EP2682610A1 - Regulator system of a hydraulic variable capacity pump - Google Patents

Abstract

The system (S) has a main stage (11) i.e. pressure-servo-controlled 3/2-way-control valve (12), fixed to a pressure line (8) and a return-flow line (19) for controlling control pressure acting at control cylinders (Z1, Z1'). A pilot valve is attached to the stage for controlling pressures, torque and/or volume. The pilot valve is connected to a pressure signal line (21) that is guided to pilot pressure control of the control valve at an inlet side. The pilot valve is attached to a low-pressure area and connected to the cylinders for quantity- and/or rotational torque control at an outlet side. The pilot valve is designed as a flow control pilot valve (24), a torque control pilot valve (25) and a pressure regulating pilot valve (34).

Description

The invention relates to a control system of a hydraulic variable displacement pump according to the preamble of patent claim 1.

From the technical information document D 7960 N, the company HAWE Hydraulik SE, Streitfeldstraße 25, 81673 Munich, July 2011-03 issue, pages 2 and 3, and page 19, license plate ZL; LLSN ; LN, such control systems for hydraulic variable displacement pumps z. As an axial piston swash plate type, known in which for a power or torque control of the main stage responsible for the pressure control is associated with a connected to the signal pressure line pilot valve. This pilot valve is a z. B. 2/2-way drain valve with spring load and pressure feedforward from the signal pressure line and is connected to the drain side with a return line. Once the pump is adjusted by the actuator cylinder, for example, from the position for maximum delivery in the direction of minimum funding, the pilot valve assumes a throttling control position, so that pressure fluid is discharged from the signal pressure line in the return line, as well as the pilot valve for pressure control. This means a loss, which increases relative to the pump flow, the farther the pump is moved towards the minimum delivery, and may for example be about 2 to 3 l / min, so that then the pump has to work increasingly for loss compensation. This significantly degrades the volumetric efficiency. These control systems offer as equipment of variable displacement pumps the important advantage of inexpensive small pilot valves, small dimensions and low weight, which is very important for use on or in vehicles. Such variable pumps are pressure-controlled via the main stage and the pilot valve, either with adjustable pressure directly to the pump to keep the system pressure constant with varying flow requirements, for example in constant-pressure systems in which different flow rates are required, or as a low-loss pressure limitation of a hydraulic system. Alternatively, the main stage can be operated as a load-sensing controller, for example with integrated pressure limitation of the system pressure, independent of the load pressure, wherein a load pressure signal of at least one consumer supplied by the variable displacement pump is fed into the signal pressure line and to the pilot valve. These two control principles can be combined with a torque controller, for example, to keep the product of pressure x flow constant, this torque controller is adjustable in a certain percentage of the drive torque of the variable displacement pump. From practice, it is also known to integrate into such a control system alternatively or in addition to the torque controller a flow regulator. This is also for this a pilot valve assigned to the single main stage and connected to the signal pressure line, which is connected to the drain side of the return line. The flow regulator uses z. B. over the entire usable pressure range before the variable pump mechanically comes to a stop to regulate over the entire pressure range, for example, a constant, or increasing or decreasing amount. For this purpose, it is known to use as pilot valve, a 2/2-way pressure control valve, for example with actuation by a proportional solenoid, it being possible to control the flow rate directly or indirectly proportional to the bias current of the proportional solenoid, that is, the flow rate with increasing Beaufschlagungsstrom for example, to increase linearly or to decrease linearly. There may be more than one unilaterally acted actuator cylinder can be provided. Also differential cylinder with double-sided pressurization, or an eccentric cradle can be used to adjust the pump. As soon as the variable-displacement pump is adjusted, for example, in the direction of minimum delivery, the pilot valve allows pressure medium to flow out of the signal pressure line to the return line, which means a relatively increasing loss in the direction of the minimum displacement adjustment pump, which degrades the volumetric efficiency.

There are also known control systems that contain several main stages without pilot valves. However, this design requires significantly higher costs, large dimensions and higher weight.

The invention has for its object to improve a control system of a hydraulic variable displacement pump, which is operated with volume control and / or torque control and a single main stage, in terms of volumetric efficiency.

The stated object is achieved with the features of claim 1.

In that the respective pilot valve at least of the flow and / or torque controller is connected to the actuating cylinder on the outlet side, the pressure medium discharged from the signal pressure line during the control does not flow as a loss into the return line but into the already lower pressure range of the actuating cylinder, so that Here, a pressure medium circuit is created, which is largely closed. Since there is a constantly adapting pressure level when the adjusting cylinder is pressurized, the torque and / or quantity control may possibly also be more stable than when the pressure medium is discharged into the substantially uniform, extremely low pressure level of the return line. Since thus drained pressure medium is not lost, despite the small-sized, cost-effective and lightweight Control system of the volumetric efficiency of the variable, for example, then significantly improved when the variable displacement is increasingly adjusted towards minimum funding.

If the pilot valve for pressure control is connected to the actuating cylinder on the outlet side, losses are minimized even more.

In an expedient embodiment, the quantity pilot valve is adjustable by a proportional solenoid against spring force either to a passage position (the delivery increases directly proportional to the charge current of the proportional solenoid) or a blocking position (the flow rate per unit time decreases indirectly proportional to the charge current of the proportional solenoid) 2 / 2-way pressure control valve. To be able to manage with a small-sized and lightweight proportional magnet, it may even be appropriate to equip the pilot valve with a proportional pressure pilot by the proportional solenoid. The application current of the proportional solenoid specifies the desired value of the quantity to be regulated. This setpoint specification could alternatively, e.g. on the pilot valve, hydraulically, pneumatically, by spring force, or otherwise done.

In another advantageous embodiment, the torque control and / or the pressure control pilot valve is a pressure-controlled from the signal pressure line forth against spring force toward a passage position 2/2 pressure relief valve.

Both pilot valve types fulfill the control function for the pilot pressure of the main stage under spring force. In this case, embodiments of the control system are possible in which e.g. in addition to the pressure regulator pilot valve only the flow control pilot valve or only the torque control pilot valve are provided.

The torque control is suitably adjustable by the spring-control pilot valve in the direction of a locking position acting spring force is adjustable. The torque control (or power control) intervenes, for example, only from a selectable pressure level within the usable pressure range and then to the maximum pressure to reduce the flow rate after a predetermined curve.

In an advantageous embodiment, the spring force of the flow control and / or torque control pilot valve is generated by a spring and by a position feedback feedback, preferably the actuating cylinder, changeable. By returning the actual position value of the variable displacement pump, the spring force can be changed with increasing adjustment of the pump in the direction of minimum delivery, for example, increased. In a structurally simple manner, the return takes place by tapping off the position of the first actuating cylinder via a cam surface and a button that changes the set spring preload or spring force. Alternatively, the feedback can also be done by using a displacement transducer, a pressure sensor, an angle sensor of the swash plate, etc. In this way, the control loop is simply closed via the pilot valve.

To operate the main stage, different interconnections of the signal pressure line are possible. The pressure in the signal pressure line can be generated by means of an inlet nozzle from the pressure line leading to the main stage in the control system itself and modified if necessary. Alternatively, the signal pressure line may be connected to a load pressure signal circuit of at least one consumer powered by the pump and separated from the pressure line.

Furthermore, it is expedient if a control line is connected to the actuating cylinder between the main stage and the actuating cylinder via a nozzle to the return line. The consequent loss of pressure medium is negligible.

Conveniently, the 3/2-way pressure control valve of the main stage in the direction of adjustment for connecting the pressure line and the first actuating cylinder from the pressure line druckvorgesteuert, that is from the delivery pressure of the variable itself, and pressure controlled in the direction of the connection of the first actuating cylinder with the return line from the signal pressure line and spring loaded. This spring load is conveniently adjustable, z. B. to produce a constant pressure level below the set by the system pressure relief valve pressure levels in variations of the flow rate.

At least one second actuating cylinder may be loaded from the pressure line and spring-biased, e.g. in such a way that the variable-speed pump starts up with maximum delivery during commissioning, for example before the control system intervenes.

In an expedient embodiment, the variable displacement pump equipped with the control system is a swashplate type axial piston pump, for example with a nominal pressure of up to about 350 bar, a maximum pressure of about 400 bar, and type-dependent with a displacement volume of 60, 90 or 110 cm ³ / rev. This design is robust and reliable and designed for flanging on power take-offs of commercial vehicle transmissions or for a standard connection with an SAE flange, and is universally suitable for other applications. The design has a high Selbstansaugdrehzahl and a low sound pressure level. The volume flow is proportional to the speed and the current displacement volume and can be infinitely adjusted. Such variable displacement pumps are particularly suitable for use with proportional directional slides and can be operated with alternating direction of rotation.

The actuating cylinders engage e.g. together on a swash plate adjusting. Suitably, the actuating cylinders are arranged in pairs and connected in parallel.

With regard to a moderate pressure level when acting on the actuating cylinder from the control system, it is expedient if this actuating cylinder has a larger pressurization surface than every second actuating cylinder. The area ratio may be between about 2: 1 to 5: 1, or even greater, controlling the pressure fluid discharged to the actuator cylinder very precisely.

The pilot valves for pressure and / or torque control may e.g. Be slide valves.

Fig. 1

ein Blockschaltbild eines Regelsystems einer Hydraulik-Verstellpumpe, in drucklosem Zustand,

Fig. 2

eine Detailvariante,

Fig. 3

eine weitere Detailvariante, und

Fig. 4

eine weitere Detailvariante.

Embodiments of the subject invention will be explained with reference to the drawing. Show it:

Fig. 1

a block diagram of a control system of a hydraulic variable displacement pump, in a pressureless state,

Fig. 2

a detail variant,

Fig. 3

another detail variant, and

Fig. 4

another detail variant.

A control system S of a hydraulic variable-displacement pump V is arranged, for example, with a control system housing 9 on or in a variable-displacement pump housing 1. The variable displacement pump V is, for example, a swashplate axial piston pump 2, whose volumetric flow is steplessly adjustable in the direction of a double arrow between maximum delivery and minimum delivery by means of a swash plate adjusting element 3. At least one actuating cylinder Z1 (and optionally a second actuating cylinder Z2) engages on the adjusting element 3. In the embodiment shown in FIG Fig. 1 is a parallel-connected pair of first actuating cylinder Z1, Z1 'and a parallel pair of second actuating cylinder Z2, Z2' provided. The actuating cylinder Z1, Z1 'contains a piston 4, on which, for example, a cam surface 5 is arranged as a position-actual feedback F of the variable V, which picks up the piston position via a mechanical button 6, and thus indirectly reports the adjustment of the variable V. The actuating cylinder Z1, Z1 'is pressurized on one side from the control system S.

Alternatively, sensors 35 (transducers, angle sensors, pressure sensors, or the like) could be used for reporting, e.g. Alternatively, at least one double-acting differential adjusting cylinder could be used to adjust the pump, or an eccentric cradle (not shown).

Each actuating cylinder Z1, Z1 'is connected at its pressurization side to a control line 7. The second actuating cylinder Z2, Z2 'are connected at their Druckbeaufschlagungsseiten to one of the variable displacement pumped pressure line 8, from which an only schematically indicated consumer M, for example, via control valves, not shown, is fed. The second actuating cylinders Z2, Z2 'further comprise springs 34, that is, are spring-biased to the variable displacement pump V as by the pressurization from the pressure line 8, for. in the direction of maximum promotion. A pressurization of the actuating cylinder Z1, Z1 'then takes an adjustment in the direction of minimum funding.

On the housing 9 of the control system S, a pressure port 10 is indicated (X, LS) on which a signal pressure in a signal pressure line 21 can either be measured or fed, for example, from a load pressure signal circuit LS of the consumer M, comes ( Fig. 2 ). In the in Fig. 1 shown embodiment, for example, the pressure in the signal pressure line 21 from the control system S itself adjustable.

For pressure control, the control system S includes a single main stage 11, which is designed as a 3/2-way control valve and connected to the pressure line 8 and a return line 19 on the one hand and to the control line 7 on the other. The 3/2-way pressure control valve 12 is pressure-controlled from the pressure line 8 via a pilot line 16 and from the signal pressure line 21 via a pilot line 13, wherein on the side of the pilot line 13, a spring force 15 is effective, which is, suitably, adjustable ,

In the position shown (non-pressurized system) connects the 3/2-way pressure control valve 12, the control line 17 with the return line 19, while the pressure line 8 is shut off. The pressure line 8 leads via an inlet nozzle 14 to the signal pressure line 21. About the inlet nozzle 14, a pressure difference is generated during operation, which converts the main stage 11 with the influence of the spring force 15 for pressure control. About the pilot control line 16, the 3/2-way pressure control valve 12 is switched after startup of the variable V in the setting for maximum promotion from the switching position shown in another switching position in which the pressure line 8 is connected to the control line 7 and the return line 19 is shut off , so that the adjusting cylinders Z1, Z1 'are pressurized and adjust the variable displacement pump V in the direction of minimum promotion, against the force of the pressurization of the second actuating cylinder Z2, Z2 'from the pressure line 8 and the biasing springs 34. The pressurization surface of each first actuating cylinder Z1, Z1' is expediently larger than the pressurization surface of the second actuating cylinder Z2, Z2 '(area ratio eg between 2: 1 to 5: 1 or greater). When controlling the 3/2-way pressure control valve 12 moves continuously between the two aforementioned switch positions.

At a node 17 of the control line 7 between the first actuating cylinders Z1, Z 'and the main stage 11 branches off a leakage line 30, in which a nozzle 18 is included, to the return line 19 from. Furthermore, the feedbacks F of the adjusting cylinders Z1, Z1 'can be connected to a leakage line 20.

From the signal pressure line 21 branch lines 22 and 22 'from. The line 22 leads to a pressure control pilot valve 34 (with suitably adjustable spring force), from the drain side, a line 31 via a node 32 to a node 33 of the control line 7 leads. A line 23 branching off from the line 22 leads to an inlet side of a quantity control pilot valve 24. The line 22 'leads to the inlet side of a torque control pilot valve 25, which is pressure-controlled from the line 22' against a spring force 22 and 2/2 Way drain valve may be formed.

The flow control pilot valve 24 is a 2/2-way pressure control valve, which is actuated by a proportional solenoid 26 against spring force 28, and, preferably, even a proportional pressure pilot 27 may have. In the in Fig. 1 In the embodiment shown, the proportional solenoid 26 actuates the valve 24 in the direction of a passage position against the spring force 28 which adjusts a shut-off position. The energization of the proportional magnet 26 is a desired value specification for the quantity control. This set point specification could also be made hydraulically, mechanically, pneumatically or otherwise (not shown). The pilot valves 25, 24, 34 are each connected at the outlet side to the node 32 and thus via the line 31 to the node 33 in the control line 7 and the respective actuating cylinder Z1, Z1 'connected to feed according to the invention pressure medium there, so that this pressure medium from the signal pressure line 21 is not lost. The pilot valves 24, 25, 34 (or only 24 or 25 and 34) are associated with the main stage 11 and in the embodiment shown in FIG Fig. 1 the pressure difference generated by the inlet nozzle 14 for the main stage 11th

Upon response (opening) of the pilot valve 25, the pressure in the signal pressure line 21 is reduced, with increasing adjustment of the first actuating cylinder Z1, Z1 'via the feedback F increases the spring force 29 and thus the pressure in the signal pressure line 21 is increased again. The pilot valve 34 only works against the spring force.

The pilot valve 24 is, as long as the proportional solenoid 26 is not energized, in the shut-off position, and has no influence on the pressure in the signal pressure line 21. If the proportional solenoid 26 is energized, then the pilot valve 24 reduces the pressure in the signal pressure line 21, with increasing Adjustment of the actuating cylinder Z1, Z1 'eg in the direction of the minimum promotion of the variable V increases the spring force 28 and thus the pressure in the signal pressure line 21 is increased again with constant energization of the proportional magnet 26.

In the in Fig. 2 shown detail variant ends the pressure line 8 to the main stage 11 and the pressure in the signal pressure line 21, for example, from the load pressure signal circuit LS used to adjust the main stage 11 against the pressure in the pilot line 16 from the pressure line 8.

In the detail variant in Fig. 3 is the pilot valve 24 'connected inversely to flow control as in Fig. 1 that is, the spring force 28 holds the control valve 24 'in the passage position shown, while the proportional solenoid 26 causes an adjustment in the direction or to the shut-off when energized against the spring force 28.

In the detail variant in Fig. 4 is the pressure control pilot valve 34 downstream not at the node 32 as in Fig. 1 but connected via a line 31 'directly to the return line 19.

Claims (15)

Control system (S) of a hydraulic variable displacement pump (V), with at least one actuating cylinder (Z1, Z1 '), which can be pressurized from the control system in the direction of the pump for minimum delivery or maximum promotion, one to a pressure line (8) and a return line (19 ) connected to the main stage (11) for regulating a control cylinder (Z1, Z1 ') acting on the control pressure, wherein the main stage (11) is a pressure-controlled 3/2-way control valve (12), and at least one of the main stage (11) associated pilot valve (24, 25, 24 ', 34) for pressure and / or torque and / or quantity control, wherein the respective pilot valve on the inlet side to a leading to a pressure pilot control of the 3/2-way pressure control valve (12) signal pressure line (21 ) and the outlet side is connected to a low-pressure region, characterized in that at least the respective pilot valve (24, 25, 24 ') for flow and / or torque control on the outlet side of the actuating cylinder (Z1, Z1 ') connected. Control system according to claim 1, characterized in that the pilot valve (34) is connected to the pressure control on the outlet side of the actuating cylinder (Z1, Z1 '). A control system according to claim 1, characterized in that the pilot control valve (24, 24 ') of the flow control by a proportional solenoid (26) against spring force (28) either in the direction of a passage position or to a blocking position adjustable 2/2-way pressure control valve, preferably with proportional pressure precontrol (27). Control system according to claim 1, characterized in that the torque control pilot valve (25) and / or the pressure control pilot valve (34) from the signal pressure line (21) against spring force (29) in the direction of a passage position druckvorgesteuertes 2/2 Pressure relief valve is. Control system according to claim 3, characterized in that the torque control pilot valve (25) and / or the pressure control pilot valve (34) in the direction of a locking position acting on spring force (29) is adjustable. Control system according to claim 2 or 3, characterized in that the spring force (28, 29) of the flow control pilot valve (24, 24 ') and / or the torque control pilot valve (28) is generated by a spring, and that the set spring force in Operation of the control system (S) by a position feedback feedback (F), preferably from Adjusting cylinder (Z1, Z1 '), can be changed, via which actual value feedback (F), preferably, the respective delivery position of the pump to the pilot valve (24, 25, 24') is transferable. Control system according to claim 1, characterized in that the signal pressure line (21) via an inlet nozzle (14) to the main stage (11) extending pressure line (8) is connected. Control system according to Claim 1, characterized in that the signal pressure line (21) is connected to a load pressure signal circuit (LS) of at least one load (M) supplied by the pump and separated from the pressure line (8). Control system according to claim 1, characterized in that between the main stage (11) and the first actuating cylinder (Z1, Z1 ') extending actuating line (7) to the actuating cylinder (Z1, Z1') additionally via a nozzle (18) to the return line ( 19) is connected. Control system according to claim 1, characterized in that the 3/2-way control valve (12) of the main stage (11) in the direction of adjustment for connecting the pressure line (8) and the first actuating cylinder (Z1, Z1 ') from the pressure line (8). durckvorgesteuert and in the direction of adjustment for connection of the first actuating cylinder (Z1, Z1 ') with the return line (19) from the signal pressure line (21) pressure-controlled and spring-loaded (15). Control system according to claim 10, characterized in that the force of the spring load (15) is adjustable. Control system according to claim 1, characterized in that the actuating cylinder (Z1, Z1 ') in the direction of the pump for minimal promotion can be acted upon, and that at least a second actuating cylinder (Z2, Z2') is provided, in the direction of the pump for maximum delivery from the Pressure line (8) is acted upon and has a spring bias (34). Control system according to at least one of the preceding claims, characterized in that the variable displacement pump (V) is an axial piston pump (2) in a swashplate design, and in that actuating cylinders (Z1, Z1 ', Z2, Z2') act on a swashplate adjusting element (3), wherein, preferably, in each case two first, parallel-connected, and two second, parallel-connected actuating cylinder are provided. Control system according to claim 13, characterized in that the actuating cylinder (Z1, Z1 ') has a larger pressurization surface than the second actuating cylinder (Z2, Z2'), preferably with an area ratio between about 2: 1 to 5: 1. Control system according to at least one of the preceding claims, characterized in that the outlet side of the adjusting cylinder (Z1, Z1 ') connected pressure regulating and / or torque control pilot valve (25, 34) is a slide valve.

Images