Belt pulley arrangement for a belt drive for driving auxiliary units of a motor vehicle, and a method for driving a motor vehicle auxiliary unit that is connected by means of a belt pulley arrangement

Abstract

A belt pulley arrangement for a belt drive for driving auxiliary units of a motor vehicle, comprising a belt pulley for introducing a torque that can be supplied by a traction mechanism, an output shaft for driving an auxiliary unit, particularly a coolant pump, an electric machine for transmitting torque between the belt pulley and the output shaft, the electric machine including a rotor connected to the belt pulley and a stator connected to the output shaft, and being able to be electrically connected to an electric energy source for the purpose of accelerating the output shaft and/or to an electric energy sink in order to decelerate the output shaft, a first rotational speed measurement device for detecting the time curve of the rotational speed of the belt pulley and/or a second rotational speed measurement device for detecting the time curve of the rotational speed of the output shaft, and a control device connected to the electric energy source and/or electric energy sink so as to control an output shaft rotational speed time curve by temporarily electrically connecting the energy source and/or energy sink in reaction to the rotational speed time curve that has been detected. The power flow between belt pulley and output shaft which can be influenced by the electric machine provides that the auxiliary unit that is connected via the output shaft does not have to be designed for the most unfavorable operating point. As a result, the auxiliary unit can have smaller dimensions which allows a reduction in the construction space for motor vehicle components and particularly in the construction space for motor vehicle auxiliary units which can be driven by the belt drive.

Claims

1. A belt pulley arrangement for a belt drive for driving auxiliary units in a motor vehicle, comprising a belt pulley for introducing a torque that is provided by a traction mechanism, a driven shaft for driving an auxiliary unit, an electric machine for transferring torque between the belt pulley and the driven shaft, wherein the electric machine has a rotor connected to the belt pulley and a stator connected to the driven shaft, wherein the electric machine has an electrical connection to an electrical energy source for accelerating the driven shaft and an electrical energy sink for braking the driven shaft, a first rotational speed measurement device that detects a time curve of a rotational speed of the belt pulley and a second rotational speed measurement device that detects a time curve of a rotational speed of the driven shaft, and a controller connected to at least one of the electrical energy source or the electrical energy sink that is configured to control the time curve of the rotational speed of the driven shaft through a time limited electrical connection of at least one of the energy source or energy sink in reaction to at least one of the detected time curves.

2. The belt pulley arrangement according to claim 1, wherein the electrical connection is variable.

3. The belt pulley arrangement according to claim 1, further comprising a switch element that provides an essentially rotationally locked coupling of the belt pulley to the driven shaft in case of a discontinued current flow for the electric machine.

4. The belt pulley arrangement according to claim 1, wherein the electric machine has windings, wherein the windings are short-circuited in case of a discontinued current flow for the electric machine.

5. The belt pulley arrangement according to claim 1, wherein the stator has permanent magnets and the rotor has windings or the stator has windings and the rotor has permanent magnets, and the windings are connected by a contactless or contacted electrical connection with electrical lines for at least one of an input or an output of electrical energy.

6. The belt pulley arrangement according to claim 5, wherein the windings are connected to a carrier, the carrier is connected by a connection piece running in a radial direction to the driven shaft or the belt pulley, the carrier has a contact element for transmitting electrical energy, comprising a slip ring of the sliding contact connection on a side pointing away from the windings.

7. The belt drive for driving auxiliary units of the motor vehicle comprising an input belt pulley that is connected to a motor shaft of the motor vehicle motor, at least one second output belt pulley coupled to the input belt pulley by a second traction mechanism for driving an allocated auxiliary unit of the auxiliary units, and at least one first output belt pulley that comprises the belt pulley arrangement according to claim 1.

8. A belt pulley arrangement for a belt drive for driving auxiliary units in a motor vehicle, comprising a belt pulley for introducing a torque that is provided by a traction mechanism, a driven shaft for driving an auxiliary unit, an electric machine for transferring torque between the belt pulley and the driven shaft, wherein the electric machine has a rotor connected to the belt pulley and a stator connected to the driven shaft, wherein the electric machine is connected electrically to an electrical energy source for accelerating the driven shaft, a first rotational speed measurement device that detects a time curve of a rotational speed of the belt pulley, and a controller connected to the electrical energy source that is configured to control the time curve of the rotational speed of the driven shaft through a time limited electrical connection of the energy source in reaction to the detected time curve of the rotational speed.

9. The belt pulley arrangement of claim 8, further comprising a second rotational speed measurement device for detecting a time curve of a rotational speed of the driven shaft, wherein the electric machine is connected electrically to an electrical energy sink for braking the driven shaft, and wherein the controller is connected to the electrical energy sink and is configured to control the time curve of the rotational speed of the driven shaft through a time limited electrical connection of the energy sink in reaction to the detected time curve of the rotational speed.

10. A method for driving an auxiliary unit of the auxiliary units connected via the belt pulley arrangement according to claim 9, comprising in the motor vehicle, at least one of inputting electrical energy into the electric machine or outputting electrical energy from the electric machine as a function of the rotational speed of the belt pulley for controlling the time curve of the rotational speed of the driven shaft.

11. The method according to claim 10, wherein the time curve of the rotational speed of the driven shaft is phase-shifted relative to the time curve of the rotational speed of the belt pulley.

12. A belt pulley arrangement for a belt drive for driving auxiliary units in a motor vehicle, comprising a belt pulley for introducing a torque that is provided by a traction mechanism, a driven shaft for driving an auxiliary unit, an electric machine for transferring torque between the belt pulley and the driven shaft, wherein the electric machine has a rotor connected to the belt pulley and a stator connected to the driven shaft, wherein the electric machine is connected electrically to an electrical energy sink for braking the driven shaft, a second rotational speed measurement device for detecting a time curve of a rotational speed of the driven shaft, and a controller connected to the electrical energy sink that is configured to control the time curve of the rotational speed of the driven shaft through a time limited electrical connection of the energy sink in reaction to the detected time curve of the rotational speed.

13. A method for driving an auxiliary unit connected via a belt pulley arrangement according to claim 12, comprising in a motor vehicle, at least one of inputting electrical energy into the electric machine or outputting electrical energy from the electric machine as a function of the rotational speed of the belt pulley for controlling the time curve of the rotational speed of the driven shaft, wherein a maximum amplitude distance A.sub.1 of the time curve of the rotational speed of the driven shaft with respect to a nominal rotational speed is less than a maximum amplitude A.sub.2 of the time curve of the rotational speed of the belt pulley with respect to the nominal rotational speed.

14. The method according to claim 13, wherein 0.00A.sub.1/A.sub.2 1.00.

15. The belt pulley arrangement of claim 12, further comprising a first rotational speed measurement device that detects a time curve of a rotational speed of the belt pulley, wherein the electric machine is connected electrically to an electrical energy source for accelerating the driven shaft, and wherein the controller is connected to the electrical energy source that is configured to control the time curve of the rotational speed of the driven shaft through a time limited electrical connection of the energy source in reaction to the detected time curve of the rotational speed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is explained below using examples with reference to the accompanying drawings, wherein the features described below can depict an aspect of the invention both individually and also in combination. Shown are:

(2) FIG. 1 a schematic sectional view of a belt pulley arrangement,

(3) FIG. 2 a schematic block diagram of the belt pulley arrangement from FIG. 1 in an overrunning mode,

(4) FIG. 3 a schematic block diagram of the belt pulley arrangement from FIG. 1 in a fail-safe mode,

(5) FIG. 4 a schematic block diagram of the belt pulley arrangement from FIG. 1 in a braking mode,

(6) FIG. 5 a basic plot of rotational speeds occurring in the belt pulley arrangement shown in FIG. 1 in a first operating mode,

(7) FIG. 6 a basic plot of rotational speeds occurring in the belt pulley arrangement shown in FIG. 1 in a second operating mode,

(8) FIG. 7 a basic plot of rotational speeds occurring in the belt pulley arrangement shown in FIG. 1 in a third operating mode, and

(9) FIG. 8 a basic plot of rotational speeds occurring in the belt pulley arrangement shown in FIG. 1 in a fourth operating mode.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(10) The belt pulley arrangement 10 shown in FIG. 1 has a belt pulley 12 with a running surface 14 that faces outward in the radial direction and by means of which a torque provided by a crankshaft of an internal combustion engine of a motor vehicle can be input to a traction mechanism, for example, flat belt. The belt pulley 12 is coupled by means of an electric machine 16 with a driven shaft 18 that can be an input shaft of an auxiliary unit, for example, a coolant pump. The electric machine 16 has a rotor 20 connected rigidly to the belt pulley 12 and a stator 22 arranged at a distance to the rotor 20 by means of an air gap. In the illustrated embodiment, the rotor 20 has permanent magnets while the stator 22 has windings. Furthermore, the stator 22 is connected rigidly to the driven shaft 18 by means of a carrier 24. The carrier 24 is constructed in a ring shape with an essentially U-shaped, axial open cross section. The carrier 24 has, on the base of the U-shaped cross section, a connection piece 26 running in the radial direction, so that a pocket 28 is formed between the stator 22 and the driven shaft 18, with a sliding contact connection 30 being provided in this pocket. The sliding contact connection 30 has slip rings 32 on the side facing away from the stator 22, with contact brushes 36 that are spring-loaded with compression springs 34 pressing against these slip rings, in order to create an electrical contact. The compression springs 34 and the contact brushes 36 connected to the compression springs 34 are guided in a contact brush guide 38. The contact brush guide 38 is connected to a stationary holder 40. The holder 40 can be connected, in particular, to a unit housing 42 of the auxiliary unit, wherein the unit housing 42 can project in the axial direction advantageously at least partially into the belt pulley 12 and/or the belt pulley arrangement 10. The holder 40 and/or the unit housing 42 can guide electrical lines 44 that can be connected electrically to the contact brushes 36. With the help of an electronic circuit 46 that is arranged completely within the belt pulley 12 and is mounted, in particular, with the carrier 24 or with the holder 40 or in a multiple-part construction with a first part with the carrier 24 and with a second part with the holder 40, an input and/or output of electrical energy can be controlled by means of the electrical lines 44, wherein the electromagnetic field between the rotor 20 and the stator 22 can be influenced. In this way it is possible, in particular, that the rotational speed of the driven shaft 18 deviates from the rotational speed of the belt pulley 12, in particular, in order to regulate an intended nominal rotational speed for the driven shaft 18 essentially independent of the rotational speed of the belt pulley 12. For this purpose, the belt pulley 12 is not connected rigidly to the driven shaft 18, but instead is supported so that it can move with relative rotation by means of a rolling bearing 48.

(11) If electrical energy E.sub.An is input as shown in FIG. 2 into the electric machine 16 by means of the electrical lines 44, the driven shaft 18 can also be accelerated to the mechanical energy An.sub.mech input by means of the belt pulley 12, so that the stator 22 of the driven shaft 18 can rotate at a rotational speed n.sub.S that is greater by a factor s than the rotational speed n.sub.R of the rotor 20 of the belt pulley 12 (overrun mode). A small portion of the input energy is lost as loss energy E.sub.V and is not transmitted to the driven shaft 18, whereby the mechanical energy Ab.sub.mech output by the driven shaft 18 is somewhat smaller.

(12) If electrical energy is input or output via the electrical lines 44 as shown in FIG. 3, in particular, the electronic circuit 46 can short-circuit the windings of the stator 22, so that the driven shaft 18 can rotate at a rotational speed n.sub.S that corresponds essentially approximately to the rotational speed n.sub.R of the rotor 20 (fail-safe mode). A small portion of the input energy is lost as loss energy E.sub.V and is not transmitted to the driven shaft 18, so that the rotational speed n.sub.S of the driven shaft 18 is, under consideration of the loss energy E.sub.V, slightly smaller than the rotational speed n.sub.R of the rotor 20, whereby the mechanical energy Ab.sub.mech output by the driven shaft 18 is somewhat smaller. The loss energy E.sub.V is, however, typically so small that the factor s equals 1 to a good approximation.

(13) If electrical energy E.sub.Ab is output from the electric machine 16 via the electrical lines 44 as shown in FIG. 4, for example, to operate another electrical load and/or to store electrical energy that has been generated, the driven shaft 18 can be braked relative to the mechanical energy An.sub.mech input via the belt pulley 12, so that the driven shaft 18 can rotate at a rotational speed n.sub.S that is smaller than the rotational speed n.sub.R of the rotor 20 by a factor s (brake mode). A small portion of the energy input from the belt pulley 12 is lost as loss energy E.sub.V and is not transmitted via the electric machine 16 to the driven shaft 18, whereby the electrical energy E.sub.Ab that can be output by the electric machine 16 to the energy sink and mechanical energy Ab.sub.mech output by the driven shaft 18 are somewhat smaller.

(14) In the plot shown in FIG. 5, the rotational speed 50 is plotted versus time 52 and the rotational speed curve 54 of the belt pulley 12 and also the rotational speed curve 56 of the driven shaft 18 are shown. If the belt pulley arrangement 10 on the driven side of a belt drive driven by a motor vehicle crankshaft is used for driving auxiliary units, the rotational speed curve 54 of the belt pulley 12 essentially corresponds to the, if necessary, already damped rotational speed curve of the crankshaft (KW) while the rotational speed curve 56 of the driven shaft 18 corresponds to the operating rotational speed of the associated auxiliary unit (Agg). In the shown embodiment, a rotational speed curve 54 of the belt pulley 12 is shown simplified with an essentially sinusoidal rotational oscillation by a nominal rotational speed 58, wherein, in real situations, the nominal rotational speed 58 can change with respect to time and/or the rotational oscillation can deviate from a pure sinusoid shape, for example, by the superposition of several different oscillations. In the shown first operating mode, the rotational speed curve 56 of the driven shaft 18 is phase-shifted by corresponding energy input and/or energy output of the electric machine 16 by approximately 90 relative to the rotational speed curve 54 of the belt pulley 12, so that oscillations that occur on mechanical components can be canceled out.

(15) In comparison to the operating mode shown in FIG. 5, in the second operating mode shown in FIG. 6, the rotational speed curve 56 of the driven shaft 18 is also damped, so that a maximum amplitude distance A.sub.1 of the rotational speed curve 56 of the driven shaft 18 relative to the nominal rotational speed 58 is less than a maximum amplitude distance A.sub.2 of the rotational speed curve 54 of the belt pulley 12 relative to the nominal rotational speed 58. In the shown embodiment, in approximation A.sub.1/A.sub.2=0.5. The damping of the rotational speed curve 56 of the driven shaft 18 shown in FIG. 5 can also be independent of a phase shift or with a different phase shift of the rotational speed fluctuations in the rotational speed curve 54 of the belt pulley 12 and in the rotational speed curve 56 of the driven shaft 18.

(16) In comparison to the operating mode shown in FIG. 6, in the third operating mode shown in FIG. 7, the rotational speed curve 56 of the driven shaft 18 is shifted by a phase shift different from 90.

(17) In comparison to the operating modes shown in FIG. 5, FIG. 6, and FIG. 7, in the third operating mode shown in FIG. 8, the rotational speed curve 56 of the driven shaft 18 is so strongly damped that all of the rotational speed fluctuations in the rotational speed curve 56 of the driven shaft 18 are essentially completely canceled out. The maximum amplitude distance A.sub.1 of the rotational speed curve 56 of the driven shaft 18 to the nominal rotational speed 58 is essentially zero, so that, in the shown embodiment, in approximation, A.sub.1/A.sub.2=0.0. The rotational speed curve 56 of the driven shaft 18 therefore essentially coincides with the nominal rotational speed 58.

LIST OF REFERENCE NUMBERS

(18) 10 Belt pulley arrangement 12 Belt pulley 14 Running surface 16 Electric machine 18 Driven shaft 20 Rotor 22 Stator 24 Carrier 26 Connection piece 28 Pocket 30 Sliding contact connection 32 Slip ring 34 Compression spring 36 Contact brush 38 Contact brush guide 40 Holder 42 Unit housing 44 Electrical line 46 Electronic circuit 48 Roller bearing 50 Rotational speed 52 Time 54 Rotational speed curve of the belt pulley 56 Rotational speed curve of the driven shaft 58 Nominal rotational speed An.sub.mech Input mechanical energy Ab.sub.mech Output mechanical energy E.sub.An Input electrical energy E.sub.Ab Output electrical energy E.sub.V Loss energy n.sub.R Rotational speed of the rotor n.sub.S Rotational speed of the stator A.sub.1 Maximum amplitude distance of the rotational speed curve of the driven shaft A.sub.2 Maximum amplitude distance of the rotational speed curve of the belt pulley