DE102018103619B3 - Linear actuator for a valve of a motor vehicle - Google Patents

Abstract

Linear actuator for a valve of a motor vehicle, comprising an electric motor (10),
a planetary gear (12) with
a ring gear (20), and
a sun wheel (22),
a spindle drive (14) with
a spindle rod (36, 36 ') having an external thread (46), which is arranged coaxially with the ring gear (20) and the sun gear (22), and
a spindle nut (38) having an internal thread (42) which meshes with the external thread (46) of the spindle rod (36, 36 '), characterized in that
the planetary gear (12) has a planetary gear (24a) driven by the electric motor (10) with a stationary axis of rotation (32a),
the spindle nut (38) rotatably connected to the sun gear (22) is connected, and
the spindle rod (36, 36 ') has an axial bearing section (48, 48'), via which the spindle rod (36, 36 ') can be displaced axially and non-rotatably relative to the ring gear (20) in a coupling unit (50, 50', 50 "). ) is stored.

Description

The invention relates to a linear actuator for a valve of a motor vehicle, comprising an electric motor, a planetary gear with a ring gear, a sun gear, and at least one planetary gear, a spindle drive with a spindle rod with an external thread, which is arranged coaxially with the ring gear and the sun gear, and a spindle nut with an internal thread, which meshes with the external thread of the spindle rod.

Such linear actuators are used for example in exhaust gas recirculation valves of motor vehicles to lift a valve body from a valve seat. As a result, a defined amount of exhaust gas can be added to the fresh air supplied to the internal combustion engine in order to reduce the pollutant emissions.

There are various versions of this exhaust gas recirculation valves known. In recent years, electric motor driven lift valves have prevailed in the field of passenger cars, in which the rotational movement of the drive shaft of the electric motor is converted into a translational movement of the valve rod. For this purpose, for example, a spindle drive can be used, wherein the valve rod is designed as a rotatably fixed spindle rod, which is guided in a rotatable spindle nut. By a rotation of the spindle nut a translational movement of the valve stem is generated.

Due to the pressure conditions, a large force may be necessary to open the valve, so that between the electric motor and the driven spindle nut usually a transmission is arranged, which underpins the rotation of the drive shaft for driving the spindle nut. As a result, a larger lifting force can be generated. As a transmission, for example, a planetary gear can be used.

From the WO 02/23032 A1 is known an exhaust gas recirculation valve with an electric motor, a planetary gear and a spindle drive. The planetary gear has a rotatable ring gear, a fixed sun gear and a revolving planet gear. The ring gear is driven by the electric motor and the planetary gear is coupled to the spindle nut of the spindle drive such that rotation of the spindle nut is generated at the peripheral speed of the planetary gear. The planetary gear has a high gear ratio between the rotational speed of the ring gear and the rotational speed of the planetary gear to produce a high torque on the spindle nut. The rotationally fixed valve rod is formed in sections as a spindle, which meshes with the rotating spindle nut. As a result, the rotation of the spindle nut is converted into an axial movement of the valve stem.

To achieve a short valve actuation time, rotation of the spindle nut with respect to the spindle rod is required at a high speed. In the from the WO 02/23032 A1 known valve with the high gear ratio is this a very powerful electric motor with a high electrical energy consumption required. Alternatively, the gear ratio of the planetary gear can be reduced to achieve a higher rotational speed of the spindle nut. As a result, however, the torque generated on the spindle nut and thus the lifting force of the valve is reduced.

It is therefore the object to provide a linear actuator for a valve of a motor vehicle, which has a high actuating speed with high actuating force. In addition, the energy requirement of the linear actuator should be low.

This object is achieved by a linear actuator for a valve of a motor vehicle having the features of the main claim 1 solved.

Characterized in that the planetary gear has a planetary gear driven by the electric motor with a stationary axis of rotation, the spindle nut rotatably connected to the sun gear, and the spindle rod has an axial bearing portion, via which the spindle rod is mounted axially displaceable and rotationally fixed to the ring gear in a coupling unit , is generated by the electric motor by means of the planetary gear simultaneously both a rotation of the spindle nut, as well as a rotation of the spindle rod with opposite direction of rotation. At the same rotational speed of the spindle nut thereby a higher relative rotational speed of the spindle nut is generated with respect to the spindle rod, and thus a higher translational actuating speed of the linear actuator. The linear actuator according to the invention thus enables a high actuating speed when using a transmission with a high transmission ratio. This allows a short positioning time of the linear actuator at the same time high power and low energy consumption of the electric motor.

Preferably, the spindle rod is guided in the circumferential direction positively and thus rotationally fixed in the coupling unit. This allows a simple and reliable rotationally fixed coupling of the spindle rod with the ring gear, which simultaneously allows an axially displaceable mounting of the spindle rod.

Particularly preferably, the coupling unit has a recess, via which the coupling unit is connected in the circumferential direction positively with the bearing portion of the spindle rod. This allows a reliable rotationally fixed connection of the spindle rod with the coupling unit, for which no additional coupling elements are needed.

In a particularly preferred embodiment, the recess has a substantially radially outwardly extending groove into which a torque-transmitting member protrudes, whose inner radial end is non-rotatably mounted on the spindle rod. The torque transmission member may for example be a spring which projects with a radially inner side into a groove provided on the spindle rod. This allows a simple and reliable rotationally fixed coupling of the spindle rod with the ring gear. Here, the form-fitting is formed in the circumferential direction by the torque-transmitting member and the groove, so that no special spindle rod cross-section is required for the rotationally fixed coupling of the spindle rod with the ring gear.

In an alternative preferred embodiment of the invention, the coupling unit has a coupling receptacle in which a coupling is arranged with two coupling elements, wherein a first coupling element is rotatably connected to the coupling unit, a second coupling member rotatably connected to the spindle rod, and the coupling elements a positive connection form in the circumferential direction. Since the positive connection is formed by the coupling, the cross sections of the coupling unit and the spindle rod need not be formed correspondingly. This allows, for example, the use of a universal coupling unit for different spindle rod designs. The coupling may for example have a simple tongue and groove connection, which forms a stable positive connection.

Advantageously, the coupling unit has a plurality of spokes, preferably three spokes, via which the coupling unit is non-rotatably connected to the ring gear, wherein the spokes have a substantially radially extending first leg and a subsequent to the first leg and substantially axially extending second leg exhibit. By means of the spokes the coupling unit is positioned both axially and radially reliable with respect to the ring gear. The axial offset between the ring gear and the coupling unit is defined over the length of the axial legs. An exact and stable positioning of the coupling unit is essential for a reliable storage of the spindle shaft in the coupling unit and thus crucial for a proper function over a long life of the linear actuator.

In an advantageous embodiment of the invention, the axial bearing portion of the spindle rod has a quadrangular cross-section, whereby a reliable positive engagement in the circumferential direction is made possible with simple production.

Preferably, the spindle nut is formed integrally with the sun gear. This allows a particularly reliable rotationally fixed connection between the spindle nut and the sun gear, for which no additional connection means or manufacturing steps are required.

Advantageously, the planetary gear has a total of three planet gears, which are preferably arranged distributed uniformly along the circumference of the ring gear. This allows a precise and stable radial positioning of the gear wheels to each other. By the plurality of planetary gears, the load of the individual gears of the transmission is reduced, thus improving the life of the transmission.

In an advantageous embodiment of the invention, the planetary gear from the driven planet gear to the rotatably connected to the spindle sun gear on a reduction, whereby a high translational force of the linear actuator can be achieved.

In a particularly advantageous embodiment of the invention, the planetary gear has a reduction ratio with a gear ratio of the driven planet gear to the sun gear in a range of eight to ten. This allows a high positioning speed of the linear actuator at the same time sufficiently high translational force.

Preferably, an axial bearing is arranged at one axial end of the spindle rod, which connects the spindle rod with a rotatably fixed and axially displaceable valve rod. As a result, the rotational and translational movement of the spindle rod can be converted into a purely translatory movement of the valve rod. This allows, for example, a lifting of a valve body of a valve seat, without causing the valve body is rotated relative to the valve seat.

In a preferred embodiment of the invention, the electric motor has a drive shaft, which is arranged parallel to the spindle rod and to which the driven planet gear is mounted rotationally fixed. This allows for a special compact and simple construction of the linear actuator.

• 1 eine perspektivische Ansicht eines erfindungsgemäßen Linearaktuators für ein Ventil eines Kraftfahrzeugs zeigt,
• 2 eine schematische Seitenansicht des Linearaktuators aus 1 zeigt, wobei die Spindelstange über ein Axiallager mit einer Ventilstange gekoppelt ist,
• 3 eine schematische Darstellung eines Planetengetriebes des Linearaktuators aus 1 zeigt,
• 4 eine schematische Darstellung einer alternativen Koppeleinheit des Linearaktuators aus 1 zeigt, wobei die Koppeleinheit eine Aussparung mit einer Nut aufweist, in welche ein drehfest mit der Spindelstange verbundenes Momentübertragungsglied ragt, und
• 5 eine schematische Darstellung einer weiteren alternativen Koppeleinheit des Linearaktuators aus 1 zeigt, wobei in einer zentralen Aussparung der Koppeleinheit eine Kupplung angeordnet ist.

An embodiment of a linear actuator according to the invention for a valve of a motor vehicle is described below with reference to the accompanying figures, wherein

• 1 shows a perspective view of a linear actuator according to the invention for a valve of a motor vehicle,
• 2 a schematic side view of the linear actuator 1 shows, wherein the spindle rod is coupled via a thrust bearing with a valve rod,
• 3 a schematic representation of a planetary gear of the linear actuator 1 shows,
• 4 a schematic representation of an alternative coupling unit of the linear actuator 1 shows, wherein the coupling unit has a recess with a groove into which a non-rotatably connected to the spindle rod torque transmission member protrudes, and
• 5 a schematic representation of another alternative coupling unit of the linear actuator 1 shows, wherein in a central recess of the coupling unit, a clutch is arranged.

The linear actuator comprises an electric motor 10 , a planetary gear 12 and a spindle drive 14 , The electric motor 10 has a drive shaft 16 on, which by the electric motor 10 is driven, so that the drive shaft 16 about a drive shaft rotation axis 18 rotates.

The planetary gear 12 includes a ring gear 20 , a sun wheel 22 and three planet gears 24a-c , The ring gear 20 and the sun wheel 22 are rotatable about a common transmission axis of rotation 26 arranged, wherein the ring gear 20 the sun wheel 22 radially surrounds. The transmission axis of rotation 26 runs parallel to the drive shaft axis of rotation 18 , The ring gear 20 has on the radial inside a ring gear 28 on. The sun wheel 22 has on the radial outer side of a sun gear 30 on and has a central Spindelstangendurchführung 31 on. The three planet gears 24a-c are radially between the sun gear 22 and the ring gear 20 arranged, with the planetary gears 24a-c evenly along the circumference of the sun gear 22 are distributed. The planet wheels 24a-c are each rotatable about a stationary Planetenraddrehachse 32a-c arranged, which are parallel to the drive shaft axis of rotation 18 and to the transmission axis of rotation 26 runs. The planet wheels 24a-c each have a planetary gear teeth on the radial outer side 34 on, which with both the ring gear 28 as well as with the sun gear 30 is engaged. The planet wheel 24a is non-rotatable on the drive shaft 16 attached so that the Planetenraddrehachse 32a the drive shaft rotation axis 18 equivalent.

The spindle drive 14 includes a spindle rod 36 and a spindle nut 38 , The spindle nut 38 is integral with the sun gear 22 formed and has a central spindle nut bore 40 with an internal thread 42 on, which is along the transmission axis of rotation 26 extends. The spindle rod 36 extends along the transmission axis of rotation 26 through the spindle rod feedthrough 31 of the sun wheel 22 therethrough. The spindle rod 36 has a threaded portion in the axial direction 44 and a storage section 48 on. The threaded section 44 is with a circular cross section and an external thread 46 Mistake. The storage section 48 has a quadrangular cross-section. The spindle rod 36 is with the threaded section 44 in the spindle nut 38 arranged so that the external thread 46 the spindle rod 36 with the internal thread 42 the spindle nut 38 combs. The spindle rod 36 is over the storage section 48 axially displaceable in a coupling unit 50 stored. The coupling unit 50 has a central recess 52 with a quadrangular cross-section, which in the circumferential direction a positive connection 54 with the storage section 48 the spindle rod 36 forms. The coupling unit 50 has three spokes 56 on, over which the coupling unit 50 rotatably with the ring gear 20 connected is. The spokes 56 each have a first radially extending first leg 58 and a substantially axially extending second leg 60 on, so that the coupling unit 50 axially spaced and radially centered to the sun gear 22 is positioned.

In operation, the planetary gear 24a from the electric motor 10 , for example as in 3 shown at a rotational speed U1 clockwise, driven. About the meshing gears 28 . 30 . 34 of the planetary gear 12 This will cause a rotation of the ring gear 20 clockwise at a rotational speed U2 and a counterclockwise rotation of the sun gear at a rotational speed U3 generated. In the present embodiment, the planetary gear 12 from the driven planetary gear 24a to the sun wheel 22 a gear ratio I in the range of eight to ten, so that in the present embodiment U1>U3> U2.

The spindle rod 36 is about the form fit 54 rotatably with the coupling unit 50 connected, and thus rotatably with the ring gear 20 connected. This results in operation during a rotation of the planetary gear 24a clockwise one Rotation of the spindle rod 36 clockwise at a rotational speed U2 , The spindle nut 38 is integral with the sun gear 22 designed so that the spindle nut 38 at a rotational speed U3 turns counterclockwise. The spindle rod 36 thus rotates with respect to the spindle nut with a relative rotational speed U4 = U2 + U3. Through the meshing threads 42 . 46 the spindle rod 36 and the spindle nut 38 this results in an axial movement of the spindle rod 36 with respect to the axially fixed spindle nut 38 , The spindle rod 36 can thus by driving the planetary gear 24a over the electric motor 10 axially along the transmission axis of rotation 26 to be moved. By driving the planetary gear 24a Clockwise or counterclockwise can be a movement of the spindle rod 36 be generated in both axial directions.

At one axial end 62 the spindle rod 36 which is on the planetary gear 12 side facing away from the coupling unit 50 stands out, as in 2 is shown schematically, a thrust bearing 64 be arranged, which is the spindle rod 36 with a rotatably fixed and axially displaceable valve rod 66 combines. This allows the rotational and translational movement of the spindle rod 36 in a purely translational movement of the valve stem 66 being transformed.

The 4 shows an alternative coupling unit 50 ' with a central recess 52 ' which has a first radially outwardly extending first groove 68 having. The spindle rod 36 ' know on the radial outside a substantially radially inwardly extending second groove 69 on which of the first groove 68 faces. In the grooves 68 . 69 is a spring 70 arranged that a positive fit 54 ' with the grooves 68 . 69 forms, so the spindle rod 36 ' rotatably with the coupling unit 50 ' connected is.

The 5 shows a further alternative coupling unit 50 " , The coupling unit 50 " has a central coupling receptacle 74 with a circular cross section. In the coupler pocket 74 is a clutch 76 with a coupling ring 78 and a clutch spring 80 arranged. The coupling ring 78 is rotatably on the radial outside with the coupling unit 50 " connected and has on the radial inside a substantially radially outwardly extending coupling groove 82 on. The clutch spring 80 protrudes with the radially outer side into the coupling groove 82 of the coupling ring 78 and protrudes with the radially inner side in the groove 69 the spindle rod 36 ' , The clutch spring 80 forms a positive connection in the circumferential direction 54 " with the coupling groove 82 and with the groove 69 over which the spindle rod 36 ' rotatably with the ring gear 20 connected is.

The inventive simultaneous opposing drive of the spindle rod and the spindle nut via the electric motor allows the linear actuator short positioning times. Due to the reduction of the driven planet gear both to the ring gear and to the sun gear at the same time high torques and thus a high translational force can be generated on the spindle rod and the spindle nut without requiring a particularly powerful electric motor is required.

It should be understood that the scope of the present application is not limited to the described embodiments. In particular, the planetary gear may have different gear ratios to adapt the linear actuator to different requirements. Furthermore, further alternative coupling units with a different positive locking geometry or another coupling are conceivable. Another non-rotatable connection between the coupling unit and the ring gear is possible, for example, over a different number of spokes.

LIST OF REFERENCE NUMBERS

10

electric motor

12

planetary gear

14

spindle drive

16

drive shaft

18

Drive shaft axis of rotation

20

ring gear

22

sun

24a-c

planetary gears

26

Gear axis of rotation

28

internal gear

30

sun wheel

31

Spindle rod bushing

32a-c

Planetenraddrehachsen

34

Planetenradverzahnung

36

spindle rod

38

spindle nut

40

Spindle nut bore

42

inner thread

44

threaded portion

46

external thread

48

bearing section

50

coupling unit

52

recess

54

form-fit

56

spoke

58

first leg

60

second leg

62

axial end

64

thrust

66

valve rod

68

groove

69

groove

70

feather

74

Kupplungsaufnahme

76

clutch

78

coupling ring

80

clutch spring

82

coupling groove

Claims (13)

Linear actuator for a valve of a motor vehicle, comprising an electric motor (10), a planetary gear (12) with a ring gear (20), and a sun gear (22), a spindle drive (14) with a spindle rod (36, 36 ') with an external thread (46) which is coaxial with the ring gear (20) and the sun gear (22) and a spindle nut (38) having an internal thread (42) which meshes with the external thread (46) of the spindle rod (36, 36 ') , characterized in that the planetary gear (12) by the electric motor (10) driven planet gear (24a) having a stationary axis of rotation (32a), the spindle nut (38) rotatably connected to the sun gear (22), and the spindle rod ( 36, 36 ') has an axial bearing section (48, 48'), via which the spindle rod (36, 36 ') is axially displaceable and non-rotatably mounted to the ring gear (20) in a coupling unit (50, 50', 50 ") , Linear actuator for a valve of a motor vehicle after Claim 1 , characterized in that the spindle rod (36,36 ') in the circumferential direction positively and thus rotatably in the coupling unit (50,50') is guided. Linear actuator for a valve of a motor vehicle after Claim 2 , characterized in that the coupling unit (50,50 ') has a recess (52,52'), via which the coupling unit (50,50 ') in the circumferential direction is positively connected to the spindle rod (36,36'). Linear actuator for a valve of a motor vehicle after Claim 3 , characterized in that the recess (52 ') has a substantially radially outwardly extending groove (68) into which a torque-transmitting member (70) protrudes, the inner radial end rotationally fixed to the spindle rod (36') is attached. Linear actuator for a valve of a motor vehicle after Claim 1 , characterized in that the coupling unit (50 ") has a coupling receptacle (74), in which a coupling (76) with two coupling elements (78,80) is arranged, wherein a first coupling element (78) rotatably connected to the coupling unit (50". ), a second coupling element (80) rotatably connected to the spindle rod (36 ') is connected, and the coupling elements (78,80) form a positive fit (54 ") in the circumferential direction. Linear actuator for a valve of a motor vehicle according to one of the preceding claims, characterized in that the coupling unit (50,50 ', 50 ") has a plurality of spokes (56), via which the coupling unit (50,50', 50") rotatably with the Ring gear (20) is connected, wherein the spokes (56) has a substantially radially extending first leg (58) and a to the first leg (58) adjoining and extending substantially axially extending second leg (60). Linear actuator for a valve of a motor vehicle according to one of the preceding claims, characterized in that the axial bearing portion (48) of the spindle rod (36) has a quadrangular cross-section. Linear actuator for a valve of a motor vehicle according to one of the preceding claims, characterized in that the spindle nut (38) with the sun gear (22) is integrally formed. Linear actuator for a valve of a motor vehicle according to one of the preceding claims, characterized in that the planetary gear (12) has a total of three planet wheels (24a-c). Linear actuator for a valve of a motor vehicle according to one of the preceding claims, characterized in that the Planetary gear (12) from the driven planet gear (24a) to the sun gear (22) has a reduction. Linear actuator for a valve of a motor vehicle after Claim 10 characterized in that the planetary gear (12) has a reduction ratio with a gear ratio (I) from the driven planet gear (24a) to the sun gear (22) in a range of eight to ten. Linear actuator for a valve of a motor vehicle according to one of the preceding claims, characterized in that at an axial end (62) of the spindle rod (36,36 ') a thrust bearing (64) is arranged, which the spindle rod (36,36') with a rotatably fixed and axially displaceable valve rod (66) connects. Linear actuator for a valve of a motor vehicle according to one of the preceding claims, characterized in that the electric motor (10) has a drive shaft (16) which is arranged parallel to the spindle rod (36, 36 ') and on which the driven planetary gear (24a) rotatably attached.

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