DE102015204588B4 - Actuator with a friction device using a wrap spring element and method for producing the wrap spring element - Google Patents

Abstract

Actuator with a friction device using a wrap spring element (1), the friction device having at least two components rotatable relative to one another, with a wrap spring element (1) which influences the efficiency / friction when the components rotate relative to one another is arranged between the components rotatable relative to one another has at least two interconnected active areas (6, 7), characterized in that the wrap spring element (1) is wound from a wire with a constant wire cross-section and its wire cross-section is at least partially reduced by at least one machining process, an inner friction surface (2) of the first active area (6) interacts with an outer diameter of a first friction partner and an outer friction surface (4) of the second active area (7) interacts with an inner diameter of a second friction partner.

Description

The invention relates to an actuator with a friction device using a wrap spring element and a method for producing the wrap spring element according to the preamble of claims 1 and 9, the friction device having at least two components that can be rotated relative to one another and the actuator, in particular, for actuating a clutch Motor vehicle is used.

Actuators are used, for example, to operate a clutch of a vehicle and can convert the rotary movement of a component into an axial movement of another component. The actuator itself can be any type of linear actuator, e.g. B. PWG actuator (PWG = planetary roller screw drive), hydraulic slave cylinder, etc ..

Planetary roller screw drives (PWG) are formed from a spindle, a spindle nut and planetary rolling elements arranged around the circumference between them and accommodated in a planet carrier. Here, the spindle, spindle nut and planetary rolling element have profiles in order to transmit a rotary movement between spindle and spindle nut, one of the components - spindle or spindle nut - being rotationally driven and the other component with a non-rotatable arrangement along the longitudinal axis of the spindle by an axial path corresponding to the set translation is relocated. Here, the planetary rolling elements have two different profile sections that mesh on the one hand with the spindle and on the other hand with the spindle nut, with one profile section on the planetary rolling element being groove-shaped and the other profile sections on the planetary rolling element generally being groove-shaped and, depending on the embodiment, a complementary thread section on the spindle or the spindle nut and correspondingly the groove section is arranged on the other component. In this way, compared to a direct mounting of the spindle on the spindle nut, translations are achieved with which a higher force is made possible per spindle rotation with less feed.

From the EP 0 320 621 A1 For example, a PWG is known in which the spindle has a thread and the spindle nut has grooves on each of which planetary rolling bodies roll by means of correspondingly complementary profile sections. Here, the axially fixed spindle, driven for example by an electric motor, is rotated relative to the non-rotatably arranged spindle nut, so that the spindle nut is forcibly displaced axially in the grooves of the spindle nut due to the frictional rolling of the planetary bodies. This results in a movement proportional to the speed of the spindle over the axial travel of the spindle nut. For this purpose, according to planetary gears, the planet carrier rotates with the planetary rollers at half speed or another ratio, depending on the design of the diameter, of the rotating component, namely spindle or spindle nut.

the DE 10 2010 047 800 A1 shows an application of a planetary roller drive in which an actuator part of a hydrostatic actuator designed as a piston of a master cylinder is axially fixedly coupled to the non-rotatable and axially displaceable spindle, the axially fixed spindle nut being driven in rotation by an electric motor, so that when the spindle nut is rotated, the spindle and Spindle nuts are displaced against each other along the axial path. Since the cylinder housing that receives the piston and forms a pressure space with it is fixed and the spindle nut is axially supported on it, the piston builds up pressure depending on the rotary drive of the spindle nut, for example to actuate motor vehicle components such as brakes, friction clutches and the like. It is particularly desirable in the case of friction clutches to quickly bridge a clearance with low load requirements by means of a high gradient and to be able to apply high loads with an electric motor with low power in the effective area of the friction clutch by means of a small gradient.

In the case of, for example, efficiency-optimized spindle drives (e.g. PWG) driven by an electric motor, particularly in actuators such as hydrostatic clutch actuators (hydrostatic clutch actuator - abbreviated as HCA) that work against a load, for example a clutch characteristic, there is a problem that a Position, a holding current and thus a holding torque in the electric motor is required because the spindle drive (e.g. with a PWG) is not self-locking. With a PWG in an HCA with a non-rotatable ring gear nut with a driven spindle on which the axial movement (relative to the spindle) is picked up, an additional reduction of the spindle pitch occurs with an ideal rolling movement (as in a toothed planetary gear / no slip), this can be varied the spindle and / or planetary roller diameter can be freely selected within limits. A decisive disadvantage of such actuators is that they require a permanent holding current or the position cannot be held in the event of a power failure / error (e.g. cable break, connector dropped). If the clutch is pressed on by the actuator, there is then a great risk that the clutch will unintentionally close. The use of wrap springs, for example for clutches, is also known. One Loop spring usually consists of a metallic wire which extends in several turns around a cylindrical part. A frictional force acts between this spring and the cylindrical part when the cylindrical part rotates. This can be influenced by tightening or releasing the wrap spring.

A wrap spring clutch usually consists of a helical spring wound on a shaft or a cylindrical body, which is attached to one side of the drive. The drag effect is based on the fact that the drag torque increases and adds up with each turn due to the friction. As a result, due to the wrap, the force causing this friction increases at the same time. In the opposite direction, there is only little friction - the spring increases its diameter somewhat, but does not unwind. Due to the friction that remains in freewheeling operation, the wrap spring is also used with slip clutches. As a freewheel element, it has a self-reinforcing (locking) effect in one direction and a cancellation of this function in the other direction, the spring only having to be rotated against its basic friction.

From the pamphlet DE 10 2007 047 394 A1 For example, a torsional vibration damper is known which has at least two parts that can be rotated to one another against the action of a damping device with energy stores acting in the circumferential direction, one of which can be connected to a drive machine and the other to a shaft to be driven, with an additional one between the two parts with the Damping device in series connected torque limiter is provided, which is effective in at least one of the relative twisting directions possible between the two parts and comprises at least one loop spring clutch, which acts as a freewheel when a predetermined angle of rotation between the two parts is reached and comprises at least one loop spring element. This solution is characterized in that at least one end of the loop spring element is non-rotatably connected to a ring element which has support areas for the energy stores acting in the circumferential direction and / or control areas for the freewheeling effect.

In a not yet published technical solution by the applicant, an assembly with a friction device with at least two mutually rotatable components, in particular for the actuation of a clutch of a vehicle, is proposed, in which between the relatively rotatable components an efficiency / the friction-influencing helical spring is arranged. In this case, the helical spring forms, at least in some areas, a loop spring, which can be a simple loop spring, a double loop spring or a loop torsion spring. The double loop spring described here has two effective areas which are arranged axially one behind the other.

Another as yet unpublished technical solution by the applicant also describes an assembly with a friction device with at least two components rotatable relative to one another, between which a loop spring is arranged, which has two loop spring areas coupled to one another, with a slight rotation of the components in one direction of rotation Friction and high friction can be generated in the other direction. The two loop spring areas are coupled by a connecting piece which is designed as a sleeve or ring and positions the two loop spring areas nested radially in one another in such a way that torques can be transmitted from the first loop spring area to the second loop spring area and vice versa. The two wrap spring areas are realized by two different wrap springs. This solution is characterized by a smaller space requirement in the axial direction. In addition, greater drag torque differences can be achieved with this design due to the different cross-sections / diameters of the inner and outer springs. However, there is the disadvantage here that the multi-part structure of the wrap spring makes assembly more difficult and the costs increase due to the use of the connecting element connecting the two wrap spring areas.

Another as yet unpublished technical solution by the applicant describes an assembly with a friction device and with at least two components that can be rotated relative to one another, with a wrap spring element which influences the efficiency / friction when the components are rotated relative to one another and which at least has two radially nested, integrally interconnected, active areas. The radially inner active area of the wrap spring element is operatively connected with its inner diameter in a rotationally fixed or frictionally locked manner to an outer diameter of the first component and the radially outer active area of the wrap spring element with its outer diameter in a frictionally or rotationally fixed manner with an inner diameter of the second component.

The use of a common wire for both spring sections results in a radially high and axially short wire cross-section to represent a high frictional torque. With realistic coverage of the Wrap spring section with low friction results in an undesirably high frictional torque in this area.

The object of the present invention is to develop an actuator with a friction device using a wrap spring element and a method for producing the wrap spring element, the wrap spring having a wrap spring geometry which, despite the use of a wire with a constant cross section over its length, is in the area of low friction despite the tolerance-insensitive (and therefore relatively large) overlap with the shaft, only a small frictional torque is generated.

The object is achieved by the characterizing features of the first and ninth patent claims. Advantageous refinements result from the subclaims.

The actuator with a friction device has at least one wrap spring element and at least two components that can be rotated relative to one another, and is used in particular for the actuation of a clutch of a motor vehicle, wherein between the components that are rotatable relative to one another, a relative rotation of the components influences the efficiency / friction The wrap spring element is arranged, which has at least two interconnected active areas, the wrap spring element according to the invention being wound from a wire with a constant wire cross section and reduced in its wire cross section at least in some areas by at least one machining process.

The wire cross-section of the wrap spring element is preferably rectangular or square and the wire cross-section is reduced from an initial cross-section to an end cross-section at least over the length of an active area by at least one cutting and / or non-cutting machining process.

As an alternative to a rectangular wire, a wire with a round cross-section or any other arbitrary cross-section can be selected whose cross-section is at least partially reduced by at least one machining operation.

The wire cross-section of the wrap spring is reduced at least in some areas over a length range by machining in the form of grinding, milling or turning or a combination of the aforementioned machining operations. Alternatively, an electrochemical ablation process can also be used to reduce the wire cross-section, which can also be combined with machining that takes place before or afterwards.

The wrap spring element is advantageously wound in one piece and has at least two active areas, which are at least two axially separate active areas with different frictional torques. A first effective area causes a lower frictional torque and a second effective area causes a higher frictional torque.

In particular, the wrap spring element is wound to a larger diameter in the second effective area for the higher frictional torque than in the first effective area for the lower frictional torque.

It has proven to be particularly advantageous if the wrap spring element has a greater number of turns / windings in the first effective area for the lower frictional torque than in the second effective area for the higher frictional torque.

In one embodiment, the wire cross-section is selected with regard to the requirements for the high frictional torque and the spring is wound in one piece over its entire length. In order to reduce this to a necessary minimum in the area of the low frictional torque, a maximum of many turns are wound for this purpose in order to lock safely when the high frictional torque is to take effect, and the wire cross-section is reduced by a subsequent machining process.

In an advantageous embodiment, the cross section of the wrap spring element is reduced in the first effective area for the lower frictional torque at its outer and / or inner diameter.

The loop spring resulting from the machining process is then comparable to a loop spring wound from a wire with a variable cross section, which, however, is significantly more complex in terms of production and is therefore not to be preferred.

Alternatively, both friction areas of the wrap spring can also be nested radially and the inner diameter of the inner wrap spring area can preferably be reduced in cross section.

1. a. Wickeln des Schlingfederelementes aus einem Draht mit konstantem Querschnitt, wobei das Schlingfederelement im Bereich für das höhere Reibmoment auf einen größeren Durchmesser gewickelt wird als im Bereich für das geringere Reibmoment,
2. b. bereichsweise Reduzieren des Querschnittes des Schlingfederelementes durch wenigstens einen weiteren Bearbeitungsvorgang.

Also according to the invention is a method for producing a loop spring element wound from wire, comprising the following steps:

1. a. Winding the wrap spring element from a wire with a constant cross section, with the wrap spring element in the area for the higher frictional torque on a larger one Diameter is wound than in the area for the lower frictional torque,
2. b. regionally reducing the cross section of the wrap spring element by at least one further machining process.

Preferably, the wrap spring element is first wound from a wire with a rectangular wire cross-section and then the wire cross-section is reduced from an initial cross-section to an end cross-section at least over the length of an effective area of the wrap-spring element by at least one cutting and / or non-cutting machining process, with a second effective area for a higher one Frictional torque is wound on a larger diameter than a first effective area for the lower frictional torque and that the first effective area for the lower frictional torque is processed at its outer and / or inner diameter to reduce the wire cross-section by at least one cutting and / or non-cutting machining process.

If the cross-section is reduced by machining the outer and / or inner diameter, at least the machined area can additionally be machined by means of a beam machining process. This can be, for example, blasting using sand or glass balls or other suitable materials, by means of which any burrs that have arisen during machining are removed and / or the surface is solidified.

• 1 ein erfindungsgemäßes Schlingfederelement 1 mit am Außendurchmesser des ersten Wirkbereiches 6 für das geringere Reibmoment abgeschliffenem Querschnitt,
• 2 eine erfindungsgemäßes Schlingfederelement 1 mit am Innendurchmesser des ersten Wirkbereiches 6 für das geringere Reibmoment abgeschliffenen Querschnitt.

The invention is explained in more detail below with reference to exemplary embodiments and associated drawings, without being restricted to these. Show:

• 1 a wrap spring element according to the invention 1 with on the outside diameter of the first effective area 6th for the lower frictional torque of the ground-off cross-section,
• 2 a wrap spring element according to the invention 1 with on the inside diameter of the first effective area 6th Ground cross-section for the lower frictional torque.

In the 1 and 2 is a loop spring element according to the invention 1 shown, which has an inner friction surface 2 which cooperates with an outer diameter of a friction partner, not shown. It's also a sanded area 3 present, which extends over the length of the inner friction surface. It is still an outside friction surface 4th present, which are in the axial direction essentially on the inner friction surface 2 adjoins and cooperates with the inner diameter of a further friction partner, not shown. The wrap spring element 1 is wound in one piece from a wire with a rectangular wire cross-section. Thereby a first effective range 6th which extends axially along the inner friction surface 2 extends and a second effective area 7th which extends axially along the outer friction surface 4th extends, formed.
In the second effective range 7th is the initial cross-section 1A of the rectangular wire used. This became the wrap spring element 1 Wrapped over its entire length, but with the starting outer diameter D6a of the first effective range 6th wound smaller than the outer diameter D7 of the second effective range 7th . Since the output cross-section 1A is the same, there is an initial inner diameter d6a of the first effective range 6th that is smaller than the inside diameter d7 of the second effective range 7th .
To in the first effective range 6th to reduce the cross-section was in the variant according to 1 in the first effective range 6th a sanded area 3 generated on the outside diameter, which is the starting outside diameter D6a to the final outer diameter D6b was reduced. This was in the first effective range 6th the wire cross-section to an end cross-section 1B reduced.

With the variant after 2 is the sanded area 3 on the inner circumference of the first effective area 7th because the output inside diameter d6a by a preferably mechanical machining process to a final inner diameter d6b was enlarged.

In both variants, the first is the effective range 6th for a lower frictional torque and the second effective range 7th designed for a higher frictional torque.

List of reference symbols

1

Wrap spring

1A

Output cross-section

1 B.

End cross-section

2

Internal friction surface

3

sanded area

4th

External friction surface

5

Original cross-section

6th

Area of low frictional torque / first effective area

D6a

Starting outside diameter of the first effective area

d6a

Starting inside diameter of the first effective area

D6b

Final outside diameter of the first effective area

d6b

Final inside diameter of the first effective area

7th

Area of high frictional torque / second effective area

D7

Outside diameter of the second effective area

d7

Inner diameter of the second effective area

Claims (10)

Actuator with a friction device using a wrap spring element (1), the friction device having at least two components rotatable relative to one another, with a wrap spring element (1) which influences the efficiency / friction when the components rotate relative to one another is arranged between the components rotatable relative to one another has at least two interconnected active areas (6, 7), characterized in that the wrap spring element (1) is wound from a wire with a constant wire cross-section and its wire cross-section is at least partially reduced by at least one machining process, an inner friction surface (2) of the first active area (6) interacts with an outer diameter of a first friction partner and an outer friction surface (4) of the second active area (7) interacts with an inner diameter of a second friction partner. Actuator after Claim 1 , characterized in that the wire cross-section of the wrap spring element (1) is rectangular and that the wire cross-section at least over the length of an active area (6, 7) by at least one cutting and / or non-cutting machining process from an initial cross-section (1A) to an end cross-section (1B) is reduced. Actuator after Claim 1 or 2 , characterized in that the wire cross-section of the loop spring is reduced at least in some areas by machining in the form of grinding or milling or turning or a combination of the aforementioned machining operations. Actuator after Claim 2 , characterized in that the wrap spring element (1) is machined without cutting using an electrochemical process. Actuator according to one of the Claims 1 until 4th , characterized in that the loop spring element (1) is wound in one piece. Actuator according to one of the Claims 1 until 5 , characterized in that the first effective area (6) and the second effective area (7) are at least two axially separated areas with different frictional torques (6, 7), the first effective area (6) having a lower frictional torque and the second effective area (7) cause a higher frictional torque. Actuator according to one of the Claims 1 until 6th , characterized in - that the wrap spring element (1) in the second effective area (7) is wound to a larger diameter than in the area for the lower frictional torque (6) and / or - that the wrap spring element (1) in the first effective area (6) for the lower frictional torque has a greater number of turns than in the second effective area (7) for the higher frictional torque. Actuator according to one of the Claims 1 until 7th , characterized in that the wrap spring element (1) is reduced in its first effective area (6) for the lower frictional torque at its outer and / or inner diameter. Method for producing a loop spring element (1) for an actuator according to Claim 1 , wherein the loop spring element is wound from wire, characterized in that: a. the wrap spring element (1) is first wound from a wire with a constant wire cross-section and then b. The wire cross-section of the loop spring element (1) is reduced at least in some areas by at least one machining process in which the outer diameter (D6a) of the loop spring element (1) is reduced. Procedure according to Claim 9 , characterized in that - the wrap spring element (1) is wound from a wire with a rectangular wire cross-section and - that the wire cross-section at least over the length of an active area (6, 7) of the wrap spring element (1) by at least one cutting and / or non-cutting machining process of an output cross-section (1A) is reduced to an end cross-section (1B), with a second effective area (7) being wound onto a larger diameter for a higher frictional torque than a first effective area (6) for the lower frictional torque and that the first effective area (6) for the lower frictional torque on its outer and / or inner diameter to reduce the wire cross-section is processed by at least one cutting and / or non-cutting machining process.

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