DE102016212389A1 - Hydraulic drive system with smooth running - Google Patents

Abstract

The invention relates to a hydraulic drive system (10, 10 ') comprising a first and a second hydraulic machine (20, 30), which are connected to one another via a first and a second connecting line (40, 50) in the manner of a closed hydraulic circuit the displacement volume of the first and / or the second hydraulic machine (20; 30) is adjustable. According to the invention, a first valve device (41) is connected between the first connecting line (40) and the second hydraulic machine (30), which only has a continuously variable first aperture (42) for a fluid flow from the second hydraulic machine (30) to the first connecting line (40). forms, wherein a control device (14) is provided, which is arranged so that the first orifice (42) is adjustable depending on the flow rate (Q) of the first hydraulic machine (20).

Description

The invention relates to a hydraulic drive system according to the preamble of claim 1.

Closed hydraulic circuits are known from the prior art, in which a first hydraulic machine are connected via a first and a second connecting line with a second hydraulic machine. A hydraulic machine is to be understood as meaning a machine which can be operated selectively as a pump and / or as a hydraulic motor. The first hydraulic machine is driven by a drive motor, wherein the second hydraulic machine drives a further device, for example a cable winch. By adjusting the displacement volumes of the first and / or the second hydraulic machine, the transmission ratio of the hydraulic drive system can be adjusted.

Such drive systems are prone to vibrations, which are particularly disadvantageous when the other device is to be moved slowly and sensitively. An advantage of the invention is that such vibrations are avoided. Further, the first and the second connecting lines, which are formed for example as a pipe or hose, can be made particularly long, without causing vibrations. In particular, when the drive system is used to drive a winch, very heavy loads can be lowered slowly and sensitively. Furthermore, the drive system according to the invention has a high safety with regard to falling down of loads connected to the second hydraulic machine.

According to claim 1, it is proposed that between the first connecting line and the second hydraulic machine, a first valve means is connected, which forms a continuously variable first aperture only for a fluid flow from the second hydraulic machine to the first connecting line, wherein a control device is provided, which is set up in that the first orifice is adjustable as a function of the flow rate of the first hydraulic machine. As a result, vibrations are avoided in an operating state in which attacks on the second hydraulic machine pulling loads that can cause cavitation in the second connection line. This is particularly thought of lowering a load with a winch, which is in rotary drive connection with the second hydraulic machine. The pressure drop at the first orifice causes the minimum compressible pressure fluid in the possibly long first connecting line can no longer act as a spring of a spring-mass oscillator. For more details on the comments to 1 directed. The pressurized fluid is a liquid and preferably hydraulic oil.

In the dependent claims advantageous refinements and improvements of the invention are given.

It can be provided that the first valve device for a fluid flow from the first connecting line to the second hydraulic machine is freely continuous. As a result, a friction-induced energy loss is avoided in another than the above-mentioned operating state, in particular when lifting a load by means of a winch.

It can be provided that between the second connecting line and the second hydraulic machine, a second valve device is arranged, which forms a continuously variable second diaphragm only for a fluid flow from the second hydraulic machine to the second connecting line, wherein the control device is arranged so that the second diaphragm is adjustable depending on the flow rate of the first hydraulic machine. As a result, vibrations are avoided in an operating state in which pressing loads on the second hydraulic machine attack, wherein the pressure in the first connecting line operates against said pressing load. Here, in particular, the lifting of a load by means of a winch is thought, which is in rotary drive connection with the second hydraulic machine. The pressure drop across the second orifice causes significant damping of these vibrations. The elasticity of the pressure fluid in the second connecting line influences the vibration behavior minimally at best.

It can be provided that the second valve device for a fluid flow from the second connecting line to the second hydraulic machine is freely continuous. As a result, a friction-induced energy loss is avoided in another than the above-mentioned operating state, in particular when lowering a load by means of a winch.

It can be provided a linearly movable valve spool, which limits the first and second aperture sections. The first and second valve means are thus formed by a common assembly. This is particularly inexpensive. It should be noted that the entire fluid flow, which circulates in a closed circuit, can flow over the first or the second orifice. The corresponding brake valve is therefore preferably made very large, so that it has low friction losses or pressure losses, if no vibration damping necessary is. The mentioned cost advantage is therefore particularly high.

It can be provided that a free cross-sectional area of the first or the second aperture is proportional to the flow rate of the first hydraulic machine. This results in a low tendency to oscillate, at the same time energy losses are avoided.

It may be provided that the relationship between a free cross-sectional area of the first and the second orifice and the flow rate of the first hydraulic machine is different, depending on whether the first hydraulic machine is accelerated or decelerated. As a result, the different vibration behavior of the hydraulic drive system during acceleration and deceleration is taken into account such that at a low tendency to oscillate simultaneously energy losses are avoided.

It can be provided that a free cross-sectional area of the first or the second orifice is maximum when the flow rate of the first hydraulic machine is greater than 60% of a maximum flow rate of the first hydraulic machine. As a result, the adjustment of the first and second aperture is optimally utilized to achieve a low tendency to oscillate with low energy losses.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination indicated, but also in other combinations or in isolation, without departing from the scope of the present invention.

The invention will be explained in more detail below with reference to the accompanying drawings. It shows:

1 a circuit diagram of a hydraulic drive system according to a first embodiment of the invention;

2 a circuit diagram of a portion of a hydraulic drive system according to a second embodiment of the invention;

3 a diagram in which the pilot pressure is plotted against the flow rate of the first hydraulic machine; and

4 a diagram in which the free cross-sectional area of the first and the second diaphragm is plotted against the pilot pressure.

1 shows a circuit diagram of a hydraulic drive system 10 according to a first embodiment of the invention. The hydraulic drive system 10 includes a first hydraulic machine 20 , which is designed for example as an axial piston machine. The first hydraulic machine 20 is powered by a drive motor 11 , which is designed for example as an electric or as an internal combustion engine, driven. The first hydraulic machine 20 preferably runs with a constant direction of rotation, being pivotable above zero, so that the direction of the fluid flow is reversible. The first hydraulic machine 20 normally runs as a pump, where they, for example, when lowering the load 13 , also can be operated by motor to the drive motor 11 to relieve or to operate this as a generator.

Next is a second hydraulic machine 30 provided, which present in rotary drive connection with a winch 12 stands. With the winch 12 For example, a load 13 with respect to the direction of gravity 16 be raised or lowered. The second hydraulic machine 30 is designed, for example, as an axial piston machine, in particular in a bent-axis design. It has an adjustable displacement volume, whereby it can be operated with two directions of rotation. Depending on the operating state, it works as a pump or as a motor.

The first and the second hydraulic machine 20 ; 30 are via a first and a second connecting line 40 ; 50 connected in the manner of a closed hydraulic circuit. When lowering the load 13 flows pressure fluid from the first hydraulic machine 20 over the second connection line 50 to the second hydraulic machine 30 and from there via the first connection line 40 back to the first hydraulic machine 20 , When lifting the load 13 the pressure fluid flows in the opposite direction. The pressurized fluid is a liquid and preferably hydraulic oil. At the first and the second connection line 40 ; 50 For example, it may be a hose or a pipe, each of which may be several meters long. The pressurized fluid is minimally compressible, with the first and second connecting conduits 40 ; 50 also have a low elasticity. That in the first or second connection line 40 ; 50 enclosed pressurized fluid can therefore form the spring of a spring-mass oscillator, wherein the load 13 the corresponding mass is.

To do this in case of lowering the load 13 To avoid, is in the return the first valve device 41 intended. The first valve device 41 is between the first connection line 40 and the second hydraulic machine 30 installed, preferably directly to the second hydraulic machine 30 is grown. The first valve device 41 has a first check valve 43 One steady adjustable first aperture 42 is connected in parallel. When lowering the load 13 is the first check valve 43 locked, since there is only a fluid flow in the opposite direction, ie from the first connecting line 40 to the second hydraulic machine 30 , lets through. So the pressure fluid has to flow over the first diaphragm 42 flow. There, it is preferably at least so much accumulated that the pressure upstream of the first panel 42 is sufficient to the weight of the load 13 to wear. The first aperture 42 For example, is designed as a 2/2-way proportional valve, which is adjustable by means of an electromagnet, which is connected to a control device 14 connected. Downstream of the first panel 42 ie in the first connection line 40 , there is only a slight pressure left. The elasticity of the pressure fluid trapped there can therefore, together with the mass of the load 13 do not make a spring mass oscillator.

Most preferably, the pressurized fluid is at the first orifice 42 more congested than this to carry the load 13 required to the speed of the second hydraulic machine 30 adjust. This speed adjustment is by appropriate adjustment of the displacement volumes of the first and / or second hydraulic machine 20 ; 30 made by the control device 14 are adjustable. The corresponding connection line is in 1 shown interrupted. The one from the first hydraulic machine 20 Provided flow determines so long the speed of the second hydraulic machine 30 until the braking effect of the first aperture 42 is no longer sufficient to cavitation in the second connection line 50 to avoid. Is the free cross-sectional area of the first panel 42 too big, the load lowers 13 faster because of its weight than desired. Preferably, the free cross-sectional area of the first panel 42 not overly small in order to avoid energy losses.

When lifting the load 13 becomes the first connection line 40 from the first hydraulic machine 20 pressurized so that the pressure there is sufficient to handle the load 13 to wear and lift at the desired speed. The first check valve 43 forms a low flow resistance for the corresponding fluid flow, so that the setting of the first diaphragm 42 plays almost no role.

In the second connection line 50 , which now forms the return, the weight of the load 13 cause no cavitation. The tendency to oscillate is accordingly significantly reduced. In order to completely exclude vibrations in this operating state, the second valve device 51 provided, which analogous to the first valve device 41 is constructed. The second valve device 51 has a second check valve 53 which has a continuously adjustable second aperture 52 is connected in parallel. The second valve device 51 is between the second connection line 50 and the second hydraulic machine 30 installed, preferably directly to the second hydraulic machine 30 is grown. The second aperture 52 will be according to the first aperture 42 through the control device 14 adjusted, the corresponding connecting line in 1 is shown interrupted. When lifting the load 13 , So with a fluid flow from the second hydraulic machine 30 to the second connection line 50 , is the second check valve 53 locked, taking it while lowering the load 13 allows an opposite fluid flow to pass substantially unhindered.

When lifting the load 13 the elasticity forms that in the first connecting line 40 enclosed pressurized fluid together with the mass of the load 13 a spring-mass oscillator. This is but through the second aperture 52 heavily steamed. The damping always takes place when the load 13 due to vibrations moved faster than that of the setting of the first and the second hydraulic machine 20 ; 30 equivalent. The corresponding additional volume flow through the second aperture 52 causes upstream of the second aperture 52 an increased pressure, which the second hydraulic machine 30 slows. Because the second aperture 52 directly on the second hydraulic machine 30 is arranged, there is almost no time lag between the change of the moving speed of the load 13 and the pressure drop across the second orifice 52 determine, so that there is an optimal damping effect.

Attention is still on the first and the second speed sensor 21 ; 31 with which the speed of the first and the second hydraulic machine 20 ; 30 is measurable. If the drive motor 11 A speed-controlled electric motor or a fixed-speed electric motor can be applied to the first speed sensor 21 be waived. The first and the second speed sensor 21 ; 31 are about one in 1 interrupted connecting line to the control device 14 connected. In particular, with the second speed sensor 31 can through the control device 14 Vibrations are detected. Preferably, then, the free cross-sectional area of each relevant first and second aperture 42 ; 52 reduced.

Between the first and the second connecting line 40 ; 50 can be connected (not shown) pressure relief valves to limit the pressure there up. The first and / or the second connecting line 40 ; 50 can be connected to a (not shown) leak oil pump to compensate for leaks.

2 shows a circuit diagram of a part of a hydraulic drive system 10 ' according to a second embodiment of the invention. The second embodiment is identical to the first embodiment except for the differences described below, so that in this regard to the comments on 1 is referenced. In the 1 and 2 are the same or corresponding parts marked with the same reference numerals.

The second embodiment is based on the consideration that it is not absolutely necessary, the first and the second aperture 42 ; 52 to operate simultaneously. Therefore, the first and the second aperture 42 ; 52 from a common valve spool 61 limited. The valve spool 61 is in a body 73 a separate brake valve 60 recorded linearly. The brake valve 60 is for direct attachment to the second hydraulic machine 30 intended.

By means of the return spring 62 becomes the valve spool 61 in the in 2 shown biased center position in which both the first and the second aperture 42 ; 52 are closed. During a movement of the valve spool 61 in 2 to the left alone opens the first aperture 42 , in a movement in the opposite direction opens only the second aperture 52 , The return spring 62 is between a separate first and a separate second spring plate 71 ; 72 clamped. The first spring plate 71 is depending on the position of the valve spool 61 at the base body 73 and / or on the valve spool 61 at. The second spring plate 72 is depending on the position of the valve spool 61 at the driver 70 or the timing cover 77 at. The driver 70 is fixed to the valve slide 61 connected. The control cover 77 is fixed to the main body 73 connected.

In the main body 73 are a first, a second, a third and a fourth channel 74 ; 75 : 76 ; 76a intended. The first connection line 40 is on the third channel 76 connected, the second connecting line 50 to the fourth channel 76a connected. The second hydraulic machine 30 is between the first and the second channel 74 ; 75 connected. The first aperture 42 is between the first and the third channel 74 ; 76 switched, with the second aperture 52 between the second and the fourth channel 75 ; 76a is switched. The first check valve 43 is between the first and the third channel 74 ; 76 switched, with only a fluid flow from the third 76 to the first channel 74 pass through. The second check valve 53 is between the second and the fourth channel 75 ; 76a switched, with only a fluid flow from the fourth 76a to the second channel 75 pass through.

The valve spool 61 can with the first pilot valve 67 in 2 to be moved to the left, leaving the first aperture 42 opens. The opposite side 78 of the valve spool 61 is present to the tank 13 depressurized. But it is also possible, the other side 78 to a second pilot valve 68 connect so that the second aperture 52 can be opened. The first and the second pilot valve 67 ; 68 are preferably identical, being in 2 once in the form of their actual shape and once simplified as a circuit diagram are shown. It is preferably in each case a 3-way pressure reducing valve which is connected to a pressure source 69 and the tank 13 connected. At the pressure source 69 it can be a separate control oil pump. The pressure source 69 but also from the first and the second connection line 40 ; 50 are formed, which are connected via a shuttle valve to a pressure reducing valve. Instead of two separate pilot valves 67 ; 68 can also be used a single pressure reducing valve, which by means of a 4/2-way valve either with the desired side of the valve spool 61 is connected, with the opposite side to the tank 13 is relieved.

3 shows a diagram in which the pilot pressure p over the flow rate Q of the first hydraulic machine (no. 20 in 1 ) is applied. The flow Q is given as a percentage of the maximum flow of the first hydraulic machine. The pilot pressure p is in particular the pressure at which the first or the second pilot valve (no. 67 ; 68 ) the valve spool (no. 61 in 2 ). The pilot pressure p is adjusted here between 0 bar and 30 bar. If the flow rate is 0% of the maximum flow, ie when the winch is stationary, the pilot pressure is 0 bar. As soon as the cable winch is to be moved, the control pressure p increases abruptly to about 7 bar, so that the respective first or second diaphragm is minimally opened. As a result, the preferably existing zero overlap in the locked center position of the valve spool is taken into account.

When accelerating 80 the winch is at about 50% of the maximum flow rate Q, the maximum pilot pressure p before. When braking 81 the winch, the pilot pressure p is lowered again only when the flow rate falls below 40% of the maximum flow rate.

4 shows a diagram in which the free cross-sectional area A of the first and the second diaphragm is plotted against the pilot pressure p. In the horizontal, both the stroke x of the valve spool and the pilot pressure p is plotted. The cross-sectional area A and the stroke x are each plotted as a percentage of the assigned maximum value. The stroke x and the pilot pressure p are due to the linear behavior of the return spring (no. 62 in 2 ) proportional to each other. Both the characteristics after 3 as well as the characteristic after 4 are nonlinear. However, these nonlinearities are designed so that there is approximately a linear relationship between the flow rate Q and the free cross section A of the first and the second diaphragm.

LIST OF REFERENCE NUMBERS

p

pilot pressure

Q

Flow of the first hydraulic machine

x

Stroke of the valve spool

A

free cross-sectional area of the first panel

10

hydraulic drive system (first embodiment)

10 '

hydraulic drive system (second embodiment)

11

drive motor

12

winch

13

load

14

control device

15

tank

16

Direction of gravity

20

first hydraulic machine

21

first speed sensor

30

second hydraulic machine

31

second speed sensor

40

first connection line

41

first valve device

42

first aperture

43

first check valve

50

second connection line

51

second valve device

52

second aperture

53

second check valve

60

brake valve

61

valve slide

62

Return spring

65

first control room

66

second control room

67

first pilot valve

68

second pilot valve

69

pressure source

70

takeaway

71

first spring plate

72

second spring plate

73

Main body of the brake valve

74

first channel

75

second channel

76

third channel

76a

fourth channel

77

control cover

78

other side

80

acceleration phase

81

braking phase

Claims (8)

Hydraulic drive system ( 10 ; 10 ' ) with a first and a second hydraulic machine ( 20 ; 30 ), which via a first and a second connecting line ( 40 ; 50 ) are connected together in the manner of a closed hydraulic circuit, wherein the displacement volume of the first and / or the second hydraulic machine ( 20 ; 30 ) is adjustable, characterized in that between the first connecting line ( 40 ) and the second hydraulic machine ( 30 ) a first valve device ( 41 ), which is exclusively for a fluid flow from the second hydraulic machine ( 30 ) to the first connection line ( 40 ) a continuously adjustable first aperture ( 42 ), wherein a control device ( 14 ) is provided, which is arranged so that the first aperture ( 42 ) depending on the flow (Q) of the first hydraulic machine ( 20 ) is adjustable. Hydraulic drive system ( 10 ; 10 ' ) according to claim 1, wherein the first valve device ( 41 ) for a fluid flow from the first connecting line ( 40 ) to the second hydraulic machine ( 30 ) is completely free. Hydraulic drive system ( 10 ; 10 ' ) according to one of the preceding claims, wherein between the second connecting line ( 50 ) and the second hydraulic machine ( 30 ) a second valve device ( 51 ) arranged exclusively for a fluid flow from the second hydraulic machine ( 30 ) to the second connection line ( 50 ) a continuously adjustable second aperture ( 52 ), wherein the control device ( 14 ) is set up so that the second aperture ( 52 ) depending on the flow rate of the first hydraulic machine ( 20 ) is adjustable. Hydraulic drive system ( 10 ; 10 ' ) according to claim 3, wherein the second valve device ( 51 ) for a fluid flow from the second connecting line ( 50 ) to the second hydraulic machine ( 30 ) is completely free. Hydraulic drive system ( 10 ' ) according to claim 3 or 4, wherein a linearly movable valve spool ( 61 ) is provided, which the first and the second aperture ( 42 ; 52 ) limited in sections. Hydraulic drive system ( 10 ; 10 ' ) according to one of the preceding claims, wherein a free cross-sectional area (A) of the first and the second diaphragm ( 42 ; 52 ) proportional to the flow (Q) of the first hydraulic machine ( 20 ). Hydraulic drive system ( 10 ; 10 ' ) according to one of the preceding claims, wherein the relationship between a free cross-sectional area (A) of the first and the second diaphragm ( 42 ; 52 ) and the flow (Q) of the first hydraulic machine ( 20 ) varies, depending on whether the first hydraulic machine ( 20 ) is accelerated or delayed. Hydraulic drive system ( 10 ; 10 ' ) according to one of the preceding claims, wherein a free cross-sectional area (A) of the first and the second diaphragm ( 42 ; 52 ) is maximum when the flow (Q) of the first hydraulic machine ( 20 ) large 60% of a maximum flow rate of the first hydraulic machine ( 20 ).

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