EP2049781A1

EP2049781A1 - Auxiliary unit drive for a motor vehicle

Info

Publication number: EP2049781A1
Application number: EP07786574A
Authority: EP
Inventors: Gary Avery
Original assignee: Daimler AG
Current assignee: Mercedes Benz Group AG
Priority date: 2006-08-11
Filing date: 2007-08-06
Publication date: 2009-04-22
Also published as: WO2008017439A1; JP2010500206A; DE102006037576A1; US20090176611A1; WO2008017439A9

Abstract

The invention relates to an auxiliary unit drive, for a motor vehicle with a planetary gearing, wherein a sun gear (S) of the planetary gearing (P) is in power-exchanging engagement with a first electric machine (EMI), a planet gear carrier (PT) is in power-exchanging engagement with an internal combustion engine (VM) and a first ring gear (H1) is in power-exchanging engagement with at least one auxiliary unit (AG). The invention is characterized by two planetary gear sets (PR1, PR2) which are mounted with their axles in the planet gear carrier (PT), a second ring gear (H2) which can be held stationary by means of a first brake (BS), wherein the first planetary gear set (PR1) meshes with the first ring gear (H1) and the sun gear (S) and the second planetary gear set (PR2) meshes with the second ring gear (H2) and with the first planetary gear set (PR1), a first clutch (KVE), by means of which the internal combustion engine (VM) can be coupled to the first electric machine (EMI), and a first freewheel (FVG), by means of which the planet gear carrier (PT) can rotate only in one rotational direction.

Description

Auxiliary drive for a motor vehicle

The invention relates to an auxiliary drive for a motor vehicle according to the preamble of claim 1.

If ancillaries such as air compressors, fans, LenkheIfpumpen or oil and water pumps, used in motor vehicles in which the ancillaries are driven at a speed proportional to the speed of the engine, they must over a wide speed range, in gasoline engines, for example, from 600 to 6000 Rpm, ie a factor of 10 in the ratio of maximum speed to lowest speed, which meet the requirements placed on it. As a result, for example, a water pump which has to supply a sufficient coolant flow when the engine is idling promotes an unnecessarily high quantity of coolant at higher engine speeds and thus causes considerable losses. Other ancillaries, in turn, provide marginal performance at idle and are rarely operated in the optimum operating range.

In order to be able to drive ancillary units when the internal combustion engine is at a standstill, it is known to provide a separate electric motor which drives the power take-off of the internal combustion engine via a freewheel. A freewheel is a device that decouples a portion of a drive train from rotational motion as load ratios change. A freewheel can be designed for example as a roller freewheel, multi-disc freewheel or sprag freewheel. A sprag freewheel consists of an inner ring, an outer ring and clamp bodies mounted in a cage. In a drive through the inner ring springs press the clamping body slightly between the inner ring and the outer ring, so that the clamping body move depending on their rotation in their receiving spaces. Because the receiving spaces of the clamping body taper away from the springs, the transmitted torque is greater, the further the inner ring is rotated relative to the outer ring. By suitable selection of the angle of attack of the forming clamping wedge, the design is absolutely non-slip - even with the best lubrication - physical reasons, it prevails the state of self-locking. The taper angle must be chosen so that it is less than or equal to the arctangent of the sliding friction coefficient μ. If the direction of rotation is reversed or if the external speed is greater than the internal speed, the clamping elements will roll in the direction of the spring and the clamping will be canceled.

Electric machines, which are operated both by motor and generator, also have the problem that they require a different ratio in motor operation than in the generator mode. This usually leads to over-dimensioning of the electric machines. For example, starter generators require a higher gear ratio in starter mode than in generator mode, resulting in an oversized design for starter operation.

Likewise, electrical ancillaries are known, which are used in particular in hybrid vehicles, as here sufficient electrical energy is available to supply the ancillaries. These are expensive.

From DE 43 33 907 C2 an accessory drive for a motor vehicle with a superposition gearbox with an input base and two output bases is known, wherein the input base is in rotary connection with an internal combustion engine, the first starting base with an auxiliary assembly and the second starting base with an induction machine operated as a generator , The speed of the auxiliary assembly is controlled by the superposition gear so infinitely that it is in a uniform and ideal as possible range. However, in regenerative operation, the regenerative power of the induction machine due to the dependence on the torque requirement of the auxiliary assembly only limited controllable. In order to move from a continuously variable ratio operation to a direct ratio mode, multiple clutches must be adversely switched.

The object of the invention is to propose an auxiliary drive for a motor vehicle according to the preamble of claim 1, which has a high efficiency both when starting the engine and when driving the vehicle by the first electric machine.

This object is achieved by an auxiliary drive for a motor vehicle having the features of claim 1. Accordingly, the accessory drive has two planetary gear sets, which are mounted with their axes in the planet, a second ring gear, which can be held by a first brake relative to a housing part, wherein the first planetary gear with the first ring gear and meshing with the sun gear and meshing the second planetary gear set with the second ring gear and the first planetary gear set, a first clutch by which the internal combustion engine is coupled to the first electric machine, and a first freewheel, through which the planet carrier is rotatable only in one direction of rotation.

When using a first clutch, by means of which the internal combustion engine can be coupled to the first electric machine, the first electric machine can directly drive the internal combustion engine, whereby the efficiency is increased and the planetary gear is spared, in particular during a warm start of the internal combustion engine. Likewise, as a result, when the first clutch is closed, the regenerative power of the first electric machine does not depend on the torque requirement of the at least one auxiliary unit. This leads to the advantage that the first electric machine can be controlled independently of the auxiliary generator as a generator or motor, and thus a boost operation by an additional drive torque of the first electric machine is possible. Furthermore, the switching of the first clutch allows a simple change between a stepless operation and a direct operation.

If the ancillary drive has a first freewheel, by means of which the planet carrier of the planetary gear can only be rotated in one direction of rotation, it is possible, even when the internal combustion engine is at a standstill, to drive the first ring gear which is in exchange for power with at least one auxiliary unit. This is particularly advantageous in vehicles that can be powered purely electrically, since here, for example, the power steering steering assist pump must be driven. In a preferred manner, in this case the ancillaries, such as Air conditioning and power steering, operated such that, for example, during an increased Lenkhelfpurapenleistung the performance of the air compressor is reduced. As a result, the sum of the required power for ancillaries can be limited.

Does the accessory drive an extended planetary gear with two planetary gear sets and two ring gears, with only the first planetary gear meshes with the sun gear of the planetary gear and the first ring gear and the second planetary gear meshes with the first planetary gear and the second ring gear, so a first brake, by the second ring gear can be held relative to a housing part, advantageously serve as a starting clutch. In this case, the internal combustion engine can be started while the auxiliary drive is running by means of a start transmission by means of the first electric machine. This engine start is characterized by low vibrations.

The planetary gear allows advantageous

a higher torque when the internal combustion engine is started by the first electric machine when the first clutch is open, in particular during a cold start,

a torque distribution between the internal combustion engine and the first electric machine during the drive of the at least one ancillary unit, in particular when the internal combustion engine is idling, and

- Continuous control of the accessory drive, whereby the operating range of the at least one auxiliary unit can be reduced with respect to its speed spectrum. By means of the ancillary drive according to the invention, the following functionalities of a hybrid drive train can advantageously be realized:

Generator function by generator operation of the first electric machine (an alternator of a vehicle with conventional drive is no longer needed),

Start / stop functionality by starting the internal combustion engine by means of the first electric machine,

- Boost function by additional drive torque of the first electric machine and

- Drive the at least one auxiliary unit by the first electric machine at standstill of the internal combustion engine.

The second freewheel, through which the first ring gear of the planetary gear, which is in power exchange with at least one auxiliary unit, is rotatable only in one direction of rotation, advantageously allows a translation, and thus a torque multiplication, when starting the internal combustion engine by the first electric machine, in particular at a cold start. As a result, a start of the internal combustion engine is advantageously possible, in which the internal combustion engine is accelerated to its idling speed, before the injection process begins. This results in reduced exhaust emissions as compared to a conventional engine start as well as a comfort-enhanced starting process, which is particularly advantageous in start / stop operation.

An embodiment of the first clutch, by which the internal combustion engine can be coupled with the first electric machine, as a centrifugal clutch leads to significant cost advantages. And the possibilities in each Operating range to drive the at least one auxiliary continuously and demand-driven and also eliminates the limitation of the maximum speed.

If the ancillary drive has a second brake, by means of which the first element of the planetary gear can be held in relation to a housing part, then it is possible to increase the rotational speed of the at least one ancillary unit. This is particularly advantageous at low engine speeds, especially when a vehicle driveline has another electric machine for generating electrical energy.

Further advantages of the invention will become apparent from the description and the drawings. Concrete embodiments of the invention are shown in simplified form in the drawing and explained in more detail in the following description. Show it

1 is a schematic representation of an accessory drive according to the invention with an extended planetary gear, a first clutch for coupling a first electric machine and an internal combustion engine and a first freewheel for determining the direction of rotation of the planet carrier,

2 shows an illustration of the rotational speeds of the at least one ancillary unit, of the internal combustion engine and of the first electric machine during starting of the internal combustion engine in an auxiliary drive according to FIG. 1;

3 shows an illustration of the rotational speeds of the at least one ancillary unit, the internal combustion engine and the first electric machine during further operation of the auxiliary drive according to FIG. 1; Fig. 4 is a schematic representation of the

Accessory drive according to Figure 1 with a second freewheel for determining the direction of rotation of the first ring gear;

5 is a representation of the rotational speeds of the at least one auxiliary unit, the internal combustion engine and the first electric machine when starting the internal combustion engine in an auxiliary drive according to Figure 4;

Fig. 6 is a schematic representation of the

Accessory drive of Figure 1 with an additional second brake for holding the sun gear;

7 shows an illustration of the rotational speeds of the at least one ancillary unit, of the internal combustion engine and of the first electric machine in an auxiliary drive according to FIG. 6;

Fig. 8 is a schematic representation of the

Accessory drive according to Figure 1, wherein the planet carrier is connectable via a second clutch with an input shaft of a drive gear, which is also in exchange with a second electric machine in the power exchange; and

9 is a schematic representation of the

Accessory drive according to Figure 4, wherein the planet carrier is connectable via a second clutch with a third ring gear of a driveline planetary gear.

Figure 1 shows an accessory drive according to the invention with an extended planetary gear P with a sun gear S, two planetary PR1, PR2 and two ring gears Hl, H2, wherein the second ring gear H2 can be held by a first brake BS against a housing part. The planets of the two planetary gear sets PR1, PR2 are each mounted with their axes in a planet carrier PT. The planets of the first planetary PRl mesh with the sun gear S and the first ring gear Hl and with the planet of the second planetary PR2. The planets of the second planetary PR2 also mesh with the second ring gear H2.

Here are a first electric machine EMI with the sun gear S, an internal combustion engine VM with the planet PT and at least one auxiliary AG with the first ring gear Hl in the power exchange. By a first clutch KVE, for example, a multi-plate clutch, the engine VM can be coupled to the first electric machine EMI.

Furthermore, the auxiliary drive has a first freewheel FVG, by means of which the planet carrier PT is rotatable relative to a housing part only in one direction of rotation. This makes it possible, even if the engine VM is at a standstill, to drive the drive of the at least one accessory AG by the first electric machine EMI. In this case, the first freewheel FVG - as represented by the straight line 1 of FIG. 2 - supports the torque of the drive of the at least one ancillary unit AG.

This is particularly advantageous for vehicles that can be driven purely electrically, so-called full hybrid vehicles, since here, for example, the power steering power steering pump must be driven while the vehicle is driving purely electrically. In a preferred manner, in this case the ancillaries, such as Air conditioning and power steering, operated such that, for example, during an increased Lenkhelfpumpenleistung the performance of the air compressor is reduced. As a result, the sum of the simultaneous power requirements of the ancillary units can be limited.

The first freewheel FVG can also be arranged elsewhere along the output shaft of the internal combustion engine VM (crankshaft), if this is favorable, for example, with regard to the available installation space.

Further advantages through the support of the planet carrier PT by means of the first freewheel FVG also result in a vehicle which is driven purely electrically.

Figure 2 illustrates the speed ratios of at least one auxiliary unit AG, the internal combustion engine VM and the first electric machine EMI. On the vertical axis, the speeds are plotted in revolutions per minute. The distances on the horizontal axis between the at least one accessory AG, the internal combustion engine VM and the first electric machine EMI result from the translations of the planetary gear P so that the rotational speeds associated with a specific operating point can be connected by a straight line. Thus, two known speeds give the speed of the third element.

If the combustion engine VM is to be started from an operating state, as shown by straight line 1 of FIG. 2, ie where the drive of the at least one auxiliary unit AG is driven by the first electric machine EMI when the first clutch KVE is open, then this is advantageous when the drive is running of the at least one accessory AG by closing the first clutch KVE possible. This process is illustrated in FIG. 2 by an arrow from the straight line 1 to the straight line 2.

In this case, however, no translation would be given when starting the engine VM. Furthermore, when the first clutch KVE is closed, it may lead to restrictions with regard to ride comfort, and in addition the operational strength due to the high load must be taken into account.

Particularly preferably, as an alternative to starting the internal combustion engine VM, without having to stop the drive of the at least one ancillary unit AG, the first brake BS, which holds the second ring gear H2, be used as a starting clutch. Starting from the state according to line 1 so the first brake BS is closed, whereby the speed line 3 passes through the point BS. The second ring gear H2 is therefore still. This leads in contrast to a direct coupling of the internal combustion engine VM with the first electric machine EMI through the first clutch KVE to a starting ratio. This engine start is also characterized by low vibrations.

4 of FIG. 3 shows a state in which the drive of the at least one ancillary unit AG is supported as required, for example only with increased power requirement of the power steering pump or the air conditioning compressor, by the first electric machine EMI and the internal combustion engine VM is idling (approximately 600 U) / min). Depending on the configuration and operating state, the first EMI electric machine in this boost mode only has to contribute 20-40% of the required power. Here, the first clutch KVE is open. If the speed of the internal combustion engine VM falls below the idling speed, for example when the vehicle comes to a halt, then the first electric machine EMI is to change from regenerative to engine operation.

According to the exemplary embodiment according to FIG. 1, at a speed at the lower limit of normal operation of the internal combustion engine VM of 900 rpm and a stationary first electric machine EMI for driving the at least one auxiliary unit AG, a speed of 1200 rpm (straight line 7 of FIG FIG. 3).

Above this speed, represented by the straight line 5, the first clutch KVE is closed so as to enable an independent generator or Boostbetrieb.

Below this speed opens at a power requirement of at least one auxiliary unit AG, the first clutch KEV and the rotational speed of the drive of at least one auxiliary unit AG is controlled via the first electric machine EMI so that it does not fall below 1200 U / min. Thus, the operating speed range for the ancillaries is limited to the bottom.

By this stepless control of the drive of the at least one auxiliary unit AG can also be the maximum speed of the drive of at least one auxiliary unit AG, such as straight line 6 shows, limit to a speed of 4500 U / min. Here, the first electric machine EMI is operated as a generator, with their power depends on the torque requirement of the drive of at least one auxiliary unit AG. This limited controllability can, for example, by another electric machine in Drivetrain of the motor vehicle to be compensated permanently.

In addition, the speed of the drive of the at least one accessory AG can be controlled as needed in this way.

Characterized in that the drive of the at least one auxiliary unit AG can be driven not only by the internal combustion engine VM, but also by the first electric machine EMI, the engine VM no longer needs to be designed so that it can ensure the functions of all ancillaries already at idle.

The first electric machine EMI, the internal combustion engine VM and the sun gear S of the planetary gear P are arranged coaxially in FIG. However, it is also possible that the first electric machine EMI is arranged outside this axis and is connected by means of a belt, chain or gear drive with the sun gear S of the planetary gear P. This results in further optimization possibilities by choosing the translation of the first electric machine EMI.

The first clutch KVE, by means of which the internal combustion engine VM can be coupled to the first electric machine EMI, is preferably embodied in a form-fitting manner. An embodiment of the first clutch KVE as a centrifugal clutch leads to significant cost advantages. Where the possibilities to drive the at least one accessory AG steplessly and demand-driven in each operating range and also to limit the maximum speed of the auxiliary unit AG, omitted.

Figure 4 shows an accessory drive according to the invention with the elements of the accessory drive of Figure 1 and a second freewheel FAG, whose one end is connected to the first ring gear Hl and the other end to a housing part. By the second freewheel FAG, the first ring gear Hl is only in one direction, namely the drive direction of the engine VM, rotatable.

As a result, as shown by the straight line 8 in FIG. 5, in an alternative method for starting the internal combustion engine VM by the first electric machine EMI, when the first clutch KVE is open, a leverage effect occurs, i. the torque at the planet carrier PT increases to about three times. By this translation, a first electric machine EMI, which can generate a mechanical power of 3 - 6 kW to drive the at least one auxiliary unit AG, easily start the engine VM.

In the starting process, which is particularly preferably applied to a cold start, the internal combustion engine VM is first brought to normal idle speed, before the injection of fuel is started. This leads compared to a conventional starting process with a starter to lower exhaust emissions and better comfort. As a result, the internal combustion engine VM can go into start / stop operation more frequently, taking into account exhaust gas limit values.

Figure 6 shows an accessory drive according to the invention, comprising the elements of the accessory drive of Figure 1 and additionally a second brake KGE, by which the sun gear S of the planetary gear P can be held against a housing part.

As the straight lines 9 and 10 make clear from FIG. 7, when the sun gear S and thus held first electric machine EMI, the rotational speed of the drive of the at least one auxiliary unit AG relative to the rotational speed of the internal combustion engine VM can be increased. This is particularly advantageous at low speeds of the internal combustion engine VM. The fact that the first electric machine EMI can not generate electrical energy in this locked-down state can be compensated, for example, by a second electric machine in the drive train of the motor vehicle.

Figure 8 shows an accessory drive according to the invention with the elements of the accessory drive of Figure 1, wherein the planet PT and thus the output shaft of the engine VM via a second clutch KVM and preferably a torsional vibration damper with a transmission input shaft GE a drive gear G is connectable.

The driving gear G is connected on the output side with an axle drive, not shown, and thus drives wheels of the motor vehicle. As a drive G preferably a change gear is used. However, it can also serve a continuously variable transmission as a driving gear G.

With the transmission input shaft GE is also a second electric machine EM2 in the power exchange, which can be operated both as a generator and motor. If the second clutch KVM is open, for example, then the vehicle can be driven solely by the second electric machine EM2. When the second clutch KVM is closed, a drive torque can be applied by the internal combustion engine VM and / or the first electric machine EMI and / or the second electric machine EM2. Here also one or both electric machines EMI, EM2 regenerative can be operated. Likewise, when the second clutch KVM is closed, the second electric machine EM2 can be used to start the internal combustion engine VM.

Instead of using the elements of the accessory drive according to FIG. 1, the elements disposed on the output side of the second clutch KVM could also be combined with elements of the auxiliary drive according to FIGS. 4 or 6.

FIG. 9 shows an accessory drive according to the invention with the elements of the auxiliary drive according to FIG. 4, wherein the planet carrier PT and thus the output shaft of the internal combustion engine VM can be connected via a second clutch KVM to a third ring gear TH of a drive train planetary gear TP. The planet carrier PT could also be connectable to another element of the driveline planetary gear TP, but would then give less advantageous gear ratios.

By a third freewheel FV2, which is connected to the third ring gear TH, a rotation of the third ring gear TH relative to a housing part only in one direction of rotation is possible.

A second electric machine EM2 is connected to a sun gear TS of the driveline planetary gear TP. A planet carrier TPT of the driveline planetary gear TP is connected to the transmission input shaft GE of the drive gear G.

Furthermore, the planet carrier TPT and thus the transmission input shaft GE by a third clutch KEG directly coupled with the sun gear TS and thus with the second electric machine EM2.

Thus, when the third clutch KEG is open and the second clutch KVM is open, it is possible to drive the motor vehicle purely electrically by means of the second electric machine EM2 with a transmission through the driveline planetary gear TP. In this case, the at least one auxiliary unit AG can be driven by the first electric machine EMI or the internal combustion engine VM.

Likewise, it is possible with open third clutch KEG and closed second clutch KVM, the motor vehicle driven with a continuously variable ratio. Here, the rotational speed of the transmission input shaft GE is controllable by the rotational speeds of the second electric machine EM2 and the internal combustion engine VM. In this mode, a geared neutral function is also possible, in which the rotational speeds of the internal combustion engine VM and the second electric machine EM2 are set such that the rotational speed of the transmission input shaft GE is zero and the motor vehicle thus stands.

When the third clutch KEG is closed and the second clutch KVM is open, the motor vehicle can be driven purely electrically by means of the second electric machine EM2 without transmission.

When the third clutch KEG is closed and the second clutch KVM is closed, the transmission input shaft GE, the internal combustion engine VM and the second electric motor EM2 have the same rotational speed, a drive of the motor vehicle by the internal combustion engine VM and / or the second electric machine EM2 is possible.

In all the drive modes described above, it is also possible to operate one or both electric machines EMI, EM2 generator.

Instead of using the elements of the accessory drive according to FIG. 4, the elements disposed on the output side of the second clutch KVM could also be combined with elements of the auxiliary drive according to FIGS. 1 or 6.

Claims

DaimlerChrysler AGPatent claims

1. auxiliary drive for a motor vehicle with a planetary gear (P), wherein

a sun gear (S) of the planetary gear (P) with a first electric machine (EMI),

- A planet carrier (PT) with an internal combustion engine (VM) and

- Are a first ring gear (Hl) with at least one auxiliary unit (AG) in the power exchange, characterized by

two planetary gear sets (PR1, PR2), which are mounted with their axes in the planet carrier (PT),

a second ring gear (H2) which can be held by a first brake (BS) relative to a housing part,

- Wherein the first planetary gear set (PRl) with the first ring gear (Hl) and the sun gear (S) meshes and the second planetary gear set (PR2) with the second ring gear (H2) and the first planetary gear set (PRl) meshes,

- A first clutch (KVE), through which the internal combustion engine (VM) with the first electric machine

(EMI) is coupled, and

- A first freewheel (FVG) through which the planet carrier (PT) is rotatable only in one direction of rotation.

Second accessory drive according to claim 1, characterized by a second freewheel (FAG) through which the first ring gear (Hl) of the planetary gear (P) is rotatable only in one direction of rotation.

3. accessory drive according to one of the preceding claims, characterized by a second brake (KGE), by which the sun gear (S) of the planetary gear (P) relative to a housing part can be held.

4. accessory drive according to one of the preceding claims, characterized in that the planet carrier (PT) of the planetary gear (P) via a second clutch (KVM) with a transmission input shaft (GE) of a drive gear (G) is connectable, wherein a second electric machine (EM2 ) is in service with the transmission input shaft (GE).

5. accessory drive according to one of the preceding claims, characterized in that the planet carrier (PT) of the planetary gear (P) via a second clutch (KVM) with an element (TH) of a driveline planetary gear (TP) is connectable, wherein the element (TH) of the driveline planetary gear (TP) by a third freewheel (FV2) is rotatable only in one direction of rotation.

6. accessory drive according to one of the preceding claims, characterized in that the first clutch (KVE) is a centrifugal clutch.