DE102011102119A1 - Dry freewheel for permanently engaged starter of internal combustion engine to decouple toothed ring starter with crankshaft/primary mass, has clamping bodies spaced from drive plate in decoupled state and prestressed by compression springs - Google Patents

Abstract

The freewheel has a flange (4) coupled with a crankshaft/primary mass, and a toothed ring (1) coupled with a starter shaft. Clamping bodies (5) are accommodated at a cage and prestressed by compression springs, where the bodies act at a drive plate (2) and the flange in a coupled state, and the springs act in different directions. The clamping bodies transmit rotational torque between the drive plate and the flange and are spaced from the drive plate in a decoupled state, where the drive plate is connected with the toothed ring.

Description

The invention relates to a permanently starter starter with a dry freewheel and is used in particular in internal combustion engines and serves to decouple crankshaft or primary mass and starter ring gear during operation by the freewheel. The freewheel works so that it transmits the moment between the crankshaft or primary mass and starter ring gear and starter shaft up to a certain speed and no torque is transmitted at an increasing speed.

A starter freewheel for an electric starting device for internal combustion engines for temporarily coupling the starter shaft with the crankshaft is also off DE 100 19 593 A1 known. The starter clutch comprises an inner ring coupled to the crankshaft, an outer ring coupled to the starter shaft and sprags effective for startup operation for frictional engagement of the two rings and a cage for the sprags and means for friction or positive engagement of the cage with the inner ring. In overtaking the clamp body are pivoted under the action of centrifugal force such that they are separated from the outer ring. The clamping body are pivotally mounted with leaf springs in a cage support ring.

According to another possible variant of a freewheel, this has means which support the clamping body in the decoupled state. The clamp bodies are fastened to the cage by means of a helical spring.

The clamping body of a freewheel can also be acted upon by a leg spring.

A disadvantage of these systems is that the prestressing of the clamping bodies takes place via installation-consuming and / or strength-critical springs, whereby a high number of parts which assume different functions (centering, spring installation, and the like) is required. Another disadvantage is that it can come by the springs used to oscillations of the clamping body by the sometimes very high centrifugal forces acting on the clamp body, which has an overall negative effect on the life of the freewheel.

Another solution relates to a dry freewheel for a permanently starter starter with a coupled to the crankshaft / the primary mass flange, coupled to the starter shaft sprocket and a cage on which a plurality of prestressed clamping body are added, each clamping body by a single compression spring with a Bias is applied. The disadvantage here is that in addition to the moment a lateral force acts on the clamping body, which generates additional friction and thus makes it difficult or prevent twisting of the clamping body. As a result, the freewheel can jam late and thus unintentionally generate high dynamic clamping forces. In this construction, with only one compression spring acting on the clamping body transverse force is equal to the spring force of the compression spring, whereby the unwanted frictional force already described is generated.

The object of the invention is the construction of a dry freewheel, which is robust and is characterized by a low friction, whereby the clamping body are pressed easier and earlier in the nip and the freewheel closes faster and with which high dynamic clamping forces are avoided.

For this purpose, the dry freewheel for a permanently starter starter coupled to the crankshaft / the primary mass flange, coupled to the starter shaft sprocket and a cage on which a plurality of spring-biased clamping body are received, on, wherein the clamping body in the coupled state on a connected to the sprocket drive plate (outer ring) and flange (inner ring) and transmit torque between the drive plate and the flange and in the decoupled state (idle) are spaced from the drive plate, according to the invention each clamp body is biased by two springs whose spring force opposite or nearly opposite. As a result, the transverse force acting on the clamping body is very low or equal to zero. Thus, almost exclusively a moment acts on the clamping body. By reducing or even eliminating the lateral force and thus the friction caused thereby, the clamping body can be pressed into the clamping gap more easily and earlier, whereby the freewheel closes faster.

Preferably, the two springs are supported on a plastic part. When the freewheel is open and the clamp swings under speed, the rotation of the clamp body is limited by a stop on the plastic part. Thus, the plastic part takes on a further function in addition to the known tasks such as guiding the clamping body and the bias and centering of the cage.

Advantageously, the springs are designed as compression springs, so that each clamping body is biased by a first compression spring and by means of a second compression spring, wherein the first compression spring and the second compression spring act in different directions.

For this purpose, the first compression spring on a first axis of action and the second compression spring on a second axis of action, which are parallel or approximately parallel or inclined at an angle less than 90 ° to each other.

Furthermore, the two effective axes should have approximately the same distance from the axis of rotation of the clamping body.

The first and the second compression spring engage in substantially opposite regions of the clamping body and thereby transmit torque to the clamping body.

By virtue of the aforementioned design features and since the essentially oppositely acting spring forces of the first compression spring and the second compression spring approximately or completely cancel each other in the force equilibrium, the clamping body is almost or completely free of transverse forces, as a result of which only very little friction is recorded.

The first compression spring is on the one hand on the plastic part and is on the other hand via a first pressure piece with the clamping body in operative connection. Analog is in each case a second compression spring on the one hand on the plastic part and on the other hand via a second pressure piece with the clamping body in operative connection. The first pressure piece and the second pressure pieces are rotatably mounted in the clamping body.

During rotation of the clamping body, the first and the second pressure piece are thereby pivotally mounted, wherein the two compression springs are actuated substantially in parallel.

Furthermore, each clamp body is assigned in addition to the lateral guide and an end stop.

Advantageously, the two compression springs are likewise based on the plastic parts and are guided laterally / axially fixed by means of the plastic parts. The plastic parts simultaneously center the cage with respect to the inner ring on the crankshaft.

The cage has two side plates and the plastic parts also cause a clamping of the cage by acting on the side panels of the cage bias.

Another function of the two plastic parts is that they prevent slipping out of the first and the second compression spring under centrifugal force in the swiveled end position of the clamp body.

The two side panels of the cage are fixedly connected to each other via spacer bolts, on which the clamping bodies are pivotally received. In the two side panels, the plastic parts are fixed, with friction surfaces are located on the plastic parts, which have contact with the flange and thereby frictionally connect the cage to the flange.

Due to the inventive design of the dry freewheel for a meshed starter vibrations and noise are reduced and increases the life in particular by the use of the compression spring. Furthermore, the dry freewheel has a robust construction with a small number of parts, which is easy to install.

The solution according to the invention ensures a substantially lateral force-free mounting of the clamping body, whereby the friction is considerably reduced. An undesirable (cross) jamming of the clamping body is thereby prevented and avoid unwanted high dynamic clamping forces, as acting on the clamp body almost exclusively a moment.

The invention will be explained in more detail with reference to an embodiment and associated drawings. Show it:

1 the cut by a freewheel,

2 the representation of the clamping mechanism in the front view.

in 1 the longitudinal section of the freewheel is shown. The starter not shown here meshes with the sprocket 1 , which with the drive plate 2 is connected as desired. About any camp 3 is the drive disc 2 with the sprocket 1 about the axis A rotatably mounted on the engine, not shown.

A flange 4 is secured against rotation on the crankshaft, also not shown here. The coupling between the flange 4 and the drive disc 2 via any number of clamp body 5 , These jam in the gap between the drive plate and the flange 4 , whereby over the clamping bodies 5 between drive plate 2 and flange 4 a torque is transmitted. This creates a frictional connection between these parts and the starting torque of the starter can be transmitted to the crankshaft.

Rotates the flange 4 faster than the drive plate 2 , the clamping force of the clamp body decreases 5 from. The freewheel releases as the clamp body 5 no contact with the drive plate 2 have, whereby no moment is transferred any more.

When the freewheel overtakes, there is a relative movement between the flange 4 , the driving disc 2 and the sprags 5 , In order to keep the wear on the aforementioned components low over the life, the clamp body should 5 Turn from a certain speed in the nip and so the direct contact with drive plate 2 and flange 4 to lose. This should be speed dependent.

When the starting process of the internal combustion engine is completed, the flange rotates 4 with the engine speed. The starter stops turning and the drive plate 2 stops too. It is therefore a necessity that the clamping body 5 in some form from the flange 4 be taken to get the necessary for twisting centrifugal force. The function of the coupling of clamping body 5 and flange 4 takes over a cage.

The cage consists of two side plates 6 , on both sides of the clamping bodies 5 arranged and about distance bolts 7 are firmly connected. On the facing inner sides of the side panels 6 are thin-walled plastic parts 8th attached.

The plastic parts 8th take over several functions simultaneously. First, they center the entire cage on the flange 4 , on the other hand, are located towards the flange 4 friction surfaces 10 on the two plastic parts 8th , These have contact with the flange 4 and are energized. Thus, the cage is frictional to the flange 4 tethered. The clamping force is achieved by preloading the side plates 6 generated and is arbitrarily adjustable. In the area of the distance bolts 7 form the plastic parts 8th , on both sides of the clamp body 5 are arranged, a lateral guide for the clamping body 5 ,

The position of the clamp body 5 is by the distance bolt 7 defined to the the clamping body 5 in a rotation axis 5 ' is pivotally mounted.

2 shows the representation of the clamping mechanism in front view with engaged clamping bodies 5 , So that the clamping body 5 swings in or out in a certain speed range, is the clamp body 5 through the first compression spring 13.1 and the second compression spring 13.1 biased. About the first and the second compression spring 13.1 . 13.2 as well as the position of the rotation axis 5 ' and the mass of the clamp body 5 the lifting or starting speed is defined. The plastic part 8th also has an end stop 14 for the clamp body 5 on.

The compression springs 13.1 . 13.2 lie on the one hand on the plastic part 8th on the other hand is the first compression spring 13.1 but a first pressure piece 15.1 with the clamp body 5 connected. The pressure pieces 15.1 . 15.2 grip at substantially equal intervals, but on different sides of the clamp body 5 at. Here are the first pressure piece 15.1 and the second pressure piece 15.2 rotatable in the clamp body 5 stored. Thus, when turning the clamp body 5 the pressure pieces 15.1 . 15.2 pivot and the first and second compression spring 13.1 . 13.2 are operated as far as possible in parallel.

The compression springs 13.1 . 13.2 are arranged so that the axis of action 13.1 'the first compression spring 13.1 and the axis of action 13.2 'the second compression spring 13.2 are approximately parallel or, as out 2 seen, are inclined α only at a low angle.

Thus, the two springs produce 13.1 . 13.2 together a defined moment M. The spring force F13.1 of the first compression spring 13.1 and the spring force 13.2 the second compression spring 13.2 However, they are oppositely directed. Since the opposite spring forces F13.1, and F13.2 cancel each other in equilibrium of forces, the clamp body is 5 almost free of lateral forces F5. This transverse force F5 generated at the contact points of the clamp body 5 with the adjacent parts, such. B. the drive plate 2 , the spacer bolt 7 and the flange 4 a friction force, which the movement of the clamping body 5 difficult or even prevented. By reducing or even eliminating the lateral force M5, the clamp body 5 lighter and thus pressed earlier in the nip, causing the freewheel closes faster.

LIST OF REFERENCE NUMBERS

1

sprocket

2

driver disc

3

camp

4

flange

5

clamping bodies

5 '

Rotary axis of the clamp body 5

5.1

end stop

6

side panels

7

Standoffs

8th

Plastic parts

9

Cage

10

friction surfaces

11

lateral guidance

13.1

first compression spring

13.1 '

Effective axis of the first compression spring 13.1

13.2

second compression spring

13.2 '

Effective axis of the second compression spring 13.2

14

end stop

15.1

first pressure piece

15.2

second pressure piece

A

axis

F5

Transverse force F5 on the clamp body 5

F13.1

Spring force of the first compression spring 13

F13.2

Spring force of the second compression spring 13

M

moment

α

angle

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10019593 A1 [0002]

Claims (10)

Dry freewheel for a permanently interlocked starter with a flange coupled to the crankshaft / primary mass ( 4 ), a ring gear coupled to the starter shaft ( 1 ) and a cage ( 9 ), on which several spring-biased sprags ( 2 ), which in the coupled state at one with the sprocket ( 1 ) associated drive plate ( 2 ) (Outer ring) and flange ( 4 ) (Inner ring) and a torque between the drive plate ( 2 ) and the flange ( 4 ) and in the decoupled state (idle) of the drive plate ( 2 ) are spaced apart, characterized in that each clamping body ( 5 ) is biased by two springs. Freewheel according to claim 1, characterized in that each clamping body ( 5 ) by means of a first compression spring ( 13.1 ) and by means of a second compression spring ( 13.2 ) is biased. Freewheel according to claim 1 or 2, characterized in that the first compression spring ( 13.1 ) and the second compression spring ( 13.2 ) act in different directions. Freewheel according to one of claims 1 to 3, characterized in that the first compression spring ( 13.1 ) a first active axis ( 13.1 ') and the second compression spring ( 13.2 ) a second active axis ( 13.2 ') and that the two effective axes ( 13.1 ' and 13.2 ' ) are parallel or approximately parallel or inclined at an angle (α) smaller than 90 ° to each other. Freewheel according to one of claims 1 to 4, characterized in that the two axes of action ( 13.1 ' and 13.2 ' ) approximately equidistant from the axis of rotation ( 5.1 ') of the clamping body ( 5 ) exhibit. Freewheel according to one of claims 1 to 5, characterized in that the first compression spring ( 13.1 ) at substantially opposite areas of the clamping body ( 5 ) and on the clamping body ( 5 ) transmit a torque (M). Freewheel according to one of claims 1 to 6, characterized in that the substantially oppositely acting spring forces (F13.1 'and F13.2') of the first compression spring ( 13.1 ) and the second compression spring ( 13.2 ) in the equilibrium of forces approximately or completely cancel and the clamping body ( 5 ) is almost or completely free of transverse forces (F5). Freewheel according to one of claims 1 to 7, characterized in that in each case a first compression spring ( 13.1 ) on the one hand on the plastic part ( 8th ) and on the other hand via a first pressure piece ( 15.1 ) with the clamping body ( 5 ) is in operative connection and in each case a second compression spring ( 13.2 ) on the one hand on the plastic part ( 8th ) and on the other via a second pressure piece ( 15.2 ) with the clamping body ( 5 ) is in operative connection. Freewheel according to claim 6, characterized in that the first pressure piece ( 15.1 ) and the second pressure piece ( 15.2 ) rotatable in the clamping body ( 5 ) is stored. Freewheel according to one of claims 1 to 7, characterized in that each clamping body ( 5 ) a lateral guide ( 11 ) and an end stop ( 14 ) assigned.

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