DE3146561C2 - - Google Patents

Description

The invention relates to a hydrostatic drive for a particularly rotary consumer hydraulic Energy that can be applied in both directions and to the Delivery line of an adjustable pump is connected, with a four-port upstream of the consumer Three-position valve trained throttle, which Pump adjusting element from the pressure drop at the throttle place is acted upon and being connected to a connection of the Valve the delivery line, to a further connection the Return line and to the other two connections of the mentioned valves leading to consumer branch lines are connected.

In the previously known systems of this type Opening width of the throttle point only through the Size of the arbitrarily selected control pressure determined. In order to is also the current flowing to the consumer and thus the Movement speed of the consumer only through this Control pressure determined. Most of them occur in practice the consumer has a characteristic in which the Movement speed the pressure of the consumer  inflowing pressure medium determined. There is also Applications where it is desired that the consumer only a predetermined force or torque occurs, d. H. the print medium to the consumer with only one certain pressure flows.

To achieve that the consumer with the print medium a certain pressure flows, it is with drives known with an adjustable pump, the adjusting member of the To act on the pump of the delivery pressure, so that with increasing delivery pressure the pump to a smaller stroke volume per Revolution and thus smaller current is set (DE-OS 21 59 766). Given the normal characteristic of the The consumer also becomes pressure when the current is lower smaller, so that it is achieved by this control that the Media pre-printed to the consumer selected pressure flows.

The invention has for its object a hydrosta table drive to create, in which the pressure medium Consumers flow with a selected pressure, though the pump is not set in the known manner.

This object is achieved according to the invention in that A pressure chamber is arranged on each side of the valve is that with an arbitrarily operable, one from  Consumer pressure independent tax pressure generating tax pressure sensor is connected, and on both sides of the valve A second pressure chamber is arranged, which is used for actuation of the valve so with the pressurized branch line connected between valve and consumer is that generated by the pressure in this pressure space Force of your control pressure in the opposite Counteracts force generated. With increasing Pressure in front of the consumer is arbitrary Lich given control pressure, i.e. counter and thus narrows the valve so that the current gets smaller and so due to the characteristics of the consumer the pressure drops again, with the addition of the narrowing of the valve also the throttling effect and thus the pressure slope on the valve is increased.

In an expedient further embodiment of the invention it is intended that starting from both branch lines a bypass line between the valve and the consumer is provided, which is connected to the return line and in that a setback opening towards the consumer Valve is arranged, which is a suction in the consumption cher enables.

In addition or instead, it may be convenient in another Another embodiment can be provided that each of the two associated with the consumer, from which Four-port / three-position valve outgoing branch lines connected to a drain line in which is controlled by the pressure in the branch line Pressure relief valve is arranged, which the Protects consumers against overload and especially at Pressure surges on the consumer opens.  

The application of the invention is particularly expedient in a drive system with one pump and several, of which consumers. In such a drive system according to an appropriate further development provided that of the branch line between valve and consumer one control pressure line leading to the setting element of the pump branches, which leads to the setting element of the pump and the Pressure behind the valve to the adjusting element of the Pump forwards and in the one to the setting element of the Pump opening check valve is arranged so only the highest consumer pressure on the setting organ of the pump as the pressure determining the pressure drop acts.

The aforementioned system can be used particularly cheaply by anyone in connection with a drive system in which the branch line to at least one other consumer an adjustable parallel circuit throttle point is arranged is net, the setting member on the one hand by the pressure in the control line and on the other hand from the pressure in front of the ser parallel throttle is applied where at the pressure in the control pressure line in the described level is the pressure via non-return valves, which acts on the consumer with the highest pressure.

It is particularly useful if the four circuit / three-position valve and, if applicable, the or the check valves and / or the or the Druckbe limit valves in the immediate vicinity of the consumer are arranged and preferably to a control unit are summarized, which is grown to the consumer.  

In the drawing is an embodiment of the invention object as a circuit diagram.

Fig. 1 shows an overall map and the other figures show the circuit diagrams of the individual parts in the overall overview of FIG. 1 only outlined parts.

Fig. 2 shows the circuit diagram for the double pump assembly 24.

Fig. 3 shows the circuit diagram for the limit load control unit 230 .

Fig. 4 shows the circuit diagram for the combination switch unit 179th

Fig. 5 shows the circuit diagram for the partial control unit 27 to the control unit 74.

Fig. 6 shows the circuit diagram to the control unit 74 or 75 with an associated load.

Fig. 7, Fig. 8 and FIG. 9 show, respectively, an overall control unit 85 or 110 or 111 with associated Ver consumer.

Fig. 10 shows the circuit diagram for a constant pressure control.

The pumps 3 and 4 are driven by the internal combustion engine 1 by means of the shaft 2 . The actuator 5 of the pump 3 is connected to a pump regulator piston 6 which is displaceable in a pump actuating cylinder 7, and this divides into two pressure chambers. 8 and 9 The pump 3 feeds into a delivery line 12 , from which the pressure chamber 9 is acted on via branch lines 13 and 14 , in which a spring 11 is arranged. The application of pressure chamber 8 is controlled via a hydraulically controlled servo control valve 10 .

The pump 4 delivers into a delivery line 15 . The adjusting organ 16 of the pump 4 is connected to a pump actuating piston 17 , which is displaceable in a pump actuating cylinder 18 and divides it into two pressure chambers 19 and 20 , a spring 21 being arranged in the pressure chamber 20 . This pressure chamber 20 is connected to the delivery line 15 via a branch line 321 and a further branch line 22 . The application of pressure to the pressure chamber 19 is controlled by a hydraulically controlled servo control valve 23 . Both pumps 3 and 4 are arranged in a common housing 24 .

Two further pumps 25 and 26 configured as constant pumps are driven by the shaft 2 (the pump 26 can, however, in another embodiment also be driven by a power take-off of the internal combustion engine 1 ).

A branch conveyor line 28 branches off from the conveyor line 12 and leads to a partial control unit 27 in which the conveyor branch line 28 is divided into two partial lines 29 and 30 . Each of the two sub-lines 29 and 30 leads to a single-edge control slide 31 or 32 , the single-edge control slide 31 being hydraulically controlled and being pressurized via a pressure transmitter control line 33 by an arbitrarily actuatable control pressure transmitter 92 arranged in the driver's cab of the excavator. In just such a manner, the hydraulically controlled Einkantensteuerschieber is acted upon via a pressure transducer 32 control line 34 with control pressure, wherein the pressure transducer control line, which is likewise arranged in the 34 to a truck, actuatable arbitrarily, other control thruster leads 93rd The single-edge control slide valve 31 and 32 each act as a measuring throttle point, through which a throttled current is conducted from the partial line 29 to the line 35 or from the partial line 39 to the line 36 . In the other position, the single edge control slide 31 connects the line 35 to the return line 37 and in the same way connects in the other position the single edge control slide 32, the lines 36 and 38 , the two return lines 37 and 38 leading together to the return branch line 39 .

The line 35 leads to a parallel circuit throttle position 40 with a slide body 41 , the back of which is acted upon by a spring 42 and by the line pressure in a control pressure 53 . From the parallel connection throttle point 40 a line 43 starts, which separates into two lines 44 and 45 , each of which leads to a pressure chamber 46 or 47 of the two connected to another in parallel, provided on the excavator for "lifting" working cylinders 48 and 49 .

In an analogous manner, the line 36 leads to a parallel circuit throttle point 50 with a slide body 51 , the rear side of which is acted upon by a spring 52 and by the pressure present in a control line 53 . From the parallel circuit Drosstelle 50 is a line 53 , which is divided into two lines 54 and 55 , of which the line 54 leads to the pressure chamber 56 of the working cylinder 48 and the line 55 leads to the pressure chamber 57 of the working cylinder 49 .

A check valve 58 , which opens towards the working cylinder 48 , is arranged in the line 54 . Between this and the working cylinder 48 , a line 59 is connected to the line 54 , which leads to a controlled pressure relief valve 60 , the discharge of which leads via line 61 and line 62 to the return partial line 39 . Furthermore, between the check valve 58 and the working cylinder 48 , a line 63 is connected to the line 54 , in which a suction check valve 64 is arranged, which on the other hand is connected to the line 62 .

In an analogous manner, a Rückschlagven valve 68 is arranged in the line 44 and a line 65 is connected between this and the working cylinder 48 , in which a suction check valve 66 is arranged, which on the other hand is also connected to the line 62 . Furthermore, a line 69 is connected to the line 44 between the check valve 68 and the working cylinder 48 , which leads to a hydraulically controlled Druckbe limit valve 70 , the drain line 71 is connected to the line 62 . The control pressure chamber of the pressure limiting valve 70 is connected via line 72 to line 54 , before the check valve 58 and in the same way, the control pressure chamber of Druckbe limiting valve 60 is connected via line 73 to line 44 before the check valve 68 . Lead line 54 pressure, the control pressure chamber of Druckbe limiting valve 70 is loaded by this pressure and thus the pressure relief valve is relieved of spring pressure, so that it opens at more or less low pressure in line 44 and vice versa, the same applies to the pressure limiting valve 60 when line 44 is upstream of check valve 68 .

These valves 58 , 64 , 60 , 70 , 68 , 66 are combined in a control unit 74 , which is directly attached to the working cylinder 48 .

An analogous valve arrangement is provided in the Steuerein unit 75 , which is attached to the working cylinder 49 .

Within the sub-control unit 27 , a line 76 is connected to the line 53 , which leads to a Rückschlagven valve 77 . A line 78 is also connected to line 43 , which leads to a check valve 79 . The two check valves 77 and 79 , on the other hand, are connected to the partial control pressure line 80 , to which the pressure spaces behind the slide bodies 41 and 51 are also connected.

In the slide body 41 , an opening of the relief check valve 94 toward the line 35 is arranged. In the same way, a relief check valve 95 opening towards the line 36 is arranged in the slide body 51 . The control pressure line 80 leads to a total control pressure line 81 , to which a control pressure branch line 83 is connected. A branch line 82 is connected to the delivery line 12 . The two branch lines 82 and 83 lead to an overall control unit 85 , from which a return line 84 emerges, which is connected to the return line 39 . The overall control unit 85 is attached to the working cylinder 86 , which serves to actuate the bucket of the excavator. The overall structure of the circuit of the total control unit 85 is analogous to the sum of the control unit 27 and the control unit 74 . There are two single-edge spool 86 and 87 , of which the single-edge spool 86 is pressurized via a pressure transmitter control pressure line 88 from an arbitrarily actuatable control pressure transmitter 90, which is arranged in the vicinity of the control pressure transmitter 92 and 93 , which act on the pressure transmitter control pressure lines 33 and 34 . Correspondingly, the single-edge control slide 87 is controlled by means of a pressure control pressure line 89 , which in turn also leads to an arbitrarily actuatable control pressure transmitter 91 which is arranged in the vicinity of the control pressure transmitter 90 , 92 , 93 .

The two, each acting as a measuring throttle control valve spool 86 and 87 is a parallel circuit throttle body 96 and 97 downstream, behind each branch at a connection point 98 and 99 to the control pressure line 83 branch line with a check valve branches 100 and 101, respectively .

The return line 39 leads to a main return line 102 , which leads directly into the housing 24 of the pumps and to which a prestressed storage tank 103 is connected.

From the pump line 4 outgoing delivery line 15 branch lines 104 , 105 , 106 from which the delivery branch line 104 to a working cylinder 107 for kinking the dipper stick and the delivery branch line 105 to a hydraulic motor 108 for driving and the delivery branch line 106 lead to a hydraulic motor 109 for swinging the excavator. The overall control units 110 and 111 are constructed in the same way as the overall control unit 85 . This means that they each contain two single-edge spools 112 or 113 or 114 or 115 and each have a parallel throttle restriction 116 , 117 , 118 or 119 , the single-edge spool 112 being acted upon by an arbitrarily actuatable control pressure transmitter 120 and the single-edge spool 113 is acted upon by a control pressure transmitter 121 and the single edge control slide 114 is acted upon by a control pressure transmitter 122 and, accordingly, the single edge control slide 115 is acted upon by a control pressure transmitter 123 . The outgoing from the total control devices 110 and 111 lines 124 and 125 all lead to a return branch line 126 , which is connected to the main return line 102 . Likewise, the return line 127 . Lines 106 and 127 are connected to a four-port / three-position directional valve 128 , which is hydraulically controlled by the two control pressure transmitters 129 and 130 and optionally either one port 131 of the hydraulic motor 109 with the delivery line 106 and the other port 132 of the hydraulic motor 109 with the return line 127 connects or vice versa connects the delivery line 106 to the connection 132 and the return line 127 to the connection 131 . Here too, an additional control unit 133 is provided, which is attached directly to the hydraulic motor 109 and in which two check valves 134 and 135 and two pressure limiting valves 136 and 137 and connections 138 and 139 are provided for a control pressure line 140 , between the control pressure line 140 and the Connections 139 and 138 check valves 141 and 142 are arranged.

The assigned to the pump 3 total control pressure line 81 continues in the control pressure line 150 , which leads to a branch line 152 , in which a throttle point 153 is arranged and which leads to a pressure chamber of the hydraulically controlled servo control valve 10 . The opposite de pressure chamber is connected via the branch line 154 to the line 14 which is acted upon by the delivery pressure in the delivery line 12 of the pump 3 .

To the line 150 , a current regulator 155 is also connected, the output of which leads into the interior of the housing 24 of the pumps 3 and 4 .

Between the throttle point 153 and the control pressure chamber of the servo control valve 10 , a Druckbe limiting valve 157 is connected to the line 152 .

From the line 13 is a line 158 which leads to a connection 159 of the servo control valve 10 , so that through this line 158 and the connection 159 from the pump 3 ge pumped pressure medium via the delivery line 12 , the lines 13 , 158 and the connection 159 can be guided through the servo control valve 10 into the pressure chamber 8 .

Between the line 158 and the line 150 there is a connecting line 160 in which a circulation throttle point 161 is arranged (this line 160 with the throttle point 161 can be omitted if the servo control valve 10 is designed with a sufficiently large negative overlap, so that when the servo control valve is in the neutral position 10 constantly leads a partial flow via the lines 12 , 13 , 158 and the connection 159 to the unpressurized container 156 or preferably into the interior of the housing 24 of the pumps 3 and 4. This solution has the advantage that the current regulator 155 does not additionally the current flowing through the circulation throttle 161 needs to be adjusted).

From the control units 110 and 111 and from the control device 133 control pressure sub-lines 162 , 163 and 164 proceed, which are connected to a total control pressure line 165 , which continues in line 166 , to which line 167 is connected to throttle point 168 and to which the current regulator 169 is connected. The place of the throttle 168 outgoing line 170 leading to a pressure chamber of the hydraulically controlled servo control valve 23, wherein the opposite pressure chamber is connected to the line 22 via the terminal 171st A pressure relief valve 172 is connected to line 170 .

The connection 173 of the servo control valve 23 is connected to the line 321 via the line 174 . Between the lines 174 and 166 , a connecting line 175 is arranged, which contains a circulation throttle 176 (the same applies here, as said in relation to the line 160 and throttle point 161 ).

An interconnection control line 177 is connected to the overall control pressure line 81 and an interconnection control line 178 is connected to the overall control pressure line 165 , these two control lines leading to the interconnection unit 179 . In this a four-port / two-position valve 182 is arranged, which is hydraulically controlled and has two control pressure chambers on each side, where an equal-sized control pressure chamber on the other side is assigned to each control pressure chamber, but it is not necessary that the two each control pressure chambers lying on one side have the same diameter. Starting from the delivery line 12 , a branch line 180 leads into the interconnection unit 179, and in the same way, starting from the delivery line 15 , a branch line 181 leads into the interconnection unit 179 . The two lines 180 and 181 are connected to the four-position / two-way valve 182 in such a way that, in the position shown, the lines 180 and 181 are connected to one another and in the other position thereof, these lines are shut off. The control pressure lines 177 and 178 are connected such that in the illustrated position of the valve slide, the lines 177 and 178 connected to each other at the other two terminals of the four-position / two-way valve 182nd

In the interconnection unit 179 there are also two pressure limiting valves 184 and 184 , of which the pressure limiting valve 184 serves to secure the delivery line 12 and is connected to this via line 180 , while the pressure limiting valve 185 serves to secure the delivery line 15 and via line 181 to this is closed.

In this case, the line 180 acted upon by the delivery pressure of the pump 3 and the line 177 leading from the control pressure assigned to the pump 3 are connected on opposite sides to pressure chambers of the same size and the line 181 acted upon by the delivery pressure of the pump 4 and that of which the Pump 4 assigned control pressure act on line 178 to arranged on opposite sides, equal-sized pressure chambers of the four / two-way valve 182 is closed in such a way that both, from the control pressure Bea lines 177 and 178 are connected to the side on which the compression spring 186 is arranged is.

The constant pump 25 sucks via the line 187 from the Ge housing 24 of the pumps 3 and 4 and promotes in a line 188 which leads to an adjustable throttle point 189 , the setting member 190 is in operative connection with the setting member of the internal combustion engine 1 , before Throttle point 189 is connected to line 188 via a line 191 , in which a filter 192 is arranged, a pressure relief valve 193 , the outlet of which is connected to a line 194 , which in turn is connected to line 195 , which is behind the throttle point 189 Continuation of line 188 forms, and which leads to further consumers, not shown in the drawing.

To the line 194 a controlled pressure relief valve 196 is also connected, the control pressure is determined via the line 197 from the pressure upstream of the throttle point 189 . The line 198 emanating from the pressure relief valve 196 leads to a throttle point 199 and the line 200 emanating therefrom leads to the container 156 via a pressure relief valve 201 . Parallel to the series-connected pressure relief valve 196 and throttle point 199 , a further pressure relief valve 202 is connected, which keeps the pressure upstream of the pressure relief valve 196 constant. The important thing is that the pressure drop at the throttle point 189 controls the pressure relief valve 196 , which in turn controls the flow to the throttle point 199 .

A limit pressure control line 203 branches off from line 198 between pressure limiting valve 196 and throttle point 199 , and a second limit pressure line 204 branches off from line 200 . The line 203 branches into two lines 205 and 206 , which each open into a control pressure chamber of the servo control valve 10 and 23 , respectively, on the same side on which this is acted upon by the delivery pressure of the associated pump 3 or 4 . Two lines 207 and 208 branch off from line 204 , each of which leads to the other side of the hydraulically controlled servo control valve 10 or 23 , each of which is acted upon by a spring.

The mode of operation is as follows: when the internal combustion engine 1 is running and the pumps 3 , 4 , 25 , 26 drive and all control pressure transmitters 93 , 92 , 91 , 90 , 120 , 121 , 122 , 123 , 130 , 129 are un-actuated, the Pumps in the zero stroke position and do not deliver. No consumer is charged. If the control pressure transmitter 92 is now actuated, the single-edge control slide 31 is actuated and opens so that it establishes a connection between the delivery line 12 and the line 44 to the cylinder 48 , the parallel connection throttle body 40 opening. At the same time the check valve 79 opens, so that the line 80 and thus the line 81 is pressurized.

Since the single-edge control slide 31 acts as a measuring throttle point, the pressure in line 35 and thus the pressure in line 43 and thus also the pressure in line 78 and in line 80 and in line 81 is lower than the pressure in the delivery branch line 28 and the delivery line 12 . The pressure in the delivery line 12 acts via lines 13 , 14 and 154 on one side of the servo control valve 10 and the pressure in the control pressure line 81 acts via lines 150 , 151 , 152 on the other side of this servo control valve, to which the Spring acts. The spring is designed so that the servo control valve 10 responds to a specific pressure difference between the pressures in the lines 154 and 152 , for example to a pressure difference of 20 bar. The result is that by means of the servo control valve 10 via the pump control piston 6, the control element 5 of the pump 3 is set such that it promotes a flow of flow which generates the predetermined pressure drop at the single-edge control slide 31 acting as a measuring throttle point. That is, is changed by changing the setting of the control pressure transmitter 92, the setting of the Einkantensteuerschiebers 31 , so the pump 3 is set to a different flow rate and on such a flow rate that in turn acting as a measuring throttle single-edge control valve 31, the predetermined pressure drop arises.

The parallel connection choke points 40 , 50 , 96 or 97 and 116 or 117 have the following effect:

If two or two different consumers assigned control pressure transmitters are actuated simultaneously, for example the control pressure transmitter 92 and the control pressure transmitter 90 , so who the two single-edge slides - in the aforementioned case, the single-edge slide 31 and the single-edge slide 86 - opened simultaneously and thus two consumers, namely here on the one hand the two working cylinders 48 and 49 and on the other hand the working cylinder 86 are connected to the same pump 3 . The same pressure acts in the two Arbeitszy alleviate 48 and 49 . However, it is unlikely that the same pressure also happens to work in the working cylinder 86 . Rather, one of the consumers will be more heavily loaded and will therefore need more pressure. Assuming that the pressure in the working cylinder 86 is higher than the pressure in the working cylinders 48 and 49 , then there is a higher pressure at the branch point 98 than in the line 43, with the result that the check valve 79 will be closed and the control line system 80 , 83 is acted upon by opening the check valve 101 from the pressure at the branch point 98 . Since this control line system also acts on the rear sides of the slide bodies 41 and 241 , but there are different pressures in front of this slide body in the line 35 or 240 , a different throttling effect is produced at the throttle points 40 and 96 , ie at the consumer 48 , 49 , which generates the lower pressure, this parallel circuit throttle 40 produces such a large pressure drop that before this parallel circuit throttle set 40 in line 35 and thus in line 28 and thus in line 12 and thus in line 82 is so high Pressure is generated as it is required by the consumer 86 , a correspondingly lower throttle effect being generated at the parallel connection throttle point 96 as a result of the pressure in the line 240 under the action of the control pressure in the line 83 , since in this case the pressure of the consumer which corresponds to the Slider body 241 acts, is large enough to the parallel circuit throttle 96 fully open, so that there is no pressure drop.

This arrangement of the parallel connection throttle points, which are struck together by the same control pressure on the rear, has the major advantage that if two consumers could take up a larger current than the pump 3 delivers, the current supplied by the pump 3 the two consumers - in the present case on the one hand the consumers 48 , 49 on the other hand the consumer 86 - is divided proportionally to the opening width of the throttle columns.

Check valves 58 and 68 act as pipe break protection. This means that if there is a leak in line 12 or line 28 or line 82 or another line connected to this and the pressure escapes, the consumer, by actuating the assigned control pressure transmitter and thus opening the assigned Neten single edge slide is connected, can not sink back under load. For example, when lifting under load and thus the working cylinders 48 and 49 are under pressure and the line 12 breaks, the check valve 58 closes. The existing in the working cylinders 48 and 49 liquid is thus enclosed and clamped so that no unwanted movement can occur, since the pressure relief valves 60 and 70 are closed ge, since there is no pressure in the lines 53 and 43 and thus the pressure relief valves 60 and 70 are not open.

However, if the single-edge control slide 31 is opened by actuating the control pressure transmitter 92, pressure is present in the line 43 , so that pressure medium flows through the lines 43 , 44 into the working cylinders 48 and 49 . The pressure in line 43 is also on line 73 in the control pressure chamber of the pressure relief valve 60 , so that it is open. That is, the pressure medium flow flowing out of the pressure chambers 56 and 57 of the working cylinders 48 and 49 can flow unhindered through the line 54 into the line 59 , the pressure limiting valve 60 , the lines 61 and 62 and into the return line 39 and thus into the return line 102 . The speed of movement of the pistons in the working cylinders 48 and 49 should be determined by the extent to which the single-edge slide 31 is open. If, as a result of external forces, the pistons in the working cylinders 48 and 49 want to lead this current, they draw in liquid with the result that the pressure in the line 44 and thus in the line 43 drops. Thus is lowered via the line 73, the pressure in the control pressure chamber of the pressure limiting valve 60 so that this closes to the extent that n where the pressure is lowered, that is, 60, a throttle effect is produced in the Druckbe relief valve that the from the Pressure chambers 56 and 57 flowing current throttles, so that the speed of movement of the pistons in the working cylinders 48 and 49 is braked by this throttling effect. The pressure relief valves 60 and 70 are also controlled by the pressure in the lines 59 and thus 54 and 69 and thus 44 . The Druckbe limit valves 60 and 70 thus also act as protection against impermissibly high pressure in the working cylinders 48 and 49 . That is, occurs as a result of overload or intermittent load, too high a pressure, depending on the direction of loading due to the too high pressure, either the pressure relief valve 60 or the pressure relief valve 70 , so that these pressure relief valves 60 and 70 also act as overload protection pressure relief valves and This is true even if none of the control pressure transmitters 92 and 93 are actuated.

Especially in such a case of the discharge of pressure medium through one of the pressure relief valves 60 and 70 , but also in any other case of suction into one of the pressure chambers 46 , 47 or 56 , 57 , the assigned suction check valve 64 or 66 opens so that over the respectively opened suction check valve 64 or 66 and line 62 and partial return line 39 line 102 can be reloaded from container 103 .

If the control pressure transmitter 92 has been actuated and thus the single-edge slide valve 31 has been opened and thus line 43 has been pressurized via the delivery line 12 and the lines 28 , 29 , 35 , and now the actuation of the control pressure transmitter 92 is ended and thus the single-edge slide valve 31 in brought the relief position, the parallel circuit throttle 40 completes completely. This would have the consequence that the last effective pressure remains in line 43 and thus holds the pressure relief valve 60 in the open position via line 73 . However, when both control pressure transmitters 92 and 93 are closed, both pressure relief valves 60 and 70 should also be closed. For this reason, a check valve 94 opening towards the pump 3 is provided in the slide body 41 , which in the said operating state has the consequence that the line 43 is relieved via the check valve 94 when the parallel circuit throttle point 40 is closed.

The valves on the other side of the control unit 74 or the corresponding valves in the control unit 85 or 100 or 111 act in an analogous manner.

If, by acting on the control pressure transmitter 92 in the pressure transmitter control pressure line 33 , such a pressure is generated that the single-edge control slide 31 opens very far, then such a strong current is required in the lines 29 , 35 and thus also 28 and the delivery line 12 that the pump 3 alone can no longer promote it. In this state, the interconnection unit 179 takes effect. As already mentioned, for controlling the pump 3 by the servo control valve 10, the spring acting on it is designed such that a certain pressure drop occurs at the single-edge control slide 31 acting as a measuring throttle point, for example a pressure drop of 20 bar. The spring 186 on the four-port / two-position valve 182 is designed such that this valve responds at a lower pressure drop, for example a pressure drop of 15 bar, between the delivery line 12 and the control pressure line 81 . The four-port / two-position valve 182 is designed such that when the slide body begins to move, the control lines 177 and 178 are first connected to one another, with the result that the pump 4 is pivoted out so far that the same pressure is present in the delivery line 15 in the delivery line 12 , this pressure being generated upstream of the throttle point 176 when no consumer is connected to the pump 4 . Upon further displacement of the slider body in the four-port / two-position valve 182, the lines are then 180 and 181 connected to each other through the valve 182 so that the delivery flow of the pump 4 in addition to the delivery line 12 of the pump 3 is fed through the four-port / two-position valve 182, where the pump 4 now swings so far that it generates exactly the flow rate that is required to generate the required pressure drop - in the given case 15 bar together with the flow rate of the pump 3 at the single-edge control slide 31 acting as a measuring throttle.

Although the consumers are immediately secured by the Druckbe limit valves 60 , 70 and the corresponding pressure relief valves to the other consumers, it is necessary to additionally secure the pump 3 and the entire system by means of a pressure relief valve, which prevents an inadmissibly high pressure Part of the system is damaged. For practical reasons, this pressure relief valve is installed in the interconnection unit 179, namely the pressure relief valve 184 is connected via line 180 to the delivery line 12 and, accordingly, to protect the pump 4 on its delivery line 15 via line 181, the pressure relief valve 185 connected. The opening of one of these pressure relief valves has the disadvantage that this pressure medium is used to discharge the highest possible pressure, which means that a lot of energy is destroyed in this pressure relief valve. This is inevitable for the reduction of short pressure surges. However, it is advantageous if it can be avoided that this pressure relief valve remains open for a long time. For this purpose, the pump 3, the pressure relief valve 157 is arranged, which is set to such a low pressure that it opens when there is a pressure in the control line 81 , which corresponds to the predetermined pressure drop at the by the Einkantenschieber 31 or 32 or . 86 and 87 given Meßdrosselstelle is below the response pressure of the pressure relief valve 184, so that 184 the pressure limiting Sven opens and before opening of the pressure limiting valve til 157 by the maximum possible pressure in line 152 is limited, with the consequence that at low rise in pressure in the Line 154 the servo control valve 10 increases the pressure in the pressure chamber 8 of the pump actuating cylinder 7 and thereby adjusts the pump 3 to a smaller stroke and thus a smaller flow, whereby it can be expected that after this control process caused by the rise in the control pressure increases, the pressure in the delivery line 12 read as a result of the reduced flow nkt is and thus the response of the pressure relief valve 184 can be avoided.

In an analogous manner, the pump 4 is assigned a corresponding pressure limiting valve 172 , which responds to the pressure in the control pressure line 166 and opens before the pressure limiting valve 185 opens.

With this pressure relief valve, however, only protection against pressure peaks is achieved during the control process of the pump. There is no protection against overloading the internal combustion engine 1 . This is achieved by the limit load control 230 . The constant pump 25 conveys through line 188 to the adjustable throttle point 189 , the setting element 190 of which is in operative connection with the setting element of the internal combustion engine 1 . The line 195 behind the throttle point leads to the control pressure sensors 90 , 91 , 92 , 93 , 120 , 121 , 122 , 123 , 129 and 130 . At this line 195 , the externally controlled pressure relief valve 196 is connected, which is influenced via line 197 by the pressure in line 188 upstream of the throttle point 189 . The pressure relief valve 196 is set to the pressure drop which is to prevail at the throttle point at the respectively provided operating speed. If this pressure drop is present, the pressure relief valve 196 is closed. If the pressure drop is smaller than intended, the pressure relief valve 196 opens and leads a current to the downstream throttle point 199 , at which a pressure drop now also arises and this pressure drop is transmitted via lines 203 and 204 as a pressure difference on both sides in the servo control valves 10 and 13 activated. This ensures that when both pumps 3 and 4 deliver to at least one consumer and the limit load control 230 intervenes, both pumps 3 and 4 are reduced proportionally, that is to say to the same extent, so that the overlaid movement of two driven working cylinders the resulting direction of movement is not changed. Be the movement speeds of two switched on consumers are in relation to each other in the same ratio as the openings of the single-edge spool, which act as measuring throttles. If the speed of the internal combustion engine 1 is reduced as a result of overloading the internal combustion engine 1 , the pressure drop at the throttle point 189 will decrease and the pressure limiting valve 196 will thus open and thus a pressure drop will occur at the throttle point 199 , which acts on both servo control valves 10 and 23 to the same extent. The setting of both pumps 3 and 4 is thus adjusted in the direction of a smaller stroke volume per revolution, but only to the extent that the pressure drop at the throttle set 199 and the pressure drop at the single-ended slide valve of the respective switched-on consumer as the measuring throttle we keep the balance. If one of the pumps 3 or 4 tends to run ahead, it immediately receives a counter signal which adjusts the two pressure drops again. In this way, the pressure drop at the one-way control valve spools of the two consumers are kept the same, with the result that this acting as a metering valve edge control spool an absolute amount, but not the ratio of the quantities to each other and thus the ratio of the speeds of movement change to each other.

The pressure relief valve 202 serves to protect the constant pump 25 . The bypass pressure relief valve 193 additionally protects the constant pump 25 in the event that the throttle point 189 is closed too far or completely. In this case, the oil flows via line 188 , line 191 , pressure relief valve 193 into line 194 .

To charge the pressure accumulator 103 , the pump 26 be used, which promotes to the steering device of the excavator, not shown in the drawing. The return from the steering device still has sufficient pressure to charge the memory 103 . For this purpose, the line 239 coming from the steering device is connected to the line 102 .

The pump 25 sucks from the housing 24 , in which the two pumps 3 and 4 are arranged, in order to ensure that an exchange of pressure medium takes place in the housing 24 . The back flowing from the steering through line 239 de pressure medium flows, as far as it is excess, from the pressure relief valve 201 into the unpressurized container 156 .

The volume of the reservoir 103 is dimensioned such that leakage losses and volume differences on the two sides of the pistons can be compensated for even when several consumers are actuated in the same direction.

The additional control unit 133 has a slightly different structure and a different mode of operation than the control units 85 or 110 or 111 . The four-port / three-position valve 128 is not only controlled by the two control pressure transmitters 129 and 130 , but it is also acted upon on the opposite side in each case by the delivery pressure in the line 131 or 132 leading to the consumer, so that when the Valves 128 via one of the control pressure sensors 129 or 130 set a state of equilibrium at the valve slide of the valve 128 . If the pressure at the consumer drops, the valve is opened further so that a larger current flows to the consumer and thus the consumer pressure increases the pressure.

Claims (5)

1. Hydrostatic drive for a particularly rotary consumer of hydraulic energy, which can be acted upon in both directions and connected to the delivery line of an adjustable pump, with a four-port / three-position valve upstream of the consumer, the setting of the pump being influenced by the pressure drop at the valve and the delivery line is connected to a connection of the valve, the return line to a further connection and branch lines leading to the consumer at the two other connections of the said valve, characterized in that a pressure chamber is arranged on each side of the valve ( 128 ) , which is connected to an arbitrarily operable, pressure-independent control pressure generating control pressure transmitter ( 129 or 130 ), and a second pressure chamber is arranged on both sides of the valve, which is used to control the valve ( 128 ) with the bottom he pressurized branch line ( 131 or 132 ) is connected between the valve ( 128 ) and the consumer ( 109 ), that the force generated by the pressure in this pressure chamber counteracts the force generated by the control pressure in the opposite pressure chamber. 2. Drive according to claim 1, characterized in that starting from each of the two branch lines ( 131 and 132 ) between the valve ( 128 ) and consumer, a bypass line is provided, which is connected to the return line ( 127 ) and in which one to the consumer non-return valve ( 134 or 135 ) is arranged. 3. Drive according to claim 1, characterized in that to each of the two connected to the consumer, from the four-port / three-position valve ( 128 ) outgoing branch lines ( 131 and 132 ) a drain line is connected, in which a controlled by the pressure in the branch line Pressure relief valve ( 136 , 137 ) is arranged. 4. Drive according to claim 1 with several consumers, characterized in that from the branch line ( 131 or 132 ) between the valve and the consumer branches off to the adjusting member ( 16 ) of the pump ( 4 ) leading control pressure line ( 140 ), in which a Setting organ of the pump ( 4 ) opening check valve ( 141 or 142 ) is arranged. 5. Drive according to one of the preceding claims, characterized in that the valve ( 128 ) and optionally further valves ( 134 , 135 , 136 or 137 ) are combined in a control unit which is arranged in the vicinity of the consumer.