DE102009034509A1 - Axle drive for vehicles - Google Patents

Abstract

The invention describes an axle drive for vehicles, comprising a left and a right output shaft (111a, 111b), a first electrical drive machine (105a) which is in operative connection with the left output shaft (111a), and a second electrical drive machine (105b), which is in operative connection with the right output shaft (111b). The first and second electric drive machines (105a, 105b) are each designed as a three-phase generator and are intended to generate a torque in one or more predetermined operating states that generates a differential torque between the left and right output shafts (111a, 111b), see above that the two output shafts (111a, 111b) can transmit torques of different sizes.

Description

The The invention relates to a transaxle for vehicles. The The invention particularly relates to a transaxle for distributing a Drive torque on at least two output shafts of a rear axle of a vehicle.

In vehicles, a drive torque generated by a prime mover is directed as needed via a transmission to the drive wheels. For power distribution differential gear are used, being used as a differential so-called. Transverse differential with respect to the direction of travel of a vehicle for the transverse distribution of the drive power to the drive wheels of a vehicle axle. For the transverse torque distribution at the rear axle of vehicles various types of differential gears are known, which are also referred to as so-called. Torque vectoring systems. Here, a distinction is made between clutch-based and clutchless systems. A clutchless torque vectoring system with an electromotive actuation, for example, from DE 103 19 684 A1 known. In this system, a single electric motor is used for the transverse torque distribution.

In addition, direct-motor, clutch-free systems (clutchless torque distribution system KMV) can be used for a transverse torque distribution on a drive axle of a vehicle. A schematic representation of such a system is exemplified in FIG 2 shown. At the in 2 shown axle drive is using two electric drive machines 105a . 105b a braking torque on a planet carrier 107 a superposition gear 107 . 109 applied. In a non-actuated case, ie at the same torque on the output shafts 111 . 111b , a drive torque flow takes place via a pinion 101 the drive shaft 100 , The drive torque is via a crown gear 102 and a bevel gear differential 103 on two output shafts 111 . 111b distributed. This corresponds to the drive flow of a conventional, passive differential with open differential. If one of the electric drive machines 105a . 105b a braking torque on the associated output shaft 111 . 111b being applied is via a pinion 106 the planet carrier 107 of the superposition gear braked. Thus, an additional torque flow from the bevel gear differential 103 over the superposition gearbox 107 . 109 on a respective output shaft 111 . 111b ,

The braking torque can be generated by electric motor braking with energy from an electrical system of the vehicle or by regenerative braking under power from the drive train. Furthermore, the additional feed of an electromotive drive torque via one of the two electric drive machines 105a . 105b possible. In this case, in particular a combined operation is advantageous, for. B. a regenerative braking with the prime mover 105a and using the recycled energy to drive the prime mover 105b , About the first electric drive machine 105a can be obtained from the powertrain performance. This is in combination with a power component, which is obtained from the electrical system, for the drive of the second drive machine 105b used. As a result, the moment to be set by the individual drive machine can be reduced.

• 1. Im inaktiven Betrieb des Achsgetriebes entstehen hohe Schleppverluste. Aufgrund der sich zeitlich bzw. rotatorisch ändernden permanentmagnetisch erregten Luftspaltfelder der EC-Maschinen treten im inaktiven Betriebszustand des Achsgetriebes, d. h. bei einer ungebremsten Geradeausfahrt des Fahrzeugs, magnetische Verluste auf. Da sich die magnetischen Schleppverluste mit mechanischen Schleppverlusten summieren, werden Kraftstoffverbrauch und CO₂-Emissionen erhöht.
• 2. Im Fehlerfall des Achsgetriebes muss ein sofortiger Wechsel des aktuellen Betriebszustands in einen vollständigen Leerlauf erfolgen. Vollständiger Leerlauf bedeutet, dass von den Antriebsmaschinen keinerlei Momente auf die Abtriebswellen aufgebracht werden. Fällt beispielsweise bei dem in 2 beschriebenen Achsgetriebe eine der beiden Antriebsmaschinen 105a, 105b aus, so muss gewährleistet sein, dass die noch arbeitende, zweite Antriebsmaschine unverzüglich in den Leerlauf überführt wird. Ohne diese Funktion besteht die Gefahr, dass das Fahrzeug aufgrund des fehlerhaften, einseitigen Betriebs und des daraus hervorgehenden Giermoments einen sicherheitskritischen Zustand einnehmen kann. Aufgrund der bereits erwähnten magnetischen Schleppverluste ist eine derartige Sicherheitsfunktion mit EC-Maschinen nur mit sehr hohem Aufwand realisierbar. Der Wechsel des Betriebszustands in den vollständigen Leerlauf kann nur durch eine Regelung realisiert werden, die das Antriebsmoment der jeweiligen Antriebsmaschinen aktiv zu Null regelt. Eine zuverlässige Ausführung der derartigen Sicherheitsfunktion ist nur sehr aufwändig realisierbar.
• 3. Ein weiterer Nachteil ist die thermische Belastung der Leistungselektronik im Rekuperationsbetrieb. Die im Rekuperationsbetrieb generierte elektrische Leistung hängt funktionsbedingt von der Drehzahl der elektrischen Antriebsmaschinen bzw. der Fahrzeuggeschwindigkeit ab. Die Regelung einer konstanten Ladespannung einer Batterie erfordert, überschüssig generierte elektrische Leistung abzuleiten. Die dabei entstehende Wärme muss durch eine geeignete Kühlung der Leistungselektronik abgeführt werden, welche wiederum zusätzliche Kosten verursacht.
• 4. Die elektrischen Antriebsmaschinen derzeitiger Achsgetriebe sind hinsichtlich kostenökonomischer und fertigungstechnischer Aspekte nur bedingt in Serienfahrzeugen einsetzbar, da permanentmagnetisch erregte EC-Maschinen sehr teuer sind.

A crucial role to ensure the described function comes here to the electric drive machines used. Existing clutchless torque vectoring systems provide for permanent magnetically excited, electrically commutated (EC) machines as prime movers. For example, permanently magnetically excited synchronous machines or transverse flux machines are used. The advantage of these drive machines is that they work wear-free and at the same time have a high power density. However, the use of permanently magnetically excited EC machines in a transaxle of the type described has the following disadvantages.

• 1. In inactive operation of the transaxle, high drag losses occur. Due to the temporally or rotationally changing permanent magnetically excited air gap fields of the EC machines, magnetic losses occur in the inactive operating state of the axle drive, ie during unrestrained straight-ahead driving of the vehicle. As magnetic drag losses add up to mechanical drag losses, fuel consumption and CO ₂ emissions are increased.
• 2. In the event of a fault in the final drive, an immediate change of the current operating state to a complete idle must occur. Full idling means that no torque is applied to the output shafts by the prime movers. Falls for example in the in 2 described axle drive one of the two prime movers 105a . 105b from, it must be ensured that the still working, second drive machine is immediately transferred to idle. Without this function, there is a risk that the vehicle may assume a safety-critical state due to the faulty, unilateral operation and the resulting yaw moment. Due to the magnetic drag losses already mentioned, such a safety function can only be realized with EC machines with very high outlay. The change of the operating state in the full permanent idling can only be realized by a control that actively controls the drive torque of the respective drive machines to zero. A reliable execution of such a safety function is very complex feasible.
• 3. Another disadvantage is the thermal load on the power electronics in Rekuperationsbetrieb. The electrical power generated in the recuperation operation depends on the function of the speed of the electric drive machines or the vehicle speed. The regulation of a constant charging voltage of a battery requires to dissipate excessively generated electric power. The resulting heat must be dissipated by a suitable cooling of the power electronics, which in turn causes additional costs.
• 4. The electric drive machines of current axle gearboxes can only be used to a limited extent with regard to cost-economic and production-related aspects in production vehicles, since permanently magnetically excited EC machines are very expensive.

It is therefore an object of the present invention to provide an axle drive, which the function described above to simpler and cheaper Way.

These The object is achieved by a axle drive with the features of claim 1 solved. Advantageous embodiments emerge the dependent claims.

The Invention provides an axle for vehicles, the one left and right output shafts, a first electric drive machine, which is in operative connection with the left output shaft, and a second electric drive machine, which with the right Output shaft is operatively connected includes. Here are the first and the second electric drive machine each as a three-phase generator designed and provided in one or more predetermined Operating conditions to generate a torque which a Differential torque between the left and right output shaft generated so that the two output shafts of different sizes Can transmit torques.

Compared to a permanently magnetically excited EC machine, the efficiency and power density are lower. In addition, three-phase generators are typically larger than the EC machines proposed for a final drive. Normally, a three-phase generator is used exclusively as a generator, for. B. used as an alternator in a vehicle. Despite these disadvantages, the use of three-phase generators in one axle drive based on a direct-motor, clutch-free KMV system is advantageous. The advantage of a three-phase generator in a axle drive according to the invention is that these represent high-volume components and thus are available at low cost. Through the use of field-oriented controls, a reduction in fuel consumption and CO ₂ emission values can be achieved. In addition, the use of three-phase generators safety advantages in case of failure of one of the two drive machines.

Especially It is envisaged that the three-phase generators are claw-pole alternators. Similarly, slip-ringless Leitstückläufer three-phase generators be used. The three-phase generators of the axle transmission according to the invention can also be designed as a double generator, with in a Rekuperationsbetrieb the supply of a two-voltage on-board network is vornehmbar. The latter variant is also of Advantage if the demand for higher performance exists. These mentioned types of three-phase generators are in large numbers used in motor vehicles typically as alternators. Due to the large quantities can These are easily and inexpensively manufactured. Consequently become the disadvantages of high costs and insufficient industrializability currently used or planned EC machines bypassed.

In an expedient embodiment is provided that the first and second electric drive machine in each case via a planetary gear are in operative connection with the axle drive, wherein a respective drive machine is a rotary component, in particular a pinion of a planet carrier, drives.

A important role in the actuation of electric drive machines the axle transmission according to the invention comes Design of power electronics too. Because three-phase generators in operation not only regenerative, but also motor work, the usual used power electronics of the alternators not used become. According to another embodiment Each of the drive machines, a control unit for controlling a Assigned control circuit, wherein the control unit as control variables at least one desired torque and a desired voltage can be fed. It is thus used a control, as to control electronically commutated machines is used. Hereby becomes a field-oriented regulation allows.

In particular, the control unit is at least one the operating state as a further control variable the electrical drive machine characterizing measured variable, in particular a mechanical angle and an angular velocity, fed.

According to one In another embodiment, the control circuit comprises a pulse width modulatable B6 bridge circuit.

According to one Another embodiment is by the control unit by means of a Switching element, in particular a semiconductor switching element, the current through an exciter winding of the electric drive machine adjustable. This enables the field-oriented regulatory procedure, the simple control and safety advantages offers.

Conveniently, the control unit is adapted to the switching element in inactive operation of the axle drive to be opened. The inactive operation of the transaxle is characterized in that an identical Torque is applied to both output shafts, d. H. no positive or negative torque application by one of the electrical Drive machines done.

It is also useful if the control unit is further adapted to the switching element in an accident to open. In the from the prior art known axle drive with EC machines is the warranty a complete idling in an accident, in which of the prime movers no torques to the output shafts may be delivered, not or only very expensive realizable. When using the axle drive in a torque vectoring system is the guarantee of a complete idling but in case of failure of high relevance. By the invention Achsgetriebe, the idle in the event of a fault by simple Interrupting the power supply to the excitation windings of that concerned Three-phase generator, by appropriate control of the semiconductor switching element, will be realized.

It is also advantageous if the control unit is designed in this way is, the switching element in the recuperation of the electrical Drive machine to control a charging voltage to control. The Control unit in conjunction with the control circuit allows Recuperation according to the functional principle of a conventional Make alternator. As the exciter field of the alternator is freely variable, can be a constant, independent of the speed Voltage to charge the battery efficiently and easily realized become. This is compared to known systems in recuperation no excess energy was converted, which subsequently again with great effort in the form of heat dissipated must become.

According to one further expedient embodiment is additional a common control for the first and the second provided electric drive machine, which is designed to is, the drive machines selectively as a generator or engine too operate. This allows the application of a braking torque necessary energy not only by electric motor braking with energy supply from the electrical system or by regenerative braking with energy supply taken from the drive train, but also the feed of electrical energy from the electric drive machine, which is not used to apply the braking torque and Accordingly, it is in recuperation.

The axle drive according to the invention makes it possible to reduce the fuel consumption and the CO ₂ emission values compared with the system described in the introduction.

This results from the fact that in the axle drive according to the invention the excitation field of the electric drive machines necessary for the regenerative and motor function of the drive machine is generated without the use of permanent magnets. Therefore, in the inactive state, e.g. As in unchecked straight ahead of the vehicle, neither Ummagnetisierungsverluste nor losses due to magnetic induction. In addition, the high towing losses of known, direct-motor clutchless systems and the resulting increases in fuel consumption and CO ₂ emissions can be significantly reduced.

The can be used in a axle drive according to the invention Three-phase generators are in large numbers used as alternators in motor vehicles. these can therefore be produced inexpensively. This can make the use more expensive Special motors, such. B. permanent magnetically excited synchronous machines, brushless DC machines or transversal flux machines, which have been proposed in known axle transmissions avoided become.

The The invention will be described in more detail below with reference to the figures. Show it:

1 a schematic representation of an inventive control of an alternator used in an axle drive according to the invention, and

2 a schematic representation of a transaxle, which is designed as a direct motor, clutchless torque vectoring system.

The construction of the axle transmission according to the invention has already been described in connection with 2 described. The axle drive according to the invention is thus based on a known from the prior art axle drive, namely a direct motor, clutchless torque vectoring system in which the previously used permanent magnetically excited EC machines are replaced by three-phase generators. The three-phase generators can be designed as Klauenpol three-phase generators with slip ring or slip-less Leitstückläufer three-phase generators. In the case of a request for a high power or the necessity that the supply of a two-voltage on-board network is possible in recuperation, the electric drive machines can also be implemented as double generators. The types of three-phase generators mentioned are typically used in motor vehicles as alternators. They are therefore available in large quantities at low cost.

An important role in the actuation of the three-phase generators in this case is the design of the control of the alternators. Since the three-phase generators operate not only as a generator but also as a motor during operation, the commonly used control, as provided for alternators, can not be used. The invention therefore proposes the use of a control as used to control electronically commutated electric drive machines. A possible embodiment of the control of an alternator in a transaxle according to 2 is in 1 shown.

With the reference number 1 are designated armature windings of the alternator. A field winding is denoted by the reference numeral 3 characterized. The armature windings 1 be via an inverter 2 , which is designed as a B6 bridge circuit fed. The inverter 2 includes six semiconductor switching elements for this purpose 2-1 . 2-2 . 2-3 . 2-4 . 2-5 . 2-6 , which in each case a freewheeling diode is connected in parallel. Two each of the switching elements 2-1 to 2-6 are connected in series to form a half bridge. The three half-bridges are connected in parallel with each other. The excitation winding 3 is connected via a series connected to this switching element 4 from a battery 5 which also serves to supply the B6 bridge circuit and this is connected in parallel. The switching element 4 is preferred as a semiconductor switching element, for. B. as a MOS-FET formed. The battery 5 is also a capacitor 10 connected in parallel.

The control of the switching elements 2-1 to 2-6 of the inverter 2 and the switching element 4 is done by a control unit 8th , The control unit 8th is designed to control a predetermined setpoint torque M _setpoint and a predetermined setpoint charging voltage U _setpoint . Optionally, in addition, a control of a predetermined mechanical angle _to the target _setpoint ω γ and a predetermined desired angular velocity take place. For this purpose, the control unit 8th a measured voltage U and measured currents I ₁ , I ₂ , I ₃ and I ₄ supplied. The voltage U is through a voltmeter 6 measured, that of the battery 5 is connected in parallel. The currents I ₁ , I ₂ and I ₃ set the currents through the armature windings 1 which are detected by corresponding measuring devices on the armature windings. The current 14 is a current flowing through the excitation winding, which is detected at this. In addition, the control unit 8th a through an angle sensor 7 measured rotation angle γ supplied. From these measured and predetermined variables, the control unit generates signals for the switching elements 2-1 to 2-6 of the inverter 2 as well as for the switching element 4 ,

By appropriate timing of the switching element 4 is in the excitation winding 3 set a current. This generates a current-variable, magnetic excitation field, which the armature windings 1 flooded the alternator. Will the switching element 4 opened, so there is no exciter field. A regenerative or motor effect of the actuator then remains completely off. Thus, the switching element 4 remain open in the inactive operation of the axle, whereby magnetic drag torques are completely avoided. In the event of an incident, on the other hand, the change to complete idling can be brought about without delay. For this purpose, only the opening of the switching element 4 required. In recuperation, however, by means of the switching element 4 a simple control of the charging voltage can be realized, whereby a constant and independent of the speed charging voltage can be ensured.

By using an alternator in a direct-drive clutchless axle drive and the described field-oriented control, a reduction in fuel consumption and CO ₂ emission levels in a vehicle can be achieved. In addition, there are safety advantages, since an immediate change to a complete idle the drive machine is possible. In recuperation operation, no excess energy is converted, which in turn results in energetic benefits. The components used are available with low unit costs, since these are already used in large quantities in the automotive sector.

LIST OF REFERENCE NUMBERS

1

Alternator

2

inverter (B6 bridge circuit)

2-1

switching element with freewheeling diode

2-2

switching element with freewheeling diode

2-3

switching element with freewheeling diode

2-4

switching element with freewheeling diode

2-5

switching element with freewheeling diode

2-6

switching element with freewheeling diode

3

excitation winding

4

switching element

5

battery

6

voltmeter

7

angle sensor

8th

control unit

9

control circuit

10

capacitor

100

drive shaft

101

pinion

102

crown

103

bevel gear

104

Sir Aßfalg: please complete.

105a

first electric drive machine

105b

second electric drive machine

106

pinion

107

planet carrier

108

Sir Aßfalg: please complete.

109

Superposition gear stage

110

Sir Aßfalg: please complete.

111

first output shaft

111b

second output shaft

MSoll

Desired torque

Ucomm

Target voltage

γSoll

mechanical Target rotation angle

ωSoll

Target angular velocity

U

measured tension

γ

measured angle of rotation

I1

measured electricity

I2

measured electricity

I3

measured electricity

I4

measured electricity

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• DE 10319684 A1 [0002]

Claims (13)

Axis transmission for vehicles, comprising: - a left and a right output shaft ( 111 . 111b ); A first electric drive machine ( 105a ), which with the left output shaft ( 111 ) is in operative connection; A second electric drive machine ( 105b ), which with the right output shaft ( 111b ) is in operative connection; - wherein the first and the second electric drive machine ( 105a . 105b ) are each designed as an alternator and are provided to generate in one or more predetermined operating states, a torque which is a differential torque between the left and right output shafts ( 111 . 111b ), so that the two output shafts ( 111 . 111b ) can transmit different sized torques. Axle drive according to claim 1, wherein the three-phase generators Claw pole three-phase generators are. Axle drive according to claim 1, wherein the three-phase generators slip-ring-type capstan rotor generators are. Axle drive according to claim 1, wherein the three-phase generators are designed as a double generator with which in a recuperation the Supply of a two-voltage on-board network is vornehmbar. Axle drive according to one of the preceding claims, in which the first and the second electric drive machine ( 105a . 105b ) in each case via a planetary gear with the axle drive in operative connection, wherein a respective drive machine ( 105a . 105b ) drives a rotary component, in particular a pinion of a planet carrier. Axle drive according to one of the preceding claims, in which each of the drive machines has a control unit ( 8th ) for controlling a control circuit ( 9 ), wherein the control unit ( 8th ) as control variables, at least one setpoint torque (M _setpoint ) and a setpoint voltage (U _setpoint ) can be supplied. Axle drive according to Claim 6, in which the control unit ( 8th ) as a further control variable at least one of the operating state of the electric drive machine characterizing measured variable, in particular a mechanical angle (γ _target ) and an angular velocity (ω _target ), can be fed. Axle drive according to Claim 6 or 7, in which the control circuit ( 9 ) comprises a pulse width modulatable B6 bridge circuit. Axle drive according to one of claims 6 to 8, in which by the control unit ( 8th ) by means of a switching element ( 4 ), in particular a semiconductor switching element, the current through a field winding ( 3 ) of the electric drive machine is adjustable. Axle drive according to Claim 9, in which the control unit ( 8th ) is adapted to the switching element ( 4 ) to be opened in inactive operation of the transaxle. Axle drive according to Claim 9 or 10, in which the control unit ( 8th ) is adapted to the switching element ( 4 ) to be opened in case of an accident. Axle drive according to Claim 9, 10 or 11, in which the control unit ( 8th ) is designed such that the switching element ( 4 ) in the recuperation of the electric drive machine to control a charging voltage. Axle drive according to one of the preceding claims, in addition to a common control for the first and the second electric drive machine provided which is adapted to the drive machines selectively to operate as generator or motor.

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