Control device and method for starting a combustion engine during coasting, vehicle having such a device, computer program for executing the method and computer-readable medium containing the program

Abstract

The invention describes a method for starting a combustion engine (2) performed by a control device (100) during coasting when the engine is off. The method comprises: the steps of controlling a clutch (9) to a partially closed state to start the combustion engine (2); the step of controlling the clutch (9) to an open state when the combustion engine (2) has been started but before the output shaft (8) of the combustion engine has reached a speed synchronized with the speed of the input shaft (10) of the gearbox; and the step of synchronizing the speed of the combustion engine (2) to the speed of the input shaft (10) of the gearbox by controlling the injection of fuel into the combustion engine (2).

Description

Technical Field

[0001] The present disclosure generally relates to a method for starting a combustion engine of a vehicle powertrain during coasting with the engine off. The present disclosure also generally relates to a control device configured to start a combustion engine of a vehicle powertrain during coasting with the engine off and a vehicle including such a control device. The present disclosure also generally relates to a computer program and a computer readable medium. Background Art

[0002] The ongoing effort to manufacture vehicles that reduce fuel consumption has created a desire to be able to reduce the speed of the combustion engine to a minimum, typically idling, in situations where no drive torque is required for continued vehicle travel. An example of a situation where no drive torque is required for continued vehicle travel may be during downhill travel. In such situations, reducing the speed of the combustion engine to a minimum may be achieved by either opening the clutch or disengaging the vehicle powertrain by placing the gearbox in neutral, in order to avoid engine braking that would occur when the vehicle powertrain was shut down. This mode of operation of the vehicle powertrain is sometimes referred to as free-wheeling, and is commonly implemented today in heavy vehicles.

[0003] By shutting down the combustion engine when it is not necessary to deliver drive torque to the drive wheels, instead of running the combustion engine at idle speed as described above, further fuel can be saved. Such an operating mode may be referred to as freewheeling with engine off.

[0004] Coasting with the engine off requires that the combustion engine can be started quickly and efficiently when the drive torque needs to be transmitted to the drive wheels again. The combustion engine can be started, for example, with the help of a starting system adapted accordingly. However, the available starting systems are not sufficient to handle the large number of starts required to achieve coasting with the engine off, and / or are expensive.

[0005] Alternatively, the combustion engine may be started using a clutch. Thus, the additional expense of an upgraded, more durable starting system that can handle a large number of required starts may be avoided. Starting the combustion engine by means of a clutch is achieved by partially closing the clutch in order to transfer torque from the input shaft of the gearbox to the output shaft of the combustion engine, thereby dragging the combustion engine.

[0006] However, there are two major disadvantages to starting a combustion engine using a clutch. The first disadvantage is clutch wear. Although engine starting generates only moderate clutch wear, the life of the clutch may be significantly reduced due to the high total number of starts of the combustion engine required if coasting with the engine off is implemented. The second disadvantage is the handling effect. Since the energy required to start the combustion engine using the clutch is taken from the drive wheels, the start of the combustion engine generates braking forces on the drive wheels. In certain situations, this in turn affects the lateral stability of the vehicle. It is therefore important that the starting procedure minimizes clutch wear and generates minimum forces on the drive wheels.

[0007] EP 2 497 940 A2 discloses an example of a method for starting a combustion engine using a clutch in combination with coasting. The method comprises controlling the clutch in three different steps. In a first step, the clutch is controlled from its open state with a first torque gradient until the clutch torque exceeds the drag torque of the combustion engine. In a second step, the clutch is controlled with a second torque gradient until the rotational speed of the combustion engine exceeds the resonant rotational speed of a dual mass flywheel arranged between the clutch and the output shaft of the combustion engine. In a third step, the clutch is completely closed so that the speed of the combustion engine matches the input-side rotational speed of the transmission in a jump-free manner. Summary of the invention

[0008] The object of the present invention is to solve the problem of the high number of starts of a combustion engine required to fully implement engine-off coasting by providing an efficient and reliable combustion engine start in combination with engine-off coasting.

[0009] This object is achieved by the subject-matter of the attached independent claims.

[0010] According to the present disclosure, a method for starting a combustion engine of a vehicle powertrain during coasting when the engine is off is provided. The method is performed by a control device. The vehicle powertrain includes a combustion engine, the combustion engine including an output shaft. The vehicle powertrain also includes a gearbox, the gearbox is arranged to selectively transfer torque between the combustion engine and at least one drive wheel, the gearbox including an input shaft. The vehicle powertrain also includes a clutch arranged between the combustion engine and the gearbox. The clutch is connected to the input shaft of the gearbox and the output shaft of the combustion engine. The method includes the following steps:

[0011] - in response to a command for starting the combustion engine, controlling the clutch to a partially closed state in order to transfer torque from the input shaft of the gearbox to the combustion engine

[0012] a combustion engine, thereby starting the combustion engine;

[0013] - when the combustion engine has been started but before the output shaft of the combustion engine has reached a rotational speed synchronized with the rotational speed of the input shaft of the gearbox, controlling the clutch to an open state; and

[0014] - Synchronizing the speed of the combustion engine to the speed of the input shaft of the gearbox by controlling the injection of fuel to the combustion engine.

[0015] According to the method according to the present disclosure, the combustion engine is started by means of a clutch, so that a separate or upgraded starting system for starting the combustion engine in conjunction with coasting when the engine is turned off is not required. As a result, the load on the starter system suitable for starting the combustion engine (if any) is reduced. This starter system can be used only to start the combustion engine when the vehicle engine is turned off at a standstill.

[0016] Furthermore, by means of the present method, the wear of the clutch is reduced, since the clutch is used only for a part of the starting sequence. More specifically, compared to previously known methods, the clutch is not partially (or fully) engaged during the entire starting sequence leading to a speed of the combustion engine at which the clutch can be fully engaged and torque is transmitted from the combustion engine to the drive wheels. Instead, the clutch will be opened after the combustion engine has been started but before the combustion engine has reached a speed at which it is synchronized with the speed of the input shaft of the gearbox.

[0017] The method also has the advantage of significantly reducing the risk of lateral stability loss during the starting sequence of the combustion engine. This is because the clutch is opened during a part of the starting sequence, and the energy transferred from the drive wheels to start the combustion engine is greatly reduced.

[0018] In response to an indication from a management system of the combustion engine that the combustion engine can be accelerated by controlling fuel injection, a step of controlling the clutch to an open state can be performed. This has the advantage of ensuring that the clutch can be safely opened for a trouble-free start of the combustion engine. In other words, it can be ensured that the clutch is opened only after sufficient torque has been transmitted from the input shaft of the gearbox to the output shaft of the combustion engine to start the combustion engine. This in turn ensures a safe start of the combustion engine.

[0019] The step of controlling the clutch to an open state may be performed in response to an indication that the rotational speed of the combustion engine has reached a predetermined rotational speed threshold. The rotational speed of the combustion engine may be easily and quickly determined by means of sensors that are already present for the purpose of controlling combustion engines in general. Thus, an early indication of when the combustion engine has sufficient rotational speed to be accelerated by controlling fuel injection may be determined. Thus, controlling the clutch to an open state may be performed at an early stage in the starting sequence. This in turn further reduces wear on the clutch.

[0020] The predetermined speed threshold may, for example, correspond to a speed that is lower than or equal to the idle speed of the combustion engine. At idle speed, it is known that the combustion engine can be accelerated by controlling the fuel injection. However, in order to reduce wear on the clutch and reduce the risk of lateral stability problems, it is advantageous to open the clutch as early as possible. Therefore, the predetermined speed threshold may advantageously be lower than the idle speed.

[0021] In response to an indication that a predetermined condition for opening the clutch is met, a step of controlling the clutch to the open state may be initiated. This enables opening of the clutch to be initiated as early as possible, which in turn further reduces wear of the clutch and the risk of loss of lateral stability. The predetermined condition for opening the clutch may be based on a prediction that the torque transmitted to the combustion engine during opening of the clutch is sufficient to bring the combustion engine to a state in which it can be accelerated by controlling fuel injection. Alternatively or in addition, the predetermined condition for opening the clutch is based on a prediction that the time taken to open the clutch is long enough for the combustion engine to reach a state in which the combustion engine can be accelerated by controlling fuel injection.

[0022] A step of controlling the clutch to a partially closed state to a predetermined transmission torque may be performed. Thus, it is ensured that the torque transmitted from the input shaft of the gearbox to the combustion engine is sufficient to drag the combustion engine. This in turn increases the reliability of starting the combustion engine.

[0023] The step of controlling the clutch to the open state may be performed after indicating that the first fuel injection into the combustion engine has occurred. Thereby, the risk of premature clutch opening during the starting sequence may be minimized. This in turn increases the reliability of starting the combustion engine.

[0024] The method may further comprise the step of controlling the clutch from the open state to the closed state when the rotation speed of the output shaft of the combustion engine is synchronized to the rotation speed of the input shaft of the gearbox. Thus, when the engine-off coasting operation has been terminated, the driving torque from the combustion engine can be fully transmitted to the drive wheels of the vehicle powertrain.

[0025] The present disclosure also relates to a computer program comprising instructions which, when executed by a control device, cause the control device to perform a method as described above for starting a combustion engine of a vehicle powertrain during coasting with the engine switched off.

[0026] The present disclosure also relates to a computer-readable medium comprising instructions which, when executed by a control device, cause the control device to perform a method as described above for starting a combustion engine of a vehicle powertrain during coasting with the engine off.

[0027] In addition, according to the present disclosure, a control device is provided, which is configured to start a combustion engine of a vehicle powertrain during coasting when the engine is turned off. The vehicle powertrain includes a combustion engine, and the combustion engine includes an output shaft. The vehicle powertrain also includes a gearbox, which is arranged to selectively transfer torque between the combustion engine and at least one drive wheel, and the gearbox includes an input shaft. The vehicle powertrain also includes a clutch arranged between the combustion engine and the gearbox. The clutch is connected to the input shaft of the gearbox and the output shaft of the combustion engine. The control device is configured to control the clutch to a partially closed state in response to an instruction for starting the combustion engine so as to transfer torque from the input shaft of the gearbox to the combustion engine, thereby starting the combustion engine. The control device is also configured to control the clutch to an open state when the combustion engine has been started but before the output shaft of the combustion engine has reached a speed synchronized with the speed of the input shaft of the gearbox. The control device is further configured to synchronize the rotation speed of the combustion engine to the rotation speed of the input shaft of the gearbox by controlling fuel injection to the combustion engine during and / or after controlling the clutch to the open state.

[0028] The control device has the same advantages as described above with respect to the corresponding method of starting a combustion engine of a vehicle powertrain during coasting with the engine off.

[0029] The control device may be configured to control the clutch to the open state in response to an indication from a management system of the combustion engine that the combustion engine may be accelerated by controlling fuel injection and / or in response to an indication that the speed of the combustion engine has reached a predetermined speed threshold. The predetermined speed threshold may correspond to a speed that is less than or equal to the idle speed of the combustion engine.

[0030] The control device may be configured to initiate control of the clutch to the open state in response to an indication that a predetermined condition for opening the clutch is met. The predetermined condition for opening the clutch may, for example, be based on a prediction that the torque transmitted to the combustion engine during opening of the clutch is sufficient to bring the combustion engine to a state in which it can be accelerated by controlling fuel injection. Alternatively or in addition, the predetermined condition for opening the clutch may, for example, be based on a prediction that the time taken to open the clutch is long enough for the combustion engine to reach a state in which the combustion engine can be accelerated by controlling fuel injection.

[0031] The control device may also be configured to control the clutch to a partially closed state to a predetermined transmission torque.

[0032] The control device may also be configured to control the clutch from the open state to the closed state when the rotational speed of the output shaft of the combustion engine is synchronized to the rotational speed of the input shaft of the gearbox.

[0033] Furthermore, the present disclosure relates to a vehicle comprising a vehicle powertrain. The vehicle further comprises a control device configured to start a combustion engine of the vehicle powertrain during coasting with the engine off as described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 schematically illustrates a side view of an example of a vehicle;

[0035] Figure 2 An example of a vehicle powertrain is schematically shown;

[0036] Figure 3 shows a flow chart schematically illustrating an exemplary embodiment of a method;

[0037] Figure 4 schematically illustrates the results of the steps of the method according to the present disclosure over time;

[0038] Figure 5 Schematically illustrated is an apparatus which may constitute, comprise or be part of a control device configured to start a combustion engine of a vehicle powertrain during coasting with the engine switched off. DETAILED DESCRIPTION

[0039] The invention will be described in more detail below with reference to exemplary embodiments and the accompanying drawings. However, the invention is not limited to the exemplary embodiments discussed and / or shown in the drawings, but may be varied within the scope of the appended claims. Furthermore, the drawings should not be considered to be drawn to scale, as some features may be exaggerated in order to more clearly illustrate the invention or its features.

[0040] The present disclosure provides a method for starting a combustion engine of a vehicle powertrain in conjunction with engine-off coasting. In other words, the present disclosure relates to a method for starting a combustion engine when engine-off coasting is terminated. During engine-off coasting, no propulsion unit of the vehicle powertrain provides any drive torque to the drive wheels. The reason for ending an engine-off coasting operation is generally that drive torque from the combustion engine is required so that the vehicle does not inadvertently lose road speed.

[0041] The vehicle powertrain comprises a combustion engine having an output shaft. The combustion engine may be the sole propulsion unit of the vehicle powertrain. Alternatively, if desired, the vehicle powertrain may comprise one or more additional propulsion units, such as an electric motor. The vehicle powertrain further comprises a gearbox arranged to selectively transfer torque between the combustion engine and at least one drive wheel of the vehicle powertrain. The gearbox comprises an input shaft. The vehicle powertrain further comprises a clutch arranged between the combustion engine and the gearbox. The clutch is connected to the input shaft of the gearbox and the output shaft of the combustion engine. The clutch may be a friction clutch.

[0042] The clutch can be controlled to different states. If the clutch is in an open state, the operational connection between the combustion engine and the drive wheels is interrupted. When the clutch is in a fully closed state, the operational connection between the combustion engine and the drive wheels is essentially rigid. In other words, the clutch is in a non-slip state in the fully closed state. The clutch can also be controlled to various partially closed states in which the clutch slips. In the partially closed state, depending on the degree of clutch closure, the clutch can transmit different amounts of torque between the output shaft of the combustion engine and the input shaft of the gearbox. Therefore, the amount of torque that can be transmitted by the clutch can be controlled by controlling the distance between the friction plates of the friction clutch.

[0043] A method for starting a combustion engine of a vehicle powertrain in combination with coasting when the engine is turned off includes a step of controlling a clutch to a partially closed state in response to an instruction for starting the combustion engine. As a result, the clutch transfers torque from an input shaft of a gearbox (which is in a rotating state due to the coasting operation) to an output shaft of the combustion engine. As a result, the combustion engine is started. The instruction for starting the combustion engine can be generated, for example, by a cruise control system of the vehicle powertrain or by any other means known in the art. The instruction for starting the combustion engine can generally be generated when a driving torque from the combustion engine is expected to be needed in the future. In other words, the instruction for starting the combustion engine is generally generated before terminating the coasting operation when the engine is turned off.

[0044] In the above steps, the clutch may be controlled to a partially closed state corresponding to a predetermined transfer torque. This may be achieved by controlling the positions of the components of the clutch, or in other words, by controlling the clutch to a predetermined slip. The predetermined transfer torque is selected to be a torque sufficient to induce a rotation of the output shaft of the combustion engine so as to start the combustion engine. Thus, this torque may be determined in any previously known manner, for example, by measuring this torque on the engine in a test bench as part of a calibration of this engine type.

[0045] The method further comprises the following steps: when the combustion engine has been started as described above but before the rotation speed of the output shaft of the combustion engine has reached a rotation speed synchronized with the rotation speed of the input shaft of the gearbox, the clutch is controlled to be in an open state. In other words, the clutch is opened before the combustion engine has reached the synchronous speed.

[0046] The step of controlling the clutch to the open state can be performed in response to an indication from the combustion engine management system that the combustion engine can be accelerated by controlling fuel injection. Thus, it is ensured that the clutch is not opened at a too early stage, which may otherwise cause a start-up failure of the combustion engine.

[0047] Alternatively, in response to an indication that the speed of the combustion engine has reached a predetermined speed threshold, the step of controlling the clutch to an open state may be performed. Compared to the alternative of controlling the clutch to an open state in response to an indication from a management system of the combustion engine, this may enable earlier initiation of clutch opening, thereby reducing clutch wear. However, reliability may be reduced compared to the alternative formed. The predetermined speed threshold may be a speed value, and it is previously known that the combustion engine has sufficient speed to allow acceleration by controlling fuel injection to the combustion engine. It should be appreciated that the predetermined speed threshold will depend on the type of combustion engine. It is well known that when at idle, the combustion engine can be accelerated by controlling fuel injection. However, the combustion engine can usually be accelerated at a much lower speed by controlling fuel injection. In order to minimize the risk of clutch wear and lateral stability loss, it is desirable to open the clutch as early as possible. Therefore, the predetermined speed threshold may be suitably a speed lower than the idle speed of the combustion engine. For example, the predetermined speed threshold may be 80% or less of the idle speed of the combustion engine. In some cases, the predetermined speed threshold may even be as low as about half of the idle speed of the combustion engine.

[0048] It will also be appreciated that, although less preferred, it is naturally possible that in some circumstances a delay in clutch opening may result and steps may be taken to control the clutch to an open state in response to an indication from a management system of the combustion engine and if the speed of the combustion engine is required to reach a predetermined speed threshold.

[0049] Given that it takes some time (albeit very short) to control the clutch to different states, the opening of the clutch can be initiated before the combustion engine can actually be accelerated by controlling the fuel injection, as long as during the time it takes to open the clutch or the time point when the clutch reaches the open state, the combustion engine will reach a state where it can be accelerated by controlling the fuel. Therefore, the step of controlling the clutch to the open state can be initiated in response to an indication that a predetermined condition for opening the clutch is met. The predetermined condition for opening the clutch can be, for example, based on a prediction that the torque transmitted to the combustion engine during the clutch opening (i.e., before the end of the clutch opening) is sufficient to enable the combustion engine to reach a state where it can be accelerated by controlling the fuel injection. Such predictions can be prepared in advance for any possible conditions of the vehicle powertrain and stored in a lookup table for subsequent use in the method described herein. Alternatively or in addition, the predetermined condition for opening the clutch can be based on a prediction that the time it takes to open the clutch from a partially closed state is long enough to enable the combustion engine to reach a state where it can be accelerated by controlling the fuel injection.

[0050] The step of controlling the clutch to the open state can be suitably performed only after indicating that the first fuel injection to the combustion engine has occurred. Thus, it can be ensured, for example, that the opening of the clutch is not performed too early in the start sequence and the combustion engine can be accelerated by controlling the fuel injection.

[0051] The step of controlling the clutch to the open state is preferably performed immediately after the step of controlling the clutch to the partially closed state for the purpose of starting the combustion engine. In other words, the clutch opening can be preferably performed as long as the combustion engine has reached or is expected to reach a state in which it can be accelerated by fuel injection before the clutch is in the open state.

[0052] The method further comprises a step of synchronizing the speed of the combustion engine to the speed of the input shaft of the gearbox by means of controlling the injection of fuel to the combustion engine. In this context, synchronization is taken to mean bringing the rotational speed of the combustion engine to a suitable rotational speed to achieve a smooth closing of the clutch without causing discomfort to the driver of the vehicle or risk of damage to the clutch. However, it is not required that the combustion engine rotates at exactly the same speed as the input shaft of the gearbox. In other words, the method comprises a step of controlling the injection of fuel to the combustion engine so as to accelerate the combustion engine to the purpose of achieving a rotational speed of the combustion engine that is the same or substantially the same as the rotational speed of the input shaft of the gearbox.

[0053] The step of synchronizing the speed of the combustion engine to the speed of the input shaft of the gearbox by controlling the injection of fuel to the combustion engine is performed after the combustion engine has been started, and the step can be initiated before the clutch has reached a fully open state. In other words, the step of controlling the clutch to the open state and the step of synchronizing the speed of the combustion engine can be performed simultaneously within a short duration of the start sequence. However, during at least a part of the step of synchronizing the speed of the combustion engine to the speed of the input shaft of the gearbox by controlling the injection of fuel, the clutch is in an open state. Suitably, the purpose is to have the clutch in an open state as much as possible during the step of synchronizing the speed of the combustion engine. This significantly reduces wear of the clutch and the risk of loss of lateral stability.

[0054] In summary, the method provides a starting sequence of a combustion engine comprising two consecutive phases. In a first initial phase, the combustion engine is started by the drag torque from the drive wheels generated by the clutch in a partially closed state. After the first phase, in a second phase, the clutch is in an open state and the combustion engine accelerates itself by controlling the fuel injection until a speed synchronized with the input shaft of the gearbox is reached.

[0055] When the speed of the combustion engine has been synchronized to the speed of the input shaft of the gearbox, the clutch can be controlled from an open state to a fully closed state. As a result, torque can be transmitted from the combustion engine to the drive wheels, so that when terminating the engine-off coasting, the vehicle powertrain can be propelled by means of the combustion engine.

[0056] Furthermore, according to the present disclosure, a control device is provided, which is configured to start a combustion engine of a vehicle powertrain in conjunction with engine-off coasting. The control device may be configured to perform any one of the above steps.

[0057] More specifically, a control device configured to start a combustion engine of a vehicle powertrain during coasting with the engine off is configured to:

[0058] - in response to a command to start the combustion engine, controlling the clutch to a partially closed state in order to transmit torque from the input shaft of the gearbox to the combustion engine, thereby starting the combustion engine,

[0059] - when the combustion engine has started but before the output shaft of the combustion engine has reached a speed synchronized with the speed of the input shaft of the gearbox, controlling the clutch to an open state, and

[0060] - During and / or after controlling the clutch to the open state, the rotational speed of the combustion engine is synchronized to the rotational speed of the input shaft by controlling the injection of fuel into the combustion engine.

[0061] Figure 1 A side view of an example of a vehicle 1 is schematically shown. The vehicle 1 comprises a powertrain 3 including an internal combustion engine 2 and a gearbox 4. A clutch (in Figure 2 ) can be arranged between the internal combustion engine 2 and the gearbox 4. The gearbox 4 is connected to the drive wheels 5 of the vehicle 1 via an output shaft 6 of the gearbox 4. The gearbox 4 is adapted to selectively transfer torque between the combustion engine 2 and the drive wheels 5 during operation of the vehicle. The vehicle 1 may also include non-driven wheels 7.

[0062] The vehicle 1 may be, but is not limited to, a heavy vehicle such as a truck or a bus. In addition, the vehicle may be a hybrid vehicle including an electric motor (not shown) in addition to the internal combustion engine 2 .

[0063] Figure 2 The vehicle powertrain 3 (eg, Figure 1 1 ) is an exemplary embodiment of a powertrain of a vehicle 1 shown in FIG. The powertrain 3 comprises a combustion engine 2 having an output shaft 8. The vehicle powertrain may also include a management system 20 of the combustion engine 2. The powertrain 3 further comprises a gearbox 4 having an input shaft 10. The powertrain 3 further comprises a clutch 9 arranged between the combustion engine 2 and the gearbox 4. The clutch 9 is connected to the input shaft 10 of the gearbox and the output shaft 8 of the combustion engine. The gearbox 4 may be, for example, an automated manual gearbox (AMT). The clutch 9 may be a friction clutch.

[0064] The vehicle powertrain 3 further comprises a control device 100, as will be described in more detail below. The control device 100 is configured to control at least a portion of the powertrain. More specifically, the control device may be configured to control the clutch 9 and the combustion engine 2. The control device 100 is configured to start the combustion engine 2 during coasting when the engine is off. If desired, the control device may optionally be configured to control further operations of the vehicle powertrain.

[0065] The control device 100 may include one or more control units. In the case where the control device 100 includes multiple control units, each control unit may be configured to control a certain function, or a certain function may be divided between two or more control units. As required, the control device 100 may be separated from the management system 20 of the combustion engine 2 including the management system 20, or may be included in the management system 20 of the combustion engine 2.

[0066] The execution of the method for starting a combustion engine as disclosed herein may be governed by programming instructions. These programming instructions are generally in the form of a computer program that, when executed in or by a control device, causes the control device to implement a desired form of control action. Such instructions may generally be stored on a computer readable medium.

[0067] Figure 3 A schematic diagram of a method for starting a vehicle powertrain (eg, Figure 2 A flow chart of an exemplary embodiment of a method for a combustion engine of a vehicle powertrain 3) is shown in FIG. Figure 3 Optional steps of the method are shown with dashed boxes. At the start of the method, the vehicle powertrain (and therefore the vehicle) is in a freewheeling operating mode with the engine off. This means, for example, that the input shaft of the gearbox is rotating, but the output shaft of the combustion engine is in a non-rotating state or at least substantially non-rotating state.

[0068] The method may comprise an initial step S101 of determining or detecting an instruction for starting the combustion engine. The instruction for starting the combustion engine may be generated, for example, by a cruise control system or the like.

[0069] The method comprises a step S102, which controls the clutch to a partially closed state in response to an instruction for starting the combustion engine. In the partially closed state, the clutch transmits torque from the input shaft of the gearbox to the combustion engine (more specifically, to the output shaft of the combustion engine). Thus, the combustion engine is started. The partially closed state may correspond to a state in which a predetermined transmission torque is imparted to the clutch.

[0070] After step S102, the method may include a step S103 of determining that the combustion engine has been started. This may be performed, for example, by determining an indication from a management system of the combustion engine that the combustion engine can be accelerated by controlling fuel injection, or by determining an indication that the speed of the combustion engine has reached a predetermined speed threshold.

[0071] The method further comprises a step S104 of controlling the clutch to an open state. Step S104 is performed after the combustion engine has been started but before the output shaft of the combustion engine has reached a rotation speed synchronized with the rotation speed of the input shaft of the gearbox.

[0072] The method further comprises a step S105 of synchronizing the speed of the combustion engine to the speed of the input shaft of the gearbox by controlling the injection of fuel to the combustion engine.

[0073] When the speed of the output shaft of the combustion engine has been synchronized to the speed of the input shaft of the gearbox, the method may include a step S106 of controlling the clutch to a fully closed state. As a result, the torque generated by the combustion engine can be fully used to drive the drive wheels of the vehicle powertrain. In other words, the engine-off coasting operation mode is terminated.

[0074] Figure 4 The results of the steps of the method according to the present disclosure over time t are schematically shown. The upper diagram shows the state of the clutch, which can change between a closed state and an open state. The middle diagram shows the torque transmitted by the clutch to the combustion engine. The bottom diagram shows the rotation speed ω of the combustion engine, respectively. E and the speed of the input shaft of the gearbox ω I .

[0075] At the first time point to, the combustion engine is in a non-rotating state, and in response to an instruction for starting the combustion engine, the clutch is controlled to a partially closed state. Due to the change in the state of the clutch, the torque transmitted by the clutch will increase (shown in the middle figure). At the second time point t1, the clutch has reached a partially closed state (as shown in the upper figure), such as a target partially closed state TS. Therefore, the combustion engine will start to rotate due to the transmitted torque (as shown in the bottom figure). At the third time point t2, the combustion engine has been started and can be accelerated by controlling the fuel injection. The speed of the combustion engine has not yet reached a speed synchronized with the speed of the input shaft of the gearbox at t2 (as shown in the bottom figure). At t2, the clutch is controlled to an open state (as shown in the upper figure), and therefore, the torque transmitted to the combustion engine by the clutch will begin to decrease (as shown in the middle figure). Preferably, the clutch is opened to an open state as quickly as possible. Between t2 and the fourth time point t3, the combustion engine is accelerated by controlling the fuel injection to the combustion engine. At the fourth time point t3, the speed of the combustion engine has been synchronized to the speed of the input shaft of the gearbox (as shown in the bottom figure), and the clutch can be controlled from the open state to the fully closed state (as shown by the dotted line in the upper figure), so that the torque generated by the combustion engine can be transmitted to the drive wheels. If the clutch is controlled in the fully closed state after t3, the torque transmitted by the clutch will increase (as shown by the dotted line in the middle figure).

[0076] Figure 5 An exemplary embodiment of the device 500 is schematically shown. The control device 100 described above may, for example, comprise the device 500, consist of the device 500, or be comprised in the device 500.

[0077] The device 500 includes a non-volatile memory 520, a data processing unit 510, and a read / write memory 550. The non-volatile memory 520 has a first memory element 530 in which a computer program such as an operating system is stored to control the functions of the device 500. The device 500 also includes a bus controller, a serial communication port, an I / O device, an A / D converter, a time and date input and transmission unit, an event counter, and an interrupt controller (not depicted). The non-volatile memory 520 also has a second memory element 540.

[0078] A computer program P is provided, comprising a routine for starting a combustion engine of a vehicle powertrain during coasting when the engine is off. The vehicle powertrain comprises a combustion engine, the combustion engine comprising an output shaft. The vehicle powertrain further comprises a gearbox, the gearbox being arranged to selectively transfer torque between the combustion engine and at least one drive wheel. The gearbox comprises an input shaft. The vehicle powertrain further comprises a clutch arranged between the combustion engine and the gearbox. The clutch is connected to the input shaft of the gearbox and the output shaft of the combustion engine. The computer program comprises a routine / instruction for controlling the clutch to a partially closed state in response to an instruction for starting the combustion engine so as to transfer torque from the input shaft of the gearbox to the combustion engine, thereby starting the combustion engine. The computer program further comprises a routine / instruction for controlling the clutch to an open state when the combustion engine has been started but before the output shaft of the combustion engine has reached a speed synchronized with the speed of the input shaft of the gearbox. In addition, the computer program comprises a routine / instruction for synchronizing the speed of the combustion engine to the speed of the input shaft of the gearbox by controlling the injection of fuel to the combustion engine.

[0079] The program P may be stored in the storage 560 and / or the read / write memory 550 in an executable form or in a compressed form.

[0080] The data processing unit 510 may perform certain functions. For example, the data processing unit 510 may implement a portion of a program stored in the memory 560 or a portion of a program stored in the read / write memory 550 .

[0081] The data processing device 510 may communicate with the data port 599 via a data bus 515. The non-volatile memory 520 may be used to communicate with the data processing unit 510 via a data bus 512. The independent memory 560 may be used to communicate with the data processing unit 510 via a data bus 511. The read / write memory 550 may be adapted to communicate with the data processing unit 510 via a data bus 514.

[0082] When data are received on the data port 599, they may be temporarily stored in the second memory element 540. When the received input data have been temporarily stored, the data processing unit 510 may be ready to implement code execution according to a computer program comprising program code for causing the control device to perform the method (or part thereof) for controlling a braking system of a vehicle as described herein.

[0083] Parts of the methods described herein may be implemented by the device 500 through the data processing unit 510 running a program stored in the memory 560 or the read / write memory 550. When the device 500 runs the program, the methods described herein are performed.

Claims

1. A method for starting a combustion engine (2) of a vehicle powertrain (3) during coasting with the engine off, the method being performed by a control device (100); the vehicle powertrain (3) comprising: A combustion engine (2), the combustion engine comprising an output shaft (8), a gearbox (4), the gearbox being arranged to selectively transfer torque between the combustion engine (2) and at least one drive wheel (5), the gearbox comprising an input shaft (10), and a clutch (9), the clutch being arranged between the combustion engine (2) and the gearbox (4), the clutch being connected to the input shaft (10) of the gearbox and the output shaft (8) of the combustion engine; the method comprising the following steps: in response to an instruction for starting the combustion engine (2), controlling the clutch (9) to switch to a partially closed state so as to transfer torque from the input shaft (10) of the gearbox to the combustion engine (2), thereby starting the combustion engine (2), wherein The invention relates to a method of initiating the step of controlling the clutch (9) to switch to an open state in response to an indication that a predetermined condition for opening the clutch (9) is satisfied, wherein the predetermined condition for opening the clutch (9) is based on a prediction that the torque transmitted to the combustion engine (2) during the opening of the clutch (9) is sufficient to bring the combustion engine (2) to a state where it can be accelerated by controlling fuel injection; controlling the clutch (9) to switch to an open state when the combustion engine (2) has been started but before the output shaft (8) of the combustion engine has reached a speed synchronized with the speed of the input shaft (10) of the gearbox; and synchronizing the speed of the combustion engine (2) to the speed of the input shaft (10) of the gearbox by controlling the injection of fuel to the combustion engine (2).

2. The method according to claim 1, wherein the step of controlling the clutch (9) to switch to the open state is performed in response to an indication from a management system (20) of the combustion engine that the combustion engine (2) can be accelerated by controlling fuel injection.

3. The method of claim 1, wherein the step of controlling the clutch (9) to switch to an open state is performed in response to an indication that the speed of the combustion engine (2) has reached a predetermined speed threshold. 4 . The method of claim 3 , wherein the predetermined speed threshold corresponds to a speed that is lower than or equal to an idle speed of the combustion engine.

5. The method according to claim 1, wherein the predetermined condition for opening the clutch (9) is based on a prediction that the time taken to open the clutch (9) is long enough for the combustion engine (2) to reach a state in which the combustion engine (2) can be accelerated by controlling fuel injection.

6. The method according to any one of claims 1 to 5, wherein a step of controlling the clutch (9) to switch to a partially closed state corresponding to a predetermined transmission torque is performed.

7. The method according to any one of claims 1 to 5, wherein the step of controlling the clutch (9) to switch to an open state is performed after an indication that a first fuel injection into the combustion engine (2) has occurred.

8. The method according to any one of claims 1 to 5, further comprising controlling the clutch (9) to switch from an open state to a closed state when the rotational speed of the output shaft (8) of the combustion engine (2) is synchronized to the rotational speed of the input shaft (10) of the gearbox (4).

9. A computer program product comprising instructions which, when executed by a control device, cause the control device to perform the method according to any one of claims 1 to 8.

10. A computer readable medium comprising instructions which, when executed by a control device, cause the control device to perform the method according to any one of claims 1 to 8.

11. A control device (100) configured to start a combustion engine (2) of a vehicle powertrain (3) during coasting with the engine off; the vehicle powertrain (3) comprising: A combustion engine (2), the combustion engine comprising an output shaft (8), a gearbox (4), the gearbox being arranged to selectively transmit torque between the combustion engine (2) and at least one drive wheel (5), the gearbox comprising an input shaft (10), and a clutch (9), the clutch being arranged between the combustion engine (2) and the gearbox (4), the clutch being connected to the input shaft (10) of the gearbox and the output shaft (8) of the combustion engine; the control device (100) being configured to control the clutch (9) to switch to a partially closed state in response to an instruction for starting the combustion engine (2) so as to transmit torque from the input shaft (10) of the gearbox to the combustion engine (2), thereby starting the combustion engine (2); the control device (100) being further configured to switch the clutch (9) to a partially closed state when the combustion engine (2) has been started The invention relates to a method for controlling the clutch (9) to switch to an open state during the operation of the combustion engine but before the output shaft (8) of the combustion engine has reached a speed synchronized with the speed of the input shaft (10) of the gearbox, wherein the control device is configured to initiate the control of the clutch (9) to switch to an open state in response to an indication that a predetermined condition for opening the clutch (9) is satisfied, wherein the predetermined condition for opening the clutch (9) is based on a prediction that the torque transmitted to the combustion engine (2) during the opening of the clutch (9) is sufficient to bring the combustion engine (2) to a state where it can be accelerated by controlling fuel injection; the control device (100) is also configured to synchronize the speed of the combustion engine (2) to the speed of the input shaft (10) of the gearbox (4) by controlling the injection of fuel to the combustion engine (2) during and / or after the control of the clutch (9) to switch to the open state.

12. A control device (100) according to claim 11, wherein the control device is configured to control the clutch (9) to switch to the open state in response to an indication from a management system (20) of the combustion engine (2) that the combustion engine can be accelerated by controlling fuel injection and / or in response to an indication that the speed of the combustion engine (2) has reached a predetermined speed threshold.

13. The control device (100) according to claim 11 or 12, wherein the control device is configured to control the clutch (9) to switch to a partially closed state corresponding to a predetermined transmission torque.

14. The control device (100) according to claim 11 or 12 is further configured to control the clutch (9) to switch from an open state to a closed state when the rotation speed of the output shaft (8) of the combustion engine (2) is synchronized with the rotation speed of the input shaft (10) of the gearbox (4).

15. A vehicle (1) comprising a vehicle powertrain (3), the vehicle further comprising a control device according to any one of claims 11 to 14.

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