EP0284989B1 - 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 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 roughly 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.

In the so-called mooring mode, a pump with a positive maximum delivery rate setting can operate with consumer quantity Q = 0 and a second are in negative maximum delivery setting. 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 small distance from one another is predetermined.

Another known and indeed 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 change the setting of the pumps cyclically once a week. In addition, an increase in pressure in stages is predetermined in this known method.

From the state of the art according to Art. 54 (3) EPC EP-A 0232722 a control device for the power control of several hydraulic pumps driven by a drive machine is described. It is not concerned with the uniform delivery rate setting of the various hydraulic pumps operating in a common working pressure system of constant pressure.

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, an additional control signal is included in the control, which is generated as a function of the volume setting of the associated machine and is given to the pressure regulator. This creates a control criterion that enables the machine to be regulated to the same volume setting with the same working pressure acting on the existing pressure regulators. The synchronism of the pumps achieved by the design according to the invention results from the fact that, depending on the control signal, which is dependent on the volume setting of the associated machine, a control characteristic, which is progressive or degressive and can be selected in terms of its steepness, is specified which, in terms of effectiveness, has the same working pressure at all Pressure regulator allows the same delivery rate setting.

Due to the presence of a progressive spring characteristic, there is a slightly progressive regulator characteristic even in known pressure regulators, but this is predefined by the spring and depends on the friction and self-adjusting forces of the adjustment and is therefore unusable for a regulator feedback.

It is also known to regulate the controller as a function of the working pressure and the volume setting of the machine in a so-called torque control, however, this takes place under completely different conditions and also for a completely different purpose, namely to achieve a favorable torque, a spring characteristic being aimed at in the form of a hyperbole, while in the embodiment according to the invention a regulator characteristic is essentially in the form of a straight line negative or positive slope results. In experiments, an increase in pressure in the controller characteristic curve has proven to be advantageous when the associated machine is swung in.

According to claims 2 to 6, tried and tested measures for generating a control signal depending on the volume setting of the machine are used. The control medium acting on the pressure regulator is blocked by the throttles depending on the respective volume setting of the associated machine and constantly regulated by the regulating valve, the regulating valve being formed by a pressure limiting valve in which the control pressure is measured against a spring and is constantly regulated. The synchronous or parallel operation is achieved by the dynamic pressure of the chokes. This leads to an increase in pressure in the controller characteristic and thus to an increase in pressure in the working pressure.

Due to the configuration according to claim 7, the synchronous operation or parallel operation is achieved without a significant increase in pressure in the working pressure. A constant working pressure is achieved in all operating states, since the control valve is acted upon directly or exclusively as a function of the working pressure, the synchronous delivery rate setting of the pumps being guaranteed by the fact that the control oil amount for the pressure regulators is divided by the control means depending on the delivery rate setting, which results in correction signals for the pressure regulator for the purpose of induction a loading of the adjusting devices ensuring synchronism.

It is possible, depending on the version of the pressure regulator, and the control valve or valves, e.g. with regard to their control edges, set the control pressure proportionally or inversely proportional to the deviation of the working pressure from the value set with the control valve.

The design according to claim 9 includes simple and practical features for remote control of the pressure regulator.

Within the scope of the invention it is possible, according to claim 10, to provide a common control valve, whereby a substantial simplification is achieved.

The embodiment according to claim 11 leads to a simple and practical construction in machines with reversible throughput direction, e.g. with reversible swivel direction for mooring or motor operation.

Fig. 1

eine hydraulische Antriebseinheit mit zwei in eine gemeinsame Arbeitsdruckleitung speisende Pumpen, die durch eine erfindungsgemäße Regeleinrichtung für den Parallelbetrieb geregelt sind,

Fig. 2

ein Steuermittel in Form eines Druckbegrenzungsventils in vergrößerter Schnitt-Darstellung;

Fig. 3 und 4

abgewandelte Ausgestaltungen der Antriebseinheit.

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

Fig. 1

a hydraulic drive unit with two pumps feeding into a common working pressure line, which are regulated by a control device according to the invention for parallel operation,

Fig. 2

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

3 and 4

modified configurations of the drive unit.

The pumps denoted by 1 are connected by line sections 2 to a common working pressure line 3 leading to a consumer B, the number of pumps being able to be increased as desired, which is illustrated by the position symbol 4, which denotes connections for further possible pumps. The pump units are identical to one another.

Each adjusting device 5 of the pumps 1 is assigned a pressure regulator 6 with a proportional control valve 7 in the form of a pressure compensator, the slide 8 of which regulates the passage of a connecting line 9 which starts from the associated working pressure line section 2 and opens into the piston chamber 10 of a cylinder 11 of the adjusting device 5 . For this purpose, the slide 8 can be acted upon on the one hand by a line section 12 with the working pressure and on the other hand by a line section 13, in which a throttle 14 is arranged, with a reduced pressure. This pressure acts in the same direction with a valve spring 15 acting on the valve slide 8, the spring force of which is optionally adjustable. The piston annular space 16 of the cylinder 11, in which a compression spring 17 is arranged for the purpose of resetting the adjusting device 5, is connected to the connecting line 9 by a line section 18 and can thus be subjected to the working pressure. The pressure regulator 6 described so far, including a 19, optionally adjustable nozzle in a discharge line 20 extending from the piston chamber 10 and a parallel line 21 connected to the latter, originating from the control valve 7, is of a conventional type and is therefore known, so that a functional description is dispensed with in detail can be. It should be emphasized that the pressure regulators 6 set a working pressure which, apart from a slight change in pressure, essentially is to be regarded as constant. The slight change in pressure in the working pressure in the control range of the pressure regulator 6 is caused by the progressive characteristic of the springs 15 and 17 as well as the friction and self-adjusting forces of the adjusting device 5 and is about 3 bar in the case of conventional pressure regulators 6.

According to the invention, each pump 1 is assigned a control means, generally designated 25, which acts on the pressure regulator 6 with a control signal which is dependent on the respective delivery rate setting of the associated pump 1. 1 and 2, the control means 25 is formed by a pressure relief valve 26, which is arranged in a line 27 branching off from the line section 13, preferably behind the throttle 14, and the control pressure p _St present in the line section 13 as a function of the delivery rate setting of the associated one Pump 1 controls. An actuator 28 in the form of a feeler pin is used to transmit the respective setting for the delivery rate setting, which at one end bears against an inclined surface 31 on the adjusting piston 29 of the cylinder 11 outside the latter and acts by means of a spring 32 on the slide of the pressure limiting valve 26 and against it Inclined surface 31 is applied. The adjusting element 28 is mounted in its longitudinal direction so that it performs a longitudinal movement when the adjusting piston 29 is displaced longitudinally, whereby it acts on the pressure limiting valve 26. The arrangement in the present exemplary embodiment is such that the pressure limiting valve 26 closes when the adjusting device 5 is pivoted in, that is to say when the adjusting piston 29 is moved to the left, as a result of which the control pressure p _{St is} increased, ie a pressure signal X is generated which corresponds to the Slider 8 of the control valve 7 against Working pressure applied. Thus, the working pressure at the control valve 7 is no longer only in equilibrium with the force of the spring 15 (controller setting), but the controller setting increases as a function of the pivoting angle a by the pressure signal X. This results in a pressure increase and a pressure increase in the pivoting in Controller characteristic. On the basis of these facts, the delivery rate setting of the pumps 1 is determined when the working pressure acting on the pressure regulators 6 is essentially the same, which results in the same delivery rate setting for the pumps 1 during operation of the pumps 1, ie parallel or synchronous operation. An effective pressure increase with regard to the desired synchronization is given when the pressure rises above the setting range of above approximately 10 bar. Very good results are achieved with a pressure increase of 20 bar.

The configuration according to the invention is also suitable for pumps which can be adjusted in both delivery directions. In this case, it is advantageous to make the arrangement such that when the pumps are in the zero position, the actuating element 28 is in the middle position relative to the length of the inclined surface 31.

2 shows, as an exemplary embodiment, a sectional view of a pressure limiting valve 26 in an enlarged view. The actuating element 28 acts by means of the spring 32, which is supported on it on the one hand and engages on the slide 33 on the other hand, on the slide 33 of the pressure limiting valve 26, which regulates the control pressure p _St , ie a control signal X, by means of control edges 34. In this case, the control edges 34 between the slide 33 and the bore 36 receiving it release or drain through a channel 37 in the valve housing 38 more or less.

The valve housing 38 is screwed into the housing of the cylinder 11 or an attachment part of the same. The slide 33 is located in an adjusting bush 39, which can be adjusted axially in the valve housing 38 by means of a thread 41 by turning an attack element, here a hexagon socket 42, and can be locked by means of a lock nut 43 screwed onto the adjusting bush 39. An input throttle 45, which corresponds to the throttle 14 according to FIG. 1, is arranged between the connection 35, which can be connected to the line 27 in FIG. 1, and a transverse bore 44 which intersects the bore 36 in the adjusting bushing 39.

3, in which the same parts are provided with the same reference numerals, differs from the above-described embodiment in that the control means 25 are formed by means of the adjusting element 28 against a spring 48 adjustable throttles 49, the outputs of which via branch lines 5) a remote control valve 51 is connected, which is formed by a pressure control valve which is connected to the drain. All pressure regulators 6 can be controlled simultaneously by means of the remote control valve 51. Between the respective branch line 5) and line 27, when the throttle 49 is completely open in the working position shown, there is a pressure difference d which is dependent on the delivery rate setting, i.e. in the present case from the swivel angle a.

4, each pump 1 is assigned a control means, generally designated 25, which throttles the amount of control oil that flows through lines 27, 58, depending on the respective delivery rate setting of the associated pump 1. The control means 25 is formed by an adjustable throttle 59, which in the line section 13 is preferably behind the throttle 14 branching line 27 is arranged and controls the amount of control oil flowing in the line section 13 or 27 depending on the delivery rate setting of the associated pump 1. The throttles 59 are each connected on the output side through the line section 58 to a common return line 61, in which a preferably remotely controllable pressure control valve 62 is arranged, which in the present exemplary embodiment is a pressure connection valve. The pressure control valve 62 is connected by a control line 63 to the working pressure line 3 and is controlled by the working pressure in such a way that it _reduces the control pressure p _St1 in the line _sections 27 and the control pressure p _St2 reduced by a pressure difference d ( _dynamic pressure) determined by the throttle 59 Line sections 58 or in the return line 61 is lowered towards the return when the working pressure exceeds the control pressure set on the control valve 62, preferably with the control spring.

The pump units are identical to one another, i.e. same pressure regulator 6 with the same spring setting 15 and same constant throttles 14 and same adjusting throttles 59 with the same throttle dependence on the swivel angle a.

In this exemplary embodiment, the control element 33 is also used to transmit the stipulation corresponding to the respective delivery quantity setting. At one end, the actuating element 33 bears against the inclined surface 34 on the adjusting piston 30 of the cylinder 11 and is acted upon by a spring against the inclined surface 34. The adjusting element 33 is mounted in its longitudinal direction so that it performs a longitudinal movement when the adjusting piston 30 is displaced longitudinally, whereby it acts on the throttle 59 or on the slide of the throttle valve. The arrangement is in the present embodiment so that the throttle 59 closes when the adjusting device 5 is _{pivoted in} , ie when the adjusting _piston 30 is moved to the left, as a result of which the control pressure p _{St1 is} increased because the amount of control oil decreases and the control pressure at the throttle 14 is reduced, ie it a pressure signal X is generated, which acts on the slide 8 of the control valve 7 against the working pressure. This means that the working pressure at the control valve 7 is no longer in equilibrium with the force of the spring 16 (controller setting), but the controller setting initially increases by the pressure signal X as a function of the delivery rate setting or the swivel angle a. This pressure increase when swiveling in the controller characteristic curve becomes However, its effect on the working pressure is compensated for by the function of the pressure control _valve 62 by lowering the pressure signal P _St2 , so that the working pressure is constant in all operating _states , although the control pressure p _St1 increases briefly when swiveling in and the back pressure pressure _causes the synchronous _{delivery rate setting} Pumps 1 guaranteed. An effective increase in the control pressure of the throttles 59 with regard to the desired synchronism occurs when the pressure rises above the setting range of above approximately 10 bar. Very good results are achieved with a pressure increase of 20 bar.

The following functional details of the control device are described briefly below, in particular according to FIG. 4.

Function of the control valves

The amount of control oil flowing through lines 13, 27, 58 to the pressure control valve 62 of the pressure regulators 6 flows through the lines 13 via the constant throttles 14 for each individual regulator of the at least two pumps 1. A back pressure is set at the throttle 14. The dynamic pressure acts on the valve slide 8 against the spring force of the spring 15.

In order to regulate the adjusting piston 30 in any pivot position between the respective end stops 22, it is necessary for the valve slide 8 to assume a central position in which the spring force of the spring 15 and the opposing dynamic pressure of the throttle 14 are in equilibrium, and the connecting line 9 and the parallel or return line 21 are in throttled connection with the actuating piston chamber 10.

With the same spring setting of the springs 15 and the same dimension of the throttle 14, the same control oil quantity is required for this on the throttles 14 and the line sections 27 for each pump.

If the quantity of control oil is greater, the valve slide 8 moves against the spring force due to increasing dynamic pressure at the throttle 14 and opens the connection from line 9 to the adjusting cylinder 11. As a result, the pump pivoting angle a is reduced to zero. If the amount of control oil is smaller, the pump swivel angle a increases towards the maximum.

Regulation of the operating pressure

The control oil quantities are combined in lines 61 and regulated by the pressure control valve 62 as a function of the operating pressure.

If the operating pressure is in equilibrium with the spring setting of the pressure control valve 62, the total control oil quantity is so large that the pivoting position of the pumps does not change.

At a lower operating pressure, the pressure control valve 62 closes so that the control oil quantity decreases and the delivery quantity of the pumps increases and the operating pressure increases.

At a higher operating pressure, the pressure control valve 62 opens, so that the control oil quantity increases and the delivery quantity of the pumps decreases and the operating pressure drops.

The pressure balance at the pressure control valve 62 depends only on the operating pressure in the connecting line 32 and the spring setting and is independent of the swivel angle α of the pumps 1.

Regulation of the parallel position

The distribution of the control oil quantity regulated by the pressure control valve 62 to the individual pumps depends, since the constant throttles 14 are the same, only on the position of the adjusting throttles-59. The throttles 59 close at a minimum flow rate and open at a maximum flow rate and enable a continuous throttle change in the intermediate positions.

If the pumps 1 have different swivel angle positions a, the control oil quantity of the pump 1 with the largest swivel angle a is the largest, the control oil quantity of the pump 1 with the smallest swivel angle a is the smallest. Since with all pressure regulators 6 the required control oil quantity is the same at the control point, pump 1 with the larger control oil quantity (larger swivel angle a) must swivel in and pump 1 with the smaller control oil quantity (smaller swivel angle a) swivel out until swivel angle a is equal and the control oil quantities are evenly divided by the adjusting throttles 59.

The configuration according to the invention is also suitable for pumps or motors which can be set in both directions of delivery. In this case, it is advantageous to make the arrangement so that when the pumps are in the zero position, the actuating element 33 is in the middle position relative to the length of the inclined surface 31.

Claims (11)

1. A regulator for at least two hydrostatic machines of variable displacement or swept volume that are linked to a common constant pressure working pressure line, wherein each machine has an adjusting device with a hydraulic adjusting piston and a pressure control device for adjusting the volume of the machine and for keeping the working pressure constant, characterised in that a control means (25) is associated with each pressure control device (6) that adjusts the pressure control device (6) proportionally to the volumetric setting by a control signal that is dependent on the respective volumetric setting of the associated machine (1).
2. A regulator according to claim 1, characterised in that the control means (25) can be controlled by a position sensor that cooperates with the adjusting device (5) or a built-on part thereof.
3. A regulator according to claim 2, characterised in that the position sensor comprises an oblique surface (31) on a part of the adjusting device (5), preferably on the adjusting piston (29), and an adjusting element (28) that follows the oblique surface (31).
4. A regulator according to any one of claims 1 to 3, characterised in that the control means (25) comprises an adjustable throttle (49) that is arranged in a control line (27, 50) serving to act on the pressure control device (6).
5. A regulator according to any one of claims 1 to 4, characterised in that the control means (25) is a pressure regulating valve, in particular a pressure limiting valve (26) or a pressure reducing valve.
6. A regulator according to claim 4 or claim 5, characterised in that the control line (27, 58) is connected to the return flow by at least one control valve (62) controlling the control pressure (P_St1, P_St2) therein.
7. A regulator according to claim 6, characterised in that the control valve (62) is acted on by the working pressure or by a pressure dependent thereon and, if the working pressure deviates from the value set by the control valve (62), either lowers or increases the control pressure (P_St1, P_St2) proportionally or inversely proportionally to the deviation, preferably by lowering it when the working pressure rises above the set value.
8. A regulator according to claim 7, characterised in that the control valve (62) is a pressure sequence valve.
9. A regulator according to claim 7 or claim 8, characterised in that the control valve (62) is a remote control valve.
10. A regulator according to any one of claims 7 to 9, characterised in that a common control valve (62) is arranged in a common return line (61).
11. A regulator according to any one of claims 2 to 10, characterised in that the machines (1) are installed to operate in both directions of flow and the position sensors are in their middle positions when the adjusting devices (5) are in their zero setting.

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