WO2008058814A1

WO2008058814A1 - Optimized damping for a hydraulic clamping system

Info

Publication number: WO2008058814A1
Application number: PCT/EP2007/060739
Authority: WO
Inventors: Werner Petri; Marco Kowalski
Original assignee: Schaeffler Kg
Priority date: 2006-11-18
Filing date: 2007-10-10
Publication date: 2008-05-22
Also published as: DE102006054393A1

Abstract

The invention relates to a hydraulic clamping system (1 ), which is used in a traction drive for internal combustion engines. The clamping system (1) comprises a housing (2) for holding a cylinder (3) in which a piston (4) is guided in a longitudinally displaceable fashion. The piston (4) bounds, together with the cylinder (3), a pressure space (8) which is filled with hydraulic fluid. During an actuating movement of the piston (14) in the direction of the pressure space (8), some of the hydraulic fluid can flow from the pressure space (8) into the reservoir space (10) in which the control valve (15a) which is integrated into the piston (14) opens after a defined pressure has been reached. A reversed actuating movement of the piston (14) causes the one-way valve (20) which is integrated into the control valve (15a) to open, as a result of which the hydraulic fluid flows into the pressure space (8) from the reservoir space (10).

Description

Name of the invention

Optimized damping for a hydraulic tensioning system

Field of the invention

The present invention relates to a hydraulic tensioning system which is used in a endless drive, in particular a belt drive of an internal combustion engine. The clamping system comprises a housing for receiving a cylinder, in which a spring-loaded and acted upon by a hydraulic fluid piston is longitudinally movably guided, which preferably interacts indirectly via a tensioning roller with the traction means. The piston delimits together with the cylinder a filled with hydraulic fluid pressure chamber. A linear actuating movement of the piston causes a flow and, associated therewith, a volume exchange of the hydraulic fluid between the pressure chamber and the reservoir. The volume exchange from the pressure chamber into the storage space takes place via a leakage gap and in the reverse direction via a one-way valve.

Background of the invention

Hydraulic clamping systems in traction drives have the task of ensuring sufficient bias of the traction device, the belt or the chain. Furthermore, it is the task of the clamping systems to dampen vibrations occurring in the traction mechanism. The damping of the hydraulic clamping system via the leakage gap, which is set between the lateral surface of the piston and the inner wall of the cylinder. The damping force of the leakage gap, which may also be referred to as a laminar gap damper, is determined by the operating state, in particular the operating temperature and the piston speed. The disadvantage produced in previous hydraulic clamping systems mainly used Laminarspaltdämpfer or Leckspaltdämpfer in the starting phase of the internal combustion engine and at low ambient temperature high damping force, combined with a disadvantageously increased load on all units that are connected to the traction drive.

A generic hydraulic tensioning system is known from JP 11 101 319 A. During a movement of the piston in the direction of the pressure chamber, a subset of the hydraulic fluid in the pressure chamber is displaced exclusively via a leakage gap, an adjusting annular gap between the piston and an inner wall of the cylinder in the direction of the storage space. An opposite piston movement causes a negative pressure in the pressure chamber, whereby a one-way valve or check valve located in the piston opens and ensures an inflow of the hydraulic fluid from the reservoir into the pressure chamber.

From the further document, DE 196 09 420 A1 discloses a hydraulic tensioning system is known, in which, comparable to the previously described prior art, with a displacement of the piston in the direction of the pressure chamber, the hydraulic fluid via an annular gap formed as a leakage gap between the piston and the Cylinder is displaced into the storeroom. A subsequent flow of the hydraulic fluid into the pressure chamber with an opposite piston movement takes place via a one-way valve positioned in the cylinder, which is connected to the reservoir via an inflow channel.

Summary of the invention

Considering the disadvantages of the known hydraulic tensioning systems, it is an object of the present invention to provide a tensioning system with a largely temperature-independent damping and a force limitation.

According to the invention, this problem is solved by the features of claim 1. According to the invention, a spring-loaded control valve is incorporated to form a further leakage gap in the piston, which exerts a limiting damping force. The design of the control valve takes place in such a way that a response, ie opening of the valve in dependence on the internal pressure, is established before a subset of the hydraulic fluid flows out via the leakage gap formed between the piston and the cylinder as an annular gap.

In the operating state, an overpressure arises in the pressure space, as a result of which a subset of the hydraulic fluid is displaced beyond the leakage gap. The overpressure determining the damping force in the pressure chamber results from the height of the leakage gap and the operating conditions, in particular the ambient temperature. All known solutions of hydraulic clamping systems show a leakage gap unchanged height, which results in no influence or adjustment of the damping force.

Deviating from this, the invention shows by the further integrated in the piston control valve a leakage gap, which automatically adjusts depending on the operating conditions, whereby always an optimum for the traction drive damping force in the operating state can be achieved.

Due to the self-adjusting temperature-independent damping of the inventive hydraulic tensioning system disadvantageous for individual units high forces due to large positioning movements of the clamping system are limited in particular in the starting phase of the internal combustion engine. The self-adjusting force limitation advantageously favors the life of the traction mechanism drive, in particular the traction means.

Due to the design of the passage cross sections and / or the spring loading of the control valve according to the invention, the damping forces of the hydraulic clamping system are largely independent of the viscosity and the temperature of the hydraulic fluid and the component temperatures of the clamping system adjustable.

Further advantageous embodiments of the invention are the subject of the dependent claims 2 to 13. A preferred embodiment of the invention provides to arrange a multi-function designed as a control valve in the bottom of the piston. The construction of this control valve includes both the function of a defined leakage gap and the function of a one-way valve. This structure simplifies the assembly and includes a cost advantage by the multi-function part is prefabricated used in the piston.

For manufacturing reasons, a leakage gap forming guide play is established between the piston and the cylinder. The volume flow passing through the control valve thereby exceeds the volume flow of the leakage gap. Furthermore, the invention includes that the bypass passage passing through the guide clearance is completely prevented by the use of a suitable sealing element.

Underlining the effectiveness of the control valve according to the invention, a defined leakage gap aspect ratio of 1 <0.4 is provided for the inventive hydraulic tensioning system. This cross-sectional ratio causes a priority main flow of the fluid through the control valve and a small bypass flow through the gap formed as an annular gap between the piston and the inner wall of the cylinder. This cross-sectional ratio causes a desired force-limited leak gap opening, whereby the entire load of the traction drive is limited.

A preferred embodiment of the control valve according to the invention further includes a truncated cone-shaped valve body which is inserted and guided in a correspondingly tapered receptacle of the piston.

An advantageous further embodiment of the invention provides that the truncated cone-shaped valve body designed so that it also includes the check valve. For this purpose, the valve body preferably includes a step-shaped bore which is intended for example for receiving a one-way valve provided as a ball valve or plate valve. As an alternative to a combined solution in which the control valve and the one-way valve form a component, it makes sense to position the one-way valve radially offset from the control valve arranged centrally in the piston.

Another inventive design of the clamping system comprises a control valve, consisting of a cylindrical and pot-shaped housing with a control bore which cooperates with a control edge of the piston. The construction of the pot-like housing also allows the inclusion of a ball valve designed as a one-way valve.

As a control valve is still a used in the piston, pressure-dependent elastically deformable housing. Preferably, the housing is made of a thin-walled plastic that constricts radially with increasing pressure in the pressure chamber of the clamping system, connected to an automatic enlargement of the leakage gap. The pot-like housing further advantageously includes in the region of the bottom a one-way valve constructed as a plate valve, whereby a compact design is established.

The invention further includes as a control valve a transverse to the axis of symmetry of the piston adjustable, a control bore enclosing a slide. An increase in pressure in the pressure chamber causes an adjustment of the slide, wherein a leakage gap or a defined throttle opening is set in a positional coincidence between the control bore and openings of the piston. As a slider is preferably a cylindrical piston which is displaceable in a receiving bore. To achieve a minimum height of the leakage gap, it is advisable, for example, to provide a truncated cone-shaped valve body of the control valve on the lateral surface with ribs or partial projections, resulting in a narrow, defined leakage gap and thus constant outflow of the hydraulic fluid from the pressure chamber adjusts the pantry. An increasing pressure in the pressure chamber, which forms an overpressure relative to the reservoir, causes a displacement of the spring-loaded valve body. The thereby increasing leakage gap limited the damping force or allows a defined adjustment of the damping force. By a suitable design of the control valve, in particular of the truncated cone-shaped valve body in conjunction with a corresponding Anfder- tion, there is an adjustment of the damping force as a function of operating conditions, in particular the pressure in the high pressure chamber and / or the component temperature.

The springing of the valve body or the adjustable slide in the clamping system according to the invention can be done in many ways. Preferably, compression springs or leaf springs are suitable. Furthermore, the invention includes a control valve, the housing of which includes elastic portions, thereby increasing the leakage gap when the pressure increases.

Brief description of the drawings

Embodiments of the invention will be explained with reference to the figures, from which further advantages and details of the invention result. The figures are schematic representations and show in longitudinal section:

Figure 1 is a hydraulic tensioning system in a known construction;

Figure 2 shows a first embodiment of a control valve according to the invention, provided with a truncated cone-shaped, designed as a multi-function part valve body;

Figure 3 shows a second embodiment of a control valve according to the invention, in which the one-way valve is arranged separately from the control valve.

Figure 4 shows a third embodiment in which the control valve is acted upon by a leaf spring; Figure 5 shows a fourth embodiment, which includes a control valve with a pot-like housing, in which at the same time the one-way valve is integrated;

Figure 6 shows a fifth embodiment with an adjustable slide as a control valve;

Figure 7 shows a sixth embodiment in which a resiliently deformable housing is provided as the control valve, which also includes a plate valve.

Detailed description of the drawings

The illustrated in Figure 1 hydraulic tensioning system 1 comprises a pot-shaped housing 2, in which a cylinder 3 is centrally introduced, which is intended to receive a longitudinally displaceable piston 4. Both the housing 2 and the piston 4 are provided with a fastening eye, 5a, 5b, with which the housing is pivotally mounted on a stationary component, such as the housing of the internal combustion engine. The piston 4 is preferably via a not shown in Figure 1 pivoting lever indirectly with a tensioner in conjunction. In the operating state, the hydraulic tensioning system 1 is subjected to a force from the traction mechanism via the tensioning roller, whereby a force "F" acts in the direction of the arrow on the piston 4. The force "F" is counteracted by a compression spring 6, which with a spring end acts on the housing 2 and the other spring end is supported on a spring plate 7, which is fixed in position on the piston 4. Vibrations of the traction means cause an oscillating movement of the piston 4. To damp these adverse adjusting movements of the piston 4, the hydraulic tensioning system 1 includes a damping device 7 a. For this purpose, a limited by the piston 4 and the cylinder 3 pressure chamber 8 is filled with a hydraulic fluid, in particular an oil. With a force "F" which exceeds a resultant force of the compression spring 6, a pressure "P" builds up in the pressure chamber 8, which causes a movement of the piston 4 and consequently a volume exchange, a flow of the hydraulic fluid. likfluids of the pressure chamber 8 via a designed as an annular gap 19 leakage gap between the lateral surface of the piston 4 and an inner wall 9 of the cylinder 3 triggers. The escaping hydraulic fluid passes into a circular-shaped reservoir space 10 which is bounded on the outside by the housing 2 and on the inside by the outer wall of the cylinder 3. With a decreasing force "F", the piston 4 is displaced from the cylinder 3 by the resultant force of the compression spring 6, whereby a pressure difference, a negative pressure in the pressure chamber 8 adjusts and the hydraulic fluid flows from the reservoir 10 into the pressure chamber 8. The inflow permits a bottom-mounted one-way valve 11 which is assigned to the cylinder 3 and which communicates with the storage space 10 via a fluid channel 12. A spring-loaded ball of the one-way valve 11 opens as soon as a pressure difference between the pressure space 8 and the storage space 10 is established.

Figures 2 to 7 each show in an enlarged view in a detailed drawing variants of damping devices according to the invention.

The damping device 13a shown enlarged in the figure 2 is formed by a centrally inserted in the piston 14 control valve 15a. The control valve 15a comprises a truncated cone-shaped valve body 16a, which is inserted into a correspondingly conical receptacle 17 of the piston and is acted upon by a compression spring 18. The designed as a multi-function part control valve 15a also serves to receive a spring-loaded one-way valve 20 which is also referred to as a check valve. When a piston force "F" exceeds a resultant of the pressure "P" in the pressure chamber 8, the piston 14 acting on the resultant force, the piston 14 shifts in the direction of the pressure chamber 8. When the force acting on the control valve 15a pressure force F _p the force of the compression spring 18 exceeds, moves a the leak gap 21 increasing adjusting movement of the control valve 15 a is. In this case, the control valve 15a opens, wherein a main flow of the hydraulic fluid passes through the leakage gap 21 forming the control valve 15a into the reservoir 10. Due to an installation play between the piston 14 and an inner wall of the cylinder 3 continues to form a bypass flow of the hydraulic fluid via the annular gap 21 forming a leakage gap. A movement of the piston 14 directed in the direction of the force "F", connected to a negative pressure in the pressure chamber 8, leads to an opening of the one-way valve 20, whereby hydraulic fluid passes from the storage space 10 into the pressure chamber 8. In the end position of FIG Control valve 15a adjusts a defined leakage gap 21, which is formed by partial arranged on the outer circumference of the valve body 16a ribs 22 and local projections, which may alternatively be arranged in the region of the receptacle 17.

FIG. 3 shows the damping device 13b, in which the one-way valve 23 is arranged radially offset from the valve body 16b in the piston 14. The remaining structure and the operation of the damping device 13b corresponds to the damping device 13a shown in FIG.

FIG. 4 shows the damping device 13a according to FIG. 2, which, as an alternative to a compression spring, includes a leaf spring 24 which interacts directly with the valve body 16a.

The damping device 13c according to FIG. 5 comprises a pot-shaped, cylindrical housing 25, which is displaceably inserted in a stepped bore 26 of the piston 14. In the illustrated end position, the control valve 15c is fixed in position on a retaining ring 27 inserted in the piston 14. A shift of the control valve 15c within the piston 14, starting from the circlip 27, allows a main flow of the hydraulic fluid from the pressure chamber 8 into the reservoir 10 as soon as an overlap occurs between the control bore 29 of the control valve 15c and a control edge 30 of the piston 14. Parallel to this, a bypass flow of the hydraulic fluid over the formed as an annular gap 21 leakage gap between the piston 14 and the cylinder 3 a. A reversal of the piston movement causes a suction of the hydraulic fluid from the reservoir 10 into the pressure chamber 8 via the one-way valve 31 integrated within the control valve 15c. The damping device 13d depicted in FIG. 6 includes a control valve 15d, which encloses a slide 33, which can be displaced transversely to an axis of symmetry 32 of the piston 14. The slide 33 inserted in a transverse bore of the piston 14 is spring-loaded supported on a stop 34 and includes a control groove of the control bore 35 a. An adjusting movement of the piston 14 in the direction of force "F" causes an increase in pressure within the pressure chamber 8. The pressure increase is simultaneously transmitted via a bore 36 of the piston 14 to the slider 33, whereby this shifts in the direction of the one-way valve 23. By overlapping the control bore 35 of the slide with the openings 37a, 37b of the piston 14, a leakage gap is established which forms the main flow of the hydraulic fluid from the pressure chamber 8 into the reservoir 10. A reverse piston movement causes a volume exchange of the hydraulic fluid from the reservoir 10 in the pressure chamber 8 via the one-way valve 23rd

The damping device 13e according to FIG. 7 comprises the control valve 15e, in which a one-way valve 38 designed as a plate valve is integrated at the same time. The control valve 15 e comprises an elastically deformable housing 39, which is inserted into a receptacle 40 of the piston 14. Between the housing 39 and the receptacle 40, a leakage gap 41 is formed, which is formed for example by ribs of the receptacle 40, in which the housing 39 is guided. A movement of the piston 14 in the direction of the pressure chamber 8, connected to a pressure increase leads to a desired elastic deformation of the housing 39, whereby the leakage gap 41 and thus the main flow of the hydraulic fluid from the pressure chamber 8 in the reservoir 10 increases. A reverse piston movement allows a subsequent flow of the hydraulic fluid from the reservoir 10 through the cup-shaped housing 39 via the plate valve designed as a 38 integrated in the housing 39 one-way valve. LIST OF REFERENCE NUMBERS

1 hydraulic clamping system

2 housings

3 cylinders

4 pistons

5a fixing eye

5b fixing eye

6 compression spring

7 damping device

8 pressure chamber

9 inner wall

10 pantry

11 one-way valve

12 fluid channel

13a damping device

13b damping device

13c damping device

13d damping device

14 pistons

15a control valve

15b control valve

15c control valve

15d control valve

15e control valve

16a valve body

16b valve body

17 recording

18 compression spring

19 annular gap

20 one-way valve

21 annular gap 22 rib

23 one-way valve

24 leaf spring

25 housing

26 stepped bore

27 circlip

28 compression spring

29 control bore

30 control edge

31 one-way valve

32 symmetry axis

33 pushers

34 stop

35 control bore

36 bore

37a opening

37b opening

38 one-way valve

39 housing

40 recording

41 leakage gap

Claims

claims

1. Hydraulic tensioning system, used in a endless drive, in particular belt drive of an internal combustion engine, comprising a housing (2) for receiving a cylinder (3) by a sprung, acted upon by a hydraulic fluid, with a traction means indirectly cooperating piston (4) is longitudinally movably guided, wherein the piston (4) together with the cylinder (3) a hydraulic fluid-filled pressure chamber (8) limited and a linear adjusting movement of the piston (4) a flow connected to a volume exchange of the hydraulic fluid from the pressure space (8 ) in a storage space (10) via an annular gap (19) between the piston (4) and the cylinder (3), wherein the designed as a leakage gap annular gap (19) by a damping device (13a, 13b, 13c, 13d) formed and in the case of a reverse displacement movement of the piston (4), a volume exchange takes place via a one-way valve (11, 20, 23, 31, 38), characterized in that the piston (4) integrates Damaged damping device (13a, 13b, 13c, 13d) includes a spring-loaded and / or pressure-dependent opening control valve (15a, 15b, 15c, 15d, 15e).

2. Tensioning system according to claim 1, characterized in that in the piston (4) constructed as a multi-functional part control valve (15a, 15c, 15e) is used, which additionally performs the function of the one-way valve (20, 23, 38).

3. Clamping system according to claim 1, characterized in that the control valve (15a, 15b, 15c, 15d, 15e) associated leakage gap to the self-adjusting leakage gap (21) between the cylinder (3) and the piston (3) in a cross-sectional ratio are designed from 1 <0.4.

4. Clamping system according to claim 1, characterized in that the control valve (15a, 15b) comprises a truncated cone-shaped valve body (16a, 16b) which is guided in a corresponding conical receptacle (17) of the piston (4).

5. Tensioning system according to claim 4, characterized in that in the valve body (16 a) of the control valve (15 a), the one-way valve (20) is introduced.

6. Clamping system according to claim 1, characterized in that radially offset from the in the piston (4) integrated control valve (15b, 15g), the one-way valve 23 is positioned.

7. A clamping system according to claim 1, characterized in that the control valve (15c) includes a cylindrical and cup-shaped housing with integrated one-way valve (23), wherein the displaceably inserted housing (25) comprises a control bore (29) with a control edge ( 30) of the piston (14) cooperates.

8. Clamping system according to claim 1, characterized in that a transverse to an axis of symmetry (32) of the piston (14) adjustable slide (33) is provided as a control valve (15d), the control bore (35) or groove together with openings (37a, 37b) of the piston (14) form a leakage gap.

9. Clamping system according to claim 1, characterized in that in the piston (14) as a control valve (15 e), a housing (39) is integrated, which is elastically deformable pressure-dependent.

10. Clamping system according to claim 9, characterized in that the

Control valve (15d) is designed as a multi-function part and includes a designed as a plate valve one-way valve (38). H. clamping system according to claim 1, characterized in that the lateral surface of the valve body (16a, 16b) and / or the control valve (15e) ribs (22) or partial projections which define a minimum height of the leakage gap (21).

12. A clamping system according to claim 1, wherein the control valve (15a, 15b, 15c, 15d) is acted upon by a compression spring.

13. Clamping system according to claim 1, wherein a leaf spring (24) with the

Control valve (15a) cooperates.