WO2009003825A1

WO2009003825A1 - Tensioning device for a traction mechanism

Info

Publication number: WO2009003825A1
Application number: PCT/EP2008/057489
Authority: WO
Inventors: Roman Kern; Reinhard Koch
Original assignee: Schaeffler Kg
Priority date: 2007-07-05
Filing date: 2008-06-13
Publication date: 2009-01-08
Also published as: DE102007031296B4; DE102007031296A1

Abstract

Disclosed is a tensioning device for a traction mechanism, especially a chain, comprising a piston that is guided in a longitudinally movable manner within a housing and is spring-loaded against the traction mechanism, a damping device for damping movements of the piston, a pressure chamber which is formed within the housing and from which hydraulic fluid, particularly engine oil, can be discharged via a leakage gap, and at least one valve that has a valve body which can be moved relative to a stationary valve section. The movable valve body (9, 15, 18, 21, 23) has a piston section which is designed such that a gap that dampens a movement of the valve body (9, 15, 18, 21, 23) is formed between the piston section (13, 24) and the stationary valve section (10).

Description

Name of the invention

Clamping device for a traction device

description

Field of the invention

The invention relates to a tensioning device for a traction means, in particular a chain, with a longitudinally movably guided in a housing, against the traction spring sprung piston and a damping device for damping movements of the piston, with a housing formed in the pressure chamber, from the hydraulic fluid, in particular engine oil, can be removed via a leakage gap and at least one valve which has a relative to a stationary valve portion movable valve body.

Background of the invention

From DE 10 2004 040 222 A1 a hydraulic tensioning device for a traction mechanism drive is known, which can be used, for example, in a chain drive of an internal combustion engine. A tensioned against a chain tensioning piston is taken longitudinally displaceable in a cylinder. The clamping piston and the cylinder limit a pressure chamber for receiving hydraulic fluid such as engine oil. Clamping movements of the clamping piston in the direction of the chain cause an enlargement of the pressure chamber, whereby due to the then adjusting negative pressure opens a check valve, so that engine oil can flow into the pressure chamber. If, on the other hand, the chain tightens, the tensioning piston is pushed inwards, away from the chain, reducing the pressure space. As the tensioning piston moves inward, engine oil is forced out of the pressure chamber by a leakage gap formed between the tensioning piston and the cylinder. The damping behavior can be influenced by the size of the leak gap. If the pressure in the pressure chamber becomes too large, an overpressure valve opens.

In practice, there is the disadvantage that check valves or pressure relief valves are excited dynamically during operation of the internal combustion engine, often they are even installed in moving components or connected to moving components in such a way that their vibration behavior is transmitted to the tensioning device. The occurring high pressure and velocity fluctuations of the hydraulic fluid to produce strong oscillatory movements of the sealing bodies of the valves, which adversely affect the function of the valves.

Summary of the invention

The invention has for its object to provide a clamping device whose dynamic behavior is improved.

To solve this problem is inventively provided in a clamping device of the type mentioned that the movable valve body has a piston portion which is formed such that when opening the valve, a movement of the valve body damping gap between the piston portion and the fixed valve portion is formed.

The invention is based on the finding that the dynamic behavior can be improved if instead of a conventional valve ball, a valve body is used with a piston portion which is formed so that between the piston portion and the fixed valve portion, a gap is formed, which has a damping effect exerts on the movable valve body. It is therefore preferred that the diameter of the Kolbenab- cut is smaller than the inner diameter of the stationary valve portion, whereby preferably an annular gap is formed. This annular gap acts as a leakage gap and prevents the occurrence of unwanted dynamic effects such as vibrations or resonance phenomena. In order to achieve an even better damping and in the opened state to achieve the fastest possible pressure reduction and the fastest possible outflow of the hydraulic fluid from the pressure chamber, it can be provided in the inventive clamping device that the piston portion at least one connected to the pressure chamber axial and has at least one associated radial bore and a stationary valve portion sealing sealing portion. According to this embodiment of the invention, the piston portion consists of a pressure chamber closing portion having the axial and the radial bore, to this section, the sealing portion connects, which has a larger diameter than the piston portion and rests on the stationary valve portion when the valve is closed , When opening the valve, the hydraulic fluid can flow out of the pressure chamber through the axial and the associated radial bore. According to one embodiment of the invention, it may also be provided that the piston section has a plurality of axial and / or radial bores.

According to an alternative embodiment of the invention, it may be provided that the piston portion has at least one groove connected to the pressure chamber and a sealing portion sealing the stationary valve portion. The at least one groove is formed on the outside of the piston portion and increases the gap formed between the piston portion and the fixed valve portion. In the closed state, a leakage of the hydraulic fluid from the pressure chamber is prevented by the sealing portion which seals the stationary valve portion and which is preferably acted upon by a spring element. In other variants, the piston portion may have a plurality of grooves connected to the pressure chamber.

According to a further variant of the tensioning device according to the invention, it can be provided that the at least one groove extends in a spiral shape. This circumferential groove also calms the dynamic behavior of the However, when opening the valve, it is ensured that the hydraulic fluid can flow out quickly.

In the clamping device according to the invention, it can also be provided that a sealing ring, in particular an O-ring, is arranged on the piston section and / or the stationary valve section. The sealing ring causes a mechanical damping of the movement of the movable valve body. In particular, the invention can be applied to a valve designed as a check valve or pressure relief valve (pressure relief valve).

Brief description of the drawings

Further advantages and details of the invention are described below with reference to embodiments with reference to the figures. The figures are schematic representations and show:

1 shows a first embodiment of a clamping device according to the invention in a sectional view.

Fig. 2 shows a second embodiment of an inventive

Tensioning means;

Fig. 3 shows a detail of a clamping device according to a third

Embodiment;

Fig. 4 shows a detail of a clamping device according to a fourth

Embodiment;

5 shows a section through the tensioning device shown in FIG. 4 along the line V-V; and

Fig. 6 shows an embodiment of a movable valve element. Fig. 1 shows a first embodiment of a hydraulic tensioning device 1, which consists essentially of a housing 2 and a longitudinally movably guided in the housing 2 piston 3. When installed, the outer end of the piston 3 bears against a chain of a traction means of an internal combustion engine.

Inside the housing 2 and a part of the piston 3, a pressure chamber 4 is formed, which is filled with a hydraulic fluid such as engine oil. A designed as a compression spring 5 spring element pushes the piston 3 as far out of the housing 2 until a balance between the spring force and the contact pressure is reached. When the piston 3 is displaced in the direction of the chain, the pressure chamber 4 increases, so that it sets a negative pressure, which causes a arranged in the bottom of the housing 2 check valve 6 opens and engine oil can flow into the pressure chamber 4.

When the chain is stretched again, the piston 3 is pressed into the housing 2, whereby the pressure chamber 4 is reduced. Through a leakage gap 7 between the piston 3 and the housing 2, engine oil is displaced from the pressure chamber 4. During normal operation, the piston 3 performs an oscillating motion, the piston travel normally being less than 1 mm. By the movement of the piston 3 there is a damping of the vibrations.

When the pressure in the pressure chamber 4 becomes too large, a pressure relief valve 8 opens, so that the engine oil can flow out through an axial opening in the piston 3. The pressure relief valve 8 comprises a movable valve body 9, which seals the pressure chamber 4 with respect to a stationary valve section 10. The movable valve body 9 is acted upon by the force of a compression spring 1 1.

As shown in Fig. 1, the movable valve body 9 consists of a first portion 12 whose outer diameter is larger than the inner diameter of the bore of the stationary valve portion 10 and one to the portion 12 integrally formed piston portion 13 which is in the closed state in the region of the stationary valve portion 10. In the closed state, the sealing of the pressure chamber 4 is carried by the portion 12 of the movable valve body, which rests on an annular surface of the stationary valve portion 10. Between the piston portion 13 and the fixed valve portion 10, an annular gap 14 is formed, which dampens the movement of the movable valve body 9, when it is dynamically excited. When opening the pressure relief valve 8, the hydraulic fluid through the annular gap 14 from the pressure chamber 4 and the front end of the piston 3 flow out.

Fig. 2 shows a second embodiment of a clamping device, wherein for identical components the same reference numerals as in Fig. 1 are used. The piston 3 and the housing 2 are constructed as in the first embodiment. Unlike in Fig. 1, the movable valve body 15 in the region of its piston portion has an axial bore 16 and a radial bore 17 connected thereto. When the pressure relief valve is closed, the movable valve body 15 rests on the annular surface of the stationary valve section 10 and closes the pressure chamber 4. When opening the pressure relief valve can hydraulic fluid from the pressure chamber 4 via the axial bore 16 and the radial bore 17 in the outer end of the piston 3 and drain from there to the outside. Through the holes 16, 17 can drain a larger volume, so that the pressure prevailing in the pressure chamber 4 pressure can be abruptly reduced.

Fig. 3 shows a further embodiment of a clamping device, wherein only the region of the pressure relief valve is shown. The movable valve body 18 consists of a piston portion 13 which is formed as in the embodiment shown in FIG. 2 and has an axial bore 16 and a radial bore 17. The sealing of the pressure chamber 4 is effected by a valve portion 19 which is formed obliquely and rests in the closed state on the annular surface 20 of the stationary valve portion 10 and the pressure chamber 4 closes. When the pressure relief valve is opened against the force of the compression spring 11, the movable valve body 18 in the in 3, so that the hydraulic fluid flows from the pressure chamber 4 via the axial bore 16, the radial bore 17 and past the valve portion 19 into the upper end of the piston 3.

4 and 5 show another embodiment of a clamping device. Fig. 4 is a sectional side view, Fig. 5 is a section along the line V-V. The movable valve body 21 has a total of four circumferentially distributed grooves 22 which extend vertically on the outside of the piston portion. The valve portion 19 seals as in the embodiment of Fig. 3 from the pressure chamber in the closed state. When opening the pressure relief valve hydraulic fluid flows from the pressure chamber 4 through the grooves 22 on the valve portion 19 over to the outer end of the piston 3. By the grooves 22 can quickly flow out a comparatively large amount of hydraulic fluid, so that the pressure is suddenly reduced.

6 shows a further embodiment of a movable valve body 23, which consists of a valve section 19 for sealing the annular surface of the stationary valve section 10 and a piston section 24 which has a spirally encircling groove 25 on its outer side. In the closed state, the groove 25 causes a calming of the movement of the movable valve body 23 when it is excited by dynamic effects. After opening the valve, the hydraulic fluid flows out through the clearance between the piston portion 24 and the recess of the stationary valve body at the valve portion 19.

reference numerals

1 clamping device

2 housings

3 pistons

4 pressure chamber

5 compression spring

6 check valve

7 leakage gap

8 pressure relief valve

9 valve body

10 valve body

11 compression spring

12 valve section

13 piston section

14 annular gap

15 valve body

16 hole

17 hole

18 valve body

19 valve section

20 ring surface

21 valve body

22 groove

23 valve body

24 piston section

25 groove

Claims

claims

1. clamping device for a traction means, in particular a chain, with a longitudinally movably guided in a housing, against the traction means-spring-loaded piston and a damping device for damping of

Movements of the piston, with a pressure chamber formed in the housing, from the hydraulic fluid, in particular engine oil, can be removed via a leakage gap and at least one valve having a relative to a stationary valve portion movable valve body, characterized in that the movable valve body

(9, 15, 18, 21, 23) has a piston section which is designed such that, when the valve is opened, a gap between the piston section (13, 24, 24) which damps the movement of the valve body (9, 15, 18, 21, 23) ) and the stationary valve portion (10) is formed.

2. Clamping device according to claim 1, characterized in that the diameter of the piston portion (13, 24) is smaller than the inner diameter of the stationary valve portion (10).

3. Clamping device according to claim 1 or 2, characterized in that the piston portion has at least one with the pressure chamber (4) connected to the axial bore (16) and at least one radial bore (17) and a stationary valve portion (10) sealing sealing portion ,

4. Clamping device according to claim 3, characterized in that the piston portion (13) has a plurality of axial and / or radial bores (16, 17).

5. Clamping device according to claim 1 or 2, characterized in that the piston portion has at least one with the pressure chamber (4) connected to the groove (22, 25) and a stationary valve portion (10) sealing sealing portion.

6. Clamping device according to claim 5, characterized in that the piston portion has a plurality of the pressure chamber (4) connected grooves (22, 25).

7. Clamping device according to claim 5 or 6, characterized in that the at least one groove (25) extends spirally.

8. Clamping device according to one of the preceding claims, characterized in that on the piston portion and / or the stationary

Valve section a sealing ring, in particular an O-ring, is arranged.

9. Clamping device according to one of the preceding claims, characterized in that the valve is a check valve (6) or an overpressure valve (8).