WO2011120488A1

WO2011120488A1 - Hydraulic system

Info

Publication number: WO2011120488A1
Application number: PCT/DE2011/000257
Authority: WO
Inventors: Reinhard Stehr; Maximilian Podschwadt
Original assignee: Schaeffler Technologies Gmbh & Co. Kg
Priority date: 2010-04-01
Filing date: 2011-03-10
Publication date: 2011-10-06
Also published as: DE102011013477A1; DE112011101092A5

Abstract

A hydraulic system having a hydraulic pump for the hydraulic supply of a gear mechanism, in particular a cone pulley transmission, which is assigned a moment sensor. In order to produce an improved hydraulic system, it is provided that the hydraulic pump is arranged in a moment flow of the gear mechanism in such a way that the hydraulic pump provides a pressure which is dependent on a moment of the moment flow.

Description

hydraulic system

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-independent 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 it is only used to provide the hydraulic pressure and thus for measuring the moment, no significant hydraulic flow, wherein 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 applied as a contact pressure on a belt of the conical pulley Umschlingungsgetriebes, wherein a related to a rotation angle of the hydraulic pump Pumpenhubvolumen the hydraulic pump and related to a linear adjustment of conical disks stroke volume of Contact chambers of the conical-pulley belt drive 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 a 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. This is a tion recording of the hydraulic pump substantially dependent 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 tap into a volume flow. Advantageously, from a system pressure to a tank pressure reduced and funded in the tank loss volume flows can be avoided.

A further preferred embodiment of the conical-pulley belt-type transmission is characterized in that the hydraulic pump is designed as a radial piston pump and the lifting pistons are arranged radially inside a cam ring having the lifting cams. Advantageously, the radial piston pump can be arranged with a comparatively small space requirement in the moment flux, wherein if no volumetric flow is tapped off, it 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.

A further 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 is preceded by an inlet valve and an outlet valve connected downstream. By means of the valves, a volume of the piston supplied and discharged be controlled flow, so that per piston reciprocating pulsating flow.

A further 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, a back dividing the piston, in particular for performing a suction work, take place due to 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:

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

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

3 shows a cross section of a hydraulic pump of the hydraulic system shown in FIG. 2 and FIG

FIG. 4 shows a longitudinal section of the hydraulic pump shown in FIG. FIG. 1 shows a schematic view of a hydraulic system 1 with a hydraulic pump 3 for the hydraulic supply of a conical-pulley transmission 5 to which a torque sensor 7 is assigned. The hydraulic system 1 shown in Figure 1 is carried out according to the prior art.

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

The starter unit 13 is the torque sensor 7 downstream. The torque sensor 7 has, for example, a torque-dependent pressure relief valve 15, which may have, for example, by means of two spreading discs not shown in more detail and rolling on rolling elements, which are arranged in the torque flow of the drive train.

The moment sensor 7, the conical-pulley 5 is connected downstream. The conical-pulley 5, a drive device 17, in particular a further gear stage or a differential and drive wheels of the motor vehicle 9 are connected downstream.

The conical-pulley comprises two conical disk pairs 19, which are looped by a belt member 21, for example a link chain. The torque flow from the drive source 11 to the drive device 17 is effected by an input side cone pulley pair 19, which is connected downstream of the torque sensor 7 via the belt 21 on an output side cone pulley pair 19, which is the drive device 17 upstream.

The cone pulley pairs 19 are each connected by means of a hydraulic pressure chamber 23 with a torque of one in the drive train of the motor vehicle. zeugs 9 held torque flow dependent contact pressure against the Umschlingungsorgan 21 pressed.

Further, the conical disk pairs 19 are adjusted to set a translation of the conical-pulley 5 by means of an adjusting device, not shown.

The hydraulic contact pressure chambers 23 are respectively connected downstream of the hydraulic pump 3. In addition, the torque sensor 7 or the torque-independent pressure limiting valve 15 of the hydraulic pump 3 is connected downstream. Thus, a pressure generated by the torque sensor 7 and dependent on the moment acts on the Anpresskamjnern 23 and thus a correspondingly dependent on the pressure hydraulic force on the belt 21.

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

Figure 2 shows a schematic view of a hydraulic system 1 according to the invention with a hydraulic pump 3. The same 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 FIG. 1, the hydraulic pump 3 is arranged in the drive train, that is to say in the torque flow of the drive train of the motor vehicle 9.

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 5. The hydraulic pump 3 is the Anpresskammern 23 downstream, in contrast, the hydraulic pump 3 itself provides a dependent of the moment of the drive train of the motor vehicle 9 pressure as output pressure. Advantageously, the torque-dependent pressure limiting valve 15 shown in FIG. 1 and connected downstream of the hydraulic pump 3 is not necessary. As a further difference, the drive train of the motor vehicle 9 according to the illustration of Figure 2 no separate coupling. Rather, the hydraulic pump 3 in addition to the function of the torque sensor 7 also fulfills the function of the starting unit 13. For this purpose, to start the motor vehicle 9, a slip of the hydraulic pump 3 can be set to one hundred percent. Corresponding, necessary for this hydraulic control valves, which derive a corresponding, promoted in this slip volume flow in a tank 25 of the hydraulic system 1, are not shown in detail in Figure 2.

3 shows a cross section of the hydraulic pump 3 shown in FIG. 2. FIG. 4 shows a longitudinal section of the hydraulic pump 3 shown in FIGS. 2 and 3. Reference will be made below to FIGS. 3 and 4 together.

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

The reciprocating pistons 13 are stepped and mounted radially displaceable longitudinally in a stepped bore 35 of a rotor 37 of the hydraulic pump 3. The rotor 37 is rotatably supported by two rolling bearings 39 to the cam ring 27.

The hydraulic pump 3 has a low-pressure inlet 41 and a high-pressure outlet 43. The high pressure outlet 43 is associated with the stepped bores 35 so that an output pressure of the hydraulic pump 3 acts on a reduced cross sectional area of the stepped reciprocating pistons 29, whereby the reciprocating pistons 29 are exposed to high pressure.

The low-pressure inlet 41 is a suction valve 45 connected downstream of each piston 31. The suction valves 45, the respective reciprocating piston 31 and a stroke volume 47 of the corresponding reciprocating piston 31 is connected downstream. The stroke volume 47 and the corresponding reciprocating piston 31 is followed by an outlet valve 49 in each case. The suction valves 45 and the outlet valves 49 are each designed as check valves. Advantageously, according to the invention, in particular in comparison with the representation of FIG. 1, to maintain the contact pressure against the belt 21, there is no need for a continuously present volume flow. Advantageously, therefore, no permanent hydraulic power, regardless of an actual need, so that an efficiency of the hydraulic system 1 is advantageously increased.

The stroke volume 47 of the hydraulic pump 3 is designed so that a transmitted drive torque of the drive train of the motor vehicle 9 required in the Anpresskammern 23 hydraulic pressure or in a variator of the Cone pulley 5 produces required mechanical contact pressure. 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. If appropriate, which is not shown in FIG. 2, they can be generated from the basic pressure of the hydraulic pump 3 by means of a suitable hydraulic circuit.

The delivery 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 shown in Figures 3 and 4, is designed as a radial piston pump. On the outside, the cam ring 27 rotates around a cylinder star of the rotor 37 having the lifting pistons 31 with the individually movable lifting pistons 31, which each have a suction valve 45 or an inlet valve and an outlet valve 49. The valves 45 and 49 are not positively controlled, designed as check valves, thereby advantageously the hydraulic pump 3 can generate a hydraulic pressure at the high-pressure outlet 43 equally even with an alternating torque sign. This can be advantageous, for example, in a push and pull operation of the motor vehicle 9. Preferably, the reciprocating piston 31, as shown in Figure 3, executed stepped. Thus, they can advantageously be arranged very close to a circumference of the rotor 37, despite a comparatively large guide length. In addition, the staging offers the possibility of applying a preferably small partial area for issuing the reciprocating pistons 31 with the outlet pressure, that is to assign them to the high-pressure outlet 43.

The lifting piston 31 roll on a Hubringkontur or the lifting cam 29 preferably roller bearings by means of bearings 33 from.

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

The reciprocating piston 31 shown in Figures 3 and 4 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 carry out the hydraulic pump 3 with axial piston and / or unroll the reciprocating piston 31 lying outside on a radially inner multiple cam.

According to the invention, the hydraulic pump 3 is arranged to fulfill the function of the torque sensor 7 in the torque flow of the conical-pulley 5 and supplies a torque-dependent pressure to the high-pressure outlet 43, which is fed to the contactor 23 for pressing the conical disk pairs 19 against the belt 21. Alternatively and / or additionally, it is possible, by means of further valves not shown in detail, to to adapt the pressure provided to an altered 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 to connect further hydraulic consumers to the hydraulic pump 3, for example adjustment chambers of the conical-disk belt drive 5, clutch actuators and / or oil cooling and / or further hydraulic consumers.

The housing of the hydraulic pump rotates. The output 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 47 related to a rotation angle.

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

Alternatively and / or additionally, it is possible to adjust the stroke volume 47 of the hydraulic pump 3 in an adjustable manner, wherein the contact pressure force can additionally be adapted to a ratio of the conical disk belt drive 1. This can be done, for example, by switching off individual reciprocating pistons 31, in particular by means of rotary valves on a shaft of the hydraulic pump 3.

A pump rotational speed or the rotational speed difference n1 minus n2 is advantageously set as slip between the drive source 11 and the conical-disk belt transmission 1, depending on a removed volume flow Q itself. Thus, a power consumption of the hydraulic pump 3 Pp _umpe = 2 * pi * M1 * (n1-n2) = 2 * pi * M1 * Q / V is also consumption-oriented. Without adjustment of the conical disks, without additional consumers and without leaks, Q = 0 and the hydraulic pump 3 with n1 = n2 and M1 = M2 as a block run and pass a drive power of the drive source 11 without loss. The hydraulic pump 3 then operates as a torque sensor 7, which advantageously requires no auxiliary power 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 upstream of the tank 25 to provide a controllable valve which opens to the tank 25, and to use the hydraulic pump 3 also as the starting unit 13. In this case, a controllable pressure relief valve limit a maximum transmittable torque of the drive source 11, a flow restrictor, in particular a diaphragm, a throttle and / or a flow control valve, set or control in series with the pressure relief valve or instead of the pressure relief valve 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 to increase the pressure at the high-pressure outlet 43 of the hydraulic pump 3 in a short time over the actually required contact pressure in order to ensure a reliable supply of downstream consumers.

LIST OF REFERENCES

I hydraulic system

3 hydraulic pump

5 conical-pulley transmission

7 moment sensor

9 motor vehicle

I I drive source

13 starting unit

15 pressure relief valve

17 drive device

19 conical disk pairs

21 wrapper

23 hydraulic pressure chamber

25 tank

27 cam ring

29 lifting cams

31 reciprocating piston

33 rolling bearings

35 stepped bore

37 rotor

39 rolling bearings

41 low pressure input

43 high pressure outlet

45 suction valve

47 stroke volume

49 exhaust valve

Claims

claims

1. Hydraulic system (1) with a hydraulic pump (3) for the hydraulic supply of a transmission, in particular a conical-pulley belt drive (5), which is associated with a torque sensor (7), characterized in that the hydraulic pump (3) so in a torque flow of the transmission is arranged, that the hydraulic pump (3) provides a torque flow-dependent pressure.

2. Hydraulic system according to claim 1, characterized in that the pressure as a contact pressure on a Umschlingungsorgan (21) of the conical-Umschlingungsgetriebes (5) is passed, wherein a on a rotation angle of the hydraulic pump (3) related Pumpenhubvolumen the hydraulic pump (3) and a On a linear adjustment of conical disks related stroke volume of Anpresskammern (23) of the conical-Umschlingungsgetriebes (5) are coordinated so that the by the hydraulic pump (3) passed through torque controls the contact pressure so that this at least required for transmitting the torque Anpressschwelldruck is.

3. Hydraulic system according to one of the preceding claims, characterized in that the hydraulic pump (3) on reciprocating piston (31) of the hydraulic pump (3) acting lifting cam (29), which are designed with respect to the direction of rotation of the hydraulic pump (3) a- symmetrical.

4. 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 pistons (31) radially within a cam lobe (29) having cam ring (27) are arranged.

5. Hydraulic system according to one of the preceding claims, characterized in that the hydraulic pump (3) is part of a starting unit (13) of the transmission.

6. Hydraulic system according to one of the preceding claims, characterized in that each of the reciprocating piston (31) in each case upstream of 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 designed stepped.

Hydraulic system according to one of the preceding claims, characterized in that a partial surface of the reciprocating piston (31) is associated with a high-pressure side, in particular a high-pressure outlet (43), of the hydraulic pump (3).

Transmission, in particular conical-pulley transmission (5), having a hydraulic system (1) according to one of the preceding claims.