DE102021124461B3 - Hydraulic system and method of operating a hydraulic system - Google Patents

Abstract

The invention relates to a hydraulic system (30) with a reversible pump (15) which has two delivery connections (23, 24) via which a hydraulic medium can be delivered from a tank (20) in opposite delivery directions in order to hydraulically close an actuating element (10). and to supply cooling and/or lubrication (2) with hydraulic medium via a supply path (6), and with a valve arrangement (25) via which hydraulic medium can be applied to an actuating piston (3) in a double-acting actuating cylinder (12). . In order to reduce the costs for manufacturing and/or operating the hydraulic system (30), a non-return/passage valve (1) pressure-controlled with the aid of a snap spring mechanism (7) is arranged in the supply path.

Description

The invention relates to a hydraulic system with a reversible pump, which includes two delivery connections, via which a hydraulic medium can be delivered from a tank in opposite delivery directions, in order to hydraulically actuate an actuating element and to provide cooling and/or lubrication via a supply path with hydraulic medium. and with a valve arrangement via which hydraulic medium can be applied to an actuating piston in a double-acting actuating cylinder. The invention also relates to 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.

From the publications DE 10 2016 115 925 A1 and WO 2018/ 014 976 A1 other hydraulic actuating devices with a pump and actuating means for engaging and/or disengaging a parking lock device are known. The German Offenlegungsschrift DE 10 2014 013 630 A1 shows a valve of a fluid line with a switching mechanism. A valve closure element can be held in at least one state, in particular the closed state and/or an open state, and/or switched between at least two states by means of at least one switching mechanism. The switching mechanism has at least two discrete switching states, between which the at least one switching mechanism can be switched by means of an external mechanical influence of force.

The object of the invention is to reduce the costs for producing and/or operating a hydraulic system according to the preamble of patent claim 1 .

The task of a hydraulic system with a reversible pump, which includes two delivery connections, via which a hydraulic medium can be delivered from a tank in opposite delivery directions, in order to hydraulically actuate an actuating element and to supply cooling and/or lubrication via a supply path with hydraulic medium , and with a valve arrangement via which an actuating piston in a double-acting actuating cylinder can be acted upon by hydraulic medium, solved in that a non-return/passage valve pressure-controlled with the aid of a snap-action spring mechanism is arranged in the supply path. The non-return/passage valve blocks in the direction of the actuating cylinder and opens, depending on the pressure, against a spring force of the snap-action spring mechanism. The snap-action spring mechanism comprises, for example, at least one Belleville spring with a Belleville spring characteristic that is non-linear. With the snap spring mechanism integrated into the check/passage valve, exactly one hydraulic actuation function plus cooling/lubricating function is provided in a simple manner. An external mechanical connection of the actuating piston can be dispensed with. 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 snap spring mechanism has a non-linear spring characteristic with a high point. This achieves in a simple manner that the non-return/passage valve only opens when the pressure in the actuating cylinder is sufficiently high that the high point of the spring characteristic of the snap-action spring mechanism is exceeded. In addition, the check/passage valve is designed in such a way that it only opens after the high point of the spring characteristic has been passed and the spring force level is lower than an opening force level. Otherwise the pressure would collapse if the non-return/passage valve opened immediately and the high point might not be overcome. With the force levels described, a desired snapper function of the pressure-controlled check valve/throughflow valve can be implemented.

A preferred exemplary embodiment of the hydraulic system is characterized in that the supply path starts from a cooling connection of the actuating cylinder. The cooling connection is advantageously arranged essentially centrally in relation to a longitudinal axis of the actuating cylinder. The two delivery connections of the reversible pump are advantageously associated with two pressure connections that are provided at the ends of the actuating cylinder. The actuating piston is advantageous haft constructed and arranged to be movable to and fro in the actuating cylinder such that the supply path is connected to one of the pressure connections on the actuating cylinder when the actuating piston assumes one of its end positions in the actuating cylinder. In this way, the pressure-controlled non-return/passage valve with the snap-action spring mechanism can be pressurized in a targeted manner via the reversible pump.

Another preferred exemplary embodiment of the hydraulic system is characterized in that the spring characteristic of the snap-action spring mechanism increases from an initial force level that is greater than a supply force level up to the high point and then drops to a final force level. A high hydraulic pressure is therefore initially required to open the check/passage valve. After the high point has been overcome, the non-return/passage valve can be kept open with a lower hydraulic pressure due to the now low restoring force in the at least one spring of the snap-action spring mechanism. The check/passage valve only closes again when the hydraulic pressure in the supply path falls further, in particular below a spring force level at the end of the spring characteristic, for example when the supply path is pressureless.

Another preferred embodiment of the hydraulic system is characterized in that the final force level is greater than zero but less than the supply force level. In this way, a stable supply of the cooling and/or lubrication with hydraulic medium is ensured in a simple manner.

Another preferred exemplary embodiment of the hydraulic system is characterized in that the initial force level is selected in such a way that the hydraulic pressure for opening the check/passage valve is greater than a hydraulic pressure at one end of a switching path of the actuating piston in the actuating cylinder but lower than that required for switching is the maximum switching pressure. The envelope path is the path of the actuating piston that the actuating piston travels between its end positions in the actuating cylinder during operation. The claimed measures ensure that the nonreturn/passage valve, which can also be referred to as a cooling nonreturn valve, only opens after complete switching, ie when the actuating piston has reached its end position or has been pressed to the stop. Advantageously, no higher operating pressure has to be made available than is required for regular actuation. This provides the advantage that the reversible pump does not have to be oversized.

The invention also relates to a non-return/passage valve with a snap-action spring mechanism, an actuating piston, an actuating cylinder, a reversible pump and/or a non-return valve for a hydraulic system as described above. The parts mentioned can be traded separately.

In a method for operating a hydraulic system as described above, the object specified above is alternatively or additionally achieved in that a hydraulic pressure in the supply path drops to a normal cooling pressure level as soon as the non-return/passage valve is opened. As soon as the check/pass valve, which can also be referred to as the cooling check valve, is open, the pressure in the cooling system drops to the normal cooling pressure level. Thus, no higher pressure than in conventional hydraulic systems is required to keep the check/passage valve open. The cooling and/or lubricating function can be switched on and off in this state. An increased pressure is only initially required for switching on.

A preferred exemplary embodiment of the method is characterized in that the non-return/passage valve closes when there is a drop in pressure and separates the supply path from an actuating circuit. If the pressure drops, the non-return/passage valve closes and separates the cooling circuit from the actuating circuit, so that the actuating function can be carried out with it, as in conventional hydraulic systems. A mechanical snap mechanism and also its adjustment of the axial path to the piston path can advantageously be dispensed with, since the claimed snap spring mechanism functions purely under pressure control or under force control.

• 1 ein Hydrauliksystem mit einer Reversierpumpe zur hydraulischen Betätigung eines Betätigungselements mit einem Versorgungspfad zur Darstellung einer Kühlungs- und/oder Schmierfunktion, in welchem ein mit Hilfe eines Schnappfedermechanismus druckgesteuertes Rückschlag-/Durchlassventil angeordnet ist; und
• 2 ein Federkraft-Weg-Diagramm zu dem Schnappfedermechanismus.

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 hydraulic system with a reversible pump for hydraulically actuating an actuating element with a supply path for performing a cooling and/or lubricating function, in which a non-return/passage valve pressure-controlled with the aid of a snap spring mechanism is arranged; and
• 2 a spring force-displacement diagram for the snap spring mechanism.

In 1 a hydraulic system 30 with a tank 20 is shown in the form of a hydraulic circuit diagram puts. With a reversible pump 15, hydraulic medium can be conveyed from the tank 20 via a suction filter 19 in opposite conveying directions.

A first delivery connection 23 is in 1 indicated to the left of the reversing pump 15. A second delivery connection 24 is in 1 indicated to the right of the reversing pump 15. The reversible pump 15 is driven by a pump motor 17 . The pump motor 17 is preferably an electric motor.

Above the reversible pump 15 is in 1 an actuating cylinder 12 is arranged. The actuating cylinder 12 is designed as a double-acting actuating cylinder. In the actuating cylinder 12 there is an actuating piston 3 in 1 movably received to the right and to the left.

at his in 1 At the left end, the actuating cylinder 12 has a first pressure connection 5 . at his in 1 At the right end, the actuating cylinder 12 has a second pressure connection 14 . The two pressure connections 5 and 14 can also be referred to as inputs of the actuating cylinder 12.

The actuating cylinder 12 has a cooling connection 11 as the third connection, which can also be referred to as the outlet of the actuating cylinder 12 . A cooling and/or lubrication system 2 is supplied with hydraulic medium via the cooling connection 11 . Between the cooling connection 11 and the cooling and/or lubrication 2 there is a non-return/passage valve 1 which blocks in the direction of the actuating cylinder 12 .

The actuating piston 3 takes in the in 1 shown state of the hydraulic system 30 its left end position or end position. In this end position or end position, the actuating piston 3 is arranged axially between the first pressure connection 5 and the cooling connection 11 .

A pressure chamber 4 in 1 is arranged to the left of the actuating piston 3 in the actuating cylinder 12 has its smallest size. A pressure chamber 13 in 1 is arranged to the right of the actuating piston 3 in the actuating cylinder 12 has its maximum size. The cooling connection 11 is connected to the second pressure connection 14 of the actuating cylinder 12 via the pressure chamber 13 .

A valve arrangement 25 includes a first tank check valve 18 and a second tank check valve 16 . The second tank check valve 16 is connected to the second pressure port 14 of the actuating cylinder 12 via the second delivery port 24 of the reversible pump 15 .

The actuating piston 3 is mechanically coupled to an actuating element 10 via a piston rod. The actuating element 10 is, for example, a switching element of a dog clutch or a parking lock.

The hydraulic connection between the cooling connection 11 of the actuating cylinder 12 and the cooling and/or lubrication 2 represents a supply path 6 in which the check/passage valve 1 is combined with a snap spring mechanism 7 . The snap-action spring mechanism 7 comprises a disk spring 8 indicated by way of example with a spring characteristic 9 which is shown in 2 is shown.

2 shows a Cartesian coordinate diagram with an x-axis and a y-axis. A spring force or a spring force level is plotted in a suitable force unit on the y-axis. An associated spring travel s is plotted on the x-axis in a suitable travel unit.

The spring characteristic 9 starts at s equal to zero at an initial force level 34 . The spring characteristic 9 rises from the initial force level 34 to a high point 36 . Then the spring characteristic 9 falls from a high point force level 35 first to a supply force level 33 , then to an opening force level 32 and finally to a final force level 31 . An opening travel assigned to the opening force level 32 is denoted by 42 on the x-axis.

Reference List

1

check/passage valve

2

cooling and/or lubrication

3

actuating piston

4

pressure room

5

first pressure port

6

supply path

7

snap spring mechanism

8th

disc spring

9

spring characteristic

10

actuator

11

cooling connection

12

actuating cylinder

13

pressure room

14

second pressure port

15

reversible pump

16

second tank check valve

17

pump motor

18

first tank check valve

19

suction filter

20

tank

23

conveyor connection

24

conveyor connection

25

valve assembly

30

hydraulic system

31

End Force Level

32

opening force level

33

supply power level

34

initial force level

35

peak force level

36

peak

42

opening path

Claims (8)

Hydraulic system (30) with a reversible pump (15) comprising two delivery connections (23,24) via which a hydraulic medium can be delivered from a tank (20) in opposite delivery directions in order to hydraulically actuate an actuating element (10) and to cooling and/or lubrication (2) via a supply path (6) with hydraulic medium, and with a valve arrangement (25) via which an actuating piston (3) in a double-acting actuating cylinder (12) can be acted upon with hydraulic medium, wherein in the a non-return/passage valve (1) pressure-controlled with the aid of a snap-action spring mechanism (7) is arranged in the supply path, the snap-action spring mechanism (7) having a non-linear spring characteristic (9) with a high point (36), characterized in that the non-return/passage valve (1) is designed so that it only opens after the high point (36) of the spring characteristic (9) has been passed and the spring force level is less than one Opening force level (32). hydraulic system claim 1 , characterized in that the supply path (6) starts from a cooling connection (11) of the actuating cylinder (12). Hydraulic system according to Claim 1 or 2, characterized in that the spring characteristic (9) of the snap-action spring mechanism (7) increases from an initial force level (34) which is greater than a supply force level (33) to the high point (36) and then to a final force level (31) falls off. hydraulic system claim 3 , characterized in that the final force level (31) is greater than zero but less than the supply force level (33). Hydraulic system according to one of Claims 1 until 4 , characterized in that the initial force level is selected such that the hydraulic pressure for opening the check/passage valve (1) is greater than a hydraulic pressure at one end of a switching path of the actuating piston (3) in the actuating cylinder (12) but lower than a is the maximum switching pressure required for switching. Check/passage valve (1) with a snap spring mechanism (7), actuating piston (3), actuating cylinder (12), reversible pump (15) and/or check valve (16, 18) for a hydraulic system (30) according to one of the preceding claims. Method for operating a hydraulic system (30) according to one of the preceding claims, characterized in that a hydraulic pressure in the supply path (6) drops to a normal cooling pressure level as soon as the non-return/passage valve (1) is opened. Method according to Claim 9, characterized in that the non-return/passage valve (1) closes when there is a drop in pressure and isolates the supply path (6) from an actuating circuit.

Images