DE102010034290A1 - Pressure-limited hydraulically damped clamping system - Google Patents

Abstract

The invention relates to a hydraulically damped tensioning system (1) which is used for tensioning a traction device in a unit or control drive of an internal combustion engine. The tensioning system (1) comprises a piston rod (4), the associated piston (3) of which is guided displaceably in a cylinder bushing (2) closed on the bottom by a one-way valve (14). The piston (3) and the cylinder liner (2) jointly delimit a pressure chamber (12) filled with hydraulic fluid. The piston (3), designed as a hollow body, also includes a reservoir (16) intended to receive hydraulic fluid, which is connected to a storage space (6) surrounding the cylinder liner (2) on the outside, the storage space (6) being surrounded by a casing tube ( 7) is enclosed. The tensioning system (1) also comprises a compression spring (9) which acts on the piston rod (4) and the cylinder liner (2) in opposite directions. To dampen an actuating movement compressing the clamping system (1), hydraulic fluid is displaced from the pressure chamber (12) into the storage chamber (6) through a leakage gap (13) formed between the piston (3) and the cylinder liner (2). In the event of an opposite actuating movement, hydraulic fluid flows from the storage space (6) into the pressure space (12) via the one-way valve (14) on the bottom side of the cylinder liner (2). To limit the pressure, a damping element (15) is integrated in the piston (3), which is acted upon by spring force on the reservoir side and forms a sealing seat (19) on the pressure chamber side with a support element. At a pressure level in the pressure chamber 12 that exceeds the force of a compression spring (20) acting on the damping element (15), the damping element (15) lifts off the sealing seat (19), whereby hydraulic fluid is additionally transferred from the pressure chamber (12) into the reservoir (16) ) is controlled.

Description

Field of the invention

The present invention relates to a hydraulically damped tensioning system which is used for tensioning a traction means in an aggregate or timing drive of an internal combustion engine. The structure comprises a piston rod whose associated piston is displaceably guided in a cylinder bush closed on the bottom side by a one-way valve and which jointly delimit a pressure chamber filled with hydraulic fluid. The piston designed as a hollow body encloses a reservoir for the hydraulic fluid, wherein the reservoir communicates with a storage space surrounding the cylinder bushing on the outside, which in turn is enclosed by a jacket tube. The tensioning system also includes a compression spring biasing the piston rod and the cylinder liner in opposite directions. To dampen actuating movements of the clamping system, a subset of the hydraulic fluid from the pressure chamber is displaced into the reservoir via a leakage gap which forms between the piston of the cylinder liner and / or via a damping element integrated in the piston. In an opposite adjusting movement hydraulic fluid can flow via the bottom-side one-way valve of the cylinder liner from the reservoir into the pressure chamber.

Hydraulically damped clamping systems are preferably used to drive ancillaries such as. Coolant pump, generator or air compressor of an internal combustion engine. The drive takes place from the crankshaft of the engine to pulleys of the respective ancillaries. To ensure a sufficient bias of the traction means, a belt of the traction mechanism drive comprises a clamping system. Thus, a uniformly high belt bias can be ensured to avoid adverse slip between the belt and the drive or driven pulleys of the traction drive. Another object of the clamping systems is to effectively damp occurring oscillations of the traction mechanism drive. For this purpose, preferably a hydraulically damped clamping system is suitable, in which the damping takes place via a self-adjusting gap between the lateral surface of the piston and an inner wall of the cylinder.

From the US 4,719,801 a hydraulically damped tensioning system is known which comprises a cylinder housing in which a piston is guided. This piston-cylinder arrangement is enclosed by a compression spring, which exerts an expanding force between the piston and the cylinder. The pressure chamber delimiting components, the piston and the cylinder, are enclosed by an outer, cup-shaped molded shell casing whose annular interior forms the non-pressurized reservoir for the hydraulic fluid of the clamping system. The retraction movement of the piston is damped by displacing a subset of the hydraulic fluid present in the pressure chamber via a leakage gap damping into the reservoir, the shear forces in the hydraulic fluid generating the damping. In contrast, an opposite adjusting movement of the piston takes place almost undamped, wherein hydraulic fluid flows through a thereby opening check valve from the pressure chamber into the reservoir.

Summary of the invention

The object of the present invention is to provide a hydraulically damped clamping system with which a largely constant bias of the traction means can be realized in the operating state.

This problem is solved on the basis of a hydraulic damped tensioning system according to the preamble of claim 1 in conjunction with its characterizing features. The following dependent claims give advantageous developments of the invention.

The construction according to the invention of the hydraulically damped tensioning system, in particular for an aggregate traction mechanism drive, comprises as a damping element a spring-loaded, cylindrical bolt which is integrated in the piston designed as a hollow body. In the installed state, the sealable via a sealing seat, outside at least one flow groove or longitudinal groove having bolts on both sides, pressure chamber side and reservoir side, with support elements in an operative connection, which allow fluid flow. This constructive concept allows a defined pressure-dependent opening of the damping element, whereby a desired constant bias of the traction means in the operating state of the traction mechanism is established.

The limitation of the compressive force via the piston formed as a hollow body, which is sealed in connection with the damping element, a cylindrical bolt, on a through-flowing sealing element or support element. If the pressure in the pressure chamber of the clamping system rises when the piston is retracted and exceeds the maximum permissible or set damping, then the damping element, also referred to as the opening element, is pressed within the piston in the direction of the reservoir, whereby a pressure equalization occurs. As soon as the pressure in the pressure chamber of the clamping system decreases, the compression spring moves the damping element. This pressure-limiting effect mode takes advantage no influence on the function of the one-way valve used on the bottom side in the cylinder liner, can be sucked through the hydraulic fluid from the reservoir into the pressure chamber.

Advantageously, the invention allows for a variably adjustable opening pressure of the damping element optimum tuning of the damping force on the respective traction drive. The opening pressure can thus be adjusted depending on the application and the damping force required for the traction drive.

The opening behavior or the opening pressure of the damping element can be variably influenced by the force of the spring integrated in the piston and acting on the damping element in the direction of the sealing seat. A fine-tuning or a further influence on the opening force can be done by changing the surface of the damping element acted upon by the hydraulic pressure.

The damping element according to the invention can preferably be used in addition to a leak gap damping, in which hydraulic fluid from the pressure chamber on the adjusting between the piston and cylinder, to be designated as an annular gap leakage gap, a subset of the hydraulic fluid is displaced into the reservoir. The damping force of the leakage gap causing a laminar slit damping in hydraulically damped tensioning systems is determined by the operating temperature and the adjusting movement of the piston. In particular, in the starting phase of the internal combustion engine and at low ambient temperatures, it can lead to disadvantageously high forces, combined with a disadvantageously increased load on individual units of the traction drive.

Due to the limited damping force of the inventively constructed, hydraulically damped clamping system is advantageously a reduced friction and reduced load on the traction means and the bearings of the individual pulleys, which are adapted to the reduced load, cost-interpretable. At the same time, the invention makes a contribution to reducing the CO ₂ emission of the internal combustion engine, due to a self-adjusting reduced fuel consumption of the internal combustion engine.

According to a preferred embodiment of the invention is provided as a pressure-limiting spring-loaded, sealed via a sealing seat damping element with at least one outside Strömungnut or longitudinal groove. As a damping element is preferably a cylindrical pin, which is integrated in the piston and the pressure chamber side and the reservoir side interacts with through-flow support elements. Advantageously, the damping element forms a sealing seat on the pressure chamber side, together with a support element fixed in position in the piston, preferably as a perforated disk. The sealing effect of the sealing seat improving is further provided according to the invention, that the cylindrical bolt, the damping element, engages positively on the pressure chamber side with a conical approach in a central opening of the perforated disc.

As a measure to allow a virtually resistance-free flow of the hydraulic fluid from the pressure chamber into the reservoir after the open damping element, the cylindrical pin includes on the outside a plurality of circumferentially distributed positioned flow grooves or longitudinal grooves.

The designed as a hollow piston comprises position offset to the damping element at least one passage, which establishes a connection between the reservoir and the storage space. Advantageously, a plurality of circumferentially distributed introduced into the piston bores are provided as overrides to allow regardless of the installation position of the clamping system, a backflow of the hydraulic fluid from the reservoir into the reservoir.

The compression spring used to act on the damping element inside the piston is supported on a separate lock washer or on an inner shelf of the piston in the region of the reservoir, away from the piston. Independently of the support, it is ensured that it does not adversely affect the hydraulic fluid flowing into the reservoir, a pressure limitation.

The damping element or the cylindrical bolt, the perforated disc and the lock washer are preferably made of steel or a plastic. For the production of the damping element is, for example, a extrusion, sintering or injection molding. The hole and lock washer are preferably made by a non-cutting process, stamping or deep drawing.

To realize a cost advantage, all components except for the compression spring of the valve unit or the valve assembly can be produced by a non-cutting process. For this purpose, in particular a punching or deep drawing process, with which the items are inexpensive to produce. Another cost advantage can be realized by the possibility of pre-assembly of the valve assembly, which can be used as a unit in the damping piston.

Brief description of the drawings

Further measures of the invention are described below in connection with the Description of a preferred embodiment explained in more detail. It shows:

1 a sectional view of an inventively designed, hydraulically damped clamping system;

2 on an enlarged scale the detail Z according to 1 ;

3 the damping element as a single part in a perspective;

4 in a single part drawing the perforated disc, which forms the sealing seat in conjunction with the damping element.

Detailed description of the drawings

The 1 shows a sectional view of the structure of a hydraulically damped clamping system 1 , which is a cylinder liner 2 includes, in which a piston 3 is guided linearly displaceable. About one as a piston rod 4 To be designated end portion is the piston 3 with a support unit 5 connected. Coincidentally, the components are cylinder liners 2 , Piston 3 and piston rod 4 each designed as sheet metal forming part. In a piston-cylinder liner unit radially spaced enclosing, a reservoir 6 forming casing pipe 7 is the cylinder liner 2 used. For sealing the storage space relative to the support unit 5 is an elastic bellows 8th intended. On the outside, the piston-cylinder bushing unit is a compression spring 9 enclosed between the support unit 5 and the cylinder liner 2 is used. The compression spring 9 causes over with the support unit 5 and the cylinder liner 2 connected fastening eyes 10 . 11 a spreading force from between a fixed pivot point and a z. B. with the clamping system 1 connected, in 1 not shown tensioner.

For damping positioning movements of the clamping system 1 in operation, damping means are in the piston 3 as well as in cooperation with the cylinder liner 2 intended. A filled with a hydraulic fluid pressure chamber 12 is from the cylinder liner 2 and the piston 3 limited. At a compression of the clamping system 1 , an adjusting movement of the piston 3 in the arrow direction, a subset of the hydraulic fluid from the pressure chamber 12 repressed. For this purpose, the hydraulic fluid flows through a between the lateral surface of the piston 3 and an inner wall of the cylinder liner 2 adjusting leakage gap 13 in the partially filled with hydraulic fluid reservoir 6 , In a relaxation phase of the clamping system 1 is due to the force of the compression spring 9 a reverse positioning movement of the piston 3 a, combined with a hydraulic fluid compensation. In this case, a subset of the hydraulic fluid flows out of the reservoir 6 via an open one-way valve 13 the cylinder liner 2 in the pressure room 12 a, clarified by the arrow in the pressure chamber 10 ,

To compensate for pressure peaks or shock loads includes the clamping system 1 a pressure limiter, consisting of a spring-loaded, in the piston 3 integrated damping element 15 , When a limit pressure within the pressure chamber is exceeded 12 the damper element shifts 15 in the direction of the arrow in the reservoir 16 , whereby a subset of the hydraulic fluid from the pressure chamber 12 in the reservoir 16 of the piston 3 or its piston rod 4 is displaced.

The 2 shows the detail "Z", according to 1 , on an enlarged scale to illustrate the damping and pressure limitation of the clamping system 1 ,

The designed as a hollow body piston 3 used pressure chamber side for receiving the damping element 15 formed as a cylindrical bolt. A cone section 17 of the damping element 15 forms together with a perforated disk used in the piston wall 18 a sealing seat 19 , Druckraumfern is between a piston side inserted lock washer 21 and the damping element 15 a compression spring 20 used, over which the damping element 15 frictionally connected to the running disk 18 is applied.

Each in the area of the leakage gap 13 introduced arrows illustrate a hydraulic fluid flow in a compression phase of the clamping system 1 in which the piston 3 the pressure room 12 reduced. The outside of the piston 3 over the leakage gap 13 displaced hydraulic fluid enters the storage room 6 , An increase in pressure or load peaks of the clamping system 1 cause an adjusting movement of the piston 3 opposite movement of the damping element 15 ,

Synchronously, there is a lifting of the damping element 15 from the sealing seat 19 , whereby a flow of the hydraulic fluid from the pressure chamber 12 in the reservoir 16 of the piston 3 on the outside in the damping element 15 introduced flow grooves 22 can be done. Axially offset to the damping element 15 or their compression spring 20 are in the piston rod 4 in particular introduced as holes transfers 23 provided via the hydraulic fluid from the reservoir 16 in the pantry 6 can flow out.

The 3 and 4 show the damping element 15 or the perforated disc 18 in a Item drawing. The damping element 15 includes a plurality of externally introduced flow grooves 22 and forms a cone section on the front side 17 which in connection with a centric opening 24 the perforated disc 18 a sealing seat 19 forms. As a measure to increase a contact surface in the region of the sealing seat 19 it makes sense, the perforated disc 18 in the area of the centric opening 24 to provide with a circumferential chamfer.

LIST OF REFERENCE NUMBERS

1

clamping system

2

cylinder liner

3

piston

4

piston rod

5

support unit

6

pantry

7

casing pipe

8th

bellows

9

compression spring

10

fastening eye

11

fastening eye

12

pressure chamber

13

leakage gap

14

one-way valve

15

damping element

16

reservoir

17

cone section

18

perforated disc

19

sealing seat

20

compression spring

21

lock washer

22

flow groove

23

crossing

24

opening

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 4719801 [0003]

Claims (7)

Hydraulically damped tensioning system ( 1 ), used for tensioning a traction means in an aggregate or timing drive of an internal combustion engine, with a piston rod ( 4 ), whose associated piston ( 3 ) in a bottom side by a one-way valve ( 14 ) sealed cylinder liner ( 2 ) is displaceably guided, which together a filled with hydraulic fluid pressure chamber ( 12 ), wherein the piston formed as a hollow body ( 3 ), a reservoir ( 16 ) forms for the hydraulic fluid, with a cylinder liner ( 2 ) outside surrounding storage space ( 6 ), which in turn is connected by a jacket tube ( 7 ) is enclosed and a compression spring ( 9 ) the piston rod ( 4 ) and the cylinder liner ( 2 ) acted upon in opposite directions and for damping adjusting movements of the clamping system ( 1 ) Hydraulic fluid from the pressure chamber ( 12 ) over one between the piston ( 3 ) and the cylinder liner ( 2 ) forming leakage gap ( 13 ) and / or in the piston ( 3 ) integrated damping element ( 15 ) in the reservoir ( 16 ) is displaced or at an opposite adjusting movement, the hydraulic fluid via the bottom-side one-way valve ( 14 ) of the cylinder liner ( 2 ) from the storage room ( 6 ) into the pressure chamber ( 12 ) flows in, characterized in that for pressure limiting in the piston ( 3 ) a damping element ( 15 ) is integrated, the reservoir side is spring-loaded and pressure chamber side with a flow-through support element a sealing seat ( 19 ). Clamping system according to claim 1, characterized in that the damping element ( 15 ) on the pressure chamber side together with one in the piston ( 3 ) position-fixed perforated disc ( 18 ) a sealing seat ( 19 ). Tensioning system according to Claim 2, characterized in that the damping element (designed as a cylindrical bolt) ( 15 ) with a cone section ( 17 ) in a centric opening ( 24 ) of the perforated disc ( 18 ) intervenes. Clamping system according to at least one of claims 1 to 3, characterized in that the damping element ( 15 ), the cylindrical bolt, outside a plurality of circumferentially spaced flow grooves ( 22 ) or longitudinal grooves. Clamping system according to at least one of claims 1 to 4, characterized in that the piston ( 3 ) position offset to the damping element ( 15 ) at least one connection between the reservoir ( 16 ) and the storage room ( 6 ) producing crossing ( 23 ). Clamping system according to at least one of claims 1 to 5, characterized in that for the application of the damping element ( 15 ) within the reservoir ( 16 ) of the piston ( 3 ) a compression spring ( 20 ) attached to an inner board or to a separate lock washer ( 21 ) of the piston ( 3 ) is supported. Clamping system according to at least one of claims 1 to 6, characterized in that the damping element ( 15 ), the perforated disc ( 18 ) and the lock washer ( 21 ) are made of steel or plastic, wherein the damping element ( 15 ) is designed as a flow press, as a sintered part or as an injection molded part and the perforated disc ( 18 ) and the lock washer ( 21 ) are produced by a non-cutting process.

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