DE102006012384A1 - Hybrid vehicle starting method, involves starting internal combustion engine in mode of operation from idleness without mechanical drive of internal combustion engine, where fuel ignition takes place after fuel injection into cylinder - Google Patents

Abstract

The method involves connecting an electric motor (EM) with a drive of an internal combustion engine (VM). The internal combustion engine is started in a mode of operation from idleness without mechanical drive of the internal combustion engine. A crank angle is aligned on its upper dead center according to the compression phase. A quantity of fuel is injected into a cylinder (Z). Ignition of fuel takes place after injection using igniting units, which are attached to the cylinder.

Description

The The invention relates to a starting method for an internal combustion engine according to the preamble of claim 1.

The Development of vehicles towards lower consumption and lowest Exhaust emissions currently shows a tendency, in addition to the internal combustion engine to integrate one or more electric motors in the drive train. Vehicles with combustion and electric motor are called hybrid vehicles designated. An advantage of hybrid vehicles is the possibility To feed back braking energy and independent due to the electric motor from the internal combustion engine to feed energy into the drive train can. Especially in city traffic with frequent start-up and braking are Hybrid vehicles can be used efficiently. In the stated application it comes due to traffic repeatedly to life of the vehicle, in which to further reduce fuel consumption of the internal combustion engine can be switched off (so-called start-stop operation). hybrid vehicles therefore have a high rate of starts. The start of the internal combustion engine should be largely comfortable and imperceptible to the driver respectively.

previously known are methods for so-called direct start of internal combustion engines, d. H. that without the use of a stored energy powered Starter the engine started directly by injection and ignition becomes. This is done by putting in a low after its top dead center The compression phase standing cylinder an injection while standing Engine takes place, wherein the mixture thus formed in the cylinder is then ignited. For this purpose, the position is preferably at the outlet of the engine evaluated the crankshaft and a favorably positioned for the direct start, about 90 ° after OT standing cylinder determined.

Such a direct start method is in the DE 103 35 401 A1 described.

For the direct start it is from the DE 101 11 928 A1 previously known to determine the position of a piston in a favorable position for the direct start. Absolute angle markers can be used on the crankshaft or, as in the DE 10 2004 001 716 A1 described by a combined evaluation of at least two sensors, which are each assigned to determine the relative position of the crankshaft and the camshaft these, the position of the crankshaft are determined. This requires absolutely measuring angle markers or the evaluation of several individual sensors. Usually 60-2 encoded encoder wheels, in which only after passing through a coded position of the encoder wheel, in the worst case after a revolution of the crankshaft, a reliable detection of the crankshaft position is possible.

From the DE 198 17 497 A1 is described a starting method for an engine with a crankshaft starter. The crankshaft starter accelerates the crankshaft to starting speed and the starting process is initiated at a favorable for the start of the engine crankshaft position. A start, without bringing the crankshaft to a starting speed, is not provided here. Furthermore, it is already known from the DE 199 60 984 A1 a method for setting a desired discharge position of the piston of at least one cylinder to produce a favorable starting position for the direct start of the engine. The outlet control takes place via a specific control of the gas exchange valves. Complex control methods are required for the run-off control systems described in the prior art. Furthermore, a drift of the parking position over time until restarting can not be avoided.

Furthermore, it is already known from the DE 197 41 294 A1 to move the crankshaft of an internal combustion engine by means of an electric motor in a suitable starting position and to generate from the movement with further action of the electric motor, a so-called "internal direct start" of the internal combustion engine by injection and ignition, wherein in the starting phase of the electric motor, a torque on the crankshaft A direct start from the standstill of the vehicle engine does not take place.At the start, foreign energy is still required for the mechanical acceleration of the crankshaft during the starting phase DE 103 60 789 a starting method in which the crankshaft is brought into a favorable starting position by means of auxiliary power and an electric or hydraulic auxiliary unit and during a correction phase an adjustment of the crankshaft takes place in such a way that thermophysical compensating operations during the service life are compensated for in the cylinder provided for starting.

Of the Invention is based on the object for a hybrid vehicle, which has a Internal combustion engine as well as over an electric motor for driving the vehicle has, a energy-optimal, comfortable starting process for the internal combustion engine too enable.

These Task is performed according to the characteristics of Claim 1 solved. Further advantageous embodiments will be apparent from the description and from the dependent claims.

Advantageously, the crankshaft through the drive or by the return fed by braking energy provided electric motor of the hybrid vehicle in a defined, favorable starting position for the direct start brought, with no additional starter unit is required by the use of provided for driving the hybrid vehicle electric motor. The crankshaft can also be moved with simple sensors into a detectable starting position and positioned there exactly. A direct start of the internal combustion engine can thus be carried out in a first mode of operation from standstill by injection and ignition, without a mechanical drive of the internal combustion engine is necessary. This results in an energy-optimal start of the internal combustion engine. The direct start itself is done quickly and quietly by the direct ignition without rotating starter. Especially for hybrid vehicles with a large number of start-stop cycles, the direct start as the starting method is to be preferred. Most of the starts take place when the engine is warm, so that favorable conditions for the direct start are available.

For hybrid vehicles can the start of the engine in another mode conventionally over the for the drive of the vehicle provided electric drive motor done so for the hybrid vehicle no additional starting unit must be provided. The selection of the start method can be dependent on carried out by engine or environmental parameters. By way of example, a Direct start depending on from the engine temperature and / or air temperature and / or oil temperature and / or cooling water temperature and / or the service life since parking. Are due to the evaluated parameters for the direct start unfavorable Environmental conditions, e.g. Cold start or long life of the engine, Thus, the start of the internal combustion engine by means of the drive motor of the Hybrid vehicle.

According to the invention advantageous a positioning of the crankshaft and thus at least one piston takes place immediately after the engine has run out, for a after a short start following the start the starting conditions for the Set direct start of the internal combustion engine. Dependent on from the service life after switching off the internal combustion engine can before a restart of the internal combustion engine, a correction of the Position positioning done.

According to the invention advantageous can be a start of the engine VM by means of the drive to the Hybrid vehicle provided electric motor EM done. this happens in particular, if after the direct start no for the safe startup of the internal combustion engine VM sufficient rotation of the crankshaft KW through one of these associated position sensor is detectable. The speed signal of the crankshaft is this with a predefined threshold and when it falls below the start is triggered by means of the electric motor.

The Invention will be described below with reference to an embodiment. A hybrid vehicle has an internal combustion engine for its drive and an electric motor which are independently separated or can be used together to drive the vehicle. The Hybrid vehicle can be designed as a parallel or serial hybrid be. The electric motor used to drive the hybrid vehicle is connected to the crankshaft of the electric motor or coupled executed with this and capable of the crankshaft of the internal combustion engine in its Able to adjust. The internal combustion engine is operated with spark ignition and has means for direct injection of fuel in the cylinder and is equipped with a control unit for controlling the ignition and Injections and for detecting the operating parameters of the internal combustion engine, an example of the speed and position of the crankshaft via a connected to the crankshaft associated sensor. The startup process of Internal combustion engine can be done in several modes. at Cold start, so a start after a longer life of the engine or at low engine temperature, the start is conventional by the electric motor used to drive the hybrid vehicle. The Use of the traction drive to start the vehicle saves the Use of another starter motor. Furthermore, the internal combustion engine with a direct start without additional external drive of the internal combustion engine can be started from standstill. This is done such that at least one favorable in one for the starting process Standing cylinder position by the injection of fuel in this cylinder and subsequent ignition is started. The for the boot process favorable Position of the cylinder is by the drive to the hybrid vehicle Used electric machine to produce. After ignition of the first cylinder the injection and ignition take place according to the cylinders following in the starting process, which in the working stroke in a position after the top dead center of the respective cylinder are located. By a position or speed the crankshaft receiving sensor becomes the position of the crankshaft certainly. For the case that after the direct start of at least one cylinder no Rotation of the crankshaft can be detected by the sensor This is a start with external auxiliary power through the drive of the hybrid vehicle used electric machine.

On the basis of a highly schematic embodiment of the invention will be explained in more detail below. A hybrid vehicle - not shown - has for its drive an internal combustion engine VM and an electric motor EM. As stated here, both are located on a crankshaft KW and form a so-called parallel hybrid. The electric motor EM and the internal combustion engine VM serve to drive the vehicle. The internal combustion engine VM has cylinders Z, which act on the crankshaft KW. According to the position of the crankshaft KW, the pistons in the cylinders Z have different positions. On the crankshaft KW there is a crankshaft sensor wheel KWG, which cooperates with a sensor S, which detects the current position of the crankshaft KW via markings G on the crankshaft sensor wheel KWG. This position is present as a signal S1 to a control unit SG. The internal combustion engine VM furthermore has units for ignition ZÜ and injection E, which open directly into the combustion chamber. The injection units E inject the fuel directly into the combustion chamber. With the described configuration two different start types are possible. In a start mode, the internal combustion engine VM can be started with the aid of the electric motor EM and in another starting mode, the internal combustion engine VM can be started by injection and ignition of the fuel-air mixture in a cylinder Z without external energy to drive the crankshaft KW (so-called direct start). , For this purpose, the crankshaft KW is brought by means of the electric motor EM in a position in which at least one cylinder Z is in a position between 10 ° and 150 °, preferably 30 ° to 100 °, after its top dead center after the compression phase. In a particularly preferred embodiment, a position about the middle position is set between 80 ° and 100 ° after the top dead center after the compression phase. Subsequently, fuel is injected into the cylinder Z and the resulting fuel-air mixture is ignited. Due to the expansion of the burning charge in the cylinder Z, the crankshaft KW is rotated about the piston and the connecting rod and the succeeding cylinder Z, which is in a position after top dead center after the compression phase, can be ignited. By means of the sensor S, the rotational speed of the crankshaft KW is monitored. If no rotation of the crankshaft KW is detected after a direct start, a start can take place via the electric motor EM.

VM

internal combustion engine

EM

electric motor

KW

crankshaft

reheat

unit to the ignition

e

unit for injection

KWG

Crankshaft generator gear

S

sensor for the Crankshaft generator gear

S1

signal of the sensor for the crankshaft sensor wheel

Z

cylinder

G

marks the donor wheel

ZK

cylinder head

Claims (6)

Starting method for a hybrid vehicle with a spark ignition Internal combustion engine (VM) with direct injection, wherein the hybrid vehicle for his Drive continues to have an electric motor (EM), the fixed or coupled to the output of the internal combustion engine (VM) is, wherein the internal combustion engine (VM) in an operating mode from the Standstill is started without mechanical stimulation by with the electric motor (EM) for driving the hybrid vehicle at least a cylinder (Z) of the internal combustion engine (VM) at its standstill in a suitable starting position between 30 ° and 150 °, preferably between 70 ° and 90 °, crank angle brought to its top dead center after the compression phase is injected and in this / these cylinder (Z) a lot of fuel and after injection by means of this cylinder (Z) assigned units for ignition (ZÜ) one ignition of the fuel. Starting method according to claim 1, characterized that the internal combustion engine (VM) directly after its departure by of the electric motor (EM) for driving the hybrid vehicle in a suitable Start position is brought, wherein by means of a sensor (S) for Position detection of the crankshaft (KW) by scanning the pulses of a the crankshaft sensor wheel (KWG) associated with the crankshaft (KW) during the Positioning movement by the electric motor (EM) a favorable starting position is detected and set. Starting method according to claim 2, characterized that in dependence from the service life between stopping and restarting the internal combustion engine (VM) before restarting the engine (VM) a correction the position positioning of the crankshaft (KW) takes place. Starting method according to claim 1 and 2, characterized that the start of the internal combustion engine (VM) in at least one other Operating mode by means provided for driving the hybrid vehicle Electric motor (EM) takes place. Starting method according to claim 4, characterized in that the start mode based on the service life after the engine temperature and / or the ambient temperature and / or the state of charge the battery required for driving the electric motor (EM) is selected. Starting method according to claim 5, characterized in that that a start of the internal combustion engine (VM) by means of the drive the hybrid vehicle provided electric motor (EM) then takes place when after the direct start no for Safe startup of the internal combustion engine (VM) sufficient rotation the crankshaft (KW) by one of these associated position sensor is detectable.