DE102021124487B3 - Hydraulic system and method of operating a hydraulic system - Google Patents

Abstract

The invention relates to a hydraulic system (1) with a reversible pump (5) that can be driven in opposite directions of rotation by a pump motor (14). In order to simplify the provision of different volume flows and/or pressure levels in the hydraulic system (1), a step-up gear (45) is arranged between the pump motor (14) and the reversible pump (5), via which the reversible pump (5) rotates in opposite directions can be driven at the same engine speed with different pump speeds in such a way that a volume flow for cooling and/or lubrication (7) is provided in a first delivery direction via a first pump outlet (11), with a volume flow for cooling and/or lubrication (7) being provided in a second delivery direction via a second pump outlet (12). hydraulic actuating pressure is provided.

Description

The invention relates to a hydraulic system with a reversible pump that can be driven in opposite directions of rotation by a pump motor. The invention also relates to a pump arrangement for a hydraulic system and a method for operating such a hydraulic system.

From the German Offenlegungsschrift DE 10 2018 112 670 A1 a hydraulic device with a pump is known, which can be connected to a coolant line for supplying a first consumer with hydraulic medium for cooling and/or lubricating it and can be connected to an activation line for supplying a second consumer with the same hydraulic medium for its actuation, wherein the Pump is designed as a reversing pump, wherein a hydraulic parking lock actuator, which has a double-acting piston, can be supplied with hydraulic medium for actuating the parking lock, wherein the piston is designed as a differential area piston or as an equal area piston, the parking lock actuator being able to be fixed in position via a locking device, the locking device being a spring-loaded Has blocking element, which is dimensioned and arranged for engagement in a shape-opposite recess.

The pamphlet DE 10 2010 018 192 A1 shows a gear shift for an oil pump rotating in one direction, through which different translations for the power transmission from the drive to the pump can be set. From the US 2017 / 0 087 975 A1 a pump drive is known in which freewheels are used to transmit different drive directions with different translations for a pump rotating in one direction.

The object of the invention is to simplify the provision of different volume flows and/or pressure levels in a hydraulic system with a reversible pump that can be driven in opposite directions of rotation by a pump motor.

The object is achieved in a hydraulic system with a reversible pump that can be driven in opposite directions of rotation by a pump motor in that a transmission gear is arranged between the pump motor and the reversible pump, via which the reversible pump can be driven in opposite directions of rotation at the same motor speed with different pump speeds that in a first conveying direction a volume flow for cooling and/or lubrication is provided via a first pump outlet, with a hydraulic actuating pressure being provided in a second conveying direction via a second pump outlet. With the hydraulic actuating pressure, a hydraulic actuating force is generated, which is used, for example, to actuate a dog clutch or a parking lock actuator. The hydraulic medium is, for example, hydraulic oil, which is also referred to as oil for short. However, the hydraulic medium can also be water. Analogously, the reversible pump can be a water pump. The speed difference provided by the transmission gear in the opposite directions of rotation of the reversible pump is preferably selected in such a way that a rather larger volume flow with a lower pressure for cooling and/or lubrication is provided in the first conveying direction, while a rather smaller volume flow is provided in the second conveying direction a greater pressure is provided for hydraulic actuation. At least two different pressure levels or volume flows can advantageously be provided by the transmission gear with only one pump motor and one reversible pump. The conveying direction or pumping direction and at the same time the conveying volume can be selected by means of the direction of rotation of the pump motor, with the pumping direction and the conveying volume being in a fixed relationship.

A preferred exemplary embodiment of the hydraulic system is characterized in that the transmission gear has two output shafts with a reverse direction of rotation. Depending on the translation, different speeds can be provided in the opposite directions of rotation of the reversible pump in a simple manner.

A further preferred exemplary embodiment of the hydraulic system is characterized in that a freewheel is assigned to each of the output shafts, with the two freewheels having the opposite freewheeling direction. This enables a desired relative rotation of the output shafts against one another during operation of the reversible pump.

A further preferred embodiment of the hydraulic system is characterized in that a first output shaft of the gearbox is drivingly associated with a first pump gear, a second output shaft of the gearbox is drivingly associated with a second pump gear which is in mesh with the first pump gear. The reversible pump is advantageously designed as a gear pump, in particular as an external gear pump. So can with the transmission gear with only one pump motor, the desired function for providing different volume flows and/or pressure levels in the hydraulic system can be ensured in a simple manner.

Another preferred exemplary embodiment of the hydraulic system is characterized in that the first output shaft is driven at the engine speed of the pump motor, with the second output shaft having a desired gear ratio. This simplifies the construction of the transmission gear considerably. In addition, the structure of a controller for driving the pump motor is simplified.

A further preferred exemplary embodiment of the hydraulic system is characterized in that the reversible pump is designed as a gear pump with two gear wheels which are in mesh with one another and which can be driven by the pump motor via the transmission gear at different speeds in opposite directions of rotation. The structure of gear pumps with two gears in mesh is known per se. The combination with the transmission gear and the freewheels allows for a comfortable operation of the hydraulic system in a simple manner.

Another preferred exemplary embodiment of the hydraulic system is characterized in that the reversible pump in the hydraulic system is hydraulically connected to a tank only with passive valves in such a way that two different volume flows and/or pressure levels are provided in the hydraulic system depending on the delivery direction of the reversible pump. In one conveying direction, for example, a rather large volume flow is provided with a low pressure to supply cooling and/or lubrication. In the other conveying direction, a rather lower volume flow is advantageously provided with a high pressure, which is sufficient to implement a desired hydraulic actuation, for example a dog clutch or a parking lock.

Another preferred embodiment of the hydraulic system is characterized in that the second pump outlet of the reversible pump is connected to an actuating cylinder via an actuating check valve and a switching valve, which is designed as a double-acting hydraulic cylinder with an actuating piston, which is mechanically coupled to a ramp arrangement, the two ramps includes, which interact with a biased by a spring device latching element. The switching valve is designed, for example, as a 2/2-way valve. One of the two pressure ports of the hydraulic cylinder can be pressurized via the switching valve, while the other pressure port is relieved into the tank. In this way, actuation, for example of a clutch, in particular a claw clutch, or a parking lock is made possible in a simple manner. The actuating cylinder designed as a double-acting hydraulic cylinder also advantageously comprises two control pressure connections which are connected to control pressure surfaces of the switchover valve via control pressure lines. The detent element, which is prestressed by the spring device, together with the ramp arrangement, represents a detent mechanism by which the actuating piston is moved mechanically via the spring device into one of its end positions, shortly before the actuating piston in the hydraulic cylinder releases one of the control pressure outlets in the direction of a switchover actuation.

The invention also relates to a pump arrangement with a reversible pump and a transmission gear for a hydraulic system as described above. The pump arrangement with the reversible pump and the transmission gear can be traded separately.

In a method for operating a hydraulic system as described above, the above-mentioned object is alternatively or additionally achieved in that, by switching the drive direction of rotation of the reversible pump via the transmission gear, either a high pressure level with a low volume flow or a high volume flow with a low pressure level is generated in the hydraulic system becomes. This makes it possible in a simple manner in the hydraulic system with only one pump motor and one reversible pump to provide a large volume flow to supply cooling and/or lubrication and to provide a sufficiently high pressure level to actuate a parking lock or a claw clutch, for example.

• 1 eine schematische Darstellung eines Hydrauliksystems mit einer durch einen Pumpenmotor in entgegengesetzten Drehrichtungen antreibbaren Reversierpumpe, wobei zwischen dem Pumpenmotor und der Reversierpumpe ein Übersetzungsgetriebe angeordnet ist; und
• 2 eine schematische Längsschnittdarstellung einer Pumpenanordnung mit einem Pumpenmotor, einem Übersetzungsgetriebe und einer Reversierpumpe, die als Zahnradpumpe ausgeführt ist.

Further advantages, features and details of the invention result from the following description, in which various exemplary embodiments are described in detail with reference to the drawing. Show it:

• 1 a schematic representation of a hydraulic system with a reversible pump that can be driven in opposite directions of rotation by a pump motor, a transmission gear being arranged between the pump motor and the reversible pump; and
• 2 a schematic longitudinal sectional view of a pump assembly with a Pum penmotor, a transmission gear and a reversible pump, which is designed as a gear pump.

In 1 a hydraulic system 1 with a tank or reservoir 2 is shown in the form of a hydraulic circuit diagram. With a reversible pump 5, hydraulic medium can be conveyed from the tank 2 via an optional filter device 3 in opposite conveying directions. The optional filter device 3 includes, for example, a suction filter.

The reversible pump 5 comprises two delivery connections 11 and 12. In the first delivery direction, the delivery connection 11 represents a first pump outlet 11. In the second delivery direction of the reversible pump 5, the delivery connection 12 represents a second pump outlet 12. The respective other delivery connection 12 and 11 then represents represents a pump inlet of the reversible pump 5.

The reversible pump 5 can be driven by a pump motor 14 in opposite directions of rotation. The pump motor 14 is preferably an electric motor.

A first tank check valve 4 is connected between the first pump outlet 11 and the tank 2 . A second tank check valve 6 is connected between the second pump outlet 12 and the tank 2 . The two tank check valves 4 and 6 each block in the direction of tank 2.

In the first conveying direction of the reversible pump 5, cooling and/or lubrication 7 is supplied with hydraulic medium via an optional cooling check valve 8 from the tank 2 via the filter device 3 and the second tank check valve 6.

In the second conveying direction of the reversible pump 5, a piston 9, also referred to as an actuating piston, is acted upon by hydraulic pressure in an actuating cylinder 10. The piston 9 in the actuating cylinder 10 is operationally connected to an actuating element 13 .

In the hydraulic system 1, hydraulic medium can be conveyed from the tank 2 via the filter device 3 and a branch 16 into an actuating branch 17 or into a supply branch 18.

In the actuating branch 17, starting from the branch 16, the second tank check valve 6, a branch 19 and an actuating check valve 20 are arranged. The check valves 6 and 20 in the actuating branch 17 lock in 1 down towards Tank 2.

Starting from the branch 16, the first tank check valve 4, a branch 22 and the cooling check valve 8 are arranged in the supply branch 18. The two check valves 4 and 8 in the supply branch 18 block in 1 down towards Tank 2.

The cooling and/or lubrication 7 is supplied with hydraulic medium from the tank 2 via the supply branch 18 . An actuating element 13 is actuated hydraulically via the actuating branch 17 . The actuating element 13 is, for example, part of a dog clutch or a parking lock.

In 1 one can see that the actuating branch 17 in the hydraulic system 1 is connected to a first connection of a switching valve 21 . A tank line 24 is connected to a second connection of the switching valve 21 . Two pressure connections of the actuating cylinder 10 designed as a double-acting hydraulic cylinder are connected to a third connection and a fourth connection of the switching valve 21 .

In the actuating cylinder 10 there is an actuating piston 9 in 1 reciprocably left and right. The actuating piston 9 can be moved in the actuating cylinder 10 in 1 on its left side or on its right side with an actuating pressure. The respective other side of the actuating piston 9 is then relieved via the changeover valve 21 and the tank line 24 in the tank 2 .

The changeover valve 21 is connected in terms of control to the actuating cylinder 10 via control pressure lines 25 and 26 . When the actuating piston 9 in the actuating cylinder 10 reaches one of its end positions, the control pressure line 25, 26 arranged on the opposite side is released at the end of its travel.

in the in 1 shown end position of the actuating piston 9 is the in 1 right pressure connection of the actuating cylinder 10 via the control pressure line 26 with the switching valve 21. When pressurized, the envelope valve 21 is in its in 1 not shown second switching position switched.

The actuating piston 9 is combined with a locking device 28 . The locking device 28 is coupled to the actuating piston 9 via a coupling rod 29 . The locking device 28 includes a ramp arrangement 30 with two from a gallery in 1 left and right sloping ramps. The ramps of the ramp arrangement tion 30 interact with a latching element 31, which is supported by a spring device 32 in 1 is biased downward. The latching element 31 is a ball, for example.

The spring device 32 moves the actuating piston 9, which can also be referred to as the switching piston, into its respective end position in the interaction of the latching element 31 with the ramps of the ramp arrangement 30, shortly before the actuating piston or switching piston 9 pushes one of the control pressure lines 25, 26 in the direction of a Actuation of the switching valve 21 releases.

The actuating piston 9 is advantageously equipped with a displacement sensor. The travel information recorded by the travel sensor makes it possible to switch off or switch over or reverse the reversible pump 5 as soon as the actuating piston 9 is about to release one of the control pressure lines 25, 26 in the direction of a switching valve actuation. This ensures that the reversible pump 5 in the hydraulic system is not constantly switched back and forth.

The reversible pump 5 is drivingly connected to the pump motor 14 with the interposition of a transmission gear 45 with a freewheel device 46 . The freewheel device 46 comprises a first freewheel 47 and a second freewheel 48.

In 2 a pump arrangement with the reversible pump 5, the pump motor 14 and the intermediate transmission gear 45 with the freewheel device 46 alone is shown schematically in longitudinal section. The reversible pump 5 can be driven in opposite directions of rotation via the pump motor 14 .

The transmission gear 45 comprises a first gear output shaft 41 and a second gear output shaft 42. The first gear output shaft 41 simultaneously represents a gear input shaft and in the present case is a pump motor shaft of the pump motor 14.

The first transmission output shaft 41, which corresponds to the pump motor shaft, can be connected to a first pump drive shaft 51 in a rotationally fixed manner via the first freewheel 47 in one direction of rotation. In the other direction of rotation, the first pump drive shaft 51 can be freely rotated relative to the first transmission output shaft 41 by the first freewheel 47 .

The second transmission output shaft 42 can be connected to a second pump drive shaft 52 in a rotationally fixed manner via the second freewheel 48 in one direction of rotation. In the other direction of rotation, the second pump drive shaft 52 is freely rotatable relative to the second transmission output shaft 42 by the second freewheel 48 .

The transmission gear 45 includes a first gear wheel 43 and a second gear wheel 44 meshing with the first gear wheel 43 . The first gear wheel 43 has a smaller outside diameter than the second gear wheel 44. The first gear wheel 43 is connected to the first gear output shaft 41 in a torque-proof manner. The second transmission gear wheel 44 is connected to the second transmission output shaft 42 in a torque-proof manner.

The reversible pump 5 is designed as an external gear pump with a first pump gear 53 and a second pump gear 54 which is in engagement with the first pump gear 53 . The first pump gear wheel 53 is connected to the first pump drive shaft 51 in a rotationally fixed manner. The second pump gear wheel 54 is connected to the second pump drive shaft 52 in a torque-proof manner.

The two transmission output shafts 41, 42 have a reverse direction of rotation due to the gear wheels 43 and 44 being in engagement with one another. The reversible pump 5 is driven directly by the pump motor 14 in a first direction of rotation. In a second direction of rotation, the reversible pump 5 is driven via the pump motor, the gear wheels 43, 44 and the second pump drive shaft 52 with the second pump gear wheel 54 with a gear ratio that can be set by the gear wheels 43, 44. The direction of rotation of the pump motor 14 can be used to select both the pumping direction and the delivery volume at the same time, both of which are in a fixed relationship due to the mechanical coupling of the pump gears 53, 54 via the transmission gear 45.

In the first direction of rotation, the reversible pump 5 is driven directly at engine speed. Due to the correspondingly lower delivery volume, a lower volume flow is generated. However, due to the given engine power of the pump motor 14, a higher pressure level can be achieved. In the second direction of rotation, a higher speed and thus a larger volume flow is provided with a translation realized by the transmission gear 45 .

In 2 are the two freewheels 47, 48 of the freewheel device 46 with the pump gears 54, 54 upstream axially. For reasons of space, however, the freewheels 47, 48 can also be arranged inside the pump gears 53, 54, in a different way to that shown.

Reference List

1

hydraulic system

2

reservoir

3

filter device

4

first tank check valve

5

reversible pump

6

second tank check valve

7

cooling and/or lubrication

8th

Refrigeration check valve

9

Pistons

10

actuating cylinder

11

first pump outlet/inlet

12

second pump outlet/inlet

13

actuator

14

pump motor

16

branch

17

actuation branch

18

supply branch

19

branch

20

Confirmation check valve

21

switching valve

22

branch

24

tank line

25

control pressure line

26

control pressure line

28

locking device

29

connecting rod

30

ramp arrangement

31

locking element

32

spring device

41

first transmission output shaft

42

second transmission output shaft

43

first gear wheel

44

second gear wheel

45

transmission gear

46

freewheel device

47

first freewheel

48

second freewheel

51

first pump drive shaft

52

second pump drive shaft

53

first pump gear

54

second pump gear

Claims (9)

Hydraulic system (1) with a reversible pump (5) which can be driven in opposite directions of rotation by a pump motor (14), characterized in that a step-up gear (45) is arranged between the pump motor (14) and the reversible pump (5), via which the reversible pump ( 5) can be driven in opposite directions of rotation at the same motor speed with different pump speeds in such a way that a volume flow for cooling and/or lubrication (7) is provided in a first conveying direction via a first pump outlet (11), wherein in a second conveying direction via a second pump outlet (12) is provided with a hydraulic actuating pressure. Hydraulic system (1) according to claim 1 , characterized in that the transmission gear (45) has two output shafts (41,42) with a reverse direction of rotation. Hydraulic system (1) according to claim 2 , characterized in that the output shafts (41,42) are each assigned a freewheel (47,48), the two freewheels (47,48) having the opposite freewheeling direction. Hydraulic system (1) according to one of the preceding claims, characterized in that a first output shaft (41) of the transmission is drivingly associated with a first pump gear (53), a second output shaft (42) of the transmission being drivingly associated with a second pump gear (54) is assigned, which is in engagement with the first pump gear (53). Hydraulic system (1) according to claim 4 , characterized in that the first output shaft (41) is driven at the engine speed of the pump motor (14), the second output shaft (42) having a desired gear ratio. Hydraulic system (1) according to one of the preceding claims, characterized in that the reversible pump (5) in the hydraulic system (1) is hydraulically connected to a tank (2) only with passive valves in such a way that, depending on the conveying direction of the reversible pump (5 ) Two different volume flows and/or pressure levels are provided in the hydraulic system (1). Hydraulic system (1) according to one of the preceding claims, characterized in that the second pump outlet (12) of the reversible pump (5) is connected via an actuating non-return valve (20) and a switching valve (21) to an actuating cylinder (10), which acts as a double-acting hydraulic cylinder is designed with an actuating piston (9) which is mechanically coupled to a ramp arrangement (30) which comprises two ramps which interact with a latching element (31) prestressed by a spring device (32). Pump arrangement for a hydraulic system (1) according to one of the preceding claims. Method for operating a hydraulic system (1) according to one of Claims 1 until 7 , characterized in that by switching the drive direction of rotation of the reversible pump (5) via the transmission gear (45) in the hydraulic system (1) either a high pressure level with a low volume flow or a high volume flow with a low pressure level is generated.

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