VALVE CAP FOR A NON-RETURN VALVE

Abstract

A non-return valve for a hydraulic tensioning system which is used in traction mechanism drives of internal combustion engines and which manipulates a hydraulic fluid flow between a pressure chamber and a reservoir. The non-return valve has a valve body which is inserted in a housing and which is embodied as a ball and which, when the non-return valve is closed, is supported in a spring-loaded fashion against a valve seat of a through-flow cross-section. When the non-return valve is open, the valve body is assigned to a valve seat of the housing and the flow cross-section (19) of the valve seat ensures a fluid flow through the non-return valve.

Description

FIELD OF THE INVENTION

The present invention relates to a non-return valve for a hydraulic tensioning system of traction mechanism drives of an internal combustion engine. In the operating state, the non-return valve enables a throughflow of hydraulic fluid from a hydraulic fluid reservoir into a high-pressure chamber in an expansion phase of the tensioning system. In the compression phase, the non-return valve has the task of limiting or preventing the hydraulic fluid flow. The structure of the non-return valve comprises a housing which is also referred to as a valve cap or holding means, in which housing in particular a valve body designed as a ball is inserted, which valve body is connected under spring loading to a throughflow cross section.

BACKGROUND OF THE INVENTION

DE 40 35 823 C1 discloses a hydraulic tensioning system for traction mechanism drives, in particular chain drives of an internal combustion engine. A tensioning piston which is pressed against the traction mechanism is held in a longitudinally movable manner in a cylinder. The tensioning piston and the cylinder delimit a pressure chamber for holding a hydraulic fluid. A movement of the tensioning piston in the direction of the traction mechanism, which may also be referred to as an expansion phase, brings about an enlargement of the pressure chamber, wherein as a result of a vacuum which is generated, a non-return valve opens, wherein hydraulic fluid can flow into the pressure chamber. In the compression phase, in the event of tensioning of the traction mechanism, the tensioning piston is loaded in the opposite direction, that is to say inwards, with the pressure in the pressure chamber increasing, as a result of which the tensioning piston moves inwards, synchronously to an activated partial amount of hydraulic fluid via a leakage gap generated between the tensioning piston and the housing. Consequently, in the compression phase, the non-return valve prevents a return flow of the hydraulic fluid from the pressure chamber into the storage chamber. Said known design leads to hydraulic adhesion of the valve body, which is designed as a ball, to the valve seat of the non-return valve.

Furthermore, a non-return valve design is known in which the valve body, which is designed as a ball, interacts with a valve seat, which is formed centrally as a bore, in the housing or the valve cap. The known non-return valves consistently have a design in which the valve body, effective closing at the start of the compression phase is hindered by a relatively narrow gap generated between the valve body, which is designed as a ball, and the housing or the valve cap, and by flow manipulation generated behind the valve body by the valve spring.

In the case of a design of the non-return valve in which the valve cap has a central flow cross section, said valve cap is closed off at the complete flow cross section of the valve by the valve body, the ball, with a space being formed between the valve spring, the valve cap and the ball, which space likewise causes hydraulic adhesion, since the hydraulic fluid cannot flow in unhindered, and is hindered on account of the sealing by the valve body and also by the valve body spring.

OBJECT OF THE INVENTION

The invention is based on the object of providing a functionally improved non-return valve with a reduced flow resistance in order to obtain an optimum inflow of the hydraulic fluid.

SUMMARY OF THE INVENTION

According to the invention, to solve said problem, a design of the hydraulic valve is provided in which, when the non-return valve is open, the valve body interacts with a valve seat of the housing, the associated flow cross section of which ensures a fluid flow through the non-return valve. According to the invention, the housing or the valve cap is designed such that a valve seat, which is assigned to the base of the housing, intentionally does not bring about a complete closure. The non-return valve according to the invention which is used in hydraulic tensioning systems ensures, in the open position, a fast and delay-free flow of the hydraulic fluid from the reservoir into the pressure chamber. Improved suction of the hydraulic fluid is thereby generated in the expansion phase, which leads to optimum switching behavior of the hydraulic valve. On the other hand, the design of the hydraulic valve according to the invention prevents a throughflow of hydraulic fluid in the compression phase. Furthermore, the measure according to the invention prevents a disadvantageous hydraulic adhesion of the valve body to the valve seat of the housing, which leads to improved hysteresis behavior during a reversal from the expansion phase into the compression phase.

Dependent claims 2-9 relate to further advantageous embodiments of the invention.

According to the invention, the valve seat on the base of the housing, which is also referred to as a valve cap, is formed by a flow cross section which does not enter into positively locking engagement with the valve body. In this way, even in the event of abutment of the valve body against the valve seat, a substantially unhindered flow of the hydraulic fluid into the pressure chamber can take place.

The flow cross sections in the base of the valve cap or of the housing may be of any desired geometrical shape, wherein regardless of their design, complete positively locking engagement is never generated between the valve body and the valve seat which forms a flow cross section. One preferred refinement provides a non-circular flow cross section which interacts with the valve body. Alternatively, according to the invention, it is expedient to insert into the base of the valve cap an oval, multi-cornered, for example triangular or tetragonal flow cross section, or a polygonal flow cross section with rounded corners.

According to the invention, it is also expedient for a plurality of flow cross sections to be arranged in the flat base of the housing or of the valve cap. Said flow cross sections are positioned such that, in an end position of the valve body against the valve seat of the base, said valve body covers the throughflow cross sections of the flow cross sections partially or in regions, such that a virtually unhindered inflow of hydraulic fluid is possible.

As a preferred example of an arrangement of a plurality of flow cross sections, three circular bores arranged close together should be provided, the outer contour of which bores forms an equilateral triangle. In the case of a central arrangement of said three bores, the valve body is supported, in an end position, on a central web between the bores, as a result of which the hydraulic fluid flow in the expansion phase is virtually uninfluenced.

It is provided in a further embodiment according to the invention that the flow cross section be formed in a convexly shaped portion of the base, with the radius of curvature of the base differing from the radius of the valve body, which is designed as a ball. For this purpose, the radius of curvature of the base is advantageously greater than that of the valve body. Alternatively suitable for this purpose is an inverse configuration, with the smaller radius of curvature of the base in relation to that of the valve body being restricted locally to a flow cross sectional region which is adjoined by a radius of curvature which is greater than that of the valve body. As a measure for preventing disadvantageous hydraulic adhesion, it is also expedient for the radius of curvature of the base, which is smaller than that of the valve body, to be provided in a stepped portion, wherein at the same time the flow cross sections are not circular but rather are, for example, oval.

The non-return valve according to the invention also includes an embodiment in which the base is designed such that a contact surface assigned to the valve body form different curvatures with two mutually perpendicular section planes which comprise in each case one movement axis of the valve body.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention are illustrated in the drawings which are described below, wherein the invention is not restricted to said exemplary embodiments. In the drawings:

FIG. 1 shows a longitudinal section of the design of a hydraulic tensioning system;

FIGS. 2a to 6c show individual part drawings of non-return valves according to the invention with differently designed flow cross sections in the base;

FIG. 2a shows a first exemplary embodiment of a non-return valve according to the invention;

FIG. 2b shows a plan view of the non-return valve according to FIG. 2a, in which the base encompasses an oval flow cross section;

FIG. 3a shows a second exemplary embodiment of a non-return valve according to the invention;

FIG. 3b shows the plan view of the non-return valve according to FIG. 3a, with a square recess as a flow cross section;

FIG. 4a shows a third exemplary embodiment of a non-return valve according to the invention;

FIG. 4b shows the plan view of the non-return valve according to FIG. 4a, with a polygonal flow cross section;

FIG. 5a shows a fourth exemplary embodiment of a non-return valve according to the invention;

FIG. 5b shows the plan view of the non-return valve according to FIG. 5a, in which the valve cap encompasses three bores arranged close together as a flow cross section;

FIG. 6a shows a fifth exemplary embodiment of a non-return valve according to the invention;

FIG. 6b shows the plan view of the non-return valve according to FIG. 6a; and

FIG. 6c shows the side view of the non-return valve according to FIG. 6b.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a sectional illustration of a hydraulic tensioning system 1 which is assigned to a traction mechanism drive and which interacts with a traction mechanism of a traction mechanism drive indirectly via a tensioning roller not shown in FIG. 1. The assembly comprises a housing 2 which is articulatedly connected in a positionally fixed and pivotable manner via a fastening lug 3a for example to a housing of the internal combustion engine. The housing 2 forms a pot-shaped component in which a cylinder 4 is inserted centrally, which cylinder 4 is designed to receive a linearly movable piston 5. The cylinder 4 in conjunction with the piston 5 delimit a hydraulic-fluid-filled pressure chamber 6 which is connected via a duct 8 of the housing 2 and a throughflow cross section 12 of the cylinder 4 to a reservoir 9 for the hydraulic fluid. Here, the reservoir 9 is delimited at the outside by the housing 2 and at the inside by the lateral surface of the cylinder 4. A pressure spring 10 which is also integrated in the cylinder 4 is supported with one spring end against a base of the housing 2 and with the other spring end against a disk 11 which is positionally fixed to the piston 5. The pressure spring 10 loads the piston 5 in the direction of a force direction “R” and brings about an actuating movement of the piston 5 and consequently the exertion of a force on a tensioning roller which is connected to the fastening lug 3b. Said piston movement, which is also referred to as an expansion movement, results in a vacuum in the pressure chamber 6, as a result of which hydraulic fluid flows into the pressure chamber 6 via the non-return valve 7 from the reservoir 9 through the duct 8 of the housing 2 and the throughflow cross section 12 of the cylinder 4. In the compression phase, during an inverse actuating movement of the piston 5 in the force direction “F”, the non-return valve 7 closes by virtue of a valve body 13 being supported sealingly on the valve seat 14. Here, the piston 5 which passes into the pressure chamber 6 displaces a partial amount of the hydraulic fluid out of the pressure chamber 6 into the reservoir 9 via a leakage gap 15 generated between the piston 5 and the cylinder 4.

FIGS. 2a-6c show variants of non-return valves designed according to the invention, which differ in particular by having differently designed flow cross sections in the base of the housing of the non-return valve.

FIGS. 2a and 2b show different views of the non-return valve 16, in which the pot-shaped housing 17, which is also referred to as the valve cap, encompasses in the base 18 an oval flow cross section 19 which forms the valve seat 21. On account of the oval shape of the flow cross section 19, the latter is not fully closed by the valve body 20, which is designed as a ball, in the end position. It is thereby possible in the expansion phase for a partial quantity of the hydraulic fluid to flow through the non-return valve 16.

According to FIGS. 3a, 3b, the base 18 of the non-return valve 16 has a square-shaped flow cross section 22, which likewise forms a valve seat 23 which is not fully closed by the valve body 20 bearing against it.

FIGS. 4a, 4b show a polygonal flow cross section 24 in the base 18 of the housing 17, which likewise does not permit complete positively locking engagement with the valve body 20.

A further variant is shown in FIGS. 5a, 5b, in which the non-return valve 16 encompasses, as a flow cross-section 26, three identically dimensioned bores which are formed in the base 18 in an equilateral triangle and which, together form a valve seat 27 which can be closed off by the valve body 20 only to a limited extent.

According to FIGS. 6a-6c, the non-return valve 16 encompasses a housing 17 with a base 18 which is designed such that a contact surface 31 assigned to the valve body 20 comprises two mutually perpendicular section planes 32a, 32b which in each case form a movement axis of the valve body 20 with different curvatures to one another.

LIST OF REFERENCE SYMBOLS

• • 1 Tensioning system
  • 2 Housing
  • 3a Fastening lug
  • 3b Fastening lug
  • 4 Cylinder
  • 5 Piston
  • 6 Pressure chamber
  • 7 Non-return valve
  • 8 Duct
  • 9 Reservoir
  • 10 Pressure spring
  • 11 Disk
  • 12 Throughflow cross section
  • 13 Valve body
  • 14 Valve seat
  • 15 Leakage gap
  • 16 Non-return valve
  • 17 Housing
  • 18 Base
  • 19 Flow cross section
  • 20 Valve body
  • 21 Valve seat
  • 22 Flow cross section
  • 23 Valve seat
  • 24 Flow cross section
  • 25 Valve seat
  • 26 Flow cross section
  • 27 Valve seat
  • 28 Flow cross section
  • 29 Valve seat
  • 30 Gap dimension
  • 31 Contact surface
  • 32a Section plane
  • 32b Section plane

Claims

1. A non-return valve of a hydraulic tensioning system of traction mechanism drives of internal combustion engines, inserted between a hydraulic-fluid-filled pressure chamber and a reservoir, comprising:

a valve body which is inserted in a housing and which is designed as a ball and which, when the non-return valve is closed, is supported under spring loading against a valve seat of a throughflow cross-section,

wherein, when the non-return valve is open, the valve body interacts with a valve seat of the housing, the associated flow cross-section of which ensures a fluid flow through the non-return valve.

2. The non-return valve as claimed in claim 1, wherein the valve seat, which is positioned in a base of the housing, prevents the valve body from being held in a positively locking manner.

3. The non-return valve as claimed in claim 1, wherein the flow cross-sections in a base of the housing are of any desired geometrical design.

4. The non-return valve as claimed in claim 3, wherein the flow cross-sections are of non-circular shape.

5. The non-return valve as claimed in claim 3, wherein the base of the housing has at least an oval, multi-cornered or polygonal flow cross-section.

6. The non-return valve as claimed in claim 1, wherein a plurality of bores is provided as a flow cross-section, with the valve body influencing a fluid flow in all the bores.

7. The non-return valve as claimed in claim 6, wherein the flow cross-section comprises three bores arranged close together.

8. The non-return valve as claimed in claim 2, wherein the flow cross-section is formed in a convexly shaped portion of the base, with a radius of curvature of the base differing from a radius of the valve body.

9. The non-return valve as claimed in claim 2, wherein the base is designed such that a contact surface assigned to the valve body form different curvatures with two mutually perpendicular section planes which each comprise one movement axis of the valve body.