disclosure as described herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 An exemplary vehicle according to the invention and an engine of the vehicle are shown in the two illustrations a) and b).

[0017] Figure 2 It means to use Figure 1 An exemplary schematic diagram of an engine braking method implemented in a vehicle.

[0018] Figures 3 to 6 is an exemplary graph comparing results obtained with the engine braking method according to the present invention and with the method according to the prior art.

[0019] Figure 7 is an exemplary graph showing an initial stage of the engine braking method according to the present invention. DETAILED DESCRIPTION

[0020] The detailed description set forth below provides information and examples of the disclosed technology in sufficient detail to enable those skilled in the art to practice the disclosure.

[0021] Vehicle 10 represents Figure 1 a). The vehicle 10 is a road vehicle, in particular a truck, comprising wheels 11. The vehicle 10 comprises an engine 12, which is Figure 1 b). The engine 12 is an internal combustion engine that is configured to use fuel to drive the wheels 11 to rotate so as to move the vehicle 10. When the engine 12 uses fuel to rotate the wheels 10, the engine 12 is in a driving mode. Conversely, when the engine 12 is used to waste energy, the engine 12 is in an "engine braking" mode, that is, the engine 12 applies braking torque to the wheels 11. Figure 1In FIG. 1 , the vehicle 10 is shown on a downhill slope S, where the vehicle 10 tends to accelerate naturally due to gravity. The engine 12 is used in an engine braking mode in order to regulate the speed of the vehicle 10 .

[0022] The engine 12 includes a main cylinder block 14 having a plurality of cylinders 16. In the example shown, the engine 12 is a four-stroke engine having six cylinders 16. For each cylinder 16, the four strokes sequentially include an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke.

[0023] When the engine 12 is running, during the intake stroke of each cylinder 16, fresh air flowing through the intake manifold 20 enters each cylinder 16 through at least one intake valve. The at least one intake valve is not shown. During the exhaust stroke, the air contained in the cylinder 16 is discharged through at least one exhaust valve and collected in the exhaust manifold 22. The at least one exhaust valve is not shown. In other words, the cylinder 16 is connected to the intake manifold 20 that collects fresh air, and is connected to the exhaust manifold 22 that collects exhaust gas from the cylinder 16. When the engine 12 is in a driving mode, fuel is injected into the cylinder and the air and fuel mixture is ignited during the compression and expansion strokes. During the subsequent exhaust stroke, the air exhausted from the cylinder 16 is hot and contains various substances and residues produced by the combustion of the fuel. The air containing these combustion residues is also called exhaust gas.

[0024] When the engine 12 is in engine braking mode, no fuel is injected into the cylinder 16 and no combustion occurs. The air exhausted from the cylinder 16 during the exhaust stroke is mostly fresh air that entered during the intake stroke and then was compressed and expanded inside the cylinder 16 during the compression and expansion strokes.

[0025] The air flowing from the cylinder 16 into the exhaust manifold 22 is also referred to as "exhaust gas". The fresh air flowing from the intake manifold 20 into the cylinder 16 is also referred to as "charge air". The intake manifold 20 is located upstream of the cylinder 16 relative to the normal air flow in the engine 12, while the exhaust manifold 22 is located downstream of the cylinder 16 relative to the normal air flow in the engine 12. In the following description, the concepts of "upstream" and "downstream" are relative to the air flow during normal use of the engine 12. "Normal use" means that the engine 12 is either in a driving mode or in an engine braking mode.

[0026] The engine 12 also includes a turbocharger 30. The turbocharger 30 includes a compressor 32 and a turbine 34, with the compressor 32 being connected to the turbine 34 via an axle 36. The turbine 34 is configured to be driven to rotate by exhaust gas flowing out of the exhaust manifold 22, while the compressor 32 is configured to increase the pressure of the charge air flowing into the intake manifold 20 and subsequently entering the cylinder 16.

[0027] When the engine 12 is in the engine braking mode, during the compression / expansion stroke in each cylinder 16, the air pressure reaches a peak value, referred to as the "peak cylinder pressure" PCP. Figure 1 In the schematic example of b), one of the cylinders 16 includes a first pressure sensor, symbolically represented here by a pressure gauge, which is configured to measure the gas pressure in the cylinder 16. Specifically, the first pressure sensor (also referred to as PCP) is configured to measure the peak cylinder pressure. Of course, in reality, there is no pressure gauge in any cylinder 16.

[0028] A second pressure sensor P2 symbolically represented by a pressure gauge is arranged on the intake manifold 20, and the second pressure sensor P2 is configured to measure the boost pressure, that is, the air pressure inside the intake manifold 20. By extension, the boost pressure is also referred to as P2. A third pressure sensor P3 symbolically represented by a pressure gauge is arranged on the exhaust manifold 22, and the third pressure sensor P3 is configured to measure the exhaust pressure, that is, the air pressure inside the exhaust manifold 22. By extension, the exhaust pressure is also referred to as P3.

[0029] The engine also includes an exhaust restriction 40 located downstream of the turbine 34 and configured to regulate the exhaust pressure P3 in the exhaust manifold 22. In the example shown, the exhaust restriction 40 is a baffle, also referred to as an “exhaust baffle.” The shape and type of the exhaust restriction 40 are not limited.

[0030] The engine 10 further includes a fourth pressure sensor P4A, symbolically represented by a pressure gauge, arranged downstream of the turbine 34 and configured to measure the turbine outlet pressure, i.e., the pressure of the exhaust gas at the outlet of the turbine 34 between the turbine 34 and the exhaust restriction 40. By extension, the turbine outlet pressure is also referred to as P4A.

[0031] The engine 10 also includes a boost pressure regulating device 42 configured to adjust the boost pressure P2 in the intake manifold 20. In the example shown, the boost pressure regulating device 42 is an intake throttle valve represented by a baffle and arranged between the turbocharger 30 and the intake manifold 20 and configured to control the boost pressure P2. The shape and type of the boost pressure regulating device 42 are not limited.

[0032] Schematically, the braking torque from the engine 12 mainly comes from a combination of two phenomena. The first phenomenon is called pumping torque, which is caused by the exhaust pressure P3 being higher than the boost pressure P2. The greater the difference between P3 and P2, the greater the braking torque. The second phenomenon is called compression release torque, or compression braking. Each cylinder 16 is advantageously equipped with a purge valve 17, which is configured to allow air compressed inside the cylinder 16 to leak from the cylinder 16 through the opening of the purge valve 17 when the engine 12 is in the engine braking mode, while each purge valve 17 remains closed when the engine 12 is in the driving mode.

[0033] Without the purge valve, when air is compressed in the cylinder 16 during the compression stroke, almost all of the mechanical energy invested by the compressed air is recovered by expansion during the expansion stroke within the cylinder 16. Due to the purge valve 17, the compressed air is released to the outside of the cylinder 16 through the opening of the exhaust valve 17, and the energy used for compression is wasted by releasing the compressed air instead of allowing it to expand inside the cylinder 16. The higher the peak cylinder pressure PCP before releasing this compressed air, the more energy is wasted, and the greater the braking torque generated by compression braking.

[0034] According to some examples, the purge valve 17 is a specific device different from the intake valve and the exhaust valve. Alternatively, the purge valve 17 includes an actuator configured to slightly open one or more existing exhaust valves when the engine 12 is in the engine braking mode. This type of purge valve is also called a "Jacobs valve", and a compression brake using such a Jacobs valve is also called a "Jacobs brake".

[0035] In short, when the engine 12 is in the engine braking mode, maximizing the braking torque involves maximizing the peak cylinder pressure PCP and the pressure difference between the exhaust pressure and the intake pressure P3-P2. To achieve this, the engine 12 is configured to implement an engine braking method that includes a phase called "dual phase" 101 during which: - the boost pressure regulating device 42 regulates the exhaust pressure P3 in the exhaust manifold 22 in a closed loop manner so as to adjust the exhaust pressure to a predetermined first threshold value, and The exhaust gas restriction device 40 controls the boost pressure P2 in a closed-loop manner in order to adjust the boost pressure P2 to a predetermined second threshold value.

[0036] Advantageously, the engine braking method comprises adjusting the opening of the purge valve 17 to a specific predetermined target value in order to maximize the braking torque of the engine 12 during the dual phase. The target value of the opening of the purge valve depends on the type, size, power, etc. of the engine 12.

[0037] Controlling the exhaust pressure P3 in a closed loop using the boost pressure regulating device 42 causes the turbocharger 30 to draw a large amount of fresh air into the engine 12, which increases the cylinder peak pressure PCP and cools the injector tip. Controlling P2 in a closed loop using the exhaust restriction device 40 reduces the expansion ratio of the turbine 34, thereby limiting the boost pressure P2 to a value significantly lower than P3 and helping to increase pumping torque. The pressure difference P3-P2 remains positive, which keeps the seal of the compressor 32 tight.

[0038] Figures 3 to 6 The results and benefits of a dual phase are shown.

[0039] Graphics 300 Figure 3 Graph 300 illustrates the variation of exhaust pressure P3 (expressed in kilopascals or kPa) with respect to the speed of engine 12 (expressed in revolutions per minute or RPM) for an exemplary vehicle 10 .

[0040] The graph 300 includes a first curve 301 showing the exhaust pressure P3 when the engine 12 is controlled according to the prior art method. Within the scope of this description, engine braking according to the prior art method means that the exhaust pressure P3 is controlled by the restriction device 40, while the turbocharger 30 is in an open loop state. The graph 300 includes a second curve 302 showing the exhaust pressure P3 when the engine 12 is controlled using the two-stage 101 method according to the present invention.

[0041] As shown in graph 300, when the engine speed is above a predetermined threshold T300 (equal to 1800 RPM in the example shown), second curve 302 is significantly higher than first curve 301. In other words, due to the present invention, when the engine speed is above threshold T300, exhaust pressure P3 is higher.

[0042] Graphics 400 Figure 4 Graph 400 illustrates the variation of boost pressure P2 (expressed in kPa) with respect to the speed of engine 12 (expressed in RPM) for an exemplary vehicle 10 .

[0043] Graph 400 includes a first curve 401 showing boost pressure P2 when engine 12 is controlled according to the prior art method. Graph 400 includes a second curve 402 showing boost pressure P2 when engine 12 is controlled using the dual stage 101 method according to the present invention.

[0044] As shown in the graph 400, for all shown engine speeds, the second curve 402 is significantly higher than the first curve 401. In other words, due to the present invention, when the engine 12 is controlled using the method according to the present invention, the boost pressure P2 is higher than when the engine 12 is controlled using the prior art method. Specifically, in the example shown, when the engine speed is above a threshold T400 (here equal to 1400 RPM), the boost pressure P2 when the engine 12 is controlled using the method according to the present invention is at least ten times higher than the boost pressure P2 when the engine 12 is controlled using the prior art method.

[0045] Graphics 500 Figure 5 Graph 500 illustrates engine braking power (expressed in kilowatts or kW) versus speed (expressed in RPM) of engine 12 for an exemplary vehicle 10 .

[0046] Graph 500 includes a first curve 501 showing engine braking power when engine 12 is controlled according to the prior art method. Graph 500 includes a second curve 502 showing engine braking power when engine 12 is controlled using the dual stage 101 method according to the present invention.

[0047] As shown in graph 500, when the engine speed is above a predetermined threshold T500 (equal to 1400 RPM in the example shown), the second curve 502 is significantly higher than the first curve 501. In other words, due to the present invention, when the engine 12 is controlled using the method according to the present invention, the boost pressure P2 is higher than when the engine 12 is controlled using the prior art method.

[0048] In other words, in order to benefit from higher braking power, the dual phase 101 is activated when the engine speed is above a predetermined threshold. In the example shown, this threshold is equal to 1400 RPM.

[0049] Due to the control method of the present invention, both the boost pressure P2 and the exhaust pressure P3 can be controlled simultaneously, thereby making the engine braking power significantly higher than the power that can be achieved by the prior art methods.

[0050] Graphics 600 Figure 6 Graph 600 illustrates the temperature of the tip of the injector nozzle (nozzle tip temperature or NTT, expressed in degrees Celsius or °C) relative to the speed of the engine 12 (expressed in RPM) for an exemplary vehicle 10 .

[0051] Graph 600 includes a first curve 601 showing the nozzle tip temperature NTT when the prior art method is used to control the engine 12. Graph 600 includes a second curve 602 showing the nozzle tip temperature NTT when the engine 12 is controlled using the dual stage 101 method according to the present invention.

[0052] As shown in the graph 600, for all the engine speeds shown, the second curve 602 is located below the first curve 601. In other words, due to the present invention, when the engine 12 is controlled using the method according to the present invention, the nozzle tip temperature NTT is lower than when the engine 12 is controlled using the prior art method. This is due to the greater air flow through the cylinder 16, because - among other factors - the boost pressure P2 in dual mode is higher compared to the prior art method, as shown in the graph 400.

[0053] When the vehicle 10 is running, moving between a flat or uphill road to a downhill road, the engine 12 must switch between the driving mode and the engine braking mode. The two-stage 101 method corresponds to the establishment state of the engine 12 in the engine braking method. Before the two-stage 101, the engine braking method according to the present invention also includes an initial stage 100, which is implemented to ensure the switching between the two-stage 101 of the driving mode and the engine's braking mode.

[0054] The initial stage 100 is divided into two sub-stages including a first stage 100A and a second stage 100B subsequent to the first stage 100A.

[0055] Since the engine 12 is initially in the driving mode, the engine 12 is controlled to switch to the engine braking mode. The engine speed related to the speed of the wheels 11 should remain substantially constant during the initial phase. During the first phase 100A, the exhaust pressure P3 is controlled by the restriction device 40 while the turbocharger 30 is in an open loop state so as to increase the exhaust pressure P3 to a predetermined first threshold value L1.

[0056] Once the exhaust pressure P3 reaches the first threshold value L1, the second phase 100B begins. During the second phase 100B, the restriction device 40 is locked in place, in other words, the restriction device 40 does not regulate the exhaust pressure P3, and the turbocharger 30 controls the exhaust pressure P3 in the exhaust manifold 22 in a closed loop manner so as to increase the boost pressure P2 to a predetermined second threshold value L2.

[0057] During the second phase 100B, if the boost pressure P2 reaches the second threshold before a predetermined period of time, the initial phase ends and the dual phase 101 begins. If the boost pressure P2 does not reach the second threshold, the dual phase 101 does not begin and the engine returns to the first phase 100A.

[0058] Graphics 700 Figure 7 Graph 700 shows the changes in several parameters of the engine 12 during the initial phase 100 and the dual phase 101. The horizontal axis is the time axis - expressed in seconds. Figure 7 In the example, the engine speed is considered constant.

[0059] The graph 700 includes a first curve 701 which shows the variation of the torque (expressed in Newton x meters or N·m) of the engine 12. On the left vertical axis, the torque is negative because the engine 12 is in the engine braking mode.

[0060] Graph 700 includes a second curve 702 showing changes in exhaust pressure P3 (expressed in kPa) relative to the right vertical axis. Graph 700 includes a second curve 702 showing changes in boost pressure P2 (expressed in kPa) relative to the right vertical axis. Graph 700 includes a third curve 703 showing changes in exhaust pressure P3 (expressed in kPa) relative to the right vertical axis. Graph 700 includes a fourth curve 704 showing changes in the set point of boost pressure P2 (expressed in kPa) relative to the right vertical axis. Graph 700 includes a fifth curve 705 showing changes in the set point of exhaust pressure P3 (expressed in kPa) relative to the right vertical axis.

[0061] In the example shown, at the initial time ti, the set point P3 of the exhaust pressure is gradually set to the first threshold value L1. The initial time ti marks the beginning of the first stage 100A. In the example shown, starting from the initial time ti, the set point P2 of the boost pressure is also gradually set to the second threshold value L2. The torque 701 at the initial time t i Previously, an initial plateau of approximately −330 N·m was shown. The exhaust pressure P3 is controlled by the restriction device 40 .

[0062] At the initial time t i The first moment t 1 , the exhaust pressure P3 starts to rise to narrow the gap with the first threshold value L1. As a result, the torque 701 decreases sharply. That is, the effect of engine braking increases. In the example shown, the first moment t 1 The difference from the initial time ti is about 0.1 seconds.

[0063] From the first moment t 1 The boost pressure P2 also starts to rise, so that the gap with the second threshold value L2 is reduced. 1 The second moment t 2 , the boost pressure P2 is obviously equal to the second threshold value L2, while the exhaust pressure P3 continues to rise, and the torque 701 continues to decrease.

[0064] At the second moment t 2 The third moment t 3 , the exhaust pressure P3 reaches a maximum value which is significantly equal to the first threshold value L1. 2 Between the instant t1 and the third instant t3 , the torque 701 continues to decrease.

[0065] The third instant t3 marks the end of the first phase 100A and the beginning of the second phase 100B. In the example shown, the boost pressure P2 is already clearly equal to the second threshold value L2, so the second phase 100B ends immediately and the dual phase 101 begins at the third instant t3. In the example shown, the duration of the initial phase 100 is clearly equal to the difference between the third instant t3 and the first instant t1, which is about 0.7 seconds here.

[0066] More generally, if during the second phase 100B, the boost pressure P2 does not reach the second threshold value L2 before a predetermined period of time, the initial phase restarts, returning to the first phase 100A. This situation may occur in abnormal circumstances, such as when a malfunction occurs in one of the components of the engine 12. Under normal circumstances, if during the second phase 100B, the boost pressure P2 reaches the second threshold value L2 before a predetermined period of time, the initial phase 100 ends and the dual phase 101 begins.

[0067] During the dual phase 101, the boost pressure regulating device 42 regulates the exhaust pressure P3 in the exhaust manifold 22 in a closed loop manner so as to regulate the exhaust pressure P3 to a predetermined first threshold value L1, while the exhaust restriction device 40 controls the boost pressure P2 in a closed loop manner so as to regulate the boost pressure P2 to a predetermined second threshold value L2. Figure 7 As shown, during the dual phase 101 , the exhaust pressure P3 , the boost pressure P2 , and the torque 701 are relatively stable.

[0068] In the example shown, the boost pressure regulating device 42 is an intake throttle valve. During the dual phase 101 , the intake throttle valve forms the boost pressure regulating device 42 and regulates the exhaust gas pressure in the exhaust manifold 22 in a closed loop manner.

[0069] In an alternative embodiment not shown, the turbocharger 30 is a variable geometry turbocharger VGT, which includes a movable element to adjust the output of the turbocharger 30, thereby forming a boost pressure regulating device 42 when the engine 12 is in the driving mode. During the dual phase 101 of the engine braking method, the variable geometry turbocharger VGT forms the boost pressure regulating device 42 and regulates the exhaust pressure P3 in the exhaust manifold 22 in a closed loop manner.

[0070] The terms used herein are only for the purpose of describing specific aspects and are not intended to limit the present disclosure. As used herein, unless the context clearly indicates otherwise, the singular forms "one", "a kind of" and "the" are intended to also include plural forms. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. It should also be understood that the terms "include" and / or "comprising" when used herein indicate the presence of stated features, integers, actions, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, actions, steps, operations, elements, parts and / or their groups.

[0071] It should be understood that although the terms first, second, etc. can be used to describe various elements in this article, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For example, without departing from the scope of the present disclosure, the first element can be referred to as the second element, and similarly, the second element can be referred to as the first element.

[0072] Relative terms such as "below" or "above" or "upper" or "lower" or "horizontal" or "vertical" may be used herein to describe the relationship of one element to another element, as shown in the figures. It should be understood that these terms and those discussed above are intended to cover different device orientations in addition to the orientations depicted in the figures. It will be understood that when an element is referred to as being "connected" or "coupled" to another element, the element may be directly connected or directly coupled to the other element, or there may be intervening elements. In contrast, when an element is referred to as being "directly connected to" or "directly coupled to" another element, there are no intervening elements.

[0073] Unless otherwise defined, all terms used herein have the same meaning as those commonly understood by those of ordinary skill in the art to which the present disclosure belongs. It should also be understood that, unless otherwise clearly defined herein, the terms used herein should be interpreted as meanings consistent with their meanings in the context of this specification and the relevant art, and should not be interpreted in an idealized or overly formal sense.

[0074] It should be understood that the present disclosure is not limited to the aspects described above and shown in the accompanying drawings; rather, those skilled in the art will recognize that many changes and modifications may be made within the scope of the present disclosure and the appended claims. In the drawings and description, various aspects have been disclosed for illustrative purposes only and not for limiting purposes, and the scope of the present disclosure is set forth in the appended claims.

Claims

1. A method for operating an engine brake of a vehicle (10) having a turbocharged internal combustion engine (12), wherein: - The engine (12) comprises: • a plurality of cylinders (16) connected to an intake manifold (20) collecting fresh air and to an exhaust manifold (22) collecting exhaust gas from the cylinders (16), • a turbocharger (30) having a compressor (32) driven by a turbine (34), the compressor (32) being configured to increase a boost pressure (P2) of the fresh air in the intake manifold (20), and the turbine (34) being configured to be driven by the exhaust gas flowing out of the exhaust manifold (22); • a boost pressure regulating device (42) configured to adjust the boost pressure (P2) in the intake manifold (20), • an exhaust restriction (40) located downstream of the turbine (34) and configured to regulate the exhaust pressure (P3) in the exhaust manifold (22), - The engine braking method comprises two phases (101), during which the following are carried out simultaneously: • the boost pressure regulating device (42) regulates the exhaust pressure (P3) in the exhaust manifold (22) in a closed loop manner so as to adjust the exhaust pressure to a predetermined first threshold value (L1), • The exhaust gas restriction device (40) controls the boost pressure (P2) in a closed loop manner so as to adjust the boost pressure (P2) to a predetermined second threshold value (L2).

2. The engine braking method according to claim 1, wherein: - the engine (12) comprises an intake throttle valve, which is arranged between the turbocharger (30) and the intake manifold (20) and is configured to control the boost pressure (P2), - During the two-phase (101), the intake throttle valve forms the boost pressure regulating device (42) and regulates the exhaust pressure (P3) in the exhaust manifold (22) in a closed-loop manner.

3. The engine braking method according to claim 1, wherein: - the turbocharger (30) is a variable geometry turbocharger (VGT) comprising a movable element to adjust the output of the turbocharger, - During the two-stage (101), the variable geometry turbocharger forms the boost pressure regulation device (42) and regulates the exhaust pressure (P3) in the exhaust manifold (22) in a closed-loop manner.

4. The engine braking method according to any one of claims 1 to 3, further comprising an initial phase (100) before the dual phase (101), wherein: - The initial phase includes: • a first phase (100A), during which the exhaust pressure (P3) is controlled by the restriction device (40) while the turbocharger (30) is in open loop in order to increase the exhaust pressure (P3) to the first threshold (L1), • a second phase (100B) following the first phase (100A) and during which, once the exhaust pressure (P3) reaches the first threshold (L1), the restriction device (40) is locked in position while the turbocharger (30) controls the exhaust pressure (P3) in the exhaust manifold (22) in a closed loop manner so as to increase the boost pressure (P2) to the second threshold (L2), - If during the second phase (101B) the boost pressure reaches the second threshold (L2) before a predetermined period of time, the initial phase (100) ends and the dual phase (101) begins.

5. The engine braking method according to any one of claims 1 to 3, wherein: - the engine (12) further comprises a purge valve (17), each purge valve being associated with a respective cylinder (16) and being configured to cause compressed air to leak from the cylinder (16) through an opening of the purge valve when activated, - The engine braking method comprises adjusting the opening of the purge valve so as to maximize the braking effect of the engine (12) during the dual phase (101).

6. The engine braking method according to any one of claims 1 to 3, wherein: - When the speed of the engine (12) expressed in revolutions per minute is higher than a predetermined third threshold, the dual phase (101) is activated.

7. A vehicle (10) comprising a turbocharged internal combustion engine (12), wherein: - the vehicle (10) is configured to implement the engine braking method according to any one of claims 1 to 3, - The engine (12) comprises: • a plurality of cylinders (16) connected to an intake manifold (20) configured to collect fresh air and to an exhaust manifold (22) configured to collect exhaust gas from the cylinders (16), • a turbocharger (30) having a compressor (32) driven by a turbine (34), the compressor (32) being configured to increase a boost pressure (P2) in the intake manifold (20), and the turbine (34) being configured to be driven by the exhaust gas flowing out of the exhaust manifold (22); • a boost pressure (P2) regulating device (42), the boost pressure regulating device being configured to adjust the boost pressure (P2) in the intake manifold (20), • An exhaust restriction (40) located downstream of the turbine (34) and configured to adjust exhaust pressure (P3) in the exhaust manifold (22).

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