EP0284988B1 - Regulator for at least two hydrostatic machines linked to a common pressure pipe - Google Patents

Description

The invention relates to a control device according to the preamble of claim 1.

If several regulated, in particular pressure-controlled, pumps feed together into a working pressure line or a consumer network, the delivery rate settings of the pumps are indefinite because, due to the approximately constant working pressure, no relationship can be derived that would ensure a uniform delivery rate setting for all pumps, i.e. parallel operation. Therefore, the pumps can take any delivery settings at any time, e.g. one pump can be in maximum and the other pump in minimum delivery setting. This has the following disadvantages.

The load and thus the wear is distributed unevenly.

Every pump drive must be designed for maximum output and 100% duty cycle, even if the maximum output is rarely reached.

The pumps oscillate at a swivel angle, even if the total amount delivered does not change. This results in losses and noises.

The so-called mooring operation can have one pump in positive maximum delivery rate setting and a second one in negative maximum delivery rate setting when consumer quantity Q = 0. The second pump swallows the flow rate that the first pump delivers. This results in increased wear and power loss and is associated with high noise levels.

It is known to force at least two pumps of variable flow rate that feed into a common working pressure line or a common consumer network by means of a mechanical linkage for synchronous or parallel operation. This measure not only leads to a loss of performance, but also requires complex, stable mechanics. In addition, this configuration results in a large and bulky construction, which makes the spatial arrangement at the place of use difficult and, in particular, an arrangement of the pumps at a relatively short distance from one another is predetermined.

Another known, namely hydraulic, method of operating at least two pumps approximately evenly, ie distributing the wear and the load evenly over all pumps over time, is the so-called cascade control. With this measure, the pumps are deliberately set to slightly different controller characteristics. The first pump regulates eg at 200 bar, the second at 205 bar and the third at 210 bar. The load is thus clearly defined and the pendulum is avoided, although the pumps are subject to different wear due to different loads. In order to achieve even wear, it is necessary, for example, to set the pumps cyclically once a week to swap. In addition, an increase in pressure in stages is predetermined in this known method.

The invention has for its object to design a control device of the type mentioned in such a way that, while ensuring a uniform load on the machines, hydraulic synchronous operation or parallel operation is achieved with one another.

This object is achieved by the characterizing features of claim 1.

In the embodiment according to the invention, the one machine is a leading machine and the at least one other machine is a slave machine. The control of the other machine includes a control signal dependent on its volume setting as the actual value and a control signal dependent on the volume setting of the one machine as the target value . As a result, the at least one other machine is regulated as a function of the volume setting of the one machine, which results in the desired parallel or parallel operation.

It is known per se to mutually include their volume settings in the regulation of the pumps in the case of cumulative torque controllers, but this takes place under completely different conditions and for a different purpose, namely to achieve a favorable torque, with spring sets being a controller characteristic curve in the form of a hyperbola is aimed for, while in the embodiment according to the invention a controller characteristic curve results essentially in the form of a straight line without a slope.

In the embodiments according to claims 2 and 5 proven means of controlling or regulating are used.

The embodiment according to claim 6 leads to a simple and practical construction in machines with reversible throughput direction.

The design according to claim 7 includes simple and practical features for remote control of the pressure regulator.

Fig. 1

einen hydraulischen Schaltplan mit einer Antriebseinheit, die zwei Pumpen veränderlicher Fördermenge aufweist, die in eine gemeinsame Arbeitsdruckleitung speisen und mit einer erfindungsgemäß ausgestalteten Regeleinrichtung für den Gleichlaufbetrieb der Pumpen;

Fig. 2

eine Abwandlung der Regeleinrichtung;

Fig. 3 und 4

weitere Ausführungsbeispiele der Regeleinrichtung;

Fig. 5

ein Steuermittel in Form eines Druckbegrenzungsventils der Regeleinrichtung in vergrößerter Schnittdarstellung.

The invention is explained below on the basis of preferred exemplary embodiments illustrated in simplified drawings. It shows:

Fig. 1

a hydraulic circuit diagram with a drive unit which has two pumps of variable delivery rate, which feed into a common working pressure line and with a control device designed according to the invention for the synchronous operation of the pumps;

Fig. 2

a modification of the control device;

3 and 4

further embodiments of the control device;

Fig. 5

a control means in the form of a pressure relief valve of the control device in an enlarged sectional view.

The pumps 1, 2 of the drive unit are of the same basic equipment, and they each have a controller 3, 4 for their adjusting device and a control means 5, which one of the delivery rate setting associated pumps 1, 2 dependent control signal X _is generated.

The controllers 3 are each formed by a pressure compensator.

The adjusting device comprises a hydraulic cylinder 6 with an adjusting piston 7, which adjusts the associated pump 1, 2 against a compression spring 9 arranged in the piston ring space 8 in the direction of low delivery or zero position and in the opposite direction in the direction of maximum delivery. For this purpose, the piston chamber 11 of the cylinder 6 is connected by a connecting line 12 to a working pressure line section 13 of the associated pump 1, 2, the working pressure line sections 13 being connected to a common working pressure line 14 leading to a consumer B. The control valve 15 of the controller 3 formed by the pressure compensator is arranged in the connecting line 12. The control means 5 is formed in the present embodiment by a pressure control valve, here a pressure relief valve 17, the slide 16 of which is adjustable via a valve spring 18 by a plunger 19 which scans an inclined surface 21 on the adjusting piston 7. The piston annulus 8 is connected by a line 10 to the connecting line 12 and is therefore subjected to working pressure.

The pumps 1, 2 or their controllers 3, 4 differ significantly in terms of regulation and the connections or piping. In the present exemplary embodiment, the regulator 3 is a pressure regulator with a proportional valve, the slide 16 of which can be acted upon by the working pressure against a valve spring 23 adjustable spring force via a line section 22 starting from the connecting line 12. Against that is Slider 16 of the regulator 4 _is acted upon by the control signal X _ist1 generated by the associated pressure relief valve 17 as the actual value and on the other hand by the valve spring 23 and the control signal X generated by the pressure relief valve 17 of the first pump as the setpoint. For this purpose, both pressure limiting valves 17 are connected on the input side to the connecting line 12 by means of line sections 24, a throttle 25 being arranged in the line sections 24 and, on the other hand, connected to the outlet. In the flow direction behind the throttle 25, a connecting line 26 branches off from the line section 24 of the pump 2, via which the slide 16 of the regulator 4 can be acted upon by the control signal X _ist1 defining the delivery rate setting of the pump 2. In contrast, branches off from the line section 24 of the pump 1 downstream of the throttle 25 is a connection line 27 from by means of which and by means of a branching-off in front of her line section 28, the control valve 15 of the pump 2, as described above with the delivery setting of the pump 1 defining pressure signal X _{is intended} as a target value X is acted upon.

The control valves 15 are basically the same valves, the function of which is determined either by connection to the working pressure (pump 1) or by connection to the pressure signal _X1 (pump 2). In regulator 3, the working pressure is weighed against the force of valve spring 23 (regulator setting) on the pressure compensator forming regulating valve 15. In the controller 4, the pressure signal X _ist1 forming the actual value _is weighed against the force of the valve spring 23 and the pressure signal X forming the setpoint X _{soll is} weighed. The arrangement of an adjustable throttle 29 in a connecting the connecting line 12 between the cylinder 7 and the control valve 15 with the associated drain line 31 Cross line 32 and a parallel line 30 starting from the control valve 15 are the same for both control valves 15.

On account of this configuration, during operation of the drive unit there is a delivery rate setting of the pump 2 as a function of the delivery rate setting of the pump 1, that is to say a parallel or synchronous operation, the parallelism or the synchronous operation being effected by changing the force of the valve spring 18 and / or the valve spring 23 of controller 4 can be set. The delivery rate settings of pumps 1, 2 and their swivel angle a can be set equally. The pump 1 thus represents a lead pump, while the pump 2 is a slave pump. In this way, the same delivery rate setting of the pumps 1, 2 can be achieved without a significant pressure increase in the controller characteristic. An essentially constant working pressure is thus maintained in the control range.

Within the scope of the invention, it is possible to assign the drive unit to more than one pump 2, which is dependent on the situation. This is indicated by a further working pressure line section 13 and a further connecting line 27 in each case at 33. One or more secondary pumps 2 can thus be regulated by a control means 2, here the pressure relief valve 17 of the lead pump 1. If the lead pump 1 fails, one of the slave pumps 2 can easily be converted into a lead pump.

The pressure regulator 3 of the lead pump 1 can be easily converted into a remotely controllable embodiment, as shown in FIG. 2. For this purpose, a connecting line 35 is arranged, which starts from the connecting line 12 carrying the working pressure and to the slide 16 of the regulator 3 on the Leads on which the valve spring 23 (compression spring) is arranged. From this connecting line 35, a line 37 branches off to the outlet behind a throttle 36, in which a remote control valve 38 formed by a pressure control valve is arranged.

In the exemplary embodiment according to FIG. 3, the pressure limiting valves 17 are preferably connected to the working pressure line 14 via a common pressure reducing valve 41 arranged in a connecting line 40, the pressure limiting valves 17 being connected to the pressure reducing valve 41 via line sections 43 containing throttles 42. The control signal X _is to the controller 4 of the lag pump 2-transmitting connection line 44 branches off between the throttle 42 and the pressure relief valve 17 of the line section 43 of the transfer pump 1 and is arranged similar to the first embodiment. The connecting line 45 transmitting the control signal X _ist1 to the controller 4 branches off between the throttle 42 and the pressure limiting valve 17 from the line section 43 of the sequence pump 2.

The embodiment shown in Fig. 4 differs from the above in that the control means 5 are formed by pressure reducing valves 50, a flow control signal dependent from the working pressure X _is or X generate _IST1 and this, urged by the plungers 19, depending on the accompanying Flow rate control will. The pressure reducing valve 50 of the lead pump 1 is arranged in a line 51 which starts from the connecting line 12 carrying the working pressure and is connected via at least one line section 52 to the regulator 4 of the follow-up pump 2 on the spring 23 side or to further follow-up pumps 2 is. The explanations according to fig. 3 and 4 have lower power loss due to the use of the pressure reducing valves 41 and 50, in particular at high working pressures.

5 shows, as an exemplary embodiment, a sectional view of a pressure control valve on an enlarged scale, which can be used as a pressure limiting valve 17 in the exemplary embodiment according to FIGS. 1 to 3 and, in principle, also in the exemplary embodiment according to FIG. 4. The actuating element 19 acts by means of the one hand supported on him and on the other hand engaging on the slide 16 spring 18 on the slider 16 of the pressure relief valve 17, which _is the control signal X by means of control edges 61 and X _IST1 adjusts. Here, the control edges 61 between the slide 16 and the bore 62 receiving it release or drain through a channel 63 in the valve housing 64 more or less.

The valve housing 64 is screwed into the housing of the cylinder 6 or an attachment part thereof. The slider 16 is located in an adjusting bush 65, which can be adjusted axially in the valve housing 64 by means of a thread 66 by turning an attack element, here a hexagon socket 67, and can be locked by means of a lock nut 68 screwed onto the adjusting bush 65. An input throttle 72 is arranged between the connection 69 and a transverse bore 71 which intersects the bore 62 in the adjusting bush 65, and the throttle 25 according to FIG. 1 and 2 or the throttle 42 according to FIG. 3 corresponds. In the exemplary embodiment according to FIG. 4, such a throttle is not required.

In all exemplary embodiments, identical parts are provided with the same reference symbols, and control signals X _ist and X _{ist1 can} also be formed using a control pressure be generated, for example, in a manner known per se by an auxiliary pump.

Claims (7)

1. A regulating device for at least two hydrostatic machines that have variable displacement or intake volumes and are linked to a common working line, wherein each machine has associated with it an adjusting device having a regulator for regulating the volume setting, characterised in that each regulator (3, 4) has associated with it control means (5) that produces a control signal (X_ist or X_ist1) in dependence upon the change in the volume setting of the associated machine (1, 2), and in that the control signal (X_ist) dependent upon the volume setting of the one machine (1) is sent as desired value (X_soll), and the control signal (X_ist1) dependent upon the volume setting of the at least one other machine (2) is sent as actual value to the regulator (4) of the other machine (2).
2. A regulating device according to claim 1, characterised in that each adjusting device is a hydraulically operable cylinder-piston unit (6, 7) and the control means (5) are pressure regulating valves, in particular pressure limiting valves (17), pressure reducing valves (50) or adjustable throttles.
3. A regulating device according to claim 2, characterised in that the regulators (3, 4) are pressure regulators.
4. A regulating device according to any one of claims 1 to 3, characterised in that the control means (5) is controllable by a position sensor that can co-operate with the adjusting device (6, 7) or an extension thereof.
5. A regulating device according to claim 4, characterised in that the position sensor comprises an oblique face (21) on a part of the adjusting device (6, 7), preferably on the adjusting piston (7), and an adjusting element (19) that senses the oblique face (21).
6. A regulating device according to claim 4 or claim 5, characterised in that the machines (1) are arranged for operation in both directions and the position sensors are in their central positions when the adjusting devices (5) are in their zero positions.
7. A regulating device according to any one of claims 1 to 6, characterised in that the regulator (3) of the one machine (1) has associated with it a remote control valve (38) preferably in the form of a pressure regulating valve.

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