EP0879374B1 - Directional valve - Google Patents

Description

The invention relates to a directional valve according to the preamble of claim 1 and with such a directional valve provided pressure reducing and flow control valves.

In Fig. 1 is an embodiment of such a directional control valve executed as a 2-way cartridge valve 2 is. This has a valve bushing 4 in which a main piston 6 is guided axially. The valve bushing 4 can be known Way fixed in a control block and thus Be part of a hydraulic circuit, to which further is discussed in more detail.

The valve socket 4 has two connections A and B, the Port B is usually the input port and is radial or laterally branching connection. Of the Output port A is arranged coaxially with the main piston 6. On the circumferential wall of the main piston 6 are radial bores 8 provided, through which the flow through the main piston 6 of the Port B can be connected to port A. With the shown Exemplary embodiment are the connection B and the radial bores 8 each designed as a bore star. In the shown in Fig. 1 The starting position is the main piston 6 via a spring 10 biased against a stop position in which the connection opened from B via the main piston 6 to the outlet port A. is. That is, in the starting position of the main piston 6 the hydraulic fluid flows through the connection in the radial direction B enters through the radial bores 8 into the interior of the Main piston 6 and is deflected by about 90 ° to port A.

By suitable design of the control block and Valve cover (not shown) can be a control pressure to the Lead the spring side of the main piston 6, over which this additionally is biased towards its starting position. This Control pressure can be, for example, from the output port A branching control pressure line can be applied.

Such valve arrangements in 2/2-way valve design include to the group of so-called logic elements, which as the main stage, for example for pressure limitation, pressure control, Pressure switching valves etc. are used. The Main stage pilot valves are assigned, for example on the valve cover, integrated in the valve cover or on can be arranged at another location of a control block.

In Fig. 3, a circuit example is shown in which the built-in valve 2 is a component of a pilot-controlled pressure reducing valve 12. This essentially exists from built-in valve 2 and a directly controlled pilot valve 14, which is designed as a pressure relief valve. The flow direction on installation valve 2 is from port B to port A, being as shown in Fig. 1 in the starting position a free volume flow is guaranteed.

The pressure at the output port A is via a control line 16 tapped and via two consecutive nozzles 18 and 20 led to the spring side of the main piston 8. Of the Desired outlet pressure at outlet connection A can be made via adjust the spring of the pilot valve 14. This output pressure acts on the piston underside of the main piston 6 and is about the control line 16 and the nozzles 18 and 20 to the spring side of the Main piston 6 out. As long as the pressure at the outlet port A is lower than the inlet pressure set on the pilot valve 14, the main piston 6 remains in its spring 10 Starting position in which the connection between A and B is complete is controlled. If the pressure at outlet port A - and thus the one between the two nozzles 18 and 20 - the exceeds the preset value, the pilot valve 14 is opened, so that control fluid via the pilot valve 14 to one Tank T flows.

The resulting control liquid flow creates the nozzle 18 a pressure drop so that due to the control fluid pressure difference between the piston underside and the spring side, the main piston 6 against the tension of the spring 10 its starting position out upwards (view according to FIG. 1) is moved and the connection from B to A is controlled until a pressure equilibrium is established. In this condition can then only as much hydraulic fluid from port B. the main piston 6 flow through to port A that the over the pilot valve 14 at A set pressure does not exceed becomes. If a consumer connected to output connection A no hydraulic fluid decreases, the main piston 6 in brought its closed position in which the connection between B and A is closed so far that only the required one Control oil volume flow reaches port A. During the control function control fluid constantly flows through the pilot valve 14 Tank T. In the embodiment shown in Fig. 3 are the two nozzles 18 and 20 and the pilot valve 14 in or formed on the valve cover 22.

When the built-in valve 2 flows through, a flow pulse acts on the bottom 24 of the main piston 6, so that this is acted upon by an impulse force F _I which acts counter to the spring force F ₁ applied by the spring 10 (see FIG. 1). At high volume flows, it can happen that the impulse force F _{1 is} greater than the spring force F ₁ , so that the main piston is moved into its closed position solely by the impulse of the flowing hydraulic fluid. In this case, the performance limit of the built-in valve 2 is reached, which limits the maximum flow rate that can be implemented. This means that if the performance limit is exceeded, the volume flow cannot be increased any further.

In Fig. 2, the outlet pressure at the outlet port A is over the throughput, the vertical, dotted lines show the performance limits represent that when using different springs 10 set. In the embodiment shown in FIG. 2 the power limit is approximately 4 bar when using a spring at 120 L / min, so that at higher volume throughputs stronger spring must be used.

However, a stronger spring 10 contains a number of Disadvantages, such as a lack of response and a lack of fine control in itself, especially at low Volume flows come into play and are not acceptable are. The minimum adjustable pressure at port A increases disadvantageous through the use of stronger springs.

In contrast, the invention is based on the object Directional valve, as well as provided with such a directional valve Pressure reducing / flow control valves to create the minimum device effort an increased performance limit have and sufficient even at low volume flows Show responsiveness.

This task is performed by the directional valve Features of claim 1, with respect to the pressure reducing valve by the features of claim 8 and in terms the flow control valve by the features of the claim 10 solved.

The measure of forming a surface difference upstream of a throttle point of the main piston, via which a force component acts on the main piston during the flow and acts on it in the direction of its starting position, the impulse force F _I acting on the main piston can be at least partially compensated, so that the Performance limit compared to the conventional solutions is raised without the need to use a stronger spring. This additional, resulting force acting in the opening direction on the surface difference effective surface arises due to the pressure drop occurring in the flowing hydraulic fluid when flowing through the radial bores. It is particularly preferred if the active surface is designed as a radial shoulder on the outer circumference of the main piston, so that it is widened in a step-like manner. In this embodiment of the active surface, the bore of the valve bushing is of course also designed accordingly.

If the main piston is designed with a radial bore star the radial shoulder is preferably in the area arranged between the radial bore star and the piston underside.

Extensive preliminary tests have shown that a Area difference of 3-10% based on the smaller main piston diameter ensures optimal results.

For manufacturing reasons, it is preferred if the radial shoulder (area difference) by means of an annular groove is formed, the radial shoulder an end face of the Ring groove forms. The other end face is then preferred trained as a sloping shoulder.

The manufacture, especially the grinding of the valve bore will be easier if the corresponding step-shaped Extension of the valve bushing formed over a circumferential groove whose one end face is the stepped extension forms.

Particularly advantageous applications of the invention Directional control valves result from a pilot operated pressure reducing valve according to claim 8 or a flow control valve according to claim 10.

Further advantageous embodiments of the invention are the subject of other subclaims.

Fig. 1 einen Schnitt durch ein aus dem Stand der Technik bekanntes Einbauventil;

Fig. 2 ein Diagramm aus dem die Leistungsgrenze des Einbauventils aus Fig. 1 in Abhängigkeit von einer verwendeten Ventilfeder dargestellt ist;

Fig. 3 eine Schaltung, bei der das Einbauventil aus Fig. 1 die Hauptstufe eines Druckreduzierventils ist;

Fig. 4 ein erfindungsgemäßes Einbauventil, wie es in einer Schaltung gemäß Fig. 3 verwendbar ist und

Fig. 5 ein weiteres Ausführungsbeispiel, bei dem das Einbauventil gemäß Fig. 4 bei einem Stromregelventil verwendet wird.

Preferred exemplary embodiments of the invention are explained in more detail below with the aid of schematic drawings. Show it:

1 shows a section through a cartridge valve known from the prior art.

FIG. 2 shows a diagram from which the performance limit of the cartridge valve from FIG. 1 is shown as a function of a valve spring used;

3 shows a circuit in which the cartridge valve from FIG. 1 is the main stage of a pressure reducing valve;

Fig. 4 shows a cartridge valve according to the invention, as can be used in a circuit according to FIG. 3 and

Fig. 5 shows another embodiment in which the cartridge valve of FIG. 4 is used in a flow control valve.

4 is a partial section of a cartridge valve according to the invention 2, wherein in the following representations the same reference numerals for corresponding components as used in Fig. 1.

The cartridge valve 2 according to the invention can, for example in the case of a pilot-controlled pressure reducing valve according to FIG. 3 or use a flow control valve according to FIG. 5, to which in following is discussed.

4, the cartridge valve 2 according to the invention has a Valve bushing 4, in the valve bore 28 of which a main piston 6 is guided axially. This is via a spring 10 biased into its initial position, in the one on the outer circumference of the main piston 6 attached stop ring 30 on a Stop surface of the valve bush 4 is present. The valve bush 4 is by means of a mounting bush 32 in a control block 26 attached and closed with a valve cover, not shown, in or on which the other indicated in FIGS. 3 and 5 Components can be arranged. The mounting bush 32 has an inner bore that is coaxial to the valve bore 28 is arranged, and which has such a diameter, that the spring-side part (top in Fig. 4) of the main piston 6 can dip into it without colliding.

The valve bushing 4 could be installed according to FIG. 1 be trained.

An input connection B is on the valve bushing 4 as a bore star, that is, as a plurality of radial bores 36 educated. In addition, several are staggered, preferably two smaller holes 38 are provided.

Fine control takes place via the smaller bores 38 at low volume flows, if the connection from B to A is controlled.

4, the main piston 6 designed as a hollow piston, with a piston crown approximately in the central region 40 is formed. This piston crown 40 engages the spring 10 to the main piston 6 in its open position (Fig. 4) to bias.

Below the piston crown 40, that is, in that of the spring 10 part of the piston jacket facing away are radial bores 8 formed, via which the hydraulic fluid from port B (Bores 36, 38) can enter the interior of the piston. This Radial bores 8 are shown in the same way as in Fig. 1 formed as a bore star, which the jacket of the Main piston 6 passes through.

In the starting position of the main piston shown in FIG. 4 6 overlap the bores 36, 38 of the connection B and the radial bores 8, so that the connection between the Ports B and A is fully open.

Below the radial bores 8 (view of FIG. 4) the main piston 6 via a radial shoulder 42 from a spring side Main piston diameter d to a main piston diameter D expanded. The radial shoulder 42 is by means of an annular groove 44 formed in the base of the radial bores 8th open and their other end face executed as an inclined shoulder 46 is.

The valve bore 28 of the valve bush 4 is above (View according to Fig. 4) of the connection B according to the diameter ratio d / D expanded radially, being in the range of radial expansion a circumferential groove 48 is formed over the lower, enlarged part of the valve bore (diameter D) from the upper, narrowed part of the valve bore 28 (diameter d) is separated.

The circumferential groove 48 and the annular groove 44 are made of manufacturing technology Reasons provided, since the adjacent to the two grooves Surfaces (peripheral surface of the main piston 6; inner peripheral surface the valve bore 28) finely machined by grinding be avoided by the grooves that the Grinding wheel when grinding the smaller piston diameter or the larger valve bore diameter up to the radial shoulders must be brought there.

In the starting position shown in Fig. 4 is the Oblique shoulder 46 of the annular groove 44 at an axial distance from the neighboring one End face of the circumferential groove 48 arranged so that the two grooves 44, 48 do not mutually in the starting position overlap.

In the area between the two grooves 44, 48 is a Annular gap 50 is formed between main piston 6 and valve bushing 4.

When hydraulic fluid flows through the built-in valve 2 there is a pressure drop along the radial bores 8, which leads to the difference area that is marked is due to the diameter difference D-d, on the radial shoulder 42 a resulting compressive force acts on the main piston 6 acted towards the starting position. That is, this Compressive force acts in addition to the force of the spring 10 in the opening direction, so that the power limit is increased.

The magnitude of the force F depends on the diameter ratio on the one hand d / D and on the other hand from the pressure drop in the radial bores 8 from. Because of this, one will endeavor the depth the annular groove 44 to be as small as possible, since the pressure drop also depends on the remaining wall thickness of the main piston 6. The same applies to the depth of the circumferential groove 48 and the annular gap 50, which is also made as small as possible should be so that the hydraulic fluid when flowing through the Installation valve 2 not to a significant extent through the annular gap 50 can flow into the circumferential groove 48, so that ensures is that a suitable pressure on the outer circumference of the Main piston 6 is present and thus the pressure drop along the Radial bores also have the required size arrangement having.

3 is the built-in valve in a control block 2 provided with a valve cover 22 in which the above described components, such as the nozzles 18, 20 and the pilot valve 14 can be provided.

In the starting position shown (Fig. 4) the cartridge valve 2 flows through, the action of the spring 10 by the force acting on the area difference is amplified, the due to the pressure drop in the radial bores 8. The Performance limit is then applied according to the additional one Pushing force shifted upwards, making a larger one Volume flow is enforceable. When the preset is reached Pressure on the spring side of the main piston 6 opens the pilot valve 14 so that the control fluid flows to the tank T and a pressure drop arises at the throttle 18, which leads to a Closing movement of the main piston (up in Fig. 4) leads. The bores 36 and 38 are closed by this closing movement, so that the connection from B to A is throttled accordingly and there is a pressure at the outlet port A, which corresponds to the pilot valve setting.

As already mentioned at the beginning, there is the cartridge valve 2 in its closed position when the one connected to port A. Consumer no hydraulic fluid decreases. At a Hydraulic fluid consumption then drops the pressure at the outlet connection A off, so that the pilot valve 14 connects to the tank T controls and the main piston 6 due to the on the spring side building control pressure back towards his Starting position is moved. First, the smaller ones Drilled holes 38, which thus at low volume flows take effect and fine control of the consumer enable with good response.

With larger volume flows, the bores 36 opened with a larger diameter until the main piston 6 in its starting position (Fig. 4) is moved back and the maximum enforceable volume flow is achieved by the above described performance limit is limited.

5 schematically shows another application example of a cartridge valve shown in FIG. 4. It will Insert valve 2 used in a 2-way flow control, whereby a pressure compensator is assigned to a throttle point for load compensation which is formed by the cartridge valve 2. The Throttle point is designed as an adjustable throttle valve 52, which is provided downstream of the built-in valve 2.

A control line branches downstream of the throttle valve 52 54 from a throttle 18 to the spring side of the main piston is led. The one at the outlet port A of the cartridge valve 2 applied pressure is - as in the embodiment described above - on the underside of the piston (Output connection side). Thus, in this embodiment the built-in valve 2 as a pressure compensator with a pressure reducing function used. In this variant, the cartridge valve is 2 open in the starting position so that the hydraulic fluid from Port B via cartridge valve 2 to A and on from there via the throttle valve 52 to the consumer, for example a Hydraulic cylinder or a hydraulic motor (not shown) flows. The pressure at the outlet of the throttle valve 52 is due to axial displacement of the main piston 6 and the associated Changes in the volume flow cross-section influenced so that the Pressure drop across the throttle valve 52 always remains constant. This pressure drop depends on the strength of the spring Piston.

If the load changes, the pressure at the outlet of the Throttle valve 52, the pressure in decreases accordingly the control line 54, which acts as a damping element Nozzle 18 is guided to the spring side of the main piston 6. By reducing the pressure on the spring side of the main piston this will counter the bias of the spring towards it Closed position moves so that the volume flow cross section is called the effective cross section of the radial bores 36 becomes. This also reduces the volume flow of the hydraulic fluid, that led via the built-in valve 2 to the throttle valve 52 becomes. The main piston 6 moves for as long as until the pressure at the output port A and thus also at the input of the throttle valve 52 has decreased by the same amount like the pressure at the outlet of the throttle valve 52 (control line 54). The pressure drop across the throttle valve 52 is thus always kept at a constant value.

In this embodiment, too, the maximum is the built-in valve 2 enforceable volume flow by pushing it up the performance limit compared to conventional solutions significantly enlarged.

The solution according to the invention therefore enables minimal device-related effort, pushing the performance limit up, so that the cartridge valve according to the invention without Change of spring 10 can be used in a further volume flow range is.

Claims (10)

1. A 2-directional control valve including a main piston (6) guided in a valve bush (4) and allowing flow of a hydraulic fluid therethrough, which enables connection of an inlet port (B) with an outlet port (A) and which is biased into its home position by means of a spring (10), characterised in that the main piston (6), upstream of a throttle point (8), is provided with a differential area effective surface (42, D-d) whereby, upon flow therethrough, a pressure force component acts on the main piston (6) such as to urge it in the direction towards its home position.
2. A 2-directional control valve in accordance with claim 1, characterised in that the effective surface is designed as a radial shoulder (42) at the outer periphery of the main piston (6), and that the valve bush (4) is steppingly expanded accordingly.
3. A 2-directional control valve according to claim 2, characterised in that the main piston (6) comprises radial bores (8) as throttle point wherethrough the hydraulic fluid may flow from inlet port (B) to outlet port (A), with the radial shoulder (42) being formed in the region between the radial bores (8) and the piston bottom facing the outlet port (A).
4. A 2-directional control valve according to claim 2 or 3, characterised in that the diameter of the main piston is enlarged by 3-10% by the radial shoulder (42).
5. A 2-directional control valve according to any one of claims 3 or 4, characterised in that the radial shoulder (42) is formed by an annular groove (44) into which the radial bores (8) of the main piston (6) open.
6. A 2-directional control valve according to claim 5, characterised in that the front surface removed from the radial shoulder (42) is designed as an inclined shoulder (46).
7. A 2-directional control valve according to any one of claims 2 to 6, characterised in that the valve bush (4) comprises a peripheral groove (48) in the region of the steppingly expanded portion.
8. A pilot controlled pressure reducing valve including a 2-directional control valve in accordance with any one of the preceding claims, wherein the pressure at the outlet port (A) is supplied to the spring side of the main piston (6) via a nozzle (18), and the pressure at the spring side may be limited by way of a pilot control valve (14).
9. A pilot controlled pressure reducing valve according to claim 8, characterised in that the pilot control valve is a direct operated or pilot operated pressure reducing valve (14).
10. A flow control valve including an adjustable throttle valve (52), upstream of which a 2-directional control valve (2) according to any one of claims 1 to 7 is arranged as a pressure compensator, wherein the pressure downstream of the throttle valve (52) is supplied to the spring side of the main piston (6) of the 2-directional control valve (2).

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