Method for operating a drive unit for a motor vehicle and corresponding drive unit

Abstract

Method for operating a drive unit for a motor vehicle, wherein the drive unit has a drive unit and, when the drive unit is started, the actual speed of the drive unit is first set to an overshoot speed and subsequently to an idle speed of the drive unit, characterized in that the starting process includes towing the drive unit to a minimum speed, from which the drive unit automatically increases its actual speed up to the overshoot speed, wherein the overshoot speed and the idle speed are set to different values ​​in different operating modes of the drive unit.wherein the overshoot speed in a first of the operating modes is set to a first overshoot speed and in a second of the operating modes to a second overshoot speed different from the first overshoot speed, and wherein the idle speed in the first operating mode is set to a first idle speed and in the second operating mode to a second idle speed different from the first idle speed, wherein the second overshoot speed is chosen to be greater than the first overshoot speed by an overshoot speed difference and the second idle speed is chosen to be greater than the first idle speed by an idle speed difference, wherein the overshoot speed difference corresponds to the idle speed difference with a tolerance of at most 50%.

Description

[0001] The invention relates to a method for operating a drive unit for a motor vehicle, wherein the drive unit has a drive assembly and, upon starting the drive assembly, the actual speed of the drive assembly is first adjusted to an overshoot speed and subsequently to an idle speed of the drive assembly. The invention further relates to a drive unit for a motor vehicle.

[0002] Prior art documents EP 3 271 564 A1 and US 2018 / 0080402 A1 are known, for example. These describe a vehicle control unit that includes an input for detecting a start request and a driving condition. The vehicle control module also includes a control module arranged to control an engine start attribute according to a first profile and a second profile. The vehicle control module also includes a selection module arranged to choose between the first and second profiles based on the detection of a predetermined driving condition in response to the detection of a start request.

[0003] Document US 2006 / 0063642A1 relates to a method for controlling the idling speeds of an internal combustion engine. The method includes operating the internal combustion engine at a first idling speed when a first device is in a first operating state, and when the first device is in a second operating state and a second device is in a first operating state, and operating the internal combustion engine at a second idling speed when the first device is in the second operating state and the second device is in a second operating state.The first idle speed is a low idle speed, and the second idle speed is a high idle speed, higher than the first idle speed. The low idle speed is selected to provide reduced clutch torque to the first device, and the high idle speed is selected to provide acceleration desired by a user.

[0004] The following documents are also known from the prior art: DE 695 20 987 T2, DE 11 2015 002 867 T5, US 2015 / 0 045 999 A1, DE 10 2016 118 756 A1, DE 197 05 865 C2, DE 10 2009 001 033 A1 and DE 10 2017 200 982 A1.

[0005] The object of the invention is to propose a method for operating a drive device which has advantages over known methods, in particular providing an expected operating behavior of the drive device for a driver of the motor vehicle.

[0006] According to the invention, this is achieved by a method for operating a drive unit with the features of claim 1. The starting process includes towing the drive unit to a minimum speed, from which the drive unit automatically increases its actual speed up to the overshoot speed, wherein the overshoot speed and the idle speed are set to different values ​​in different operating modes of the drive unit, the overshoot speed being set to a first overshoot speed in a first operating mode and to a second overshoot speed different from the first overshoot speed in a second operating mode, and the idle speed being set to a first idle speed in the first operating mode and to a second idle speed different from the first idle speed in the second operating mode.wherein the second overshoot speed is chosen to be greater than the first overshoot speed by an overshoot speed difference and the second idle speed is chosen to be greater than the first idle speed by an idle speed difference, wherein the overshoot speed difference corresponds to the idle speed difference with a tolerance of at most 50%.

[0007] Advantageous embodiments with appropriate further developments of the invention are specified in the dependent claims.

[0008] The drive system serves to propel the motor vehicle, thus providing the drive torque directed towards propelling the vehicle. The drive system is preferably an integral part of the motor vehicle, but can, of course, also be separate from it. To provide the drive torque, the drive system includes the drive unit. Preferably, the drive unit is an internal combustion engine. However, other configurations of the drive unit are also conceivable. In any case, the drive unit provides the drive torque, for example, via an output shaft.

[0009] Before the drive torque can be provided by the drive unit, it must first be started. Starting involves increasing the actual speed of the drive unit, particularly from a standstill, i.e., from a speed of zero. For example, to start the drive unit, it is first towed using an external torque. Preferably, this towing is carried out in such a way that the actual speed of the drive unit is increased to a minimum speed. The minimum speed is understood to be the speed of the drive unit above which it can continue to increase its actual speed independently without the aid of the external torque.

[0010] In particular, for towing, a torque source is coupled to the drive unit, the drive unit is towed until it reaches its minimum speed, and then the torque source is decoupled from the drive unit. The torque source can be, for example, an electric machine, especially a traction motor and / or a starter. However, it is also possible to use at least one wheel of the vehicle as a torque source, especially when the vehicle is already in motion.

[0011] The primary goal of starting the engine is to bring it up to idle speed. Idle speed is defined as an engine speed higher than the minimum speed, ensuring smooth operation and low fuel consumption. For example, during starting, the engine speed is typically increased from the minimum speed to idle speed, ideally continuously. However, to accelerate the starting process, it is preferable to first set the engine speed to the overshoot speed and then to idle speed. The overshoot speed is defined as an engine speed higher than both the idle speed and the minimum speed.Preferably, the overshoot speed is at least 20%, at least 40% or at least 60% greater than the idle speed.

[0012] In summary, during startup, the actual speed of the drive unit is initially increased to the overshoot speed, which is higher than the idle speed. Subsequently, the actual speed of the drive unit is reduced again until the idle speed is reached. By accepting the higher overshoot speed, the idle speed is reached particularly quickly. Preferably, the actual speed of the drive unit changes continuously until the idle speed is reached and is then held constant for at least a certain period of time. In particular, the drive unit is held at idle speed after it is reached without any input from the driver or a driver assistance system.

[0013] To achieve a particularly strong emotional connection between the customer and the vehicle, different operating modes can be selected on the drive system. This means that the drive system can be operated, or is operated, in one of several selected modes. For example, one of the operating modes is geared towards a comfortable driving experience, characterized by particularly low fuel consumption and / or a high level of comfort. Another operating mode, on the other hand, might be optimized for a sporty driving experience, enabling particularly high performance.

[0014] The two operating modes always have different idle speeds. In particular, the idle speed is lower in the mode geared towards comfortable driving than in the mode optimized for sporty driving. This allows the necessary drive torque to be provided particularly quickly when the vehicle needs to accelerate. This means that different idle speeds are set when the engine is started in the different operating modes. However, if the overshoot speed is set identically in both modes, this behavior is not readily apparent to the driver.

[0015] To achieve consistent and plausible behavior of the drive unit across all operating modes, the overshoot speed and the idle speed should be set to different values ​​in different operating modes of the drive system. This means that not only will the idle speed have different values ​​in the different operating modes, but this will also apply to the overshoot speed.

[0016] For example, there is a linear relationship between the overshoot speeds and the no-load speeds in the different operating modes. This means, in particular, that the overshoot speeds of the several operating modes are in a specific first ratio to each other, and the no-load speeds of the different operating modes are in a second ratio, where the second ratio is equal to the first. More generally, it is preferred that the overshoot speed of one of the operating modes is chosen to be larger the higher the no-load speed of that operating mode. Conversely, the overshoot speed of the operating mode is chosen to be smaller the lower the no-load speed of that operating mode.

[0017] In other words, the invention provides for adjusting the overshoot speed depending on the idle speed of the respective operating mode. Therefore, if different idle speeds exist in the operating modes, the overshoot speeds of these operating modes also differ. Put another way, the overshoot speeds of operating modes with different idle speeds are also different from one another. This results in consistent behavior of the drive system for the driver of the vehicle. In particular, it is not intended that the overshoot speeds be identical for operating modes with different idle speeds. Thus, in the operating mode geared towards comfortable driving, not only is the idle speed set for such comfortable driving, but the overshoot speed is also selected accordingly.The same applies analogously to an operating mode that is tailored to sporty driving.

[0018] The invention provides that the overshoot speed is set to a first overshoot speed in a first operating mode and to a second overshoot speed that differs from the first overshoot speed in a second operating mode. Thus, at least two operating modes are provided, namely at least the first operating mode and the second operating mode. When the drive unit is started in the first operating mode, the actual speed of the drive unit is initially set to the first overshoot speed and then to the no-load speed of the drive unit. The overshoot speed used when starting the drive unit therefore corresponds to the first overshoot speed that is stored for the first operating mode.

[0019] If, however, the drive unit is started in the second operating mode, the second overshoot speed is used as the overshoot speed. When starting the drive unit in the second operating mode, the actual speed of the drive unit is first set to the second overshoot speed and then to the idle speed. The two overshoot speeds, i.e., the first overshoot speed and the second overshoot speed, are different from each other. This ensures the previously mentioned consistent behavior of the drive system.

[0020] The invention provides that the idle speed is set to a first idle speed in the first operating mode and to a second idle speed that differs from the first idle speed in the second operating mode. The same principles apply to the idle speed as to the overshoot speed. If the drive unit is started in the first operating mode, the first idle speed is used. However, if the drive unit is started in the second operating mode, the second idle speed is used, which differs from the first idle speed.

[0021] It is preferably intended that when the drive unit is started in the first operating mode, the actual speed of the drive unit is first set to the first overshoot speed and then to the first idle speed. If, however, the drive unit is started in the second operating mode, the actual speed of the drive unit is first set to the second overshoot speed and then to the second idle speed. Again, this serves to ensure consistent behavior of the drive system and, accordingly, to achieve a strong emotional connection between the driver and the vehicle.

[0022] The invention provides that the starting process includes towing the drive unit to a minimum speed, from which the drive unit automatically increases its actual speed up to the overshoot speed. The drive unit is preferably started from a speed of zero. Therefore, the drive unit is stationary before starting. During starting, the drive unit is initially towed using an external torque until its actual speed corresponds to the minimum speed. The minimum speed is the lowest speed of the drive unit from which it can automatically increase its actual speed even without the use of the external torque.

[0023] Preferably, as already explained, the drive unit is first coupled to a torque source for towing, which provides the external torque. The drive unit is towed to the minimum speed by means of the torque source and then decoupled from it. Subsequently, the drive unit is controlled in such a way that it increases its actual speed from the minimum speed towards the overshoot speed, in particular up to the overshoot speed. The overshoot speed is set to different values ​​in the different operating modes, namely, in particular, to the first overshoot speed or the second overshoot speed. This achieves the advantages already described.

[0024] The invention provides that the second overshoot speed is higher than the first overshoot speed, and the second idle speed is higher than the first idle speed. The first overshoot speed and the first idle speed of the first operating mode serve in particular to achieve comfortable driving, whereas the second overshoot speed and the second idle speed of the second operating mode are designed for a particularly sporty driving style. To achieve the aforementioned consistent behavior, the speeds of the second operating mode, i.e., both the overshoot speed and the second idle speed, are higher than the speeds of the first operating mode. Again, this serves to achieve the advantages already mentioned.

[0025] The invention provides that the second overshoot speed is selected to be greater than the first overshoot speed by an overshoot speed difference, and the second idle speed is selected to be greater than the first idle speed by an idle speed difference, wherein the overshoot speed difference corresponds to the idle speed difference with a tolerance of at most 50%, preferably at most 40%, preferably at most 30%, or preferably at most 25%.

[0026] The difference between the second and first overshoot speeds is the overshoot speed difference, and the difference between the second and first idle speeds is the idle speed difference. For example, the overshoot speed difference corresponds exactly to the idle speed difference, so the second overshoot speed is greater than the first overshoot speed by the same speed difference by which the second idle speed is greater than the first. However, a certain tolerance may be allowed, whereby the overshoot speed difference deviates from the idle speed difference by no more than 50%, no more than 40%, no more than 30%, or no more than 25%, either upwards or downwards. In any case, the desired consistent behavior is achieved.

[0027] A preferred embodiment is one in which the overshoot speed difference is at least as large as the idle speed difference, but particularly preferably larger by a factor of at least 2, at least 3, at least 4, or at least 5. Even more preferably, the factor is at least 7.5 or at least 10. In this case, the overshoot speed difference is significantly larger than the idle speed difference, namely by at least one of the aforementioned factors. In absolute terms, the overshoot speed difference is preferably at least 500 rpm, at least 600 rpm, or at least 700 rpm, and / or the idle speed difference is at most 500 rpm, at most 250 rpm, at most 100 rpm, or at most 50 rpm. The idle speed difference can therefore be comparatively small. However, it is always non-zero and preferably always at least 50 rpm.

[0028] A further development of the invention provides that the second idle speed is selected to be at least 30%, at least 50%, or at least 60% higher than the first idle speed. There is thus a significant difference between the two idle speeds for the different operating modes. For example, the first idle speed is at most 850 rpm, at most 800 rpm, or at most 750 rpm, whereas the second idle speed is at least 975 rpm, at least 1,125 rpm, or at least 1,200 rpm. The difference between the idle speeds is selected such that it results in different starting behavior of the vehicle in the different operating modes and also in different acoustic behavior. This also serves to achieve consistent behavior.

[0029] Alternatively, the difference between the idle speeds can also be smaller. For example, the difference is at least 50 rpm, at least 100 rpm, or at least 200 rpm. Additionally or alternatively, it is at most 600 rpm, at most 400 rpm, or at most 200 rpm. The first idle speed, for example, is at most 800 rpm or at most 825 rpm, and the second idle speed is at least 850 rpm or at least 900 rpm.

[0030] A further development of the invention provides that, based on the position of a control element, an operating mode is selected from the first and second operating modes, and the overshoot speed and the idle speed of the selected operating mode are used to start the drive unit. The control element is preferably located in the interior of the vehicle. In particular, the control element can be operated by the driver of the vehicle while seated. The control element is, for example, located on an instrument panel in the vehicle's cockpit.

[0031] The control element is, for example, a button, a switch, a touchscreen, or the like. Using the control element, the driver can select an operating mode from the available modes, specifically the first and second operating modes. The engine speeds stored for this operating mode are then used to start the engine. These engine speeds include, in particular, the overshoot speed and the idle speed. The described procedure allows for easy selection of the desired vehicle behavior.

[0032] A further development of the invention provides that the drive unit is coupled to a gearshift of the drive system only after the drive unit has been started. The drive unit is connected to at least one wheel of the vehicle via the gearshift. Preferably, the drive unit is connected to several wheels of a wheel axle of the vehicle via the gearshift and an axle differential. In this case, the drive unit is connected to the axle differential via the gearshift, and the gearshift is connected to the multiple wheels via the axle differential.

[0033] Before starting, or immediately at the beginning of the starting process, the drive unit is decoupled from the transmission. The starting procedure is then carried out as previously described. Only subsequently is the transmission reconnected to the drive unit, allowing the vehicle to be propelled by the drive unit. This ensures an unaffected start of the drive unit.

[0034] The invention further relates to a drive system for a motor vehicle, in particular for carrying out the method as described in this description, wherein the drive system has a drive unit and is designed and configured to first adjust the actual speed of the drive unit to an overshoot speed and then to an idle speed when the drive unit is started. It is provided that starting includes towing the drive unit to a minimum speed, from which the drive unit automatically increases its actual speed up to the overshoot speed, wherein the drive system is further designed and configured to adjust the overshoot speed and the idle speed to different values ​​in different operating modes of the drive system.wherein the overshoot speed in a first of the operating modes is set to a first overshoot speed and in a second of the operating modes to a second overshoot speed different from the first overshoot speed, and the idle speed in the first operating mode is set to a first idle speed and in the second operating mode to a second idle speed different from the first idle speed, wherein the second overshoot speed is chosen to be greater than the first overshoot speed by an overshoot speed difference and the second idle speed is chosen to be greater than the first idle speed by an idle speed difference, wherein the overshoot speed difference corresponds to the idle speed difference with a tolerance of at most 50%.

[0035] The features and combinations of features described in the description, in particular those described in the following figure description and / or shown in the figures, can be used not only in the combinations specified, but also in other combinations or individually, without departing from the scope of the invention. Thus, embodiments that are not explicitly shown or explained in the description and / or the figures, but which are evident from or derivable from the described expressions, are also to be considered as encompassed by the invention.

[0036] The invention is explained in more detail below with reference to the exemplary embodiments shown in the drawing, without limiting the invention. The only embodiment shown is... Fig. 1 a diagram showing two curves for the actual speed of a drive unit of a drive device during a start-up of the drive unit.

[0037] The Fig. Figure 1 shows a diagram in which two curves, 1 and 2, each represent the actual rotational speed of a drive unit of a drive device over time. These curves, 1 and 2, of the actual rotational speed occur during the start-up of the drive unit or are set during the start-up process.

[0038] The starting of the drive unit is described below using the curve 1 of the actual speed, which is used for a first operating mode. Before starting, or at the beginning of the starting process, the drive unit is at rest, i.e., it has a speed of zero. During starting, the drive unit is initially pulled forward, in particular until the actual speed reaches a minimum speed n.M has been reached. Subsequently, the towing process is stopped and the drive unit automatically increases its actual speed, namely up to an overshoot speed n. U1 The actual speed is then reduced again until it finally reaches an idle speed. L1 has been reached. It is clearly visible that the overshoot speed n U1 significantly higher than the idle speed n L1 .

[0039] It may be provided that the actual speed of the drive unit is adjusted after reaching the overshoot speed n. U1 first, the engine speed is reduced to a level lower than the idle speed n. L1 However, such undershooting is only slightly pronounced, so the actual speed is less than the idle speed. L1 quickly reached. The curve 1 of the actual speed of the drive unit occurs during a start-up of the drive unit in the first operating mode.

[0040] If, however, the drive unit is started in a second operating mode, this occurs according to curve 2 of the actual speed of the drive unit. It can be seen that the minimum speed n M The actual rotational speed is identical or at least nearly identical for both curves 1 and 2. However, during curve 2, the actual rotational speed reaches an overshoot speed n. U2 , which is significantly higher than the overshoot speed n U1 according to the curve 1. Likewise, the idle speed n L2 According to the second curve 2, significantly higher than the idle speed n L1 according to the first course 1. It may be provided here that a speed between the overshoot speeds n U2 and n U1 The present ratio is equal to that between the idle speeds n L2 and n L1 The present ratio is... Alternatively, the relationship lies between the overshoot speeds n U2 and n U1the same speed difference or at least almost the same speed difference as between the idle speeds n L2 and n L1 .

[0041] Profile 1 is set in the first operating mode and profile 2 in the second operating mode of the drive unit. For example, the first operating mode serves to achieve a particularly comfortable driving experience, while the second operating mode is designed for a sporty driving style. This is achieved through the use of different overshoot speeds n U1 and n U2 as well as the different idle speeds n L1 and n L2 In each of the operating modes, a consistent behavior of the drive system or drive unit is achieved for the driver of the motor vehicle. REFERENCE MARK LIST: 1. Course 2 Course

Claims

[1] Method for operating a drive unit for a motor vehicle, wherein the drive unit has a drive unit and when the drive unit is started, the actual speed of the drive unit is first set to an overshoot speed and then to an idle speed of the drive unit, characterized by, that starting includes towing the drive unit to a minimum speed, from which the drive unit automatically increases its actual speed up to the overshoot speed, wherein the overshoot speed and the idle speed are set to different values ​​in different operating modes of the drive device, wherein the overshoot speed is set to a first overshoot speed in a first of the operating modes and to a second overshoot speed different from the first overshoot speed in a second of the operating modes, and the idle speed is set to a first idle speed in the first operating mode and to a second idle speed different from the first idle speed in the second operating mode,wherein the second overshoot speed is chosen to be greater than the first overshoot speed by an overshoot speed difference and the second idle speed is chosen to be greater than the first idle speed by an idle speed difference, wherein the overshoot speed difference corresponds to the idle speed difference with a tolerance of at most 50%. [2] Method according to claim 1, characterized by , that the second idle speed is chosen to be at least 30%, at least 50%, or at least 60% higher than the first idle speed. [3] Method according to any one of the preceding claims, characterized by , that based on the position of a control element, an operating mode is selected from the first operating mode and the second operating mode, and the overshoot speed and the idle speed of the selected operating mode are used to start the drive unit. [4] Method according to any one of the preceding claims, characterized by , that only after the drive unit has been started is the drive unit coupled to a gear-changing transmission of the drive device. [5] Drive unit for a motor vehicle, in particular for carrying out the method according to one or more of the preceding claims, wherein the drive unit has a drive unit and is designed and configured to first adjust the actual speed of the drive unit to an overshoot speed and then to an idle speed of the drive unit when the drive unit is started, characterized by, that starting includes towing the drive unit to a minimum speed, from which the drive unit automatically increases its actual speed up to the overshoot speed, wherein the drive device is further designed and configured to set the overshoot speed and the idle speed to different values ​​in different operating modes of the drive device, wherein the overshoot speed in a first of the operating modes is set to a first overshoot speed and in a second of the operating modes to a second overshoot speed different from the first overshoot speed, and the idle speed in the first operating mode is set to a first idle speed and in the second operating mode to a second idle speed different from the first idle speed,wherein the second overshoot speed is chosen to be greater than the first overshoot speed by an overshoot speed difference and the second idle speed is chosen to be greater than the first idle speed by an idle speed difference, wherein the overshoot speed difference corresponds to the idle speed difference with a tolerance of at most 50%.

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