DE102011013477A1 - hydraulic system - Google Patents

Abstract

Hydraulic system with a hydraulic pump for the hydraulic supply of a transmission, in particular a conical pulley belt transmission, to which a torque sensor is assigned. In order to provide an improved hydraulic system, it is provided that the hydraulic pump is arranged in a torque flow of the transmission in such a way that the hydraulic pump provides a pressure that is dependent on a torque of the torque flow.

Description

The invention relates to a hydraulic system with a hydraulic pump for the hydraulic supply of a transmission, in particular a conical-pulley, which is associated with a torque sensor and a power supply by means of the hydraulic system.

Hydraulic systems for the hydraulic supply of a transmission are known. The transmission can be, for example, a conical-pulley transmission with a variably adjustable transmission ratio. The conical-pulley belt drive can be connected to a drive source, for example an internal combustion engine, and can set a drive ratio, for example, as part of a drive train of a motor vehicle. For this purpose, conical-pulley-belt transmissions usually have two pairs of conical disks, which are looped by a belt. To set the translation, a distance of each paired conical disks can be varied, wherein by means of a contact pressure of the conical disks against the belt member a friction necessary for torque transmission is generated. It is known to adapt this contact pressure to a torque actually present in the drive train or the conical-pulley transmission, in particular to control the contact pressure as a function of the torque sensor. In known hydraulic systems for adjusting the contact pressure, the hydraulic pump is assigned as accessory to the drive train, in particular the drive source, wherein a speed and depending on a volume flow of the hydraulic pump depend on a speed of the drive train or the drive source. An occurring power loss of the hydraulic system thus depends on an operating state of downstream hydraulic components of the hydraulic system, a current system pressure and the speed of the drive train.

The object of the invention is to provide a hydraulic system according to the preamble of claim 1, which is simple in construction and inexpensive to produce. In particular, the efficiency of the hydraulic system should be improved.

The object is achieved in a hydraulic system with a hydraulic pump for supplying hydraulic power to a transmission, in particular a conical-pulley, which is associated with a torque sensor, characterized in that the hydraulic pump is arranged in the torque flow of the transmission that the hydraulic pump is dependent on a moment of the torque flow Provides pressure. Advantageously, the pressure can be used directly for setting a torque-dependent contact pressure on conical disks of the transmission. Advantageously, the hydraulic pump in only one unit fulfills the function of the hydraulic supply of the hydraulic system and that of the torque sensor. Advantageously, the pressure is not dependent on an operating state possibly further existing hydraulic components. Advantageously results at the output of the hydraulic pump, if this is used only to provide the hydraulic pressure and thus for measuring the moment, no significant hydraulic flow, with an efficiency of the hydraulic system advantageously no longer depends on the speed of the transmission. Advantageously, thereby an overall efficiency of the hydraulic system and thus of the transmission can be improved.

A preferred embodiment of the conical-pulley belt transmission is characterized in that the pressure is passed as a contact pressure on a Umschlingungsorgan of the conical-pulley, wherein a reference to a rotation angle of the hydraulic pump pump stroke volume of the hydraulic pump and related to a linear adjustment of conical disks stroke volume of Anpresskammern of Conical pulley-belt transmission are coordinated so that the passed through the hydraulic pump torque controls the contact pressure so that it is above a minimum torque required for transmitting the Anpressschwelldruck. Under a Anpressschwelldruck that contact pressure can be understood, in which slipping of the Umschlingungsorgans can be just barely avoided. Advantageously, it can be ensured by the design of the hydraulic pump and the transmission or a variator of the transmission that slippage of the belt can be avoided in all operating conditions of the transmission. Advantageously, the hydraulic pump is arranged in a torque flow of the transmission, in particular a drive train, which has the transmission. A volume flow depends advantageously not on a speed of the drive source and / or the transmission, but by a slip occurring by means of the hydraulic pump in the drive train. Thus, a power consumption of the hydraulic pump essentially depends on a volume requirement of downstream hydraulic components. Advantageously, slip occurs due to the hydraulic pump only when actually downstream consumers of the hydraulic system pick up a volume flow. Advantageously, from a system pressure to a tank pressure reduced and funded in the tank loss volume flows can be avoided.

Another preferred embodiment of the conical-pulley is characterized in that the hydraulic pump is designed as a radial piston pump and the lifting pistons are arranged radially within a cam cam having the lifting cam. Advantageously, the radial piston pump can be arranged with a comparatively small space requirement in the torque flow, which, if no volume flow is tapped, runs along as a block, ie has no power consumption. Advantageously, by means of the reciprocating piston a comparatively low leakage can be realized in a small space and with little effort.

Another preferred embodiment of the conical-pulley belt transmission is characterized in that the hydraulic pump is part of a starting unit of the transmission. Advantageously, a volume flow conveyed by the pump can be adjusted, for example by means of a controllable valve connected downstream of the hydraulic pump, wherein the slip is adjusted infinitely between one hundred percent and a minimum slip occurring during driving, for example, of zero percent during a starting process can be. It is conceivable that the hydraulic pump completely replaces an otherwise usually existing clutch. Alternatively and / or additionally, it is conceivable that an otherwise usually existing clutch is still provided, but this is designed smaller.

Another preferred embodiment of the conical-pulley belt transmission is characterized in that each of the reciprocating piston upstream of an inlet valve and an outlet valve is connected downstream. By means of the valves, a reciprocating piston supplied and discharged volume flow can be controlled so that per piston reciprocating pulsating flow occurs.

Another preferred embodiment of the conical-pulley belt transmission is characterized in that the pistons are stepped. Advantageously, more pistons can thus be provided within the cam ring, resulting in an overall more uniform volumetric flow and / or a more uniform transmission ratio of the hydraulic pump which is dependent on a rotational angle.

A further preferred embodiment of the conical-pulley belt transmission is characterized in that a partial surface of the pistons is assigned to a high-pressure side of the hydraulic pump. Advantageously, resetting of the pistons, in particular for carrying out a suction work, can take place on the basis of a pressure force of the high-pressure side induced on the partial surfaces.

The invention further relates to a transmission, in particular a conical-pulley, with a hydraulic system described above. This results in the advantages described above.

Further advantages, features and details emerge from the following description in which an exemplary embodiment is described with reference to the drawing. The same, similar and / or functionally identical parts are provided with the same reference numerals. Show it:

1 a schematic view of a hydraulic system for supplying a belt pulley according to the prior art;

2 a schematic view of a hydraulic system according to the invention for supplying a conical-pulley belt;

3 a cross section of a hydraulic pump of in 2 shown hydraulic system and

4 a longitudinal section of in 3 shown hydraulic pump.

1 shows a schematic view of a hydraulic system 1 with a hydraulic pump 3 for the hydraulic supply of a belt pulley belt drive 5 , which is a moment sensor 7 assigned. This in 1 shown hydraulic system 1 is performed according to the prior art.

The conical-pulley transmission 5 is part of a drive train of a motor vehicle only partially shown 9 , The drive train of the motor vehicle 9 has a drive source 11 on, for example in the form of an internal combustion engine. The drive source 11 is a starting unit 13 downstream. The starting unit 13 For example, it may have a dry multi-plate clutch, a wet multi-plate clutch, a hydrodynamic converter, an electric machine and / or the like.

The starting unit 13 is the moment sensor 7 downstream. The moment sensor 7 For example, has a torque-dependent pressure relief valve 15 on, for example, by means of two unspecified and rolling on rolling elements spreading discs, which are arranged in the torque flow of the drive train may have.

The moment sensor 7 is the belt pulley 5 downstream. The conical-pulley transmission 5 are a driving device 17 , in particular another Gear stage or a differential and drive wheels of the motor vehicle 9 downstream.

The conical-pulley transmission has two conical pulley pairs 19 on, by a belt 21 , For example, a link chain, are entwined. The torque flow from the drive source 11 on the drive device 17 takes place from an input side cone pulley pair 19 that the moment sensor 7 downstream is via the belt 21 on an output side cone pulley pair 19 , that of the drive device 17 upstream.

The conical disk pairs 19 are each by means of a hydraulic pressure chamber 23 with one of a moment in the powertrain of the motor vehicle 9 occurring torque flow dependent contact pressure against the Umschlingungsorgan 21 pressed.

Furthermore, the cone pulley pairs 19 for setting a translation of the conical-pulley transmission 5 adjusted by means of an adjusting device not shown.

The hydraulic pressure chambers 23 are each the hydraulic pump 3 downstream. In addition, the moment sensor 7 or the torque-dependent pressure relief valve 15 the hydraulic pump 3 downstream. This acts by means of the moment sensor 7 generated and dependent on the moment pressure on the Anpresskammern 23 and thus a correspondingly dependent on the pressure hydraulic force on the Umschlingungsorgan 21 ,

The hydraulic pump 3 is as an accessory of the drive source 11 mechanically assigned, wherein a drive speed of the hydraulic pump 3 from a rotational speed of the drive source 11 directly depends.

2 shows a schematic view of a hydraulic system according to the invention 1 with a hydraulic pump 3 , Identical parts are provided with the same reference numerals, so that in the following only the differences will be discussed. In contrast to the representation according to 1 is the hydraulic pump 3 in the drive train, ie in the torque flow of the drive train of the motor vehicle 9 arranged.

A drive speed of the hydraulic pump 3 depends on a slip or a speed difference between the drive source 11 and an input shaft of the conical-pulley transmission 5 from. The hydraulic pump 3 is the pressure chambers 23 downstream, in contrast, the hydraulic pump 3 even one of the moment of the drive train of the motor vehicle 9 provides dependent pressure as output pressure. This is advantageous in 1 shown, the hydraulic pump 3 downstream torque-dependent pressure relief valve 15 not mandatory.

Another difference is the drive train of the motor vehicle 9 according to the representation of 2 no separate coupling on. Rather, the hydraulic pump meets 3 in addition to the function of the torque sensor 7 also the function of the starting unit 13 , This can for starting the motor vehicle 9 a slip of the hydraulic pump 3 be set to one hundred percent. Corresponding, necessary for this hydraulic control valves, the corresponding a, in this slip promoted flow in a tank 25 of the hydraulic system 1 derive, are in 2 not shown in detail.

3 shows a cross section of in 2 illustrated hydraulic pump 3 , 4 shows a longitudinal section of the in the 2 and 3 illustrated hydraulic pump 3 , The following is on the 3 and 4 referred to together.

The hydraulic pump 3 has an outer housing forming cam ring 27 on. The cam ring 27 has lift cams 29 on, on the reciprocating piston 31 roll. The reciprocating pistons 31 roll by means of associated rolling bearings 33 on the lift cams 29 of the cam ring 27 from.

The reciprocating pistons 13 are stepped and radial longitudinally displaceable in a stepped bore 35 a rotor 37 the hydraulic pump 3 stored. The rotor 37 is by means of two rolling bearings 39 rotatable to the cam ring 27 stored.

The hydraulic pump 3 has a low pressure input 41 and a high pressure outlet 43 on. The high pressure outlet 43 is the stepped holes 35 assigned, so that an output pressure of the hydraulic pump 3 on a reduced cross-sectional area of the stepped reciprocating 29 acts, causing the reciprocating pistons 29 be issued pressurized.

The low pressure input 41 is ever reciprocating 31 a suction valve 45 downstream. The suction valves 45 is the respective reciprocating piston 31 or a stroke volume 47 of the corresponding reciprocating piston 31 downstream. The stroke volume 47 or the corresponding reciprocating piston 31 is each an exhaust valve 49 downstream. The suction valves 45 and the exhaust valves 49 are each designed as check valves.

Advantageously, according to the invention, in particular in comparison to the representation of 1 , To maintain the contact pressure against the Umschlingungsorgan 21 not always available Volume flow required. Advantageously, therefore, no permanent hydraulic power, regardless of an actual need, so that an efficiency of the hydraulic system 1 is advantageously increased.

In the 2 illustrated hydraulic pump 3 is located in the torque flow of the drive train of the motor vehicle 9 , The stroke volume 47 the hydraulic pump 3 is designed so that a transmitted drive torque of the drive train of the motor vehicle 9 in the pressure chambers 23 required hydraulic pressure or in a variator of the conical-pulley belt 5 required mechanical contact pressure generated. Decisive is a contact pressure in a so-called Underdrive (UD) or a minimum in this operating condition for a perfect torque transfer Anpressschwelldruck. Other translations require lower contact pressures at a given moment. You can, if necessary, what not in 2 is represented by suitable hydraulic circuit from the base pressure of the hydraulic pump 3 be generated.

The flow rate and thus a slip speed of the hydraulic pump 3 are advantageous for a flow rate of these downstream hydraulic consumers. This advantageously ensures demand-based power consumption.

The hydraulic pump 3 as in the 3 and 4 shown, is designed as a radial piston pump. Outside, the cam ring rotates 27 around one the reciprocating pistons 31 having cylinder star of the rotor 37 with the individually movable reciprocating pistons 31 , each one a suction valve 45 or an inlet valve and an outlet valve 49 exhibit. The valves 45 and 49 are not positively controlled, designed as check valves, thereby advantageously the hydraulic pump 3 even with a changing moment sign equally a hydraulic pressure at the high pressure outlet 43 can generate. This can for example in a push and a train operation of the motor vehicle 9 be beneficial.

Preferably, the reciprocating pistons 31 , as in shown, stepped executed. Thus, they can be advantageous despite a comparatively large guide length very close to a circumference of the rotor 37 to be ordered. In addition, the grading offers the possibility of a preferably small partial area for the exhibition of the reciprocating pistons 31 To act on the output pressure, so this the high pressure output 43 assigned.

The reciprocating pistons 31 roll on a Hubringkontur or the lifting cams 29 preferably roller bearings by means of rolling bearings 33 from.

A number of reciprocating pistons 31 and a number of lift cams 29 are preferably coordinated so that the smallest possible variation in eifern conversion factor arises moment to pressure. Advantageously, prime numbers can be provided for this purpose. Alternatively and / or additionally, the hydraulic pump 3 be designed so that the smallest possible lateral force between the cam ring and the cam ring 27 and the cylinder star or the rotor 37 results. For this, the hydraulic pump 3 be designed symmetrically. The number of reciprocating pistons 31 can, for example 9 be.

The in the 3 and 4 illustrated reciprocating piston 31 are against the stepped bore 35 by means of a gap fit in a fluid-tight abutting contact. Alternatively and / or additionally, it is possible to provide additional sealing elements, in particular elastomeric seals and / or piston rings.

Alternatively and / or additionally, it is possible to use the hydraulic pump 3 to perform with axial piston and / or the reciprocating piston 31 unrolling on a radially inward multiple cam.

According to the invention, the hydraulic pump 3 to fulfill the function of the torque sensor 7 in the moment flow of the conical-pulley belt drive 5 arranged and delivers a torque-dependent pressure to the high pressure outlet 43 , for the contact pressure of the conical disk pairs 19 to the belt 21 on the pressure chambers 23 is headed. Alternatively and / or additionally, it is possible, by means of further valves, not shown, to the high-pressure outlet 43 adapt the pressure provided to a changed contact pressure requirement and / or reduce it for other consumers.

Advantageously, the differential speed of the hydraulic pump 3 and thus the power consumption of a retrieved oil quantity dependent.

Alternatively and / or additionally, it is conceivable for the hydraulic pump 3 nachzuschalten further hydraulic consumers, such as adjustment of the conical-pulley belt 5 , Clutch actuators and / or oil cooling and / or other hydraulic consumers.

The housing of the hydraulic pump rotates. The outlet pressure at the high pressure outlet 43 results from the passed moment. A speed difference n1 minus n2 results from a demanded volume flow and the stroke volume related to a rotation angle 47 ,

The hydraulic pump 3 according to 2 the moment, for example a drive torque or a braking torque, is impressed. Advantageously, this generates a torque-proportional output pressure or system pressure p = 2 * pi * M / V, as it is directly for the contact pressure of the conical disks of the cone pulley pairs 19 against the belt 21 is usable. Here, pi are the circle number, M the applied moment and V the displacement volume of the hydraulic pump 3 ,

Alternatively and / or additionally, it is possible to increase the displacement 47 the hydraulic pump 3 adjustable interpreted, the contact pressure in addition to a translation of the conical-pulley belt transmission 1 is customizable. This can be done, for example, by switching off individual reciprocating pistons 31 take place, in particular by means of rotary valves on a shaft of the hydraulic pump 3 ,

A pump speed or the speed difference n1 minus n2 is advantageous as a slip between the drive source 11 and the conical-pulley transmission 1 depending on a volume flow Q removed itself. This is advantageous also a recorded power of the hydraulic pump 3 P _pump = 2 * pi * M1 * (n1 -n2) = 2 * pi * M1 * Q / V consumption oriented. Without adjustment of the conical disks, without further consumers and without leaks, Q = 0 and the hydraulic pump 3 with n1 = n2 and M1 = M2 circulating as a block and a drive power of the drive source 11 pass lossless. The hydraulic pump 3 then works as a moment sensor 7 , which advantageously requires no auxiliary energy in the form of oil flow or flow of the pressure medium.

Alternatively and / or additionally, it is possible for the hydraulic pump 3 downstream and the tank 25 upstream to provide a controllable valve to the tank 25 opens, and the hydraulic pump 3 also as the starting unit 13 to use. In this case, a controllable pressure relief valve, a maximum transmissible torque of the drive source 11 limit, a flow restrictor, in particular a diaphragm, a throttle and / or a flow control valve, in series with the pressure relief valve or instead of the pressure relief valve set or control a maximum slip speed at a start.

Alternatively and / or additionally, it is conceivable to design the contact pressure or contact surfaces of the conical disks comparatively small, so that the contact pressure is always system pressure-determining. Alternatively and / or additionally, it is conceivable that the pressure at the high-pressure outlet 43 the hydraulic pump 3 increase over the actually required contact pressure in order to ensure a secure supply of downstream consumers.

LIST OF REFERENCE NUMBERS

1

hydraulic system

3

hydraulic pump

5

Conical disks-belt transmission

7

torque sensor

9

motor vehicle

11

a drive source

13

starter

15

Pressure relief valve

17

driving device

19

Conical disk pairs

21

encircling

23

hydraulic pressure chamber

25

tank

27

cam ring

29

lift cams

31

reciprocating

33

roller bearing

35

stepped bore

37

rotor

39

roller bearing

41

Low pressure input

43

High pressure outlet

45

suction

47

displacement

49

outlet valve

Claims (9)

Hydraulic system ( 1 ) with a hydraulic pump ( 3 ) for the hydraulic supply of a transmission, in particular a conical-pulley belt transmission ( 5 ), to which a moment sensor ( 7 ), characterized in that the hydraulic pump ( 3 ) is arranged in a torque flow of the transmission such that the hydraulic pump ( 3 ) provides a torque flow dependent pressure. Hydraulic system according to claim 1, characterized in that the pressure as a contact pressure on a belt ( 21 ) of the conical-pulley belt transmission ( 5 ), wherein an angle of rotation of the hydraulic pump ( 3 ) related pump stroke volume of the hydraulic pump ( 3 ) and a related to a linear adjustment of conical disks stroke volume of Anpresskammern ( 23 ) of the conical-pulley belt transmission ( 5 ) are coordinated with each other so that by the hydraulic pump ( 3 ) transmitted torque controls the contact pressure so that it is above a minimum torque required for transmitting the Anpressschwelldruck. Hydraulic system according to one of the preceding claims, characterized in that the hydraulic pump ( 3 ) on reciprocating pistons ( 31 ) of the hydraulic pump ( 3 ) acting lifting cams ( 29 ), which with respect to the direction of rotation of the hydraulic pump ( 3 ) are designed asymmetrically. Hydraulic system according to one of the preceding claims, characterized in that the hydraulic pump ( 3 ) is designed as a radial piston pump and the reciprocating piston ( 31 ) radially within one of the lift cams ( 29 ) having cam ring ( 27 ) are arranged. Hydraulic system according to one of the preceding claims, characterized in that the hydraulic pump ( 3 ) Part of a starting unit ( 13 ) of the transmission is. Hydraulic system according to one of the preceding claims, characterized in that each of the reciprocating pistons ( 31 ) each have a suction valve ( 45 ) and an outlet valve ( 49 ) is connected downstream. Hydraulic system according to one of the preceding claims, characterized in that the lifting pistons ( 31 ) are stepped. Hydraulic system according to one of the preceding claims, characterized in that a partial surface of the reciprocating piston ( 31 ) a high pressure side, in particular a high pressure outlet ( 43 ), the hydraulic pump ( 3 ) assigned. Transmission, in particular conical-pulley transmission ( 5 ), with a hydraulic system ( 1 ) according to any one of the preceding claims.

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