DE102015206464A1 - hydraulic power unit - Google Patents

Abstract

The invention relates to a hydraulic unit (10) having a low-pressure pump (12) for discharging hydraulic fluid (20) with a low pressure (p12), a drive (16) connected to the low-pressure pump (12) for driving, a high-pressure pump (14) for discharging hydraulic fluid (20), which is under high pressure (p14), wherein one of the high-pressure pump (14) maximum deliverable pressure is greater than one of the low-pressure pump (12) a maximum deliverable Pressure, and a clutch (28), by means of which the high-pressure pump (14) reversibly in a torque flow to the drive (16) is switchable. According to the invention, it is provided that the coupling (28) is connected to the low-pressure pump (12) such that the coupling (28) can be actuated by means of hydraulic fluid (20) with low pressure (p12).

Description

The invention relates to a hydraulic power unit with (a) a low pressure pump for discharging hydraulic fluid at a low pressure, (b) a drive connected to the low pressure pump for driving, (c) a high pressure pump for discharging hydraulic fluid, which is under high pressure, wherein a maximum of the high-pressure pump pressure can be greater, in particular at least four times as large as one of the low-pressure pump maximum pressure releasable, and (d) a clutch, by means of which the high-pressure pump reversible in a torque flow with the drive is switchable.

Such hydraulic units are used to provide hydraulic fluid at at least two different pressure levels. It is known to rigidly couple the high pressure pump and the low pressure pump so that the drive always drives both pumps. This has the disadvantage that frictional losses and / or hydraulic losses also occur in the high-pressure pump when no pressurized fluid under high pressure is required.

The invention is based on the object to reduce disadvantages in the prior art.

The invention solves the problem by a generic hydraulic pump in which the coupling is connected to the low-pressure pump, that the coupling by means of hydraulic fluid with low pressure can be actuated.

In other words, the clutch is designed so that its switching state can be changed by supplying hydraulic fluid that is at the pressure level generated by the low-pressure pump. It is possible that the actuation by means of the hydraulic fluid, which is under low pressure, further opens the clutch or that it is closed further.

An advantage of the invention is that for actuating the clutch only a switching device, such as a valve, is necessary. The hydraulic pump according to the invention is therefore simple and therefore robust.

It is also advantageous to improve the system efficiency, since the high pressure pump only runs when high pressure fluid is needed.

It is a further advantage that the high pressure pump can then be simply switched out of the torque flow when it is not needed. This prevents friction losses and increases efficiency.

In the context of the present description, the low-pressure pump is understood to mean, in particular, a pump which, due to the design, can bring hydraulic fluid to a maximum low pressure which is significantly lower than the pressure which can be maximally generated by the high-pressure pump. In particular, the ratio between the maximum high pressure and the maximum low pressure is greater than four. Of course, it is possible, but not necessary, that the low-pressure pump always produces the same low pressure. For example, the low pressure can fluctuate. Decisive is that the low pressure does not exceed a given maximum low pressure.

It is possible, but not necessary, for the high pressure pump to always deliver the same high pressure. In particular, it is conceivable that the high-pressure pump at least temporarily emits a pressure which is even smaller than the low pressure. What matters, however, is that the high-pressure pump is designed so that it can deliver a maximum high pressure, which is significantly greater than the maximum low pressure.

Under the high pressure is understood in particular the pressure under which the hydraulic fluid is when it was pressurized by the high-pressure pump. By low pressure is meant the pressure of the hydraulic fluid under which the hydraulic fluid is under pressure from the low pressure pump.

According to a preferred embodiment, the clutch is adapted to slip upon application of low pressure with slip and transmit drive torque to the high pressure pump such that the high pressure pump delivers hydraulic fluid at a high pressure greater than the low pressure. By including the clutch with slip, it is understood, in particular, that the high pressure pump does not rotate at the speed with which it rotates when the clutch is fully engaged. It is possible, but not necessary, that when the clutch is engaged with slip, a lower torque is transmitted than when fully engaged.

Because the high pressure pump delivers hydraulic fluid at a high pressure that is greater than low pressure, pressurized fluid is available at a higher pressure level. It is possible, and is a preferred embodiment, that the high pressure the high pressure pump delivers when the clutch is coupled with slip is less than the maximum high pressure. It is then possible by fully engaging the clutch to increase the high pressure to the maximum possible high pressure, so that several pressure levels can be generated with the hydraulic unit.

More preferably, the clutch is connected to the high pressure pump so that increasing the torque transmitted from the clutch to the high pressure pump causes an increase in high pressure, wherein increasing the high pressure causes the drive torque on the high pressure pump to increase. For this purpose, in particular the pressure side of the high pressure pump is connected to the clutch via a pressure line.

If hydraulic fluid is passed to the clutch at low pressure, it will slip. The high-pressure pump is then driven, supplying hydraulic fluid at a higher pressure, thus actuating the clutch in the same direction as the low-pressure hydraulic fluid. As a result, according to one embodiment, the clutch is closed further, that is to say that the slip continues to drop and the clutch finally couples without slip. Since the high-pressure pump delivers hydraulic fluid under high pressure, the clutch can be made comparatively small because a high clutch pressure is applied.

Alternatively, increasing the high pressure causes the drive torque to be reduced to the high pressure pump.

According to a preferred embodiment, the coupling is connected by means of a pressure line to the high-pressure pump, wherein the pressure line is designed so that a sudden pressure increase at a pressure side of the high-pressure pump, which is a differential pressure .DELTA.p greater than the clutch pressure in the clutch, after a half-life leads to a clutch pressure which is greater by half of the differential pressure Δp, wherein the half-life is at least 200 milliseconds, in particular at least 500 milliseconds, more preferably at least 1000 milliseconds. For example, a cross section of the pressure line is chosen so small that the requirement is met. The smaller the cross-section, the larger the half-life. As a result, a sudden increase in the clutch pressure and the high pressure is avoided.

According to a preferred embodiment, the pressure line has a flow-influencing device, in particular a throttle, a valve and / or a pressure reducer. High-pressure fluid flows into the coupling through the pressure line. The faster the pressure builds up in the clutch, the faster the clutch closes. This is a positive feedback. By the flow rate influencing device, the strength of this positive feedback can be influenced. It is thus possible to influence a pressure curve in the pressure oil circuit. It is favorable if the flow-influencing device is adjustable in its throttling action. The pressure curve is the dependence of high pressure on time. In particular, it may be advantageous that the high pressure does not rise too fast to its maximum value. In this case, it is favorable if, for example, a throttle is present in the pressure line. This prevents a too rapid increase in the pressure in the clutch and thus a too rapid increase in the high pressure to its maximum value.

Preferably, the coupling is connected by means of a switching line with the low-pressure pump, wherein the switching line comprises a solenoid valve, in particular a proportional valve. By means of the solenoid valve, the clutch can be set to low pressure, so that the drive torque is partially transmitted to the high-pressure pump.

According to the invention is also a marine gearbox with a hydraulic unit according to the invention, wherein the low-pressure pump is part of a lubricating oil circuit. Lubricating oil must be permanently provided at a relatively low pressure level. The low-pressure pump is therefore particularly suitable as a lubricating oil pump.

Under a marine gear is understood a transmission that is designed for installation in a ship. For this purpose, it must preferably be constructed so that it can switch to maximum reverse drive at maximum forward speed. In particular, the marine gear is therefore a reversing gear. It is favorable if the marine gear for transmitting has a power of at least 250 kilowatts.

Preferably, the high-pressure pump is part of a pressure oil circuit. For example, the pressure oil circuit comprises a hydraulic actuator, such as a clutch. Such hydraulic actuators are used only sporadically, so that it is not necessary that permanently hydraulic fluid is present at high pressure.

In the following the invention will be explained in more detail with reference to the accompanying drawings. Showing:

1 a diagram of a hydraulic pump according to the invention, in which the clutch is open,

2 the hydraulic unit according to 1 in which the clutch with slip couples and

3 the hydraulic unit with closed clutch,

4 a pressure curve of the high pressure and

5 with the subfigures 5a . 5b and 5c an inventive hydraulic unit having a linkage for switching the clutch.

1 shows a hydraulic unit according to the invention 10 with a low pressure pump 12 , a high pressure pump 14 and a drive 16 , which is formed in the present case by an electric motor. The drive 16 However, for example, it may also be an internal combustion engine, for example a main or auxiliary diesel of a ship. The drive 16 is non-rotatable with the low-pressure pump 12 coupled, in the present case by means of a shaft 18 ,

The low pressure pump 12 gives hydraulic fluid 20 in a switching line 22 which is under a low pressure p ₁₂ . The pressurized hydraulic fluid 20 could therefore also be referred to as low-pressure hydraulic fluid. The hydraulic fluid is, for example, oil, in particular lubricating oil.

The high pressure pump 14 is via a double check valve 24 with the switching line 22 connected. The switching line 22 also includes a solenoid valve 26 , with which the pressure p in the switching line 22 to a clutch 28 can be switched through. At the solenoid valve 26 it can be a proportional valve, but it is not necessary.

1 shows the solenoid valve 26 in its zero pressure position, in which the clutch 28 via a return line 30 with a swamp 32 connected is. In the swamp 32 For example, ambient pressure can prevail.

Because the clutch 28 pressure-free, it is in the present embodiment in the open state. For example, to clutch plates 34.1 . 34.2 , ... by a spring 36 kept at a distance. Will the clutch 28 with hydraulic fluid 20 acted upon, so presses the hydraulic fluid 20 on a piston 37 , in turn, the clutch discs 34.1 . 34.2 , ... compresses and so the clutch 37 at least partially closes.

It can be seen that the switching line 22 with a lubricating oil receiver 38 connected is. In the in 1 shown operating position supplies the hydraulic unit 10 the lubricating oil receiver 38 with lubricating oil, but it is only provided hydraulic fluid to low pressure p ₁₂ . The oil receiver 38 is part of a lubricating oil circuit 39 which also includes the connection lines.

2 shows the solenoid valve 26 in its switching position, in which the switching line 22 the coupling 28 supplied with low pressure p ₁₂ . A p ₁₂ in the clutch 28 thus increases to the p ₁₂ . The low pressure p ₁₂ is so strong that the clutch 28 with slip couples. This means that a rotational frequency of a drive side of the clutch and thus usually a rotational frequency n _{16 of} the drive 16 greater than a rotational frequency n _{28 of} the clutch 28 on its output side.

By doing that, the clutch 28 with slip, a drive torque M _{28 is} applied to the high pressure pump 14 transfer. The high pressure pump 14 thereby brings hydraulic fluid 20 at high pressure p ₁₄ , which is greater than the low pressure p ₁₂ . This will switch the double check valve 24 and thereby the high pressure p ₁₄ to the clutch 28 created. So because the pressure side of the high-pressure pump 14 now with the clutch 28 is connected, the clutch pressure p _{28 increases} to the high pressure p ₁₄ .

The connection between the high pressure pump 14 and the clutch 28 is called a pressure line 40 designated. It should be noted that the pressure line 40 partly with the switching line 22 may be identical and in the embodiment shown also. The pressure line 40 is in connection with a pressure oil receiver 42 , For example, a clutch or other hydraulic actuator, the part of a pressure oil circuit 43 is.

Due to the increasing pressure in the clutch 28 takes the slip in the clutch 28 continue until the clutch is finally fully engaged. In this state are the drive 16 and the high pressure pump 14 rotatably connected.

3 shows the condition in which both pumps 12 . 14 Promote fluid. It can be seen that both pumps 12 . 14 through a common supply line 44 from the swamp 32 be supplied with hydraulic fluid. From the oil receiver 38 and pressure oil receiver 42 Returning hydraulic fluid flows into the sump 32 ,

4 shows the pressure _{curve of} the clutch pressure p _{28, SdT} (t) in the clutch 28 in a hydraulic unit according to the prior art. It can be seen that the clutch _pressure p _SdT (t) abruptly increases and decreases, which is often undesirable. Also marked is a calculated pressure curve p ₁₄ (t) for a hydraulic unit according to the invention. After a switching point t _s , the pressure p _{14 increases} comparatively slowly. At a time t ₁ , the high-pressure pump starts 14 to promote. Due to the feedback effect, the drive torque M _{28 increases} as well as the result of the high pressure p ₁₄ and thus the clutch pressure p _28th

The rate of increase in pressure of the clutch pressure p ₂₈ can be reduced by providing - as provided in a preferred embodiment - in the pressure line 40 between the pressure side of the high-pressure pump 14 and the clutch 28 a flow rate influencing device 45 (see. 1 ) is arranged. Alternatively or additionally, a cross section of at least part of the pressure line 40 be chosen so that the pressure line the effect of the flow rate influencing device 45 Has. So can the in 4 shown clutch pressure curve p ₂₈ (t) can be achieved.

At a switching time t _2, the clutch engages 28 full, that is without slippage, and the high pressure p ₁₄ reaches its maximum value p _{14, max} . This corresponds to the maximum pressure that the high pressure pump 14 supplies.

By means of a flow-influencing device 45 , For example, a throttle, the pressure rise in the clutch 28 be delayed. Thus, the strength of the positive feedback and thus the time between the switching point and the time when the full high pressure is applied, can be set.

The 5a . 5b and 5c show a further embodiment in which the coupling 28 a linkage 46 by means of which the force of a pressurized cylinder 48 on the clutch discs 34 is transmitted. The functioning does not differ from that for the 1 to 3 has been described.

LIST OF REFERENCE NUMBERS

10

hydraulic power unit

12

Low pressure pump

14

High pressure pump

16

drive

18

wave

20

hydraulic fluid

22

switching line

24

Double check valve

26

magnetic valve

28

clutch

30

return

32

swamp

34

clutch discs

36

feather

37

piston

38

Oil receiver

39

Lubricating oil circuit

40

pressure line

42

Pressure oil receiver

43

Pressure oil circulation

44

supply line

45

Flow influencing device

46

linkage

48

cylinder

p ₁₂

low pressure

p ₁₄

high pressure

p ₂₈

clutch pressure

Ap

differential pressure

M ₂₈

Driving torque

n

rotational frequency

t _s

switching point

Claims (9)

Hydraulic unit ( 10 ) with (a) a low-pressure pump ( 12 ) for discharging hydraulic fluid ( 20 ) with a low pressure (p ₁₂ ), (b) a drive ( 16 ) connected to the low-pressure pump ( 12 ) is connected to drive, (c) a high-pressure pump ( 14 ) for discharging hydraulic fluid ( 20 ), which is under high pressure (p ₁₄ ), one of the high-pressure pump ( 14 ) maximum deliverable pressure is greater than one of the low-pressure pump ( 12 ) maximum deliverable pressure, and (d) a clutch ( 28 ), by means of which the high-pressure pump ( 14 ) reversibly into a torque flow with the drive ( 16 ) is switchable, characterized in that (e) the coupling ( 28 ) so with the low-pressure pump ( 12 ), that the coupling ( 28 ) by means of hydraulic fluid ( 20 ) can be actuated with low pressure (p ₁₂ ). Hydraulic unit ( 10 ) according to claim 1, characterized in that the coupling ( 28 ) is designed so that when it is subjected to low pressure (p ₁₂ ), it couples with slip and a drive torque (M ₂₈ ) to the high-pressure pump ( 14 ), so that the high-pressure pump ( 14 ) Hydraulic fluid ( 20 ) with a high pressure (p ₁₄ ), which is greater than the low pressure (p ₁₂ ). Hydraulic unit ( 10 ) according to claim 2, characterized in that - the coupling ( 28 ) with the high-pressure pump ( 14 ) is connected so that an increase of the of the clutch ( 28 ) on the high-pressure pump ( 14 ) (M ₂₈ ) causes an increase of the high pressure (p ₁₄ ), and that - the increase of the high pressure (p ₁₄ ) an increase of the drive torque (M ₂₈ ) on the high pressure pump ( 14 ) causes. Hydraulic unit ( 10 ) according to one of the preceding claims, characterized in that - the coupling ( 28 ) by means of a pressure line ( 40 ) with the high-pressure pump ( 14 ) and - the pressure line ( 40 ) is formed such that a sudden increase in pressure on a pressure side of the high-pressure pump ( 14 ), which is a differential pressure Δp greater than the clutch pressure p ₂₈ in the clutch, after a half-life to a Clutch pressure leads, which is greater by half of the differential pressure Ap, - wherein the half-life is at least 200 milliseconds. Hydraulic unit ( 10 ) According to one of the preceding claims, characterized in that the pressure line ( 40 ) a flow rate influencing device ( 45 ), in particular a throttle, a valve and / or a pressure reducer. Hydraulic unit ( 10 ) according to one of the preceding claims, characterized in that - the coupling ( 28 ) by means of a switching line ( 22 ) with the low-pressure pump ( 12 ) and - the switching line ( 22 ) a solenoid valve ( 26 ), in particular a proportional valve. Marine gearbox with (a) a hydraulic power unit ( 10 ) according to one of the preceding claims, (b) wherein the low-pressure pump ( 12 ) Part of a lubricating oil circuit ( 39 ). Marine gearbox according to claim 7, comprising (a) a hydraulic power unit ( 10 ) according to one of the preceding claims, (b) wherein the high-pressure pump ( 14 ) Part of a pressure oil circuit ( 43 ). Marine gearbox according to claim 8, characterized by a coupling ( 28 ), the part of the pressure oil circuit ( 43 ) and for switching by means of hydraulic fluid ( 20 ), which is under high pressure (p ₁₄ ) is formed.

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