DE19947922A1 - Method for operating hybrid vehicle controls mode of operation of electric motor/generator unit according to charge level of vehicle battery - Google Patents

Abstract

The method relates to the mode of operation of the electric motor/generator. Under normal running conditions the battery charge level is checked to determine if it is sufficient to support motor mode. If it is not, or a point is reached when it is insufficient, the IC engine alone drives the vehicle. When braking if the battery charge is low the generator mode is selected. When a full charge level is reached or is already present the braking energy is dissipated in a braking resistance

Description

The present invention relates to a method for operating a hybrid vehicle according to the preamble of claim 1.

Motor vehicles with internal combustion engines have so far not been able to do so locally be operated emission-free. For a vehicle that is with is driven by a hybrid drive, this is through Switching off the internal combustion engine and operating the Electric motor possible.

A generic hybrid vehicle is from DE-A-44 46 485 known in which kinetic vehicle energy from the drive Electric motor is converted into electrical power that either by charging a traction battery or Driving an internal combustion engine via a coupled, then generator working in the engine mode are absorbed can.

To a hybrid vehicle with the greatest possible protection of the To brake friction brakes as well as the traction battery proposed to brake with variable braking force components, by activating an engine brake operation when the Traction battery is fully charged or its temperature is outside a specified charging temperature range or that provided by the drive electric motor electrical power associated charging current exceeds the predetermined limit.

In heavy commercial vehicles is used as a wear-free brake a hydrodynamic or an electrodynamic retarder  used the kinetic energy when braking in heat implements. Here are particularly high demands on the Reliability of the braking system is provided.

The object of the invention is a method for operating a vehicle, in particular a commercial vehicle, provide with which a hybrid drive adapted to the situation can be used.

This object is achieved in a method for Operating a vehicle according to the preamble of the claim 1 solved by the features in the characterizing part of claim 1.

According to the invention, a hybrid vehicle with a main drive and an electric machine in which the electric machine in Engine operation and / or in generator operation, wherein in generator mode kinetic vehicle energy from the Electrical machine converted into electrical power and in an energy storage unit is stored, operated so that a cycle first checks whether a Drive request or a braking request for that Vehicle is present, with the drive request it is checked whether a withdrawal of energy from the Energy storage unit taking into account Threshold values is permissible and there is a permissible removal Energy is extracted and made available to power the vehicle becomes. On the other hand, if withdrawal is not permitted, energy will only be used provided by the main drive.

If no drive request has been made, it is checked whether there is a braking request, and if there is one Brake request is checked to see if there is an input of energy the energy storage unit taking into account Thresholds is permitted. If the supply is allowed, there will be Energy and thus kinetic energy of the vehicle in the energy storage unit stored. If not allowed  In contrast, supply becomes energy in an energy dissipation unit submitted. The cycle is then repeated.

When checking the admissibility of the Extracting energy from the energy storage unit Threshold values to characterize a permissible Discharge current and / or a permissible discharge voltage and / or an allowable energy content and / or an permissible temperature of the energy storage unit used.

Furthermore, when checking the Permissibility of supplying energy to the Energy storage unit threshold values for characterization an allowable charging current and / or an allowable Charging voltage and / or a permissible energy content and / or a permissible temperature of the energy storage unit used.

In a preferred development of the method, the Permissibility of supplying energy to the Energy dissipation unit threshold values for characterizing a maximum permissible current and / or a maximum permissible Charging voltage and / or a maximum permissible temperature of the Energy dissipation unit used.

In a further preferred development, is omitted low vehicle speeds below one Threshold speed an energy input into the Energy storage unit.

In a further preferred development, Vehicle speeds below one Threshold speed a target braking torque depending on the current speed limited.  

In a further preferred development, Determination of the drive request and / or the brake request an accelerator pedal for an actuation process checked.

It is proposed to use a brake unit in a vehicle through an electric machine and an energy storage unit replace. A retarder unit in is particularly preferred a commercial vehicle by an electric machine and a Energy storage unit and an energy dissipation unit in the form a braking resistor unit replaced.

The advantage is that the energy generated during deceleration be buffered and then used to drive the Vehicle can be used.

The vehicle is no longer during the switching process no drive, but the switching breaks are with the Bridged electric machine.

The electric machine supports in certain Speed ranges in which the internal combustion engine does little Outputs the internal combustion engine.

Further advantages and refinements of the invention result itself from the description and the accompanying drawing.

It is understood that the above and the Features to be explained below not only in the combination given in each case, but also in others Combinations or alone can be used without the To leave the scope of the present invention.

The invention is based on an embodiment in the Drawing is shown schematically and is below  Described in detail with reference to the drawing. It demonstrate

Fig. 1 shows the arrangement of an electric machine with an energy storage unit and a Energieabführeinheit in a preferred hybrid vehicle,

Fig. 2 is a schematic representation of the process flow and

Fig. 3 input variables and output variables of a preferred controller.

In Fig. 1, a preferred arrangement is illustrated for performing the method according to the invention of a preferred drive system. A conventional hydrodynamic or electrodynamic retarder unit for a preferred commercial vehicle is replaced by an electric machine 1 and an energy storage unit 8 . Preferred energy storage units are a battery and / or a capacitor and / or a flywheel. Optionally, an energy dissipation unit 9 , preferably a braking resistor unit, can also be provided in order to meet any safety regulations for commercial vehicles. The energy dissipation unit 9 ensures that, when the energy storage unit 8 is charged, further power generated during braking in an emergency can be dissipated by heating the energy in the energy dissipation unit 9 .

The electric machine 1 is connected to a transmission 2 , so that a driving or braking torque can be given to a driven shaft 3 by the electric machine 1 via the transmission 2 . The driven shaft 3 is acted upon in the usual manner by an internal combustion engine 4 via the output 5 with a corresponding torque. The internal combustion engine 4 can be uncoupled from the transmission 2 by means of a clutch 6 , so that the electric machine 1 can give a positive or negative torque to the drive wheels independently of the internal combustion engine 4 .

The electric machine 1 is connected to a converter 7 . via the converter 7 is the electric motor 1 with a memory unit 8, for example. B. a battery, and an energy dissipation unit 9 , preferably a braking resistor unit, in connection. The braking resistor unit is provided to absorb braking energy of the electric machine 1 and convert it into thermal energy if the energy storage unit 8 has reached a state of charge that should not or should not be exceeded. For this purpose, the converter 7 is assigned a switching device, which can preferably be controlled, and which the electrical machine 1 can connect to the energy storage unit 8 or the energy dissipation unit 9 .

A preferred method for operating a preferred vehicle is shown in FIG. 2.

To decelerate a vehicle, the electric machine 1 acts as a generator. The electric machine 1 applies a braking torque to the drive shaft 3 . The resulting electrical energy is stored in the energy storage unit 8 .

When driving the vehicle, the electric machine 1 extracts electrical energy from the energy storage unit 8 and thus drives the vehicle in addition to the main drive 4 , preferably an internal combustion engine.

In addition, compliance with physical limits is advantageously checked, such as. B. from a battery control unit, not shown, predetermined current and voltage limits when a battery is used as the energy storage unit 8 . This improves the operational safety of the hybrid vehicle.

The vehicle is operated according to the preferred method described below, which is preferably repeated cyclically. At the beginning of the cycle, a first step is queried as to whether there is a drive request, ie whether the driver has a power request, for example by actuating the accelerator pedal. If so, a query is made as to whether the energy content of the energy storage unit 8 is sufficient to provide the electric machine 1 with a torque corresponding to the current operating state and / or the new, desired operating state. If so, energy is taken from the energy storage unit 8 . If no, drive power is drawn from the internal combustion engine 4 and the current cycle is ended. After completing the cycle, the next cycle can begin with the first step at the beginning of the cycle.

However, if the energy content of the energy store 8 is sufficient, the removal of energy from the energy store 8 is permissible. For this purpose, it is checked whether a threshold value during the removal, for example a maximum or minimum power limit and / or a maximum or a minimum discharge current and / or a maximum or minimum discharge voltage and / or a minimum and / or maximum temperature of the energy store 8 and / or a maximum or minimum temperature of the converter 6 is exceeded or fallen below. If not, the cycle has ended and the next cycle can begin. If a power limit is exceeded, power is again provided not by the energy storage unit 8 but by the internal combustion engine 4 . Then the cycle is over.

If, on the other hand, it is determined in the first step of the cycle that there is no drive request, e.g. B. the accelerator pedal has not been actuated, then it is checked whether there is a braking request, for example by actuating the brake pedal. If not, the cycle is finished and the next cycle can begin. If so, it is checked whether the energy storage unit 8 is charged or whether a maximum storage limit has been reached which should not be exceeded. If this limit is reached, braking energy generated during braking is fed into the braking resistor unit 9 and converted into thermal energy and the end of the cycle is reached. If it is permissible to supply energy to the energy store, ie if the energy store 8 can still absorb energy, then energy is supplied to the energy storage unit 8 and stored there. The end of the cycle has been reached and the new cycle can begin.

Of course, other parameters that characterize the current operating state of the vehicle, such as the state of the energy store 8 and / or the state of the braking resistor unit 9 , can also be taken into account. It is favorable to also provide such threshold values for the converter 2 and / or the electric machine 1 .

In Fig. 3, a preferred controller is shown with input variables and output variables. In order to carry out the method according to the invention, these input variables are made available to a controller in the vehicle and converted into output variables for activation with specification of the target torque of the electric machine 1 , the target torque of the main drive 4 and the energy dissipation unit 9 . The main drive 4 here is preferably an internal combustion engine.

A battery is preferably used here as the energy storage unit 8 . In other types of energy storage units, the monitoring parameters or threshold values for the battery are replaced by the parameters relevant to the respective energy storage unit 8 . The energy dissipation unit 9 is preferably formed by a braking resistor unit.

The braking resistor unit is formed here by four separate braking resistors, which can be energized individually or can be electrically connected in series and / or in parallel. The braking resistors are preferably monitored individually. The braking resistor unit or energy dissipation unit 9 is preferably cooled by a coolant.

The braking setpoint torque M2 of the electric machine, the actual torque M3 of the electric machine, battery state of charge SOC, maximum permissible voltage U1, current voltage of battery U2, minimum permissible voltage of battery U3, maximum permissible current of battery I1, current of battery I2, minimal serve as input variables permissible current of the battery I3, temperature TEM of the electric machine 1 , vehicle speed v.

Favorable possible input variables are:
M1: the total setpoint torque specified by the accelerator pedal in relation to the internal combustion engine 4
M2: Target braking torque for braking
M3: Actual torque of the electric machine 1
v: vehicle speed
n1: speed of the internal combustion engine 4
n2: speed of the electric machine 1
x1: gear engaged in the vehicle x2: clutch position (0.1, 0 = clutch open, 1 = clutch closed)
SOC: battery charge status (0. 1; 0 = empty, 1 = full)
U1: maximum permissible voltage of the battery
U2: current voltage of the battery
U3: minimum permissible voltage of the battery
I1: maximum permissible current of the battery
I2: current of the battery
I3: minimum permissible current of the battery
TEM: temperature of the electric machine 1
θ1: temperature of braking resistor 1
θ2: temperature of braking resistor 2
θ3: temperature of braking resistor 3
θ4: temperature of braking resistor 4
θ5: temperature of the coolant of the braking resistor unit 9 .

The outputs on the right mean:
M4: Target torque of the electric machine 1
M5: Target torque of the internal combustion engine 4
Y: Control of braking resistor unit 9 (value from 0 to
1, 0 = no current through braking resistor unit 9 , 1 = full current through braking resistor unit 9 )

It is advantageous to limit the setpoint torque M4 of the electric machine 1 for the drive and braking cases. The target torque M4 is preferably limited when predetermined physical limits, e.g. B. temperatures are exceeded. The setpoint torque M4 of the electric machine 1 is preferably multiplied by a value between 0 and 1 when approaching a threshold value which must not be exceeded or undershot. For this purpose, an auxiliary threshold value near the threshold value is set when the threshold value is approached in the permitted range. For the permitted values in between, the target torque is multiplied by the interpolated value between 0 and 1. The transition between full setpoint torque M4 and no setpoint torque M4 = 0 is not abrupt, but is carried out smoothly.

It is particularly advantageous with commercial vehicles, with very low speeds v no recuperation of the Provide braking energy, approximately below a threshold of Speed of preferably 5 km / h. So that will  prevents z. B. when the brake pedal is pressed Vehicle standstill (v = 0) requested a negative torque and unintentionally reversing the vehicle is initiated.

For this purpose, a characteristic curve is preferably stored in the controller, which outputs a number between 0 and 1 depending on the speed v. Below the threshold, this number is 0, with a further, somewhat higher auxiliary threshold, e.g. B. over 7 km / h, this number is 1, intermediate values for speeds between the threshold and the auxiliary threshold are interpolated. The output value is multiplied by the braking setpoint torque of the electric machine and thus limits it. The slow increase between 5 and 7 km / h ensures smooth transitions. Similarly, the target electrical machine torque can also be reduced by other physical limits, e.g. B. for current and voltage limits, which are predetermined for the energy storage unit 8 and / or the energy dissipation unit 9 , and / or for threshold values of the temperature of the converter 2 and / or the electric machine 1 .

It is also determined from the actuation of the accelerator pedal whether the driver wants to drive or brake the vehicle. A positive braking target torque of the electric machine 1 has priority. The result (+1 = driving, -1 = braking) is evaluated in the controller and switched through accordingly. In the case of a drive, the process is very similar to that in the case of braking, so the process is only explained in more detail for the braking case.

In the event of braking, a positive braking setpoint torque is negated because a negative electric machine torque is used for braking shall be. With the negated braking target torque is a Evaluation factor x3 multiplied (value between 0 and. 1). This means that the target electric motor torque is reached predefined threshold values are reduced.  

The output Y controls the braking resistor unit 9 (value between 0 and 1), ie the converter 2 is assigned a switching device which switches between the energy storage unit 8 and the energy dissipation unit 9 and connects the electric machine 1 either to the energy storage unit 8 or to the energy dissipation unit 9 .

The target electric motor torque M4 is preferably limited by two characteristic diagrams which record the state of charge of the battery and the current and voltage limits of the battery. Both supply values between 0 and 1 and are multiplied together. If one of the two values is below 1, the overall result is also below 1. In this case, part of the energy is conducted via the braking resistor unit 9 .

The setpoint value Y of the control of the braking resistor unit 9 is further multiplied by a factor F = 0 when the limit temperatures of the braking resistor unit 9 are exceeded and by a factor F = 1 at permissible values at a sufficient distance from a predetermined limit temperature.

The limiting factor by current I, voltage U and battery state of charge SOC is compared with the limiting factor of the braking resistor temperatures θ1, θ2, θ3, θ4. The maximum of the two values is used for the limitation of the electric machine target torque M4. This ensures that braking torque can be generated even when the battery is full. If both limiting factors are reduced, then braking with the electric machine 1 is only possible with limited power.

The additional monitoring of the Electric machine temperature TEM, which limits the Electrical machine target torque M4 leads.  

The limitation of the current and voltage limits U, I will preferably carried out with PID controllers.

The fuel consumption of a vehicle can advantageously be reduced by recuperating the braking energy. In heavy commercial vehicles, the electric machine 1 acts as a permanent brake. A retarder or the like can thus be saved.

The maximum torque of the drive unit 4 can be briefly increased by switching on the electric machine 1 , e.g. B. for overtaking or inclines. The internal combustion engine 4 can thus be made smaller. Low power of the internal combustion engine 4 at low speeds is compensated for by the electric machine 1 .

The electric machine 1 can support the starting process and can be used when maneuvering.

In areas where no internal combustion engine is operated the vehicle can still be locally emission-free with the help the electric drive are moved, e.g. B. in warehouses.

The drive unit is redundant. If the Internal combustion engine can continue with the electric motor be, e.g. B. to leave the road.

The electric machine can be used for active steaming Powertrain vibrations are used.

The electric machine 1 can support switching operations, preferably the vehicle is also driven during the switching operation. This is particularly helpful for heavy commercial vehicles, which lose a lot of speed, especially on uphill gradients during the shifting process.

Claims (8)

1. A method for operating a hybrid vehicle with a main drive ( 4 ) and an electric machine ( 1 ), in which the electric machine ( 1 ) is operated in motor mode and / or in generator mode, wherein in generator mode kinetic vehicle energy from the electric machine ( 1 ) into electrical Power is converted and stored in an energy storage unit ( 8 ), characterized in that

• that a cycle first checks whether there is a drive request or a braking request for the vehicle,
• - That it is checked when the drive request has been made, whether a removal of energy from the energy storage unit ( 8 ) is permissible taking into account threshold values, if there is a permissible withdrawal there energy is taken and provided to drive the vehicle, if the withdrawal is not permitted, energy is only available from the main drive is made, or if no drive request has been made,
• - That it is checked whether there is a braking request, if the braking request is present, it is checked whether the supply of energy into the energy storage unit ( 8 ) is permissible, taking into account threshold values, if the supply is permissible, energy is supplied there and thus kinetic energy of the vehicle in the energy storage unit ( 8 ) is stored, energy is released into an energy dissipation unit ( 9 ) when the supply is not permitted, and
• - that the cycle is then repeated.

2. The method according to claim 1, characterized in that when checking the permissibility of the removal of energy from the energy storage unit ( 8 ) threshold values of a permissible discharge current and / or a permissible discharge voltage and / or a permissible energy content and / or a permissible temperature of the energy storage unit ( 8 ) can be used. 3. The method according to claim 1, characterized in that when checking the permissibility of the supply of energy in the energy storage unit ( 8 ) threshold values of a permissible charging current and / or a permissible charging voltage and / or a permissible energy content and / or a permissible temperature of the energy storage unit ( 8 ) can be used. 4. The method according to claim 1, characterized in that the permissibility of the supply of energy in the energy dissipation unit ( 9 ) threshold values of a maximum permissible current and / or a maximum permissible charging voltage and / or a maximum permissible temperature of the energy dissipation unit ( 9 ) are used. 5. The method according to claim 1, characterized in that at low speeds (v) of the vehicle below a threshold speed (v1) an energy supply in the energy storage unit ( 8 ) is omitted. 6. The method according to claim 1, characterized, that at vehicle speeds below one Threshold speed (v1) a braking target torque depending on the current speed (v) is limited.   7. The method according to claim 1, characterized, that when approaching a threshold the Electric machine target torque is limited by when approaching to the threshold value the electric machine setpoint torque with a Value is multiplied between 0 and 1. 8. The method according to claim 1, characterized, that to determine the drive request and / or the brake request an accelerator pedal for an actuation process is checked.