Vehicle with an internal combustion engine and an automated transmission

Abstract

Vehicle with an internal combustion engine (1) and an automated transmission (2), wherein the automated transmission comprises at least one clutch element (10), wherein in the event of deceleration of the vehicle - that at least one clutch element can be operated with slippage, - via which at least one coupling element a drag power can be transferred to the combustion engine, and - the internal combustion engine is capable of being towed by the drag power transmitted via the at least one clutch element during overrun shutdown, characterized in that - that the vehicle has a belt-driven generator, - that the vehicle has auxiliary units that can be operated via a belt, - that the internal combustion engine has a belt drive, and - that a drag torque drives the belt at a drag speed to operate the generator and the auxiliary equipment.

Description

[0001] The invention relates to a vehicle with an internal combustion engine and an automated transmission, wherein the automated transmission comprises at least one clutch element.

[0002] The coasting mode of a motor vehicle or hybrid vehicle, known to those skilled in the art, involves utilizing the vehicle's kinetic energy during rolling phases to maintain the highest possible rolling speed and thus achieve the greatest possible rolling distance. According to document DE 10 2008 029 453 A1, for example, the vehicle's engine is decoupled from the rest of the drivetrain to reduce the braking effect of the engine's drag torque. The traction phase following a rolling phase can begin at a later time and / or occur with lower engine power due to the maintained rolling speed or achieved rolling distance. This creates potential for fuel savings.

[0003] Fuel consumption can be further reduced while coasting by not only decoupling the engine from the drivetrain and running it fired at idle instead of towing it at high engine speed, but also by switching it off completely and then restarting it during a subsequent traction phase. In this case, however, the electrical consumers supplied via the engine belt drive, such as the generator or the air conditioning compressor, are no longer supplied. Therefore, compared to a conventional vehicle electrical system, support measures for the on-board electrical system are required, for example through additional electrical energy storage devices and adjustments to the energy management system. Furthermore, recuperation is not possible in either variant of coasting mode, i.e. with the combustion engine fired at idle or with the engine switched off.This means that the vehicle's kinetic energy cannot even be partially used to feed electrical energy into the vehicle's electrical system and, if necessary, to charge electrical energy storage devices.

[0004] EP 2 269 882 A2 describes vehicle coasting in conjunction with a so-called gliding mode. According to the strictest interpretation of the state of the art, this does not actually constitute coasting, since the combustion engine is fired during coasting and transfers a lower drive torque to the drive axle via a slip-operated clutch, thus transferring the vehicle into a gliding mode. This extends the coasting phase.

[0005] An alternative method for saving fuel during vehicle coasting is so-called recuperation with overrun cut-off. In this method, the engine's fuel supply is interrupted during the coasting phase. The engine remains coupled to the drivetrain and is towed without fuel. This type of operation is also known as engine braking. This allows high torque, for example from the generator, to be converted into electrical power at high engine speeds without fuel consumption, thereby further increasing the engine's braking effect. If the kinetic energy converted into electrical power is used to charge electrical energy storage devices in the vehicle's electrical system, this is also referred to as recuperation.

[0006] DE 101 46 742 A1 shows a method for controlling and / or regulating the drag torque in a drive train of a vehicle, wherein in overrun mode the power introduced into the drive train by the wheels is transmitted via a controllable clutch, and wherein the torque transmitted via the controllable clutch is controlled or regulated in such a way that the drive engine is operated at a speed equal to or greater than the idling speed.

[0007] DE 100 63 751 A1 shows a method for operating an internal combustion engine in which the drag or braking power of the internal combustion engine is regulated by intervening in the valve control in order to obtain recuperation power during overrun or braking operation of the internal combustion engine while maintaining the braking or deceleration behavior of the motor vehicle expected by the driver.

[0008] It is an object of the invention to provide an improved vehicle with an internal combustion engine and an automated transmission.

[0009] This object is achieved by a vehicle with an internal combustion engine and an automated transmission according to claim 1. Advantageous embodiments and further developments of the invention emerge from the dependent claims.

[0010] According to the invention, when the vehicle decelerates, the at least one clutch element can be operated with slip, a drag power can be transmitted to the internal combustion engine via the at least one clutch element, and the internal combustion engine can be towed with the drag power transmitted via the at least one clutch element during overrun cut-off. Furthermore, the vehicle has a generator and additional units that can be operated via a belt. The internal combustion engine comprises a belt drive, wherein the drag torque drives the belt at the towing speed in order to operate the generator and the additional units. As a result, mechanical power is tapped from the crankshaft by the belt drive, so that part of the drag power is transmitted to the additional units via the engine. The other part of the drag power is converted into heat by the towed engine as drag power loss.

[0011] In this document, overrun cutoff refers to the interruption of the fuel supply to the combustion engine when no power is being demanded from the engine via the accelerator pedal. In other words, this occurs when the accelerator pedal or gas pedal is not being depressed. Such driving phases are also referred to as overrun phases. In contrast, there are traction phases, during which a power demand is being placed on the engine.

[0012] During a coasting phase, the moving vehicle decelerates due to driving resistance, which consists of air resistance, rolling resistance, and internal vehicle frictional resistance. The latter frictional resistance includes, for example, the engine brake of the towed, overrun-disabled engine. The loss generated by the engine brake is referred to in this document as drag power loss.

[0013] The advantage of the invention is that drag loss is minimized by the fact that a significantly smaller proportion of the vehicle's kinetic energy is transferred to the engine as drag energy via the clutch element than with full power transmission between the transmission and engine. The proportion of the combustion engine's drag power converted into heat corresponds to the drag loss. Drag loss increases with engine speed. The engine brake is therefore used to a lesser extent, so that the vehicle's kinetic energy can be converted into a greater rolling range during a coasting phase, analogous to coasting mode, than in pure towing mode. A subsequent towing phase begins later and / or requires less acceleration of the vehicle and is therefore associated with lower fuel consumption.

[0014] For the purposes of this document, automated transmissions may include, for example, a dual-clutch transmission, an automated manual transmission, a continuously variable transmission or a torque converter automatic transmission.

[0015] In the case of a torque converter automatic transmission with a hydraulic clutch, a torque converter, and a torque converter lockup clutch, the clutch element according to the invention is understood to be the torque converter lockup clutch. Multi-plate clutches used in a torque converter automatic transmission always establish a frictional connection within the transmission within the meaning of this invention.

[0016] In contrast, a dual-clutch transmission has two clutches, which, depending on the design, can be either dry-running friction disc clutches or wet-running multi-plate clutches. In a dual-clutch transmission, the clutch element according to the invention corresponds to a friction disc clutch or a multi-plate clutch. In this case, two clutch elements can also be operated with slip.

[0017] An automated manual transmission usually has a dry-running friction disc clutch. The clutch element according to the invention corresponds to the friction disc clutch in this case.

[0018] A further advantage of the invention is that the engine can be towed at low speeds. The engine runs unfired and at low speeds, so the power dissipated by the engine as frictional heat is minimal, yet torque can still be tapped at the crankshaft. For this reason, this type of operation can also be referred to as sail-tow operation.

[0019] According to a preferred embodiment of the invention, the slip of the at least one clutch element can be controlled by a control unit. The drag power transmitted to the combustion engine can be adjusted by the control unit.

[0020] The towing power transmitted to the motor in the form of towing speed and torque is adjustable. This offers the advantage that the towing power transmitted to the motor can be minimized as a controlled variable to increase the range in sail towing mode, with the mechanical power tapped at the motor shaft by the belt drive acting as a manipulated variable.

[0021] The belt drive can supply various auxiliary units with mechanical power. This allows the generator, in particular, to operate, allowing the vehicle's electrical system to supply a large number of safety- and comfort-relevant consumers with electrical power.

[0022] According to a further variant of the present invention, the control unit can adjust a drag speed of the internal combustion engine and a drag torque of the internal combustion engine based on the transmitted drag power. When fired, the internal combustion engine has an idle speed range, with the drag speed being in the range of the idle speed range or below the idle speed range toward lower speeds.

[0023] This ensures that during sail towing, the maximum amount of mechanical power that can be transferred to the auxiliary units is approximately equal to the maximum power demanded by these auxiliary units when the engine is idle. This is advantageous because a towing speed that does not exceed the idle speed range ensures low towing power losses and a reliable supply to the auxiliary units.

[0024] It can also be advantageous if the generator charges an electrical energy storage device that is part of the vehicle.

[0025] In this way, the vehicle's braking energy can be recovered if the power demand of the auxiliary units falls below the engine's available power during coasting. This also enables recuperation, as is familiar to experts from conventional towing.

[0026] The invention is based on the following considerations: Coasting mode is a well-known technique in motor vehicles. This opens the power flow between the combustion engine and transmission when the driver is not depressing the accelerator pedal. As a result, the vehicle is not decelerated by the high drag power loss of the combustion engine when coasting. The vehicle retains most of its kinetic energy, which does not need to be recovered when the accelerator pedal is depressed. The resulting potential savings are approximately 5-10%, depending on driving style and driving cycle. While the power connection is opened, the combustion engine idles, decoupled from the drivetrain, and drives auxiliary units such as the air conditioning compressor, generator, vacuum pump, water pump, etc., via the belt drive, consuming fuel.

[0027] Alternatively, the engine can be shut down during coasting, as with common engine start-stop functions, which can further save fuel. To power auxiliary components in this operating state, the functionality of the conventional 14-volt electrical system is extended to supply electrical consumers. This also protects the electrical system and the consumers against a voltage drop when the combustion engine is restarted.

[0028] In both variants of coasting mode, no kinetic energy is recuperated in the vehicle. Furthermore, vehicle functions must be ensured during coasting by idling the engine with fuel supply or by complex on-board power system support measures.

[0029] As an improvement measure for vehicles with automatic transmissions, it is proposed to partially engage the torque converter lockup clutch of the automatic transmission during coasting operation, coasting the combustion engine at an adjustable minimum speed without fuel supply. The adjustable partial engagement of the torque converter lockup clutch creates slip between the engine shaft and the drive shaft, thus coasting the combustion engine to drive auxiliary components. Slip-controlled operation is feasible with modern torque converter lockup clutches. The resulting power loss at the torque converter lockup clutch due to high slip at low speed and low torque transfer is within the power loss design range of modern, wet torque converter lockup clutches.However, in conventional operation of a torque converter lockup clutch, power loss typically occurs at an operating point characterized by the transmission of high torque with low slip. The generation of power loss at different operating points does not conflict with either the functional principle of the torque converter lockup clutch or the widespread oil circuit cooling concept. Only the additional power loss generated at the torque converter lockup clutch during coasting operation as a result of increased use must be considered when designing the clutch with regard to durability and longevity.

[0030] A particularly advantageous feature of coasting mode with towing power transferred to the combustion engine via a slip-controlled torque converter lock-up clutch is that, during coasting, the auxiliary units and generator can be operated without fuel supply, and the vehicle electrical system does not require additional energy sources beyond a standard starter battery. Due to the power loss of a combustion engine during towing, which increases disproportionately with increasing engine speed, the loss of kinetic energy from the vehicle is not very significant for the range of coasting mode. To support the vehicle electrical system and supply consumers, a low engine speed below the engine idle speed is sufficient.This has the positive effect that the vehicle can sail “long distances” with low power loss via the torque converter lock-up clutch and low power loss due to engine drag, without the need for additional, complex support measures for the on-board electrical system.

[0031] A preferred embodiment of the invention is described below with reference to the accompanying drawings. Further details, preferred embodiments, and developments of the invention will emerge from these. Without limiting the generality, the embodiment describes a vehicle with a torque converter automatic transmission as the automated transmission. In detail, schematically Fig. 1 drivetrain with torque converter lock-up clutch Fig. 2 Drag loss of an unfired combustion engine

[0032] The Fig. Figure 1 shows the drivetrain of a vehicle with an internal combustion engine (1) and a torque converter automatic transmission (2). The internal combustion engine has a pulley for a frictional belt drive (5). This can be designed as a V-ribbed belt. The rotating engine can drive several units via the belt drive. These include, for example, a generator (7) and an air conditioning compressor (6). Additional units can be integrated into the belt drive, e.g., a water pump, a power steering pump, or a fan.

[0033] The torque converter automatic transmission has a hydraulic clutch (8) between an engine-driven impeller, the pump wheel, and a driven impeller of the transmission, the turbine wheel. Several sets of planetary gears are arranged downstream of the turbine wheel. Multi-plate clutches (9) and freewheels brake individual parts of the transmission's planetary sets in order to engage a specific gear. The hydraulic clutch also includes a hydrodynamic converter, known as the torque converter (8). The converter consists of another impeller, the guide wheel, located essentially between the pump wheel and the turbine wheel, which improves power transmission to the stationary turbine wheel when starting.The torque converter features a slip-controlled lock-up clutch (10) that connects the impeller and turbine wheel to form a single unit in higher gears. When the torque converter lock-up clutch is engaged, slippage between these two impellers is eliminated, increasing transmission efficiency. The power is transferred from the transmission to a drive shaft connected to the transmission (3) of the rear axle (4). The slip control of the lock-up clutch can be implemented, for example, by a transmission control unit as a control unit (11).

[0034] Fig. Figure 2 shows the drag power loss P of an internal combustion engine as a function of engine speed n. Drag power refers to the external power required to rotate the internal combustion engine without firing. Drag power loss increases exponentially with engine speed, obeying the relationship P = M · n · 1 / 9549.

[0035] If the driver fully releases the accelerator, the vehicle is in overrun mode. In conventional overrun mode, the engine is overrun, meaning that with a frictional connection between the drive shaft and the engine crankshaft via the transmission, the engine is rotated against its internal friction and inertia, utilizing the vehicle's kinetic energy. Because the vehicle is decelerated in the process, this engine overrun is also referred to as engine braking. During engine overrun, the fuel supply is interrupted to save fuel. The unfired engine overrun mode is known to experts as overrun cutoff.

[0036] In modern vehicles, the generator's output can be increased during coasting, so that the generator draws more torque from the engine. This slightly increases the braking force of the engine brake. The additional electrical power provided by the generator can be used to charge an electrical energy storage device in the vehicle during towing. This is usually a lead-acid battery with a nominal voltage of 12 volts. This recovery of the vehicle's kinetic energy, known as recuperation, contributes to fuel savings by reducing the average power requirements of the generator during traction phases with fuel supply. The on-board electrical system can be supplied at least partially with the recuperated energy. Recuperation mode is Fig. 2 is referred to as area A.

[0037] The point B in Fig. 2 describes another form of coasting operation of the motor vehicle which is intended to save fuel. This operation is also referred to as coasting operation and contradicts the functional principle of recuperation. During coasting operation the engine is disconnected from the rest of the drive train. This means that the engine is not dragged, and the vehicle's kinetic energy does not induce rotation of the engine. Therefore no drag power is generated by the engine, and the engine brake is ineffective. The vehicle thus retains a large part of its kinetic energy by rolling without power during the coasting phase. A traction phase following the coasting phase creates potential for fuel savings, as the vehicle's kinetic energy not dissipated during the coasting phase does not need to be built up again through fuel consumption. During coasting operation the combustion engine is idling.The engine also supplies the auxiliary components via the belt drive. In particular, electrical consumers and the vehicle's electrical system can be supplied via the generator. The engine's idle speed and idle torque are regulated depending on the generator's load requirements. The idle speed is typically within a range of approximately 500–1000 revolutions per minute.

[0038] Additional fuel savings potential is achieved by idling the combustion engine and then shutting it down during coasting. This means the engine is at a standstill. Fig. 2, this is designated as point C. However, compared to powered coasting mode B, unpowered coasting mode C requires additional measures to supply the auxiliary units and the vehicle's electrical system with electrical power. Restrictions on comfort, for example, in the air conditioning of the passenger compartment, or even possible functional limitations of safety-relevant chassis systems, are unacceptable. Therefore, measures to stabilize the electrical system are necessary. This could include an additional energy storage device installed in addition to the electrical system battery or the integration of a generator into the drive shaft. Automated restarting of the combustion engine is also necessary.

[0039] No recuperation is possible in either coasting mode B or coasting mode C. In fired coasting mode B, the battery can only be charged using fuel, while in unfired coasting mode C, the generator has no input torque.

[0040] In Fig. 2, another vehicle operating variant is described as area D, which is compatible with the Fig. 1 described drive train. In this case, during overrun, the engine initially remains frictionally connected to the rest of the drive train, i.e., a gear is selected and engaged by the transmission. However, the lock-up clutch is opened, so that the turbine wheel is not firmly connected to the impeller. Via the adjustable slip of the torque converter lock-up clutch, the torque of the turbine wheel can be partially transferred to the impeller, whereby the speed of the turbine wheel exceeds the speed of the impeller. Thus, a low towing power is transferred to the engine at a low speed. In this way, the engine can be towed without ignition, whereby the speed can be adjusted as a controlled variable by the slip control of the torque converter lock-up clutch. Slip-controlled torque converter lock-up clutches are part of the state of the art transmission technology. Since, according to Fig. 2 Since the drag power loss in range D is very low at low engine speeds, the vehicle's kinetic energy is used to coast the vehicle with low engine braking force while the engine is towed at low speed. Since this corresponds to the principle of coasting, the operating mode presented here can therefore be referred to as coasting tow.

[0041] Sail towing offers numerous advantages: Utilizing the low engine braking force at low engine speed during towing only slightly impacts the effectiveness of sailing. However, since the engine runs without consuming fuel, the belt drive can continue to power the auxiliary units. Complex measures to support the vehicle's electrical supply are unnecessary.

[0042] A modern vehicle generator, depending on the model, has a maximum output of 2-3 kW. With a generator efficiency of 80%, this results in a maximum power consumption of 2.5 to 3.75 kW. The maximum power consumption of modern air conditioning compressors is around 5 kW. In the example case where, during sail towing, the generator and air conditioning compressor require a power level of one-third of their maximum power, for example, around 3 kW of power must be transferred from the towed engine to the auxiliary units. If the engine is towed at 800 revolutions per minute, this correlates with a torque of around 35 Nm. For example, assuming a four-cylinder engine with a maximum output of 80 kW, the towing power loss at a towing speed of 800 revolutions per minute is around 1.5 kW.The total drag power to be transferred to the combustion engine via the torque converter lock-up clutch at an engine speed of 800 revolutions per minute, with the engine delivering 3 kW of power to auxiliary units, is therefore approximately 4.5 kW. The torque to be applied to the engine is therefore approximately 50 Nm according to P = M n 1 / 9549. According to the state of the art, torque converter lock-up clutches are designed for a slip Δn between the impeller and turbine wheel at the rated torque of the combustion engine. For common models in continuous operation, this is approximately 70 revolutions per minute with a rated torque of approximately 600 Nm. The power loss generated via the torque converter lock-up clutch and dissipated as heat by oil cooling is, according to P, v= M · Δn · 1 / 9549, or approximately 4.3 kW. The maximum slip occurring with a torque converter lock-up clutch designed in this way at the exemplary torque of 50 Nm during sail-tow operation is therefore approximately 820 revolutions per minute between the impeller and the turbine wheel. The turbine wheel therefore has a maximum of approximately 1600 revolutions per minute - at the exemplary towing speed of 800 revolutions per minute and based on the design for continuous operation. For example, if 5th gear is engaged, which corresponds to a gear ratio of approximately 0.9:1, the rear axle rotates at approximately 600 revolutions per minute with a rear axle gear ratio of 3:1. With a tire size of 195 / 50 R15, this results in a vehicle speed in sail-tow operation of approximately 65 km / h.

[0043] At higher vehicle speeds, either a higher speed or a higher torque must be transmitted to the towed engine to limit the power loss via the torque converter lock-up clutch. This results in increased energy loss at higher speeds according to Fig. 2 or increased recuperation power with an increase in belt drive torque. This increased energy loss can be counteracted by optimizing the design of the torque converter lockup clutch for short-term operation with higher slip. This could be achieved, for example, by increasing the cooling capacity.

[0044] However, for example, in short-distance operation, the heating of the transmission oil by sailing can also be beneficial. Sailing leads to faster oil heating, thereby increasing the efficiency of the transmission over a short distance. Sailing can then be used as an influencing parameter for controlling or regulating transmission oil heating.

[0045] Overall, sailing tow combines the advantages of towing with overrun cutoff and recuperation with the benefits of unpowered sailing. On the one hand, the low engine speed results in a long sailing range, and on the other, the auxiliary units and the on-board electrical system are supplied with mechanical and electrical power via the towed engine. List of reference symbols n Engine speed (in 1 / min) P v Drag power loss (in kW) P Towing power (in kW) M Torque (in Nm) A Towing operation of the unfired engine with recuperation B Sailing operation with open clutch and fired engine idle C Sailing operation with clutch open and engine stopped D Sail towing operation via torque converter lock-up clutch and unfired engine 1 combustion engine 2 automatic transmissions 3 rear axle transmission 4 rear axle 5 Belt drive 6 air conditioning compressor 7 Generator 8 Hydraulic clutch and converter 9 multi-plate clutches 10 torque converter lock-up clutch 11 Control unit

Claims

[1] Vehicle with an internal combustion engine (1) and an automated transmission (2), wherein the automated transmission comprises at least one clutch element (10), wherein upon deceleration of the vehicle - that at least one coupling element can be operated with slip, - via at least one coupling element, a towing power can be transmitted to the combustion engine, and - the combustion engine can be towed with the towing power transmitted via at least one clutch element during overrun cut-off, characterized by , - that the vehicle has a belt-driven generator, - that the vehicle has additional units that can be operated via a belt, - that the combustion engine has a belt drive, and - that a drag torque drives the belt at a drag speed to operate the generator and the auxiliary units. [2] Vehicle according to claim 1, characterized by , - that the slip of the at least one clutch element can be controlled by a control unit (11), - the transmitted towing power can be adjusted by the control unit. [3] Vehicle according to claim 2, characterized by , - that the control unit can adjust a drag speed of the combustion engine and a drag torque of the combustion engine by means of the transmitted drag power, - that the combustion engine has an idle speed range when fired, - that the towing speed is in the range of the idle speed range or below the idle speed range in the direction of lower speeds. [4] Vehicle according to one of the preceding claims, characterized by , - that the vehicle has an electrical energy storage device, - that the generator charges the electrical energy storage unit.

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