DE102017217832A1 - Starting procedure in a hybrid vehicle - Google Patents

Abstract

A drive train (102) for a hybrid vehicle (100) comprises an internal combustion engine (105) and an electric machine (125) connected by means of a separating clutch (115). To start the internal combustion engine (105), the internal combustion engine (105) is towed by the electric machine (125). In this case, after at least partial closing of the separating clutch (115), a crankshaft (110) connected to the internal combustion engine (105) is accelerated. For energy and power saving, the acceleration of the crankshaft (110) is effected with a minimum torque predetermined by a control device (165), and the crankshaft (110) is given a minimum speed corresponding to the minimum of a minimum speed for igniting the internal combustion engine ( 105) and one for an oil pressure supply of the separating clutch (115) sufficient minimum speed is predetermined.

Description

The present invention relates to a method for starting an internal combustion engine arranged in a hybrid vehicle drive train by an electric machine, which is coupled to the internal combustion engine within the drive train via a separating clutch. When the disconnect clutch is closed, the combustion engine is towed by the electric machine. Furthermore, the invention relates to a hybrid vehicle with electric machine and internal combustion engine in a common drive train, which is preferably designed and configured to carry out the method described herein in whole or in part.

State of the art

A method for controlling a hybrid vehicle drive train with electric motor and engine, in particular internal combustion engine is in DE 10 2015 207 009 A1 described. Therein it is disclosed that the torque provided by an electric motor is applied to a crankshaft during a start of the engine for its towing. The torque required for an engine start is thereby to be divided into two separate torque requirements - one for turning the engine over a first compression moment and one for further towing the engine subsequently required towing torque.

In US 9 102 327 B2 two start modes for the engine of a hybrid electric vehicle are described. To start, first a clutch is engaged, and then the engine is started up with the driving force of the electric motor. In a first starting mode, the engine is started from the rest position to an acceleration request of the driver. In the second start mode, the engine is started from the rest position without a driver request, wherein the torque transmitted by the clutch is kept smaller during the approach of the engine than in the first start mode.

At a start of the internal combustion engine with the electric machine in which the combustion engine is towed by closing the clutch, it can be crucial in cold or empty battery that this start is performed with the lowest possible energy consumption or the lowest possible power.

An object underlying the present invention is to develop an improved technique for starting the engine in a powertrain of a hybrid electric vehicle. The object is achieved by means of the subject matters of the independent claims. Subclaims give preferred embodiments of the invention again.

Disclosure of the invention

The invention is based on a technical application of the physical law that the mechanical power results from the multiplication of the required torque with the rotational speed. According to the invention, these two quantities are minimized.

The minimum torque required for accelerating the crankshaft of the internal combustion engine VM is communicated to a functional control associated with the functional components of the drive train by an engine control unit or is stored in a device in the form of, for example, temperature-dependent characteristic maps or temperature-dependent characteristic curves. The minimum speed is determined by the minimum of a minimum speed required by the engine VM to ignite (possibly a temperature versus temperature characteristic stored in the control unit) and the minimum speed required for the oil pressure supply to the disconnect clutch K0 is required for the torque to be transmitted (temperature-dependent).

In an exemplary embodiment, the electric machine is controlled to the certain minimum speed, and then the disconnect clutch K0 accelerated or jumped to a torque value just below the specific torque. Then the torque of the disconnect clutch K0 brisk or steady, but not jumped further.

In a further optional embodiment of the method according to the invention, a function control is used to check or monitor whether the internal combustion engine starts to rotate and then runs independently. In such a case, the separating clutch is driven to reduce the torque.

According to another optional embodiment of the method according to the invention, in the event that the rotational speed is insufficient, the starting torque with the separating clutch K0 To transmit, the speed of the electric machine can be further raised to improve the oil supply.

In the context of the invention is also a hybrid vehicle, in which the drive train is designed for at least partially carrying out the method according to the invention. The control device used for this purpose is preferably an electronic data processing device and thereto arranged to carry out the method described herein in whole or in part. In particular, the controller may comprise a programmable microcomputer or microcontroller, and the method may be in the form of a computer program product with program code means. Features or benefits of the method may be related to the controller and the associated powertrain, and vice versa.

In a particular optional embodiment of the invention, the control means comprises a motor control part (e.g., conventional engine control unit) and a function control part, the function control part being connected on the input side to an output of the motor control part for receiving a value or datum for the minimum torque.

Expedient and efficient is the use of customary in engine control maps or curves for deriving engine-specific values for the respective minimum torque and / or for the respective minimum speed for igniting the engine or sufficient oil pressure supply to the clutch. For this purpose, according to an optional invention training, the control device is to be provided with a storage medium and one or more output interfaces for the output of values derived from the characteristic maps or characteristic curves mentioned. In a further refinement of this concept, the abovementioned function control part of the output interface can be connected to obtain a signal, value or datum for the minimum torque.

• 1 schematisch einen Antriebsstrang eines Hybridelektrofahrzeugs in Funktionsblöcken;
• 2 zeitliche Verläufe von Moment, Drehzahl und Druck in einem Antriebsstrang; und
• 3 ein Ablaufdiagramm eines Verfahrens zum Steuern eines Antriebsstrangs

darstellt.The invention will now be described in more detail with reference to the attached figures by means of an exemplary embodiment, in which:

• 1 schematically a drive train of a hybrid electric vehicle in function blocks;
• 2 temporal courses of torque, speed and pressure in a drive train; and
• 3 a flowchart of a method for controlling a powertrain

represents.

1 gives an overview of the essential components and functions in the drive of a typical hybrid vehicle 100 , in particular a hybrid electric vehicle. This has a hybrid powertrain 102 essentially, by an internal combustion engine 105 (VM), one with its crankshaft 110 connected separating clutch 115 (K0) and one via a disconnect clutch output shaft 120 connected, electric machine 125 (EM) is made out. The electric machine 125 is preferred with a DC / inverter 130 (GWR) operated on his the electric machine 125 opposite side for bidirectional energy flow with the connection of a battery 135 connected is. An output shaft 140 the electric machine 125 is via an output clutch 145 and a downstream output gear 150 with a differential 155 for road bikes 160 coupled. The output clutch 145 can structurally in the output gearbox 150 be integrated.

The functions of this arrangement can be performed by a control unit 165 (CU) are triggered and controlled, which can be conveniently implemented electronically, for example, with microcomputer or microcontroller. The control unit (CU) 165 receives for processing input signals and / or input data, in particular from rotational speed sensors 170 respectively. 175 for the internal combustion engine (VM) 105 or the electric machine (EM) 125 and controls the separating clutch ( K0 ) 115 For example, via a (not shown) hydraulic pump and the electric machine (EM) 125 indirectly via the DC / inverter (GWR) 130 at.

2 contains three superimposed time charts for pressure, speed and torque, each plotted over time as the abscissa. Vertically crossing the abscissa, dotted lines mark points in time t0 . t1 . t2 . t3 . t4 and t5 , The diagrams shown show typical characteristics of parameters on an exemplary powertrain 102 in one embodiment.

In the lowest time chart 205 is over time the fluid operating pressure p_K0 the disconnect clutch 115 K0 applied, which is zero until the start time t0, where the engine starting process begins, ie, the disconnect clutch 115 K0 is open. At the start of the start t0, the operating pressure p_K0 is suddenly increased and then gradually lowered in the further course. From about the time t5, at which the speed n_VM of the internal combustion engine 105 has reached its setpoint n_soll_VM, the operating pressure p_K0 has risen again to a steady state value near the initial operating pressure at time t0. Here is the disconnect clutch 115 closed or slip-regulated.

Further, at the start time t0, the electric machine becomes 125 to their minimum speed n_min_EM driven, as in the middle timing diagram 210 is shown. This is sized to the electric machine 125 the transmission and in particular the separating clutch 105 can supply with sufficient oil pressure. Due to the minimum speed n_min_EM of the electrical machine 125 arises, as in the upper time diagram 215 for the torque is shown a Moment m_EM of the electric machine 125 , In the further course according to the upper moment-time diagram 215 the clutch torque m_K0 of the disconnect clutch run 115 and the moment m_EM of the electric machine 125 from a time in the time interval t0 - t1 to a time in the time interval t3 - t4 largely congruent.

In the time interval t1 - t2, according to the mean time diagram 210 through the intervention of the electric machine 125 in the crankshaft 110 the internal combustion engine 105 approached, as can be seen by an increase in its speed n_VM in the mean time diagram in the time interval t1 - t2. This means that now for the internal combustion engine in the time interval t1 - t2 the starting process begins. In the subsequent time interval t2 - t3, the increase is congruent with the speed n_EM of the electric machine 125 until, in the further following time interval t3 - t4, the rotational speed n_VM of the internal combustion engine 105 has reached its setpoint n_soll_VM. For the period from the start time t0 to the time t4, where the engine has now reached its target speed n_soll_VM, finds a speed control for the electric machine 125 and the internal combustion engine 105 instead of. Furthermore, in the time interval from t2 to t5, a filtering of the torque corresponding to the driver's request may take place, for example when engine interventions, torque changes or reductions and the like are pending.

According to top timing chart is before the start time t0 in the electric machine 125 a reserve torque EM_R held in reserve for the start. That of the electric machine 125 maximum applicable torque is with the designation EM_G for clarity in the top timing diagram 215 located. At the end of the time interval t1-t2, the torque values m_EM of the electrical machine reach 125 and m_K0 of the disconnect clutch 115 first maximum values, wherein the value of the torque m_K0 of the separating clutch 115 may be just below the specified torque. With the vertical arrow between the negative torque value m_VM and a dashed horizontal line above it, which is horizontal or constant in the time interval t1-t2 in the positive torque value range, the towing and the activation of the internal combustion engine 105 illustrated. At the beginning of the subsequent time interval t2-t3 fall according to the top timing diagram 215 these torque values abruptly, while the torque m_VM of the internal combustion engine 105 soaring. At the same time take, as in the middle speed-time diagram 210 represented, the rotational speeds n_EM of the electric machine 125 and n_VM of the internal combustion engine 105 ramp up until the subsequent time interval t3 - t4. In this time interval t3 - t4 then the idle speeds n_L of the electric machine 125 and the internal combustion engine 105 reached. By the internal combustion engine 105 can then take over the load from the electric motor 125 take place, as is illustrated for the time interval t5 - t6 by the increase of the torque m_Vm. At the same time, the electric machine 125 with their now negative moment m_EM switch to a generator operation.

3 shows a flowchart of a startup procedure 300 , in particular for a drive train 102 a hybrid vehicle 100 the kind of 1 , According to 3 will be at the beginning of the procedure 300 a query 305 then carried out whether a start of the internal combustion engine 105 VM is requested. If so, the next step will be 310 the electric machine 125 EM started up to the specified minimum speed. Further, according to step 315 the separating clutch 115 K0 "Fast", ie jumped to a value just below the specified torque. This value is reached, as by the query 320 detectable, will in the next step 325 a control of the separating clutch 115 K0 carried out to the effect that there is a steady increase in torque. Is according to query 330 found that the internal combustion engine 105 VM has started, can in the next procedural step 335 a reduction of the torque of the separating clutch 115 K0 take place, as well as out 2 , upper timing diagram, in the time interval of t2-t4.

LIST OF REFERENCE NUMBERS

100

hybrid vehicle

102

powertrain

105

Internal combustion engine (VM)

110

crankshaft

115

Disconnect coupling ( K0 )

120

Disconnecting clutch output shaft

125

electric machine (EM)

130

DC / Inverter (GWR)

135

battery

140

output shaft

145

output coupling

150

output gear

155

differential

160

road wheels

165

Control unit (CU)

170

Speed sensor for internal combustion engine (VM)

175

Speed sensor for electric machine (EM)

205

lower time diagram

210

middle timing diagram

215

upper time diagram

300

method

305

Query whether startup VM

310

Control step electric machine to minimum speed

315

Activation step Disconnecting clutch to minimum torque

320

Query whether minimum torque has been reached

325

Activation step Disconnecting clutch for steady torque increase

330

Query, if internal combustion engine is running

335

Control step Disconnect clutch to reduce torque

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102015207009 A1 [0002]
• US 9102327 B2 [0003]

Claims (10)

Method (300) for starting an internal combustion engine (105) arranged in a hybrid vehicle drive train (100) by an electric machine (125) which is coupled to the internal combustion engine (105) within the drive train (100) via a separating clutch (115), wherein after at least partially closing the separating clutch (115) accelerates a crankshaft (110) connected to the internal combustion engine (105) and the internal combustion engine (105) is towed by the electric machine (125), characterized in that the acceleration of the crankshaft (110 ) is effected with a minimum torque (m_EM) predetermined by a control device (165), and the crankshaft (110) is given a minimum speed (n_VM) which corresponds to the minimum of a minimum speed for igniting the internal combustion engine (105) and for an oil pressure supply of the separating clutch (115) is predetermined sufficient minimum speed (n_min_EM). Method (300) according to Claim 1 wherein the electric machine (125) is controlled to the minimum speed (n_min_EM), and then the disconnect clutch (115) is driven to a torque value below the predetermined torque. Method (300) according to Claim 2 , Wherein the torque (m_K0) of the separating clutch (115) is raised even further after being driven. Method (300) according to one of the preceding claims, wherein a function control for monitoring or monitoring is used in that the internal combustion engine (105) rotates and then runs independently. Method according to one of the preceding claims, wherein the separating clutch (115) is driven to reduce its torque when the internal combustion engine (105) runs independently. Method (300) according to one of the preceding claims, wherein the oil supply of the separating clutch (115) is dependent on the rotational speed (n_EM) of the electric machine (125) and it is monitored whether the minimum rotational speed (n_min_EM) of the electric machine (125) is sufficient for a transmission of the minimum torque with the separating clutch (115), and if not sufficient, the rotational speed (n_EM) of the electric machine (125) is further increased. Hybrid vehicle (100), in particular designed for at least partially carrying out the method according to one of the preceding claims, with electric machine (125) and internal combustion engine (105), which are both coupled to one another via a separating clutch (115), wherein a control device (165) Electric machine (125), the internal combustion engine (105) and / or the separating clutch (115) controlled, characterized in that the control device (165) is designed and / or circuit-technically designed and adapted to the electric machine (125) and / or the separating clutch (115) to provide a minimum torque and a minimum speed, each sufficient for a start of the internal combustion engine, (105) to control. Hybrid vehicle (100) after Claim 7 wherein the control means (165) comprises a motor control part and a function control part, and the function control part is connected on the input side to an output of the motor control part for receiving a value or datum for the minimum torque. Hybrid vehicle (100) after Claims 7 or 8th wherein the control device (165) with a storage medium and one or more output interfaces for one or more maps or characteristics for deriving values for the respective minimum torque and / or for the respective minimum speed for igniting the internal combustion engine (105) and / or is provided for sufficient oil pressure supply of the separating clutch. Hybrid vehicle (100) after Claims 8 and 9 wherein the output control section connects the function control section to receive a minimum torque signal, value or date.

Images