EP1872018B1 - Pilot valve for a hydraulic motor - Google Patents

Abstract

A pilot valve (3) is designed as a directional control valve in which a control slide (20) is movably disposed in a longitudinal bore (22) of the valve body (21) so as to control the flow of hydraulic oil between two working connecting bores (A, B), a pump connecting bore (P), and a reservoir connecting bore (T). A check valve (32) which is biased with the aid of a bias spring (33) is disposed within the control slide (20). The check valve (32) is connected to an auxiliary control groove (28) via a first transversal bore (29) while being connected to the B-reservoir groove (23) via a second transversal bore (31). The check valve (32) is to be opened from working connecting bore B while the auxiliary control groove (28) is arranged between the B control groove (24) and the B reservoir groove (23) and is delimited on both sides by means of sealing cylindrical areas (35, 36).

Description

The invention relates to a control valve for a hydraulic motor according to the preamble of claim 1.

Hydromotors are used, for example, in cranes for driving hydraulic winches. With such a winch, loads can be lifted and lowered.

Out DE-A1-39 41 802 is a hydraulic directional control valve is known, which allows a load pressure independent control of a hydraulic motor. Out DE-C2-41 36 991 For example, a directional control valve is known that can be used for the same purpose.

From the operation of hydraulic motors, which are usually designed as axial piston machines, more rarely than radial piston machines, results from the design that the flow is not uniform, but fluctuates cyclically, so pulsates, as for example in "H. Ebertshäuser: Fluid Power from A to Z", United specialist publisher Krausskopf / Ingenieur-Digest, 1st edition 1989, on pages 31 and 353-354 is mentioned. This inevitably results in torque fluctuations, which make themselves uncomfortable especially at low speeds. If an initially resting load is lifted, then the movement takes place from standstill more or less jerky. The same effect occurs when the load has almost reached its position, so that the final position is almost reached. Pulsations of the movement are also very disturbing here. Such a control valve is also in US 2004/0226292 disclosed. The invention has for its object to provide a control valve which prevents the previously described torque fluctuations and pulsations without the need for an additional valve assembly, which was previously used to reduce the pulsation or torque fluctuation.

The above object is achieved by the features of claim 1. Advantageous developments emerge from the dependent claims.

An embodiment of the invention will be explained in more detail with reference to the drawing.

• Fig. 1 ein Schema einer Ansteuerung für einen Hydromotor,
• Fig. 2 eine Ventilbaugruppe als Zusatzaggregat für die Funkion "Heben" gemäß einer Lösung nach dem Stand der Technik,
• Fig. 3. eine Ansicht eines Steuerschiebers innerhalb eines Ventilkörpers, und
• Fig. 4 bis 7 Ausschnitte der Stellung des Steuerschiebers relativ zu einer Steuerkante.

Show it:

• Fig. 1 a diagram of a control for a hydraulic motor,
• Fig. 2 a valve assembly as an accessory for the function "lifting" according to a solution according to the prior art,
• Fig. 3 , a view of a spool within a valve body, and
• Fig. 4 to 7 Cutouts of the position of the spool relative to a control edge.

In the Fig. 1 a hydraulic motor 1 is shown, which drives a not shown in detail winch for lifting and lowering a load 2. Arrows on the hydraulic motor 1 is shown that the one direction of rotation of the hydraulic motor 1 causes the lowering of the load 2, the opposite direction of rotation of the hydraulic motor 1, the lifting of the load. The hydraulic motor 1 is controllable by a control valve 3 designed as a directional control valve with the usual load connections A and B and with a pump connection P and a tank connection T. This corresponds to the known prior art. This also applies to an inserted into the supply line to the hydraulic motor 1 load-holding valve 4, which serves to control the load during lowering.

In the "lifting" operation, the hydraulic oil flows from the pump port P of the control valve 3 and the A-line through the self-opening check valve of the load-holding valve 4 to the hydraulic motor 1 and drives it. At the same time, an identical amount of hydraulic oil from the hydraulic motor 1 flows through the B-line through the control valve 3 to the tank port T. The proportional flow amount control is performed by the proportional control of the control valve 3. This is shown in the hydraulic circuit diagram of the control valve 3.

In "sink" mode, the flow direction is reversed. The movement control is effected by the proportionally controllable load-holding valve 4.

As a hydraulic motor 1 comes in such applications preferably a Hubverdrängermaschine used, for example, an axial piston machine, as shown in "Dubbel: Taschenbuch for mechanical engineering", Springer-Verlag, 19th edition, on page H5. However, this widespread type of machine has the disadvantage that the flow is not uniform, because this has a considerable degree of non-uniformity δ. It may even follow that at the beginning of the Lifting the load 2, so at very low speed of the hydraulic motor 1, the load 2 drops briefly. This also applies when reducing the speed to stop the load 2. A rational work is hardly possible and there are dangerous moments.

To remedy this serious problem at least partially, it has been attempted to reduce the non-uniform rotational movement at slow speed by the inclusion of a valve assembly 10, for example, in the corresponding return line from the hydraulic motor 1, as shown in the Fig. 2 is shown. Here, in the course of the B-line valve assembly 10 is arranged, which consists of two mutually parallel check valves, namely a biased check valve 11 and a non-biased check valve 12. The applicant itself has created in 2001 such a valve assembly. Thus, a partial compensation of the pressure fluctuations in the lifting operation is possible. The hydraulic oil flowing from the hydraulic motor 1 to the control valve 3 must pass through the valve assembly 10. Because the non-biased check valve 12 is flowed in the reverse direction, this locks, so that the hydraulic oil can flow only through the biased check valve 11, if its pressure is higher so the force of the biasing spring. This creates the significant effect that the hydraulic motor 1 is hydraulically biased, with the result that the uneven startup at low speed is greatly improved in a very simple manner. The degree of non-uniformity δ of the rotary motion is improved.

A solution with such an additional valve assembly 10 is complicated to manufacture and expensive and requires space. But the invention is also particularly the object of improving such a solution in terms of functionality.

In the Fig. 3 is a view of a spool 20 within a valve body 21 shown, which are the control valve 3 associated. In a longitudinal bore 22 of the valve body 21, the spool 20 is axially displaceable, which is indicated by a double arrow. The axial displaceability is effected, as usual in such proportionally operating control valves, by means of at least one drive, wherein electrical, hydraulic or pneumatic drives find uses. Since in the present case, the number and type of drive for the spool 20 does not matter, such a drive has not been shown in the figure.

As is usual with such control valves, transverse bores are present in the valve body 21, which lead up to the longitudinal bore 22. In the Fig. 3 five such transverse bores are shown, namely, seen from the right, a tank connection bore T, a first working connection bore A, a pump connection bore P, a second working connection bore B and a further tank connection bore T. For constructional reasons, two tank connection bores T are shown, which are generally inside the valve body 21 are merged. The background is that each of the working connection bores A, B must be operationally connectable to the tank connection bore T or to the pump connection bore P in order to enable "lifting" and "sinking" operation.

The spool 20 has, in order to produce the various connections between the terminal bores T, B, P, A and T, profiled annular grooves. Seen from the left, these are a B-tank groove 23, a B-control groove 24, a pump groove 25, an A-control groove 26 and an A-tank groove 27. The principle is common to most directional control valves.

The relative position of the spool 20 in the longitudinal bore 22 is shown in the Fig. 3 such that the pump connection bore P is completed, that is, there is no connection to one of the adjacent working connection bores A, B. It follows that the hydraulic motor 1 stands still because no hydraulic oil is supplied to it. Shown is the zero or neutral position.

According to the invention, however, the control valve 3 shown here for a hydraulic motor 1 ( Fig. 1 ), an additional narrow auxiliary control groove 28 which is disposed between the B-tank groove 23 and the B-control groove 24. At the bottom of this Hilfssteuernut 28 begins a first transverse bore 29 which opens into a longitudinal bore 30, the other end is in communication with a second transverse bore 31. This second transverse bore 31 establishes a connection to the B-tank groove 23 and thus to the tank connection bore T. The most significant feature of the invention is now that in this longitudinal bore 30 a biased check valve 32 is arranged with a biasing spring 33, in such a way that it is to be opened by a higher pressure from the working port bore B ago. The mode of action will be described in more detail later.

Advantageously, the control edge for controlling the volume flow between the working port bore B and the second tank port bore T is particularly configured. On both sides of the auxiliary control groove 28, the spool 20 has short cylindrical sections, namely to the right of a sealing cylinder 35 and to the left of a biasing cylinder 36. To the left, join two frustoconical sections, namely a first control taper portion 37 with a weaker surface inclination and then a second control cone section 38 with a stronger surface inclination.

In the Fig. 4 to 7 In each case, an identical section of the control valve 3 is shown in the Fig. 3 is shown with a dotted circle. The aim is to show how the object of the invention is achieved with the inventive and advantageous agents.

In the Fig. 4 It is shown that one of the working port bore B associated control edge 40 is located in the region of the sealing cylinder 35. Thus exists between the working port bore B and the further left tank connection bore T ( Fig. 3 ) no connection. Because thus also the auxiliary control groove 28 is covered with the transverse bore 29 beginning therein from the control edge 40, the pressure prevailing in the working port bore B does not act in the transverse bore 29 into it. This condition is given when, as in Fig. 3 shown, the connection of the pump port hole P is shut off both the working port hole A and only working port bore B, so that the hydraulic motor 1 (FIG. Fig. 1 ) stands still. Again, the zero or neutral position is shown.

In the Fig. 5 is that state shown in which the spool 20 is moved so far to the right against the control edge 40, that now in the working port bore B prevailing pressure can act because of the exposed auxiliary control groove 28 in the transverse bore 29. In this state, the hydraulic motor 1 ( Fig. 1 ) in function, because at the same time, which from the Fig. 3 can be derived, because of the right shift of the spool 20 hydraulic oil from the pump connection bore P to the first working port bore A and from there to the hydraulic motor 1 flows. However, the hydraulic oil flowing back from the hydraulic motor 1 to the tank at the same time can not now travel directly from the working port bore B to the tank connection bore T located further to the left, because this path is blocked by the sealing action of the pretensioning cylinder 36. The returning hydraulic oil consequently pushes the preloaded check valve 32 located in the longitudinal bore 30. As a result, according to the pressure in the working port bore B increases to a value by the force of the biasing spring 33 of the check valve 32 (FIG. Fig. 3 ) is determined.

By this pressure increase in the working port bore B, the hydraulic motor 1 is hydraulically biased, with the result that the uneven startup at low speed is greatly improved in a very simple manner. Accordingly, the degree of non-uniformity δ can not practically work as a non-uniform rotational movement during slow starting. Incidentally, this also applies to the slow speed after a delay from faster running.

In the Fig. 6 the state is shown with still further control of the control valve 3 in the "lifting" mode. Here now lies the control edge 40 through the opposite Fig. 5 further movement of the spool 20 to the right so that the first control taper portion 37 with the weaker surface inclination lies to the right of the control edge 40. Thus, hydraulic oil can now flow between the control edge 40 and the first control cone portion 37. In this state flows from the hydraulic motor 1 ( Fig. 1 ) to the tank back flowing hydraulic oil both through the check valve 32 ( Fig. 3 ) as well as over the ring cross section between control edge 40 and control taper portion 37 therethrough. The further the control piston 20 is moved to the right, the greater the flow of hydraulic oil between the control edge 40 and control cone portion 37th That the check valve 32 does not close immediately when the control edge 40 comes into the region of the first control taper portion 37, is because that due to the flow between the control edge 40 and the control cone section 37, an equally high dynamic pressure is created as over the prestressed check valve 32.

If the spool 20 against the Fig. 6 even further moved to the right, namely in one in the Fig. 7 shown position in which the control edge 40 is now in the range of the second control cone portion 38 with the stronger surface slope, the resulting from the flow dynamic pressure is smaller because of the now larger free passage cross-section for the hydraulic oil, which means that now the check valve 32 (FIG. Fig. 3 ) closes. Hydraulic oil then flows only through the free space between the control edge 40 and the two control cone sections 37, 38. The hydraulic oil flow and thus the speed of the hydraulic motor 1 are now so large that the aforementioned effect of the large degree of unevenness δ no longer occurs. In this now larger free passage cross section, the flow resistance Δp is now reduced. This leads to less heating of the hydraulic oil, which is a particular advantage.

Advantageously, the biasing spring 33 is dimensioned so that the resulting return bias is about 25 bar.

Advantageously, the surface inclination of the first control cone section 37 is dimensioned approximately such that the angle to the imaginary cylindrical surface of the control spool 20 is approximately 16 °. The surface inclination of the second control cone portion 38 is advantageously about 26 °. The dimensions otherwise depend on the size of the control valve 3, ie of its maximum flow. But then it does not require any inventive step to optimize this measure.

The invention is always applicable when loads are to be lifted in devices with a hydraulic motor.

Claims (6)

1. Control valve (3) for a hydraulic motor (1), by means of which loads (2) can be raised in a device, where the control valve (3) is designed as a directional control valve, in which a control slide (20) is installed in a longitudinal bore (22) of a valve body (21) with freedom to slide back and forth to control the flow of hydraulic oil between two working connection bores (A, B), a pump connection bore (P), and a tank connection bore (T), where the control slide (20) has a B-to-tank groove (23), a B control groove (24), a pump groove (25), an A control groove (26), and possibly an A-to-tank groove (27), where a check valve (32) spring-loaded by a pretensioning spring (33) is located inside the control slide (20),
   characterized in that;
   the check valve (32) being connected at one end to an auxiliary control groove (28) by way of a first transverse bore (29) and at the other end to the B-to-tank groove (23) by way of a second transverse bore (31),
   the check valve (32) can be opened from the side of the working connection bore B; and the auxiliary control groove (28) is located between the B control groove (24) and the B-to-tank groove (23) and is limited on both sides by cylindrical sealing surfaces (35, 36).
2. Control valve (3) according to Claim 1, characterized in that the pretensioning spring (33) is dimensioned in such a way that it generates a return-flow pretension of approximately 25 bars.
3. Control valve (3) according to Claim 2, characterized in that, in the direction toward the B-to-tank groove (23), a first truncated cone-shaped control cone section (37) adjoins the pretensioning cylinder (36) which forms one of the cylindrical surfaces.
4. Control valve (3) according to Claim 3, characterized in that the taper of the first control cone section (37) is designed so that the angle to the imaginary surface of the cylinder of the control slide (20) is approximately 16°.
5. Control valve (3) according to Claim 4, characterized in that a second truncated cone-shaped control cone section (38) adjoins the first truncated cone-shaped control cone section (37).
6. Control valve (3) according to Claim 5, characterized in that the taper of the second control cone section (38) is designed so that the angle to the imaginary surface of the cylinder (20) is approximately 26°.

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