WO1996041975A1

WO1996041975A1 - Driving chain take-up device

Info

Publication number: WO1996041975A1
Application number: PCT/EP1996/001683
Authority: WO
Inventors: Hermann Stief; Thomas Ullein; Dieter Schmidt
Original assignee: Ina Wälzlager Schaeffler Kg
Priority date: 1995-06-10
Filing date: 1996-04-23
Publication date: 1996-12-27
Also published as: DE19680418C1

Abstract

A take-up device for the chain or belt of an internal combustion engine, for example of the camshaft drive, has a cylindrical take-up housing (2) that contains a piston (1) stressed by a compression spring (13). Housing (2) and piston (1) can slide in the axial direction in relation to each other. The part that can slide in relation to the fixed part in the chain take-up direction is surrounded by a first ring-shaped stop that limits its backward motion. The first ring-shaped stop is designed as a restraining clamp (15) whose legs are radially prestressed to engage a locking groove (16) of the take-up device housing (2). When sliding, the legs can be axially supported on a supporting surface of the housing (3).

Description

Tensioning device for a chain drive

description

Field of the Invention

The invention relates to a tensioning device for the chain or the belt, for example for the camshaft drive of an internal combustion engine, with a cylindrical tensioner housing and a piston arranged therein and acted upon by a compression spring, which are axially displaceable relative to one another, the shifting relative to the fixed part in the chain tensioning direction ¬ bare part is surrounded by a first stop ring limiting its return movement.

Background of the Invention

Such a tensioning device is arranged in the empty run of the chain drive. The compression spring introduces the clamping forces into the empty run of the timing drive. There, on average, lower tension forces occur during normal operation than in the working or traction strand, so that the compression spring can be designed in accordance with these lower tension forces. As a result of the force of the compression spring, the piston acting on the chain moves. Tensioner housing unit apart and generates the required chain tension.

This unit can be designed as a hydraulic damping device with an oil reservoir, a high pressure chamber and a check valve located between them. Gut hydraulic oil, which supports the action of the compression spring due to its pressure, can be pressed out of the high-pressure chamber via the leakage gap formed by the piston and the tensioner housing while overcoming the fluid friction Piston-tensioner housing-Eipheit with force impacts from the chain drive.

When using such a tensioning device, the required chain tension can be undershot in special cases in which the high-pressure space is not yet or only partially filled with oil and the pressure of the oil in the high-pressure space has not or has not yet built up. Then the tensioning device can suddenly move in under the action of force impulses from the chain drive, because there is no sufficient damping effect. A special case exists, for example, also in the case of an engine of a motor vehicle if it is turned off in the upward direction of travel with the forward gear engaged, so that the engine wants to turn backwards as a result of the vehicle weight. This creates a train in the empty strand of the chain. In such a case, the piston / tensioner housing unit of the hydraulic pressure force generator is completely retracted in such a case without a stop ring limiting the return, due to the greater chain tension. If the empty span is suddenly relieved again by starting the engine, the necessary chain tension is missing here due to the piston being retracted far, and the chain may be struck in an uncontrolled manner. The chain on the camshaft drive can then jump over one or more teeth on the drive gear. This results in a timing adjustment of the valve train, which results in engine damage, for example, by hitting the valve plate on the piston crowns.

From DE-OS 36 36 918 a clamping device of the type mentioned is known. There, the piston, which can be extended from the fixed tensioner housing, acts on the chain to be tensioned in the tensioning direction. When this chain tensioner is started up, the first stop ring snaps into a first locking groove in the tensioner housing. This position is the beginning of the chain tensioning area. If the pressure in the high-pressure chamber is not sufficient to bring the piston to a standstill under load, a stop edge of the piston hits the first stop ring. This will cause the piston to retract the tensioner housing is limited. The stop ring thus acts as a kickback or sinking protection.

Stop rings of this type are made from a wire, whereby a certain minimum wire diameter must not be undercut due to the interaction in terms of the dimensional tolerances and strengths of the components. With this minimum diameter, the wire of the stop ring, which must be able to be slightly changed in the ring diameter during operation, already has a high degree of rigidity, which increases significantly when changing to a smaller ring diameter while maintaining the same wire diameter.

Summary of the invention

The invention has for its object to provide a tensioning device that manages with a smaller installation space and therefore has overall smaller dimensions than previously known chain tensioners.

This object is achieved according to the invention in that the first stop ring is designed as a two-leg, U-shaped retaining clip, the legs of which engage in a radially prestressed manner in a locking groove of the displaceable part and can be axially applied to a fixed stop when it is displaced. By using a retaining clip instead of a circular stop ring for the sink protection, the stiffness of this limiting member can be kept within acceptable limits with a reduced diameter of the locking groove without needing to reduce the wire diameter. With unchanged. Stiffness of the first stop ring designed as a retaining clip, the force of the compression spring can also remain the same, so that the action of an undesirably high or widely varying spring force on the chain to be tensioned is avoided.

As a displaceable part, the tensioner housing can be guided in a cylinder bore of a fixed receiving housing, the fixed stop being arranged on the receiving housing and being formed by a second stop ring. which is inserted radially biased into an inner circumferential groove of the receiving housing. But it is also possible that the piston is guided as a displaceable part in the tensioner housing, which is inserted into a cylinder bore of a fixed receiving housing.

On the tensioner housing, a plurality of locking grooves designed as outer circumferential grooves for receiving the retaining clip can be arranged one behind the other at axial intervals. In the position of the tensioner housing fully inserted into the receiving housing, a transport securing bracket can be attached to the receiving housing, which engages in a circumferential groove of the tensioner housing. This can be arranged between the retaining clip and the second stop ring. The transport securing bracket is removed after mounting the tensioning device on the motor, whereupon the operating position of the tensioning device is set. The retaining clip now forms the mechanical lowering protection for the tensioner housing, so that its return stroke in the receiving housing is limited in the event of an empty high-pressure space and a high force acting from the chain. In addition, the retaining clip acts as a mechanical protection against disintegration, it holds the assembly of the piston-tensioner housing-receiving housing together.

The tensioner housing and the piston can additionally be held together by an outwardly preloaded locking ring which partially projects radially into a circumferential groove of the piston and can otherwise be axially applied to a ramp of the tensioner housing surrounding it. In this case, the circumferential groove of the piston can be embodied with a groove base diameter that is smaller than the diameter of the retaining ring and that allows the groove to be fully accommodated.

The piston and the tensioner housing can be steel parts, while the receiving housing can consist of an aluminum alloy. Brief description of the drawings

Embodiments of the invention are shown in the drawings and are described in more detail below. Show it:

1 shows the front view of a tensioning device pointing in the chain tensioning direction;

FIG. 2 shows a bottom view of the receiving housing of the clamping device according to arrow II in FIG. 1;

FIG. 3 shows a longitudinal section through the tensioning device in the retracted state of the tensioner housing;

Figure 4 shows a longitudinal section along line IV-IV of Figure 3 by the

Tensioning device, but with extended tensioner housing;

5 shows a longitudinal section through a modified clamping device in the retracted state;

6 shows a longitudinal section through the modified tensioning device according to line VI-VI of FIG. 5, but in the extended state.

Detailed description of the drawings

The tensioning device according to the invention shown in FIGS. 1 to 4 consists of a piston 1, a tensioner housing 2 and a receiving housing 3. The piston is inserted as a fixed part with one end into the tensioner housing 2 which acts as a displaceable part and is designed as a cylinder body and held with a securing element, which is referred to here as a securing ring 4. This is located in an outer circumferential groove 5 of the piston 1, from which it partially protrudes radially. With the relative movement between the piston 1 and the tensioner housing 2, the locking ring 4 can strike a ramp 6 of the tensioner housing 2 and thereby prevent further relative movement. For assembly, the locking ring 4 is pushed radially completely into the circumferential groove 5 of the piston 1. After the tensioner housing 2 has been plugged in, the locking ring 4 springs back radially.

In the connection area between the piston 1 and the tensioner housing 2, a check valve 7 is arranged, which separates a high-pressure chamber 8 of the tensioner housing 2 from an oil reservoir 9 of the piston 1. The piston 1, designed as a cylinder body, is supported with its end facing away from the check valve 7 on the bottom of the receiving housing 3, in the cylinder bore 10 of which it is arranged. The piston 1 is thus fixed with the receiving housing 3. It is supplied with hydraulic oil via an oil inlet opening 11 and an oil transfer groove 12, which oil enters the oil reservoir 9.

In the tensioner housing 2, a compression spring 13 is arranged, which is supported at one end on the piston 1 and at the other end on the bottom of the tensioner housing 2 facing away from the piston 1. This Druckfe¬ der 13 causes the extension of the tensioner housing 2 from the receiving housing 3 and from the piston 1 away in the chain tensioning direction, while power surges from the chain retracting the tensioner housing 2 against the action of the - compression spring 13 in the receiving housing 3 and over Cause piston 1. The check valve 7 working with a ball as the closure body can open when the tensioner housing 2 is extended and is closed when it is retracted. When retracting, the hydraulic oil located in the high-pressure chamber 8 comes out of the tensioner housing 2 via the leakage gap 14, which is located between the piston 1 and the tensioner housing 2. This pressing out of hydraulic oil from the high-pressure chamber 8 of the tensioner housing 2 is associated with high fluid friction and therefore has a damping effect on the chain to be tensioned, which transmits its force surges to the tensioner housing 2.

The tensioner housing 2 is surrounded by a two-leg U-shaped retaining clip 15, which acts as a first stop ring and for which housing 2 a plurality of locking grooves arranged one behind the other in the axial direction are provided. For example, the tensioner housing 2 has a first latching groove 16, a second latching groove 17 and a third latching groove 18 as seen from its bottom in the direction of the piston 1. The retaining clip 15 can engage in one of the locking grooves 17 or 18 and thereby hinder the further inward movement of the tensioner housing 2 into the receiving housing 3 because it comes to rest against an oblique stop surface 19 there.

In Figure 3, the clamping device is shown in its transport position, the tensioner housing 2 is fully inserted into the receiving housing 3 and is held there by a transport securing bracket 20 which engages in the circumferential groove 21 of the tensioner housing 2 in the bottom region of the tensioner housing 2. The locking groove 16 serves to prevent the retaining clip 15 from snapping into the circumferential groove 21, which is required for the transport of the tensioning device. The transport securing bracket 20 axially abuts a second stop ring 22 which is held in an inner circumferential groove of the receiving housing 3. Moving the tensioner housing 2 out of the receiving housing 3 is not possible as long as the transport securing bracket 20 is still at a peripheral point in the peripheral groove 21 of the tensioner housing 2.

The tensioning device is assembled for shipping as follows: After the piston 1, the check valve 7, the compression spring 13 and the tensioner housing 2 have been assembled, the retaining clip 15 is pushed axially onto the tensioner housing 2, whereby it reaches the first locking groove 16. Then the piston-tensioner housing unit prepared in this way is inserted into the cylinder bore 10 of the receiving housing 3 and then the tensioning housing is completely pressed into the receiving housing 3 against the action of the compression spring 13. Now the second stop ring 22 can be inserted into the groove provided in the receiving housing 3. The transport securing bracket 20 is then inserted into the receiving housing 3 in a direction transverse to the axial direction, it reaching the circumferential groove 21 of the tensioner housing 2. The tensioner housing 2 can no longer due to the action of the compression spring 13, move out of the receiving housing 3, because the transport securing bracket 20 resting on the second stop ring 22 prevents such a movement. The housing can now be shipped and screwed into place on the engine, for which it is provided with two screw holes 23.

This tensioning device shown in FIGS. 1 to 4 works as follows: after being screwed onto the motor, the transport lock 20 of the tensioner is removed, as a result of which it moves into its working position. When the tensioner housing 2 extends out of the cylinder bore 10 of the receiving housing 3 due to the action of the compression spring 13, the retaining clip 15, which is located in the first locking groove 16 of the tensioner housing 2 and is biased against it, is carried along by the tensioner housing 2 until it is present at the second stop ring 22. Such an extension can be due to chain elongation z. B. possible due to wear. If the tensioner housing 2 now extends further, the retaining clip 15 moves relative to the tensioner housing 2 and snaps into the next locking groove 17. If the engine z. B. parked on a mountain, so that the tensioner housing 2 is pushed back into the receiving housing 3 as a result of a high chain force in the empty run while overcoming the force of the compression spring 13, the retaining clip 15 arrives at the inclined stop surface 19 of the receiving housing 3 and prevents This prevents further retraction or lowering of the tensioner housing 2. This prevents the timing chain from jumping over the teeth of its drive gear when the engine is restarted. In addition, this return stroke limitation means that less oil is pressed out of the high-pressure chamber 8, and as a result the amount of oil required for filling the high-pressure chamber 8 when the engine is started is smaller, which is important in order to avoid noises which could occur due to a lack of damping.

At the same time, the tensioning device also ensures a minimal return stroke of the tensioner housing 2, which is required to compensate for eccentricities of the chain wheels, thermal expansion and to provide a damping stroke. is borrowed. This stroke can be seen in FIG. 3 as the distance between the holding clip 15 and the second stop ring 22.

In the modified tensioning device according to the invention shown in FIGS. 5 and 6, a piston 24 is guided as a displaceable part in a cylindrical tensioner housing 25 which forms the fixed part and is made of steel. This has a welded-on valve seat plate 26 at one end and is inserted with it into a receptacle housing 27 made of aluminum. At the end of the tensioner housing 25 facing away from the valve seat plate 26, the receptacle housing 27 has a caulking 28 at least at one circumferential point, by means of which the tensioner housing 25 is held in the receptacle housing 27 and secured against rotation. The valve seat plate 26 is supported on the bottom of the receiving housing 27.

A check valve 29 is located within the tensioner housing 25 and closes the interior, which acts as a high-pressure chamber 30 for hydraulic oil, with respect to an oil supply line. The oil is supplied through an oil inlet opening 31, an oil transfer groove 32 of the receiving housing 27 and a central bore in the valve seat plate 26.

In the tensioner housing 25, a compression spring 33 is arranged in a bore of the piston 24 forming the high-pressure chamber 30, which is supported at one end on the piston 24 and at the other end on the valve seat plate 26 of the tensioner housing 25. This compression spring 33 causes the piston 24 to extend out of the tensioner housing 25 in the chain tensioning direction, while power shocks from the chain cause the piston 24 to retract into the tensioner housing 25 against the action of the compression spring 33. The check valve 29, which works with a ball as the closure body, can open when the piston 24 is extended and is closed when the piston is retracted. When retracting, the hydraulic oil located in the high-pressure chamber 30 comes out of the high-pressure chamber 30 via the leakage gap 34, which is located between the piston 24 and the tensioner housing 25. This pushing out of hydraulic oil from the high pressure chamber 30 is with a high liquid connected friction and therefore has a damping effect on power surges that the chain to be tensioned transmits to the piston 24.

The piston 24 is surrounded by a two-legged U-shaped retaining clip 35 which acts as a first stop ring and for which a plurality of locking grooves arranged one behind the other in the axial direction are attached to the piston 24. For example, the piston 24 has a first latching groove 36, a second latching groove 37 and a third latching groove 38 as seen from its outer end face in the direction of the tensioner housing 25. In the fully retracted state, the holding clip 35 engages in the first locking groove 36. When the piston 24 is extended, it can engage in one of the locking grooves 37 or 38 and thereby hinder the further inward movement of the piston 24 into the tensioner housing 25 because it comes to rest against an inclined stop surface 39 there.

5 shows the tensioning device in its transport position, the piston 24 has been completely moved into the receiving housing 27 and is held there by a transport securing bracket 40 which engages in the circumferential groove 41 of the piston 24 in the outer end region of the piston 24. The locking groove 36 serves to prevent the retaining clip 35 from snapping into the circumferential groove 41, which is required for the transport of the tensioning device. The transport securing bracket 40 bears axially against a second stop ring 42 ′ which is held in an inner circumferential groove of the receiving housing 27. Moving the piston 24 out of the tensioner housing 25 and the receiving housing 27 is not possible as long as the transport securing bracket 40 is still at a peripheral point in the peripheral groove 41 of the piston 24. For mounting the clamping device on site at the engine, the housing 27 is provided with two screw holes 43. The assembly for the shipping and the operation of this tensioning device modified according to FIGS. 5 and 6 correspond to the assembly and operation described for the tensioning device according to FIGS. 1 to 4.

With the invention, clamping devices with mechanical anti-sink protection are created, which have a very small outer housing diameter, both for example under 14mm. This results in only a small space requirement for such a clamping device. It is simple and inexpensive to manufacture. Only a small amount of tension is required to operate your locking system. The tensioning devices according to the invention have simply constructed transportation locks for mounting on the motor for locking the displaceable part (the tensioner housing 2 or the piston 24) with the transportation securing brackets 20, 40.

The retaining clips 15, 35 of the tensioning devices can consist of a spring steel which is bent in a U-shape and pre-tensioned so that they always rest on the circumference of the displaceable part (the tensioner housing 2 or the piston 24). In the tensioning device shown in FIG. 5, the piston 24 is unlocked by pulling the transport securing bracket 40 and, due to the spring force of the compression spring 33 and the engine oil pressure acting in the high-pressure chamber 30, extends from the tensioner housing 25 in the chain tensioning direction. Due to its pretensioning, the holding clamp 35 is initially carried along by the piston 24 until it rests on the second stop ring 42. When the piston 24 is extended further, the holding clip 35 slides along the piston 24 and snaps into the next locking groove 37 when the chain is correspondingly elongated. If the piston 24 can no longer be held by the chain against the end pressure force when the engine is switched off and the engine hydraulics has failed, it moves back into the tensioner housing 25. The hydraulic oil in the high-pressure chamber 30 is pressed out through the leakage gap 34.

This retraction of the piston 24 is stopped when the holding clip 35 bears against the oblique stop surface 39 (FIG. 6) of the tensioner housing 25. This prevents the chain from jumping over on the chain wheel of the timing drive and prevents the chain from rattling when the engine is started again. At the same time, a minimum return stroke of the piston 24 in the tensioner housing 25 is also ensured in this tensioning device, which is required to compensate for eccentricities of the chain wheels and thermal expansions and to provide a damping stroke. Reference numbers I ente

1 piston 23 screws hole

2 tensioner housings 24 pistons

3 receptacle housing 25 tensioner housing

4 circlip 26 valve seat plate

5 circumferential groove 27 receiving housing 6 ramp 28 caulking

7 check valve 29 check valve

8 high pressure room 30 high pressure room

9 Oil storage room 31 Oil inlet opening

10 cylinder bore 32 oil transfer groove 1 1 oil opening 33 compression spring

12 Oil overflow groove 34 Leak gap

13 compression spring 35 retaining clip

14 leakage gap 36 first locking groove

15 retaining clip 37 second locking groove 16 first locking groove 38 third locking groove

17 second locking groove 39 oblique stop surface

18 third locking groove 40 transport securing bracket

19 oblique stop surface 41 circumferential groove

20 Transport securing bracket 42 second stop ring 21 circumferential groove 43 screw holes

22 second stop ring

Claims

Expectations

, Housing 1. tensioning device for the chain or belt of an internal combustion engine, such as the camshaft drive with a cylindrical Spannerge¬ and, disposed therein by a compression spring acting pistons which are relatively axially displaceable, wherein the displaceable relative to the fixed part in ^r chain tensioning direction Part is surrounded by a first stop ring limiting its return movement, characterized in that the first stop ring is designed as a retaining clip (15, 35), the legs of which engage in a radially prestressed manner in a locking groove (16 to 18, 36 to 38) of the displaceable part and when it is shifted axially against a fixed stop.

2. Device according to claim 1, characterized in that as the displaceable part, the tensioner housing (2) is guided in a cylinder bore (10) of a fixed receptacle housing (3), the fixed stop being arranged on the receptacle housing (3) and by a second stop ring (22) is formed, which is inserted radially pre-stressed in an inner circumferential groove of the receiving housing (3).

3. Apparatus according to claim 2, characterized in that on the tensioner housing (2) a plurality of locking grooves formed as outer circumferential grooves (16,

17, 18) are arranged one behind the other for receiving the retaining clip (15) at axial intervals.

4. The device according to claim 2, characterized in that in the receiving housing (3) fully inserted position of the tensioner housing

(2) a transport securing bracket (20) can be attached to the receiving housing (3), which engages in a circumferential groove (21) of the tensioner housing (2).

5. The device according to claim 4, characterized in that the transportsi¬ securing bracket (20) between the retaining clip (15) and the second stop ring (22) is arranged.

6. The device according to claim 2, characterized in that the Spannerge¬ housing (2) and the piston (1) are held together by an outwardly preloaded securing ring (4) which is partially in a circumferential groove (5) of the piston (1 ) protrudes radially and can also be axially applied to a ramp (6) of the tensioner housing (2) surrounding it.

7. The device according to claim 6, characterized in that the circumferential groove (5) of the piston (1) is designed with a smaller than the diameter of the safety ring (4), the complete inclusion of which groove base diameter is designed.

8. The device according to claim 1, characterized in that the piston (1) and the tensioner housing (2) are steel parts, while the receiving housing (3) consists of an aluminum alloy.

9. The device according to claim 1, characterized in that as a displaceable part, the tensioner housing (2) in a cylinder bore (10) of a fixed 'receiving housing (3) is guided, the fixed stop on the receiving housing (3) being arranged and is formed by a second stop ring (22) which is pressed into the cylinder bore (10) of the receiving housing (3).

10. The device according to claim 1, characterized in that as a displaceable part of the piston (24) in the tensioner housing (25) is guided, which is inserted into a cylinder bore of a fixed receiving housing (27), the fixed abutment surface on the receiving housing ( 27) and is formed by a second stop ring (42) which is inserted in a radially prestressed manner in an inner circumferential groove of the receiving housing (27).