DE102017105804B4 - Traction device clamping unit for a traction device drive - Google Patents

Abstract

Traction device tensioning unit (1) for a traction device drive of a motor vehicle, comprising a housing (2) with a hydraulic tensioner (3), the hydraulic tensioner (3) being a cylinder (4) formed in the housing (2) with an axially movable piston (5 ), wherein a pressure chamber (6) is formed at least axially between the cylinder (4) and the piston (5), characterized in that at least one first leakage gap (7a) radially between the cylinder (4) and the piston (5) with a first leakage gap height (16a) and a second leakage gap (7b) with a second leakage gap height (16b) for realizing a leak from the hydraulic tensioner (3), the two leakage gap heights (16a, 16b) being of different designs, the at least two leakage gaps (7a, 7b) are arranged axially in series and an outlet (8) is formed axially between the two leakage gaps (7a, 7b), the outlet (8) being hydraulic with an adjusting element nt (9) for setting the leakage from the hydraulic tensioner (3) is connected, and wherein the adjusting element (9) has at least one open and one closed switching position for setting a rigidity of the hydraulic tensioner (3).

Description

The invention relates to a hydraulic traction device for a traction drive of a motor vehicle.

It is generally known that traction device tensioning units serve mainly to compensate for manufacturing tolerances, traction device elongation and wear. A tensioning effect is realized by the traction means tensioning unit, which acts on the traction means, usually a chain or a belt, via a tensioning rail.

From the DE 10 2009 034 047 A1 results in a chain drive tensioner system with variable passage. The chain drive tensioner system comprises a chain drive tensioner with a tensioner body that has at least one exit hole that defines a first passage path. The chain drive tensioner system further includes a tensioner piston assembly operably engaged with the tensioner body, the tensioner piston assembly being movable between a first position that allows flow through the first passageway and a second position that substantially blocks flow through the first passageway is.

The object of the present invention is to further develop a traction device tensioning unit and in particular to control the rigidity and damping of the traction device tensioning unit as required.

A traction mechanism tensioning unit according to the invention for a traction mechanism drive of a motor vehicle comprises a housing with a hydraulic tensioner, the hydraulic tensioner having a cylinder formed in the housing with an axially movable piston therein, a pressure chamber being formed at least axially between the cylinder and the piston, radially between the cylinder and the piston have at least one first leakage gap with a first leakage gap height and a second leakage gap with a second leakage gap height for realizing a leak from the hydraulic tensioner, the two leakage gap heights being of different designs, the at least two leakage gaps being arranged axially in series and an outlet is formed axially between the two leakage gaps, the outlet being hydraulically connected to an actuating element for setting the leakage from the hydraulic tensioner, and the actuating element at least has an open and a closed switching position for setting a rigidity of the hydraulic tensioner.

The term leakage gap is to be understood as a gap or channel which is formed radially between an outer circumferential surface of the piston and an inner circumferential surface of the cylinder and is provided for guiding a fluid or fluid, in particular for guiding motor oil out of the hydraulic tensioner. The leakage gap height corresponds to half the diameter difference between the outer diameter of the piston and the inner diameter of the cylinder.

If the traction device wears out, for example, the traction device becomes longer, which results in sagging of the traction device. In order to compensate for the sag of the traction device, the piston of the hydraulic tensioner extends outwards from the cylinder and thus tensions the traction device.

The engine oil is provided for the oil supply to the traction mechanism clamping unit and thus also for the axial adjustment of the piston. The oil pressure in the pressure chamber of the hydraulic tensioner therefore depends on the pressure of the engine oil. In particular, the piston is designed as a hollow piston, the pressure chamber then extending into the piston and thus having a larger volume. Furthermore, the hollow piston serves to receive a compression spring, which is provided to generate a minimal preload on the piston. In particular, the compression spring creates a vacuum on the piston.

The respective leakage gap guides the engine oil radially between the cylinder and the piston in the axial direction. In particular, the oil pressure in the pressure chamber depends on the flow rate of the engine oil through the respective leakage gap.

The open switching position of the switching element enables the engine oil to flow along the first leakage gap to the drain and from there out of the hydraulic tensioner. In particular, the engine oil is returned to the oil circuit of the hydraulic tensioner via an oil catch basin or an oil pressure line. In contrast, the closed switching position of the switching element extends the flow of the engine oil out of the hydraulic tensioner by the second leakage gap. Because the engine oil flows along the first leakage gap, out of the hydraulic tensioner via the second leakage gap. Since the engine oil has to flow through both leakage gaps until it emerges from the hydraulic tensioner, the rigidity of the hydraulic tensioner increases. Consequently, the rigidity of the hydraulic tensioner is higher when the control element is in a closed switching position than when the hydraulic tensioner is in an open switching position. Furthermore, it is also conceivable that the control element in addition to the open and closed switching position has any number of intermediate positions for adjusting the rigidity of the hydraulic tensioner. The first leak gap height of the first leak gap is greater than the second leak gap height. However, it is also conceivable to make the second leakage gap height larger than the first leakage gap height. In particular, the difference between the two leakage gap heights is less than 500 μm, preferably less than 100 μm.

Preferably, more than two leakage gaps can also be provided, an outlet with an actuating element being provided between each two leakage gaps in order to adjust the flow through the leakage gaps from the hydraulic tensioner. Thus, an outlet with control element is provided axially between two leakage gaps.

A circumferential annular groove is preferably formed axially between the at least two leakage gaps, the circumferential annular groove being hydraulically connected to the outlet. The at least two leakage gaps are therefore hydraulically connected to one another via the circumferential annular groove. The circumferential annular groove is embedded radially in the cylinder and, like the at least two leakage gaps, is provided for guiding the engine oil out of the hydraulic tensioner. The diameter of the annular groove and the diameter of the respective diametrically larger leakage gap section are at least the same size, preferably the diameter of the annular groove is larger than the diameter of the respective diametrically larger leakage gap section. Alternatively, a groove or a stiffening is provided in the cylinder wall over a partial area of the circumference, which is, for example, sickle-shaped or as segments. Furthermore, it is also conceivable for a correspondingly large difference between the two leakage gap heights not to provide an annular groove in the housing. It should be noted in which direction the piston tilts preferably under an initiated operating load.

The piston is preferably of stepped design with a first and a second piston diameter. The simpler manufacture of the traction device clamping unit is advantageous, the annular groove for a switchability of the traction device clamping unit being designed to be relatively larger.

Furthermore, the control element is preferably designed as a hydraulic valve. In particular, the control element is designed as a 2/2-way valve. The hydraulic valve is preferably actively controlled. For example, the hydraulic valve is a map-controlled switching or proportional valve. Alternatively, the hydraulic valve is controlled passively. For example, the hydraulic valve is designed as a pressure relief valve or as a temperature-dependent valve comprising a bimetal.

The sequence preferably has an aperture, the aperture being a constant or variable aperture, the variable aperture being in particular switchable or variably adjustable. The engine oil escapes primarily through the ring groove into the drain, the orifice causing additional variable throttling of the engine oil, which can be both constant and changeable. As a result, more engine oil is pressed through the second leakage gap. It is advantageous that the variable or switchable design of the diaphragm achieves a more precise and finer adjustability of the rigidity and damping of the traction device tensioning unit.

According to a preferred embodiment, the first leakage gap has a first gap length and the second leakage gap has a second gap length, the two gap lengths being designed differently. In particular, the length ratio of the two gap lengths is between 0.1 and 10. Furthermore, a step is formed upstream of the first leakage gap, which limits the gap length of the leakage gap to one side, the circumferential annular groove on the cylinder being the gap length of the first leakage gap to the other side downstream limited. Furthermore, the position and gap length of the first leakage gap are independent of the position of the piston. By varying the leakage gap heights, a wider, adjustable range for the damping force of the traction device tensioning unit is realized, in particular if, in addition to the leakage gap heights, the gap lengths are also changed.

The invention includes the technical teaching that a compression spring for generating an axial clamping force on the piston is arranged axially in the pressure chamber between the cylinder and the piston. A check valve is preferably arranged upstream of the pressure chamber. A hydraulic pump is preferably arranged upstream of the check valve. The hydraulic pump conveys the engine oil from a catch basin provided via the check valve into the hydraulic tensioner.

• 1a eine schematische Schnittdarstellung zur Veranschaulichung des Aufbaus einer ersten Ausführungsform einer erfindungsgemäßen Zugmittelspanneinheit mit einem Stellelement, das eine offene Schaltstellung aufweist,
• 1 b eine schematische Schnittdarstellung zur Veranschaulichung des Aufbaus der erfindungsgemäßen Zugmittelspanneinheit nach 1a, wobei das Stellelement eine geschlossene Schaltstellung aufweist,
• 2 eine schematische Schnittdarstellung zur Veranschaulichung des Aufbaus einer zweiten Ausführungsform der erfindungsgemäßen Zugmittelspanneinheit,
• 3 eine schematische Schnittdarstellung zur Veranschaulichung des Aufbaus einer dritten Ausführungsform der erfindungsgemäßen Zugmittelspanneinheit,
• 4a eine schematische Schnittdarstellung zur Veranschaulichung des Aufbaus einer vierten Ausführungsform der erfindungsgemäßen Zugmittelspanneinheit, wobei ein Kolben in einer ersten Stellung vorliegt, und
• 4b eine schematische Schnittdarstellung zur Veranschaulichung des Aufbaus der erfindungsgemäßen Zugmittelspanneinheit gemäß 4a, wobei der Kolben in einer zweiten Stellung vorliegt.

Further measures improving the invention are described below together with the description of four preferred exemplary embodiments of the invention with reference to the six figures. Show it

• 1a 2 shows a schematic sectional illustration to illustrate the structure of a first embodiment of a traction device tensioning unit according to the invention with an actuating element which has an open switching position,
• 1 b is a schematic sectional view illustrating the structure of the traction device according to the invention 1a , wherein the control element has a closed switching position,
• 2nd 2 shows a schematic sectional illustration to illustrate the structure of a second embodiment of the traction device tensioning unit according to the invention,
• 3rd 2 shows a schematic sectional illustration to illustrate the structure of a third embodiment of the traction device tensioning unit according to the invention,
• 4a is a schematic sectional view illustrating the structure of a fourth embodiment of the traction device tensioning unit according to the invention, wherein a piston is in a first position, and
• 4b is a schematic sectional view to illustrate the structure of the traction device according to the invention 4a , wherein the piston is in a second position.

According to the 1a , 1b , 2nd , 3rd , 4a , 4b has a traction device tensioning unit according to the invention 1 for a - not shown here - traction drive of a - not shown - motor vehicle a housing 2nd with a hydraulic tensioner 3rd on. The hydraulic tensioner 3rd includes one in the housing 2nd trained cylinder 4th with an axially displaceable piston 5 . The piston 5 In the present case, it is designed as a hollow piston and comes to bear axially on a tensioning rail (not shown here) which is intended to keep a traction means under tension. Axial between the cylinder 4th and the piston 5 is a pressure chamber 6 in the cylinder 4th educated. This pressure chamber 6 extends into the piston 5 inside. There is also a compression spring 11 to generate an axial clamping force on the piston 5 in the pressure chamber 6 axially between the cylinder 4th and the piston 5 arranged. The piston 5 is via a check valve 17th with a fluid - not shown here - acted upon. The check valve 12th is upstream of the pressure chamber 6 arranged. Upstream of the check valve 12th is a hydraulic pump 13 arranged the fluid from a catch basin 14 in the hydraulic tensioner 3rd promotes.

Radially between the cylinders 4th and the piston 5 are a first leakage gap 7a with a first leakage gap height 16a and a second leakage gap 7b with a second leakage gap height 16b to realize a leak from the hydraulic tensioner 3rd educated. The two leakage gap heights 16a , 16b are concentric, but it is also an eccentric design of the leakage gap heights 16a , 16b possible. The first leakage gap also has 7a a first gap length 17a and the second leakage gap 7b a second gap length 17b on, the two gap lengths 17a , 17b are trained differently. The two leakage gaps 7a , 7b are axially adjacent, the first leakage gap height 16a is greater than the second leakage gap height 16b . Alternatively, the second leakage gap height 16b larger than the first leak gap height 16a be formed. Axially between the two leakage gaps 7a , 7b is a process 8th trained, the process 8th hydraulic with an actuator 9 to adjust the leakage from the hydraulic tensioner 3rd connected is. For this purpose, the control element 9 an open and a closed switching position for setting a rigidity of the hydraulic tensioner 3rd on. The actuator 9 is designed as a hydraulic valve and is actively controlled by means of a control element (not shown here). The two leakage gaps 7a , 7b are trained differently. Axially between the two leakage gaps 7a , 7b is a circular ring groove 10th on the cylinder 4th formed, the circumferential annular groove 10th the two leakage gaps 7a , 7b hydraulically with each other and with the drain 8th connects. That through the process 8th drained fluid is through a refill channel 19th the supply line 15 upstream of the check valve 12th fed. In the supply line 15 there is supply pressure.

To 1a has the control element 9 the open switch position, which is also the basic position, because the position is kept de-energized. As a result, the fluid flows out of the pressure chamber 6 along the first gap length 17a the first leakage gap 7a over the circumferential ring groove 10th in the process 8th through the open actuator 9 , and from the refill channel 19th in the supply line 15 . Hence, the fluid becomes after the first leakage gap 7a via the control element 9 derived. The second leak gap height 16b is less than the first leak gap height 16a trained and forms the primary piston guide. Due to the relatively large first leakage gap height 16a there is a soft hydraulic tensioner in the open switch position 3rd by which the tractive forces are limited. It is also conceivable, depending on the design, that the fluid is secondary over the second gap length 17b the second leakage gap 7b dissipate. Furthermore, the process forms 8th and the actuator 9 a lower flow resistance than the first leakage gap 7a with the first leakage gap height 16a and the first gap length 17a .

In 1b has the control element 9 the closed switch position. As a result, the fluid flows out of the pressure chamber 6 along the first gap length 17a the first leakage gap 7a over the circumferential ring groove 10th in the second leakage gap 7b and from there over the second Gap length 17b in the catch basin 14 . Because of the greater flow resistance due to the lower second leakage gap height 16b the rigidity of the hydraulic tensioner increases 3rd compared to the open switching position of the control element 9 according to 1a . Thus, the hydraulic tensioner has 3rd to 1b relatively tough behavior.

According to 2nd has the control element 9 in a second embodiment of the traction device tensioning unit 1 the open switch position. As a result, the fluid flows out of the pressure chamber 6 along the first leakage gap 7a over the circumferential ring groove 10th in the process 8th . In the process 8th is an aperture 20th formed, which can be designed both as a constant diaphragm or throttle, and as a variable diaphragm or throttle. Furthermore, the variable orifice can be switchable or variably adjustable, as a result of which the flow resistance can be varied in a targeted manner. For a closed switching position of the control element - not shown here 9 in the second embodiment be on 1b referred.

In 3rd has the control element 9 in a third embodiment of the traction device tensioning unit 1 the open switch position. The third embodiment differs from that in FIG 2a illustrated second embodiment in that the leakage gap height 16a the first leakage gap 7a is smaller than the leakage gap height 16b the second leakage gap 7b . As a result, the fluid flows out of the pressure chamber 6 along the first leakage gap 7a over the circumferential ring groove 10th both in the process 8th that the aperture 20th has, as well as through the second leakage gap 7b with the larger second leakage gap height 16b in the catch basin 14 . It is advantageous to fine tune the traction forces. In a - not shown here - closed switching position of the control element 9 in the third embodiment, the fluid flows out of the pressure chamber 6 along the first and second leakage gaps 7a , 7b in the catch basin 14 .

After the 4a and 4b has the control element 9 in a fourth embodiment of the traction means tensioning unit 1 the open switch position. The piston 5 has a first and a second piston diameter 18a , 18b on, the two piston diameters 18a , 18b are axially adjacent and the first piston diameter 18a upstream of the second piston diameter 18b is trained. The cylinder has a constant diameter which is interrupted axially by the circumferential annular groove. Hence the leakage gap heights 16a , 16b over the two piston diameters 18a , 18b given. The circumferential ring groove 10th is designed to be larger in order to enable the traction means forces to be switched over the entire working range, the axial groove length being designed such that the piston is guided in a sufficiently stable manner 5 is guaranteed.

According to 4a is the piston 5 shown in a first position, in which the arrangement of the piston 5 in the cylinder 4th is shown for a relatively new traction device. Furthermore, the present arrangement is present when an engine (not shown here) of a motor vehicle having the traction device tensioning unit is very hot. Wear of the traction device makes the traction device longer, which results in sagging of the traction device. The piston moves to compensate for the sag of the traction mechanism 5 of the hydraulic tensioner 3rd according to 4b out of the cylinder 4th outwards and thus tension the traction mechanism. The first gap length 17a is relatively short, so the flow resistance is low and the hydraulic tensioner 3rd is set relatively soft.

Under the rigidity of the hydraulic tensioner 3rd is to understand a tension reaction stiffness. Consequently, the tensioner reaction stiffness decreases due to the increased volume flow of the fluid when the actuating element 9 is open.

Reference list

1

Traction device clamping unit

2nd

casing

3rd

hydraulic tensioner

4th

cylinder

5

piston

6

Pressure chamber

7a, 7b

Leakage gap

8th

procedure

9

Actuator

10th

circumferential ring groove

11

Compression spring

12th

check valve

13

hydraulic pump

14

Catch basin

15

supply line

16a, 16b

Leakage gap height

17a, 17b

Gap length

18a, 18b

Piston diameter

19th

Refill channel

20th

cover

Claims (10)

Traction device tensioning unit (1) for a traction device drive of a motor vehicle, comprising a housing (2) with a hydraulic tensioner (3), the hydraulic tensioner (3) being a cylinder (4) formed in the housing (2) with an axially movable piston (5 ), wherein a pressure chamber (6) is formed at least axially between the cylinder (4) and the piston (5), characterized in that at least one first leakage gap (7a) radially between the cylinder (4) and the piston (5) is designed with a first leakage gap height (16a) and a second leakage gap (7b) with a second leakage gap height (16b) for realizing a leak from the hydraulic tensioner (3), the two leakage gap heights (16a, 16b) being different, the at least two leakage gaps (7a, 7b) are arranged axially in series and an outlet (8) is formed axially between the two leakage gaps (7a, 7b), the outlet (8) being hydraulic with an actuating element ent (9) for setting the leakage from the hydraulic tensioner (3), and wherein the control element (9) has at least one open and one closed switching position for setting a rigidity of the hydraulic tensioner (3). Traction device tensioning unit (1) Claim 1 , characterized in that a circumferential annular groove (10) is formed axially between the at least two leakage gaps (7a, 7b) on the cylinder (4), the circumferential annular groove (10) being hydraulically connected to the outlet (8). Traction device tensioning unit (1) according to one of the preceding claims, characterized in that the first leakage gap (7a) has a first gap length (17a) and the second leakage gap (7b) has a second gap length (17b), the two gap lengths (17a, 17b) are trained differently. Traction device tensioning unit (1) according to one of the preceding claims, characterized in that the piston (5) is of stepped design with a first and a second piston diameter (18a, 18b). Traction device tensioning unit (1) according to one of the preceding claims, characterized in that the adjusting element (9) is designed as a hydraulic valve, the hydraulic valve being controlled actively or passively. Traction device tensioning unit (1) according to one of the preceding claims, characterized in that the outlet (8) has a diaphragm, the diaphragm being a constant or variable diaphragm, the variable diaphragm being switchable or variably adjustable. Traction device clamping unit (1) according to one of the preceding claims, characterized in that the adjusting element (9) is designed as a proportional valve. Traction device clamping unit (1) according to one of the preceding claims, characterized in that a compression spring (11) for generating an axial clamping force on the piston (5) in the pressure chamber (6) is arranged axially between the cylinder (4) and the piston (5) is. Traction device tensioning unit (1) according to one of the preceding claims, characterized in that a check valve (12) is arranged upstream of the pressure chamber (6). Traction device tensioning unit (1) Claim 9 , characterized in that a hydraulic pump (13) is arranged upstream of the check valve (12).

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