DE19680418C1 - IC engine chain or belt tensioner - Google Patents

Abstract

In the tensioner housing (2) is located a spring actuated piston, with the housing and piston relatively slidable. The part, slidable in the chain tensioning direction w.r.t. the fixed part, is surrounded by a first stop ring, limiting its resetting motion. The front stop ring is in the form of a holding clamp (15), whose shanks engage an arrester groove (16-18) of the slidable part with a radial prestress. On displacement of the slidable part, the shanks abut a fixed stop. The tensioner housing is pref. guided in a cylindrical bore (10) of a fixed retainer housing (3).

Description

Field of the Invention

The invention relates to a tensioning device for the chain or the belt an internal combustion engine, for example the camshaft drive a cylindrical tensioner housing and one arranged therein from a compression spring loaded piston which is axially relative to each other are slidable, the opposite to the fixed part in chain tension Part that can be moved in the direction of a return movement surrounding first stop ring.

Background of the Invention

Such a tensioning device is in the empty run of the chain drive arranged. The compression spring guides the tension forces into the empty run of the timing drive. There occur on average during normal operation lower tension forces than in the work or train section, so that Compression spring can be designed according to these lower clamping forces can. Due to the force of the compression spring, the one acting on the chain moves Piston-tensioner housing unit apart and generates the required chain tension.

This unit can be used as a hydraulic damping device with a Oil storage room, a high pressure room and one in between Check valve be formed. Hydraulic oil in it, which due to its pressure, the effect supports the compression spring, can  the leakage gap formed by the piston and the tensioner housing Overcoming the fluid friction from the high pressure room be pressed when the piston-tensioner housing unit with force shocks is acted upon by the chain drive.

When using such a clamping device, in special cases, which the high-pressure chamber is not yet or only partially filled with oil and the pressure of the oil in the high pressure room is not or not yet has built up, the required chain tension is not reached. Then the clamping device under the action of force shocks Chain drive suddenly retract because of sufficient damping effect is not present. There is also a special case, for example with an engine of a motor vehicle if this is in the direction of travel is turned uphill with the forward gear engaged so that the engine wants to turn backwards due to the weight of the vehicle. This creates a train in the empty strand of the chain. Without one that limits the return In such a case, the stop ring is the after a long engine standstill Piston tensioner housing unit of the hydraulic pressure generator completely retracted due to the greater chain tension. If so the engine is suddenly relieved by starting the engine, the necessary chains are missing due to the piston being retracted far tension and there can be an uncontrolled beating of the chain. Then the chain on the camshaft drive can have one or more Skip teeth on the drive gear. This will make one Control time adjustment of the valve train causes, for example, by Knocking the valve disc onto the piston crowns will result in engine damage Has.

The document EP 0 615 076 A1 shows a chain tensioning device a receiving housing and a piston cylindrical tensioner housing. The piston is in a bore of the Receiving housing arranged in the axial direction, with its  Return stroke movement is limited by a ratchet device. For this is one in the correspondingly solid housing additional cross hole required, in which a ratchet piston is led. The ratchet piston has an angled end surface. As a result, a tooth is formed on it, which in the circumferential grooves of the retractable piston can engage. For the movement of the A compression spring is provided on one end of the ratchet piston, while on the other, formed by the angled end face Pressure oil is present at the front. For this you must also in the Receiving housing supply lines can be arranged.

From the publication DE 36 36 918 A1 is a tensioning device known type. There it works from the solid Retractable piston extendable pistons in the clamping direction towards exciting chain. When putting this chain tensioner into operation the first stop ring snaps into a first locking groove of the Tensioner housing. This position is the beginning of the chain tension area. If the pressure in the high pressure chamber is not sufficient to Bringing the piston to a stop under load hits a stop edge the piston onto the first stop ring. This will make the Return movement of the piston into 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, being a certain minimum wire diameter due to the interaction with regard to the dimensional tolerances and strengths of the components may fall below. With this minimum diameter, the Wire of the stop ring, the ring diameter during operation must be able to be changed slightly, but already has a high rigidity when changing to a smaller ring diameter while maintaining same wire diameter increases significantly.

Summary of the invention

The invention has for its object to a tensioning device create that requires less installation space and therefore overall has smaller dimensions than previously known chains Stretcher.

This object is achieved in that the first Stop ring is designed as a retaining clip, the legs of which are radial pre-tensioned and engage in a locking groove of the sliding part the displacement of which can be axially applied to a fixed stop. By the use of a retaining clip instead of a circular stop Ringes for the sinking protection can with reduced diameter of the Rastrille the stiffness of this limiting device within portable limits can be held without reducing the wire diameter. With unchanged rigidity of the first designed as a retaining clip Stop ring, the force of the compression spring can remain the same, so that the action of an undesirably high or widely varying spring force on the chain to be tensioned is avoided.

The tensioner housing can be moved in a cylinder bore be guided by a fixed housing, the fixed stop on Receiving housing arranged and by a second stop ring is formed, which is radial in an inner circumferential groove of the receiving housing is used biased. But it is also possible that as slidable part of the pistons is guided in the tensioner housing, which in a cylinder bore of a fixed receiving housing is plugged in.

Several can be on the tensioner housing as outer circumferential grooves trained locking grooves for receiving the retaining clip in axial Distances can be arranged one behind the other. In the in the housing  fully inserted position of the tensioner housing is a trans port securing bracket can be attached to the receptacle housing, which in an order catch groove of the tensioner housing engages. This can be between the Holding bracket and the second stop ring may be arranged. The Transport safety bar is after the assembly of the clamping device on Motor removed, whereupon the operating position of the tensioning device sets. The retaining clip now forms the mechanical sink protection for the tensioner housing, so that its return stroke in the receiving housing in the case of an empty high-pressure room and a high one off the chain acting force is limited. In addition, the bracket acts as mechanical decay protection, it holds the piston- Tensioner housing receptacle together.

The tensioner housing and the piston can also move from one to the other externally biased locking ring are held together, which partially protrudes radially into a circumferential groove of the piston and the rest can be axially applied to a ramp of the tensioner housing surrounding it. In this case, the circumferential groove of the piston with one against the Reduce the diameter of the circlip, its complete The groove base diameter that enables the recording to be made.

The piston and the tensioner housing can be steel parts, while that 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:

FIG. 1 is pointing in the chain tensioning direction end view of a clamping apparatus;

Figure 2 is a bottom view of the receiving housing of the Spannvor direction according to arrow II of Fig. 1.

3 shows a longitudinal section through the clamping device in the retracted state of the tensioner housing.

Fig. 4 shows a longitudinal section along line IV-IV of Figure 3 by the clamping device, but with the tensioner housing extended.

Figure 5 shows a longitudinal section through a modified Spannvorrich device in the retracted state.

Fig. 6 shows a longitudinal section through the modified Spannvorrich 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 3rd 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 is 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 the 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 connecting 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 megehousing 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 compression spring 13 effects the extension of the tensioner housing 2 from the accommodating case 3 and the piston 1 continues in the chain tensioning direction during power surges from the chain against the action of the compression spring causes the retraction of the tensioner housing 2 13 in the receptacle housing 3 and via the piston. 1 The check valve 7 , which works 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 in the high pressure chamber 8 through the leak gap 14 comes out of the tensioner housing 2, which is located between the piston 1 and the tensioner housing. 2 This pressing out of hydraulic oil from the high-pressure space 8 of the tensioner housing 2 is associated with a high level of 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 acting as a first stop ring, for which a plurality of locking grooves arranged one behind the other in the axial direction are attached to the tensioner housing 2 . Thus, the tensioner housing 2 from its bottom towards the piston 1 seen one after the other a first detent groove 16, a second locking groove 17 and a third locking groove 18. In one of the locking grooves 17 and 18 , the retaining clip 15 can engage and thereby hinder the further inward movement of the tensioner housing 2 in the receiving housing 3 , because there surface 19 comes into contact with an oblique stop.

In Fig. 3, the clamping device is shown in its transport position, the tensioner housing 2 is fully retracted 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 safety bracket 20 rests axially against a second stop ring 22 which is held in an inner circumferential groove of the receiving housing 3 . Moving out of the tensioner housing 2 from the accommodating case 3 is not possible as long as the transport securing bracket 20 is still located at one circumferential location in the peripheral groove 21 of the tensioner housing. 2

The jig is for the shipment mounted follows as: After assembly of the piston 1, the check valve 7, the compression spring 13 and the tensioner housing 2, the retainer clip is slid axially onto the tensioner housing 2 15, wherein it enters into the first locking groove sixteenth Then, the thus prepared piston tensioner housing unit is used of the receptacle housing 3 in the cylinder bore 10, and then the tensioner housing is fully pushed into the receptacle housing 3 against the action of the compression spring. 13 The second stop ring 22 can now 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 move out of the receptacle housing 3 due to the action of the compression spring 13 because the transport securing bracket 20 resting on the second stop ring 22 prevents such a movement. The receptacle housing can now be shipped and screwed into place on the engine, for which purpose it is provided with two screw holes 23 .

This clamping device shown in FIGS . 1 to 4 works as follows: After screwing on the motor, the transport lock 20 of the tensioner is removed, as a result of which it moves into its working position. Upon extension of the tensioner housing 2 from the cylinder bore 10 of the receptacle housing 3 due to the action of the compression spring 13, the holding bracket 15, which is located in the first locking groove 16 of the tensioner housing 2 and is biased against this, carried by the tensioner housing 2, until it abuts the second stop ring 22 is present. Such extension can be due to chain elongation such. 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 hill, so that the tensioner housing 2 due to a high chain force on the slack side by overcoming the force of the compression spring 13 is pushed back into the receptacle housing 3, 15 reaches the retaining clip to the inclined stop surface 19 of the receptacle housing 3 and verhin changed so further retraction or lowering of the tensioner housing 2 . This prevents the timing chain from skipping the teeth of your drive gear when the engine is restarted. In addition, is pushed out by this return stroke of the high pressure chamber 8 less oil, and thereby the, which is important when starting the engine for the filling of the high-pressure chamber 8 required amount of oil low in order to avoid noises which might occur due to lack of damping.

The tensioning device also ensures a minimum return stroke of the tensioner housing 2 , which is necessary to compensate for eccentricities of the chain wheels, thermal expansion and to provide a damping stroke. This stroke can be seen in FIG. 3 as the distance between the retaining 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 .

Inside the tensioner housing 25 there is a check valve 29 , which closes the interior, which acts as a high-pressure chamber 30 for hydraulic oil, from 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 extension of the piston 24 from the tensioner housing 25 in the chain tensioning direction during power surges from the chain, the retraction of the piston 24 against the action of the compression spring 33 in the tensioner housing 25 cause. 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 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 pressing out of hydraulic oil from the high-pressure chamber 30 is associated with a high level of fluid friction and therefore has a damping effect on power surges which the chain to be tensioned transmits to the piston 24 .

The piston 24 is surrounded by a two-legged U-shaped retaining clip 35 acting as a first stop ring, 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 oblique stop surface 39 there.

In Fig. 5 the clamping device is shown in its transport position, the piston 24 is completely retracted into the receiving housing 27 and is held there by a transport securing bracket 40 which engages in the outer end region of the piston 24 in a circumferential groove 41 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 lies 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 . The receptacle housing 27 is provided with two screw holes 43 for fastening the clamping device to the engine at the place of use. The Monta ge for shipping and the operation of this according to FIGS. 5 and 6 modified clamping device correspond to the assembly and operation described for the clamping device according to FIGS. 1 to 4.

With the invention, clamping devices with mechanical sinking protection are created, which can be executed with a very small outer diameter, for example less than 14 mm. 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 for the mounting on the motor for locking the displaceable part (the tensioner housing 2 or the piston 24 ) with the transport securing brackets 20 , 40 simply constructed transport locks.

The holding brackets 15 , 35 of the clamping devices can consist of a spring steel which is bent in a U-shape and pretensioned so that they always rest on the circumference of the displaceable part (the clamping housing 2 or the piston 24 ). In the Spannvor direction 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 have 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 retaining 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 sprocket 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 necessary to compensate for eccentricities of the chain wheels and thermal expansions and to provide a damping stroke.

List of reference numbers

1

piston

2nd

Tensioner housing

3rd

Receptacle

4

Circlip

5

Circumferential groove

6

ramp

7

check valve

8th

High pressure room

9

Oil storage room

10th

Cylinder bore

11

Oil inlet

12th

Oil transfer groove

13

Compression spring

14

Leakage gap

15

Bracket

16

first locking groove

17th

second notch

18th

third notch

19th

sloping stop surface

20th

Transport safety bar

21

Circumferential groove

22

second stop ring

23

Screw hole

24th

piston

25th

Tensioner housing

26

Valve seat plate

27

Receptacle

28

Caulking

29

check valve

30th

High pressure room

31

Oil inlet

32

Oil transfer groove

33

Compression spring

34

Leakage gap

35

Bracket

36

first locking groove

37

second notch

38

third notch

39

sloping stop surface

40

Transport safety bar

41

Circumferential groove

42

second stop ring

43

Screw hole

Claims (9)

1. tensioning device for the chain or the belt of an internal combustion engine, for example the camshaft drive, with a cylindri's tensioner housing and an arranged therein, acted upon by a compression spring piston which are axially displaceable relative to one another, the slidable relative to the fixed part in the 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 radial groove in a locking groove ( 16 to 18 , 36 to 38 ) of the displaceable part and at the displacement of which can be axially applied to a fixed stop. 2. Apparatus according to claim 1, characterized in that the tensioning housing ( 2 ) is guided in a cylinder bore ( 10 ) of a fixed receiving housing ( 3 ) as a displaceable part, the fixed stop being arranged on the receiving housing ( 3 ) and by a second stop ring ( 22 ) is formed, which is inserted in the receiving housing ( 3 ) radially biased. 3. Device according to claim 2, characterized in that on the tensioner housing ( 2 ) a plurality of locking grooves ( 16 , 17 , 18 ) designed as outer circumferential grooves are arranged one behind the other at axial intervals for receiving the retaining clip ( 15 ). 4. The device according to claim 2, characterized in that in the fully inserted into the receiving housing ( 3 ) position of the tensioner housing ( 2 ) a transport securing bracket ( 20 ) on the receiving housing ( 3 ) can be attached, which in a circumferential groove ( 21 ) of the Tensioner housing ( 2 ) engages. 5. The device according to claim 4, characterized in that the transport 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 tensioner housing ( 2 ) and the piston ( 1 ) are held together by an outwardly biased locking ring ( 4 ) which partially projects radially into a circumferential groove ( 5 ) of the piston ( 1 ) and otherwise it can 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 ) with a smaller than the diameter of the locking ring ( 4 ), the complete inclusion of which groove base diameter is executed. 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 the 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 ) arranged and formed by a second stop ring ( 42 ), which is inserted radially biased into an inner circumferential groove of the receiving housing ( 27 ).