DE102016217541A1 - Hydraulic drive system with several supply lines - Google Patents

Abstract

The invention relates to a hydraulic drive system (10) having a first and at least one second supply line (31; 32) and a return line (30), wherein at least one actuator is provided, which can be connected via an associated valve assembly optionally with at least one of said feed lines (31 32) and / or the return line (30) can be brought into fluid communication, wherein the first supply line (31) to a first pump (21) is connected, each second supply line (32) each connected to an associated second pump (22) is, wherein the return line (30) to a tank (12) is connected. According to the invention, a drive device (40) is provided, which has a plurality of output shafts (51; 52) each in rotational drive connection with an associated first or second pump (21; 22), the drive device (40; 41) being arranged such that Energy between the output shafts (51, 52) via the drive device (40, 40 ') is interchangeable.

Description

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

From the EP 791 754 B1 is a hydraulic drive system known. The hydraulic drive system has a first and a second supply line and a return line. A plurality of actuators is connected to the said lines and can be brought into fluid communication with said lines via a respectively assigned valve assembly. Each supply line is connected to a respective associated pump with the return line connected to the tank.

An advantage of the hydraulic drive system according to the invention is that it is particularly energy efficient. This applies in particular to an operating state in which a pulling load acts on one of the actuators. Further, the various supply lines can be operated in a simple manner with a different pressure level, so that this also improves the energy efficiency.

According to the independent claim it is proposed that a drive device is provided, which has a plurality of output shafts, which are respectively in rotary drive connection with an associated first or second pump, wherein the drive device is arranged so that energy is exchangeable between the output shafts via the drive device. In an operating state in which one of the pumps operates by motor, the energy provided by this pump can thus be conducted via the drive device to the other pump. This happens without appreciable losses in the form of waste heat.

The hydraulic drive system is preferably operated with a pressurized fluid, which is most preferably a liquid, in particular hydraulic oil. As far as in the context of the present application of a pump is to be hereby express that time predominantly a pumping operation is provided, preferably a motor operation is also possible.

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

It can be provided that the drive device comprises at least one electric motor, which is connected in each case to an associated speed setting device, so that its speed is adjustable. In the EP 791 754 B1 pumps are provided with adjustable displacement. These are typically operated at a constant speed, for example, the speed at which the corresponding internal combustion engine has optimum efficiency. In the context of the present invention, the proposed speed adjustment is used to operate the hydraulic drive system energy-optimal. The at least one electric motor can be connected to an electrical supply network. The electrical supply network can be connected to a rechargeable battery. The speed setting device can be designed, for example, as a frequency converter.

It can be provided that the output shafts are part of a mechanical transfer gear, wherein the transfer gear has as many rotational degrees of freedom as output shafts are available. Energy can be exchanged between the drive shafts in a mechanical way via the transfer gearbox. In this case, a very high efficiency can be achieved, so that the energy losses are low. Next can be dispensed with the pressure control of the at least one second supply line. The local pressure is coupled according to the transmission ratio of the transfer gear to the pressure in the first supply line. The distribution gear is, for example, a planetary gear. This typically has two rotational degrees of freedom. Multiple planetary gears can be combined to achieve more than two rotational degrees of freedom.

It can be provided that the distribution gear has a single input shaft, which is in rotary drive connection with an associated first electric motor. Because of the transfer gear, in addition to the first electric motor, no further electric motor is necessary to drive the at least two pumps.

It can be provided that the output shafts are in rotary drive connection with a respective associated electric motor, wherein the electric motors are connected to a common electrical supply network, wherein via the electrical supply network energy between the electric motors is at least indirectly interchangeable. The speeds of the various electric motors can thus be adjusted independently of each other, so that the pressures in the various supply lines can be largely selected independently. The electrical supply network may be connected to a rechargeable battery, said energy exchange being effected indirectly via the battery.

It can be provided that the first and the at least one second pump between the first supply line and the return line are connected in series, wherein the at least one second supply line is connected in each case between two of said pumps. Thus, only a slight pressure gradient occurs at the individual pumps, which is smaller than the highest pressure in the first supply line. Accordingly, the driving torques are low. In particular, in conjunction with a distribution gear torque ratios arise, which can be realized with simple distribution gears.

It can be provided that the first pump has a constant or an adjustable displacement volume, wherein the at least one second pump has a constant displacement volume. In a particularly cost-effective hydraulic drive system, all pumps have a constant displacement volume, for example, they are designed as external gear pumps. The first pump, with which the highest-pressure first supply line is supplied, may have an adjustable displacement volume, wherein it is designed for example as an axial piston pump. By adjusting the respective displacement volume, the ratio of the pressures in the first and the second supply line can be adjusted, in particular when the above-mentioned distribution gear is used.

It may be provided that a first supply line is connected to a first pressure sensor, wherein the first pressure sensor and the at least one speed control device are connected to a control device, wherein the control device is arranged so that the measurable by means of the first pressure sensor pressure in the first supply line can be adjusted by adjusting the speed of the at least one electric motor to a predetermined or predetermined desired value. Accordingly, an electronic control of the pressure in the first supply line takes place, which is particularly cost-effective in the context of the present invention. Preferably, a control device is used which comprises a programmable digital computer. This can easily be used for further control tasks in the context of the hydraulic drive system.

It can be provided with an adjustable first control orifice, the first supply line via the first control orifice is connected to the tank, wherein the first pressure regulator is arranged so that the pressure in the first supply line by adjusting the first control orifice to a predetermined or specifiable setpoint is einregelbar. As a result, the pressure in the first supply line can be adjusted faster. A position sensor may be provided by means of which the position of the first control diaphragm can be measured, the position sensor being connected to the control device for transmitting the corresponding position value. If the at least one second supply line is in each case assigned a separate electric motor, the at least one second supply line can also be connected to a respectively assigned second pressure sensor, wherein the pressure control is carried out analogously to the first supply line.

It can be provided that a second pressure regulator is provided with an adjustable second control orifice, wherein the return line is connected via the second control orifice with the tank, wherein the second pressure regulator is arranged so that the pressure in the return line by adjusting the second control orifice on a predetermined or predetermined setpoint is einregelbar. By suitable adjustment of the pressure setpoint of the second pressure regulator, the energy which is contained in the pressure fluid flowing back into the return line can be used, in particular to relieve the drive of the second pump. This saves energy.

It can be provided that a check valve is connected between the return line and the tank, which allows only a fluid flow from the tank to the return line. As a result, cavitation in the return line can be avoided.

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 an actuator-side part of a hydraulic drive system according to the invention;

2 a circuit diagram of the pump-side part of a hydraulic drive system according to a first embodiment of the invention;

3 a circuit diagram of the pump-side part of a hydraulic drive system according to a second embodiment of the invention; and

4 a circuit diagram of the pump-side part of a hydraulic drive system according to a third embodiment of the invention.

1 shows a circuit diagram of an actuator-side part of an inventive hydraulic drive system 10 ; 10 '; 10 '' , This part of the hydraulic drive system 10 ; 10 '; 10 '' is identical in all three embodiments of the invention. The hydraulic drive system 10 ; 10 '; 10 '' includes a first and a second supply line 31 ; 32 and a return line 30 , The mentioned lines 30 ; 31 ; 32 For example, may be formed as channels in a valve block, which pass through the valve block over its entire length. The mentioned lines 30 ; 31 ; 32 are on in 1 fluid-tightly closed at the right end, being at the opposite end to the pump-side part of the hydraulic drive system 10 ; 10 '; 10 '' are connected, which in the 2 to 4 is shown.

The hydraulic drive system 10 ; 10 '; 10 '' in the present case comprises two actuators 11 , where the number of actuators 11 can be chosen largely arbitrarily. At the actuators 11 These are, for example, hydraulic cylinders and / or hydraulic motors. The actuators 11 each have an associated valve assembly 60 to the first and the second supply line 31 ; 32 and the return line 30 connected. With the valve assembly 60 On the one hand, the direction of movement and the speed of movement of the associated actuator 11 be set, with this the first directional control valve 60 is provided. This is in the form of a continuously adjustable 4/3-way valve, which is electromagnetically adjustable, it is to the control device 20 connected. It can also be adjusted from which supply lines 31 ; 32 the actuator 11 can be supplied with pressurized fluid. This is the second directional valve 62 provided, which between the supply lines 31 ; 32 and the first directional valve 61 is switched. The second directional valve 62 is designed as a 2/3-way valve, which is electromagnetically adjustable, it is to the control device 20 connected. In one switching position, the first supply line 31 with the first directional valve 61 connected, wherein in the other switching position, the second supply line 32 with the first directional valve 61 connected is. It can also be set in which lines 30 ; 31 ; 32 that from the actuator 11 coming pressurized fluid to flow back. This is the third directional valve 63 provided, which between the return line 30 or first supply line 31 and the first directional valve 61 is switched. The third way valve 63 is designed as a 2/3-way valve, which is electromagnetically adjustable, it is to the control device 20 connected. In one switching position is the return line 30 with the first directional valve 61 connected, wherein in the other switching position, the first inlet run line 31 with the first directional valve 61 connected is.

In addition, it is conceivable that the actuator 11 backflowing pressure fluid in the second supply line 32 is conductive. It should also be noted that other circuit variants of the valve assembly 60 exist, which have the same function as the above-described valve assembly 60 , For example, each line 30 ; 31 ; 32 be assigned in each case two continuously adjustable 2/2-way valves, which in each case to an associated port of the relevant actuator 11 are connected.

Attention is still on the third pressure sensors 13 , wherein at both terminals of an actuator 11 one pressure sensor each 13 connected, in turn, to the control device 20 connected. With the pressure sensor 13 On the one hand, the load pressure can be measured against which the actuator 11 is working. According to the DE 103 40 993 A1 can be controlled by the load pressures of the delivery pressure of the pump. The pressure around return is particularly relevant in those cases where pulling loads on an actuator 11 attack, so that the energy contained in the returning pressurized fluid can be reused elsewhere. On the basis of the corresponding return pressure can be decided, for example, in which position the third directional control valve 63 is to switch to achieve optimum energy efficiency.

It should be noted that the pressures in the pipes 30 ; 31 ; 32 are preferably different. The return line 30 has the lowest pressure, the pressure in the first supply line 31 is highest. The second supply line 32 has a pressure which lies between the aforementioned extreme values.

2 shows a circuit diagram of the pump-side part of a hydraulic drive system 10 according to a first embodiment of the invention. The hydraulic drive system 10 has a first and a second pump 21 ; 22 , which in the present case each have a constant displacement volume, wherein they are designed for example as external gear pumps. The first and the second pump 21 ; 22 usually promote pressurized fluid in the respectively associated first and second supply line 31 ; 32 , However, it is possible, for example, an operating state in the pressurized fluid from the first supply line 31 over the first pump 21 in the lower pressure second supply line 32 flows, leaving the first pump 21 is powered by a motor. The same applies to the second pump 22 ,

The first and the second pump 21 ; 22 are between the first supply line 31 and the return line 30 connected in series. The second supply line 32 is between the first and the second pump 21 ; 22 connected so that the pressure there between the pressure in the first supply line 31 and the pressure in the return line 30 lies. The first pump 21 is in rotary drive connection with a first output shaft 51 where the second pump 22 in rotary drive connection with a second output shaft 52 stands.

The drive device 40 includes a mechanical distribution gearbox 50 , which corresponds to the number of supply lines 31 ; 32 has two rotational degrees of freedom, where it is designed for example as a planetary gear. The distribution gearbox 50 has in addition to the already mentioned output waves 51 ; 52 an input shaft 53 , The input shaft 53 is in rotary drive connection with a first electric motor 41 , At the distribution gearbox 50 During operation, a torque equilibrium is established, which causes the torques on the input shaft 53 and the first and second output shafts 51 ; 52 are in a fixed relationship to each other, which of the gear ratios in the distribution gear 50 depends. Thus, the pressure drops are on the first and the second pump 21 ; 22 in a corresponding ratio, so that the desired pressure gradation in the first and the second supply line 31 ; 32 and the return line 30 results.

It should be noted that the speeds of the input shaft 53 and the first and second output shafts 51 ; 52 are not in a fixed relationship. When the first pump 21 as mentioned above is operated by a motor, the direction of rotation of the first output shaft is reversed 51 with respect to the direction of rotation in normal operation, so that energy from the first output shaft 51 over the distribution gearbox 50 to the second output shaft 52 and / or to the input shaft 53 is transmitted.

The first electric motor 41 is to a first speed control device 43 electrically connected. At the first speed setting device 43 it may be, for example, a frequency converter, by means of which the speed of the input shaft 53 is adjustable. The first speed control device 43 is connected to an electrical supply network 45 connected, which is preferably designed as a DC voltage network. The supply network 45 For example, it can be connected to the public power grid via a rectifier. The electrical supply network 45 is connected to a rechargeable battery. In the above-mentioned motor operation of the first pump 21 It can happen that the energy fed back from the second pump 22 can not be completely removed. In this case, the direction of rotation of the input shaft rotates 53 compared to the control mode, so that the first electric motor 41 is operated as a generator, whereby he electrical energy in the electrical supply network 45 feeds back. This energy is preferably used to power the battery 46 to load.

Next is on the first pressure sensor 33 to indicate, with the pressure in the first supply line 31 is measurable. The first pressure sensor 33 is to the already mentioned control device 20 connected, which in turn to the first speed control device 43 connected. The control device 20 is set up in the manner of a pressure regulator. It determines from the measured values of the third pressure sensors (No. 13 in 1 ) the highest load pressure. This is increased by a predetermined pressure difference to determine a pressure setpoint. The speed of the first electric motor 41 is from the control device 20 adjusted so that the first pressure sensor 31 measured actual pressure is equal to the pressure setpoint. The control device 20 works preferably as a continuous linear controller, in particular as a P or as a PD controller. The corresponding regulator is controlled by the control device 20 preferably calculated time-discretely. The control device 20 preferably comprises a programmable digital computer. The pressure in the second supply line 32 results from the transmission ratio of the transmission 50 and the pressure in the first supply line 31 and the return line 30 ,

Attention is still on the second pressure regulator 80 and the check valve 83 , With the second pressure regulator 80 should the pressure in the return line 30 be raised above the ambient pressure to a defined value. The pressure setpoint of the second pressure regulator 80 is electrically adjustable, with the second pressure regulator 80 for presetting the pressure setpoint to the control device 20 connected. The second pressure regulator 80 has a continuously adjustable second control panel 81 which is between the return line 30 and the tank 12 is switched. By means of the second control panel 81 can that be from the return line 30 to the tank 12 flowing pressurized fluid are accumulated, so that the pressure in the return line 30 increases. The check valve 83 is between the tank 12 and the return line 30 switched, with only a fluid flow from the tank 12 to the return line 30 allows. This should allow cavitation in the return line 30 be avoided.

When the control device 20 based on the measured values of the third pressure sensors (No. 13 in 1 ) a pulling load on one of the actuators 11 detects, it is possible the pressure setpoint of the second pressure regulator 80 increase, so the pressure in the return line 30 increases. This reduces the drive for the first pump 21 required drive power. In the context of the present invention, it is also possible to increase said pressure setpoint so much that it is higher than the pressure in the second supply line 31 lies. The second pump 22 is then operated by a motor, with the corresponding energy through the distribution gearbox 50 to the first pump 21 and / or to the first electric motor 41 is directed.

3 shows a circuit diagram of the pump-side 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, in which regard to the comments on 1 and 2 is referenced. In the 1 to 3 are the same or corresponding parts provided with the same reference numerals.

In the second embodiment, the second pressure regulator and the check valve (No. 80 ; 83 in 2 ) waived, the return line 30 directly to the tank 12 connected. The pressure in the return line 30 is therefore substantially equal to the pressure in the tank 12 ,

Next was the electronic control of the pressure in the first supply line 31 replaced by a hydraulic pressure control. This allows the pressure in the first supply line 31 be adjusted faster. It is a first pressure regulator 70 provided, which is a continuously adjustable first control panel 71 having. The first supply line 31 is about the first control dial 71 with the tank 12 connected. The first control panel 71 or the corresponding valve slide is in the opening direction of the pressure in the first supply line 31 acted upon, wherein it is acted upon in the opposite direction by a spring whose bias is electromagnetically adjustable. The corresponding solenoid is connected to the control device 20 connected.

The setting of the first control dial 71 is by means of a position sensor 72 measurable, which to the control device 20 connected. By means of the position sensor 72 For example, operating states can be detected in which the first control orifice 71 is wide open. These operating states are associated with high energy losses. To avoid this, the control device lowers 20 by means of the first speed setting device 43 the speed of the first pump 21 from. This has the consequence that the first control panel 71 closes so that the energy losses decrease. When the position sensor 72 indicates that the first control dial 71 is completely closed, the speed of the first electric motor 41 through the control device 20 raised so far until the first control panel 71 is minimally open.

4 shows a circuit diagram of the pump-side part of a hydraulic drive system 10 '' according to a third embodiment of the invention. The third embodiment 10 '' is identical to the first embodiment except for the differences described below, in this regard to the comments on 1 and 2 is referenced. In the 1 . 2 and 4 are the same or corresponding parts provided with the same reference numerals.

In the second embodiment, the second pressure regulator and the check valve (No. 80 ; 82 in 2 ) waived, the return line 30 directly to the tank 12 connected. The pressure in the return line 30 is therefore substantially equal to the pressure in the tank 12 ,

Instead of the transfer gear (No. 50 in 2 ) are a first and a separate second electric motor 41 ; 42 intended. The first and the second output shaft 51 ; 52 are each from the motor shaft of the respective electric motor 41 ; 42 educated. The first and the second electric motor 41 ; 42 ; are each to an associated first and second speed control device 43 ; 44 electrically connected. The first and second speed control devices 43 ; 44 , which are designed for example as a frequency converter, are connected to a common electrical supply network 45 connected. The electrical supply network 45 For example, it is designed as a DC voltage network, where it is connected to a rechargeable battery 46 connected.

As in the first embodiment, the first supply line 31 to a first pressure sensor 33 connected, which is used in the context of an electronic pressure control, wherein the speed of the first electric motor 41 is adjusted to the pressure in the first supply line 31 to regulate to a predetermined first pressure setpoint.

In an analogous manner, the second supply line 32 to an associated second pressure sensor 34 connected, which in turn to the control device 20 connected. As part of a pressure control, the speed of the second electric motor 42 by means of the second speed setting device 44 adjusted to the pressure in the second supply line 32 to regulate to a predetermined second pressure setpoint. This allows the pressures in the first and the second supply line 31 ; 32 be regulated independently of each other.

If one of the pumps 21 ; 22 in the context of the pressure control goes into the engine operation, is of the electric motor in question 41 ; 42 electrical energy in the supply network 45 fed back. This electrical energy can be used to drive the other electric motor 42 ; 41 to drive or to the battery 46 to load. It is understood that in the battery 46 stored energy can be used to power the electric motors 41 ; 42 drive.

LIST OF REFERENCE NUMBERS

10

hydraulic drive system (first embodiment)

10 '

hydraulic drive system (second embodiment)

10 ''

hydraulic drive system (third embodiment)

11

actuator

12

tank

13

third pressure sensor

20

control device

21

first pump

22

second pump

30

Return line

31

first supply line

32

second supply line

33

first pressure sensor

34

second pressure sensor

40

Drive device (first embodiment)

40 '

Drive device (second embodiment)

41

first electric motor

42

second electric motor

43

first speed setting device

44

second speed control device

45

electrical supply network

46

battery

50

distribution gear

51

first output shaft

52

second output shaft

53

input shaft

60

valve assembly

61

first way valve

62

second way valve

63

third directional valve

70

first pressure regulator

71

first control panel

72

position sensor

73

Setpoint adjustment device

80

second pressure regulator

81

second control panel

83

check valve

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 791754 B1 [0002, 0007]
• DE 10340993 A1 [0026]

Claims (11)

Hydraulic drive system ( 10 ; 10 '; 10 '' ) with a first and at least one second supply line ( 31 ; 32 ) and a return line ( 30 ), wherein at least one actuator ( 11 ) is provided, which via an associated valve assembly ( 60 ) optionally with at least one of said supply lines ( 31 ; 32 ) and / or the return line ( 30 ) can be brought into fluid communication connection, wherein the first supply line ( 31 ) to a first pump ( 21 ), each second supply line ( 32 ) each to an associated second pump ( 22 ), the return line ( 30 ) to a tank ( 12 ), characterized in that a drive device ( 40 ; 40 ' ) is provided, which several output shafts ( 51 ; 52 ), each with an associated first or second pump ( 21 ; 22 ) are in rotary drive connection, wherein the drive device ( 40 ; 40 ' ) is arranged so that energy between the output waves ( 51 ; 52 ) via the drive device ( 40 ; 40 ' ) is interchangeable. Hydraulic drive system ( 10 ; 10 '; 10 '' ) according to claim 1, wherein the drive device ( 40 ; 40 ' ) at least one electric motor ( 41 ; 42 ), which in each case to an associated speed control device ( 43 ; 44 ) is connected so that its speed is adjustable. Hydraulic drive system ( 10 ; 10 ' ), according to any one of the preceding claims, wherein the output waves ( 51 ; 52 ) Component of a mechanical transfer gear ( 50 ), wherein the distribution gear ( 50 ) has as many rotational degrees of freedom as output shafts ( 51 ; 52 ) available. Hydraulic drive system ( 10 ; 10 ' ) according to claim 3, appended to claim 2, wherein the distribution gear ( 50 ) a single input shaft ( 53 ), which in rotational drive connection with an associated first electric motor ( 41 ) stands. Hydraulic drive system ( 10 '' ) according to claim 2, wherein the output waves ( 51 ; 52 ) with an associated electric motor ( 41 ; 42 ) are in rotary drive connection, wherein the electric motors ( 41 ; 42 ) to a common electrical supply network ( 45 ) are connected, whereby via the electrical supply network ( 45 ) Energy between the electric motors ( 41 ; 42 ) is at least indirectly interchangeable. Hydraulic drive system ( 10 ; 10 '; 10 '' ) according to one of the preceding claims, wherein the first and the at least one second pump ( 21 ; 22 ) between the first supply line ( 31 ) and the return line ( 30 ) are connected in series, wherein the at least one second supply line ( 32 ) between each of two pumps ( 21 ; 22 ) connected. Hydraulic drive system ( 10 ; 10 '; 10 '' ) according to claim 6, wherein the first pump ( 21 ) has a constant or an adjustable displacement volume, wherein the at least one second pump ( 22 ) has a constant displacement volume. Hydraulic drive system ( 10 ; 10 '' ) according to one of claims 2 to 7, wherein a first supply line ( 31 ) to a first pressure sensor ( 33 ), the first pressure sensor ( 33 ) and the at least one speed control device ( 43 ; 44 ) to a control device ( 20 ) are connected, wherein the control device ( 20 ) is arranged so that the means of the first pressure sensor ( 33 ) measurable pressure in the first supply line ( 31 ) by adjusting the rotational speed of the at least one electric motor ( 41 ; 42 ) is einregelbar to a predetermined or predetermined setpoint. Hydraulic drive system ( 10 ' ) according to one of the preceding claims, wherein a first pressure regulator ( 70 ) with an adjustable first control panel ( 71 ) is provided, wherein the first supply line ( 31 ) over the first control diaphragm ( 71 ) with the tank ( 12 ), the first pressure regulator ( 70 ) is set up so that the pressure in the first supply line ( 31 ) by adjusting the first control diaphragm ( 71 ) is einregelbar to a predetermined or predetermined setpoint. Hydraulic drive system ( 10 ) according to one of the preceding claims, wherein a second pressure regulator ( 80 ) with an adjustable second control panel ( 81 ) is provided, wherein the return line ( 30 ) via the second control diaphragm ( 81 ) with the tank ( 12 ), the second pressure regulator ( 80 ) is set up so that the pressure in the return line ( 30 ) by adjusting the second control panel ( 81 ) is einregelbar to a predetermined or predetermined setpoint. Hydraulic drive system according to claim 10, wherein between the return line ( 30 ) and the tank ( 12 ) a check valve ( 83 ), which only a fluid flow from the tank ( 12 ) to the return line ( 30 ) allows.

Images