EP0676547A1 - Flow control device for a high pressure hydraulic system and a valve for a load-lowering brake - Google Patents

Abstract

The quantity regulator for high pressure hydraulics has pressure medium flowing to and from a hydraulic actuator limited independently of pressure and/or load alterations. A measurement diaphragm (9) is incorporated which for each flow direction has a pressure balance measurement diaphragm (25-29) adjusting the pressure difference indicated by the measurement diaphragm. At least one conduit branches off the hydraulic circuit. The measurement diaphragm with the two pressure balance regulating diaphragms are arranged in a two-direction sink brake valve with exclusive two-way flow regulating function in a section of a work pressure conduit. <IMAGE>

Description

The invention relates to a flow control device according to the preamble of claim 1 and a lowering brake valve of the type specified in the preamble of claim 7.

In the magazine "HYDRAULICS AND PNEUMATICS", June 1964, pp. 72 to 75, two-way flow controllers are explained, which contain a metering orifice and a regulating pressure compensator orifice and keep the pressure medium quantity constant regardless of pressure changes from a predetermined response pressure. 1, 2, 4 and 8, a two-way flow regulator is arranged in the working pressure line. 3, 5, 6, 7, the two-way flow regulator is arranged in a bypass line to the tank. Two-way flow regulators arranged in the working pressure line are often used as so-called lowering brake valves in order to limit the maximum movement speed of a hydraulic consumer, either in one or the other flow direction, the flow regulator being part of a quantity control device for the high pressure hydraulics.

A quantity control device known from DE-A-39 38 560 limits the speed of a hydraulic consumer which can only be acted upon from one side in two directions of movement in different ways. The flow control device namely forms a two-way flow controller for lowering movements and a three-way flow controller for lifting movements. A common orifice plate, through which the same flow direction flows when lifting and lowering, is assigned to two parallel pressure compensator orifice plates.

This quantity control device has a complicated structure and is only useful for a single hydraulic consumer supplied by the pump, the pressure medium flowing out of which plays no role in the control thereof when lifting to the tank. In the case of several consumers supplied by a common pressure source, this is unsuitable because the pressure medium flowing to the tank impairs the supply to other consumers. In a lifting device such as a forklift, in particular an electrically powered forklift, this quantity control device would be unsuitable because electrical energy is wasted due to the pressure medium pumped to the tank when lifting, or pressure medium is missing when supplying other parallel consumers.

In the case of lifting devices, in particular forklift trucks, several hydraulic consumers are usually provided, at least one of which is of secondary importance in the sense that it does not have to carry out any lifting and lowering movements, but rather serves to control the movement of a device component which is essentially always moved with the same load. For example, this would be a double-acting hydraulic cylinder for pivoting the lifting device back and forth, which is directionally controlled via a directional control valve. The maximum speed of the swivel movement is limited in each direction. In more modern lifting devices of this type, a speed-controlled pump in the hydraulic circuit is also common, the delivery rate of which is proportional to the pump speed, and which can be regulated in such a way that it delivers an increasing delivery rate practically from standstill with increasing speed. With the speed-controlled pump, the subordinate hydraulic consumer can be moved up to its limit speed in the respective direction of movement selected by the directional control valve start up. The limit speed is maintained by a lowering brake in each direction. Two lowering brake valves are provided for the two directions of movement, each of which limits the amount of pressure medium flowing out in its working pressure line, while it opens unthrottled in the inflow direction. The construction effort of two lowering brakes in the working pressure lines is high because a measuring orifice and a pressure compensator orifice and a bypass for the unthrottled flow are required for each flow direction.

In a hydraulic control device known from DE-A-34 22 978 of a hydraulic consumer which can be acted upon from two sides, the working line connected to the piston-side working chamber of the hydraulic consumer contains a single control orifice which interacts with one orifice plate each of two orifice plates provided in the direction of the control valve, in order to to regulate the flow dependence of the deflection of the directional control valve in each flow direction, namely either the quantity flowing in to the piston-side working chamber or the quantity flowing out of the piston-side working chamber. Due to the two measuring orifices alternately assigned to the single control orifice, a multi-position directional control valve is also required to swap the pressure compensator control pressures in order to control the pressure compensator accordingly in each flow direction. Furthermore, the pressure compensator is expressly structurally separated from the directional control valve containing the measuring orifices and the multi-position directional control valve. This requires a considerable amount of construction work and considerable circuit and space requirements.

Further state of the art for technological Background is contained in: DE-A-31 39 944, FR-A-25 51 171, MACHINE DESIGN, July 18, 1963, Cleveland, US, pp. 168-184, and DE-A-36 05 980.

The invention has for its object to provide a flow control device and a lowering brake valve of the type known from DE-A-39 38 560, in which the speed limitation of the hydraulic consumer in both directions of movement is possible with little structural effort and reduced circuitry and space requirements.

The object is achieved according to the invention with the quantity control device according to claim 1 or the lowering brake valve according to claim 7.

Despite the speed limitation of the hydraulic consumer, the quantity control device does not allow unnecessary pressure medium to flow unused in both directions of movement. As a result, other consumers provided in parallel are properly supplied even during a control process of the aforementioned hydraulic consumer. In the event that no other hydraulic consumer is actuated or is present at the same time, the safety valve normally provided in the pressure supply can be used to discharge excess pressure medium. The flow control device is particularly suitable for cooperation with a speed-controlled pump, which enables speed control until the flow control device intervenes and also provides the required delivery rate for several consumers. In addition to the hydro consumer monitored with the flow control device no further hydraulic consumers are actuated, then the speed-controlled pump can only deliver the required delivery rate, so that no pump drive energy is wasted. This is particularly advantageous in the case of lifting devices whose hydraulic pump is supplied by a battery.

In the bidirectional lowering brake valve, both two-way flow controllers are combined with a common measuring orifice in one and the same working pressure line. This reduces the construction effort and the space required. There is no need to intervene in the other working pressure line. In spite of the quantity control or speed limitation, no excess pressure medium is wasted for both directions of movement of the hydraulic consumer because no pressure medium is released to the tank in the two-way flow regulator function.

The flow control device according to claim 2 uses excess pressure medium to supply at least one other hydraulic consumer. Excess pressure medium could be released via the safety pressure relief valve.

In the embodiment according to claim 3, the subordinate hydraulic consumer processes only as much pressure medium as the pressure compensator orifice plate allows. This benefits primary, other hydro consumers, the operation of which is not impaired by the subordinate hydraulic consumer, which is limited in both directions to maximum speeds.

In the embodiment according to claim 4, the pump provides only as much pressure medium as that Pressure compensator orifice plate at the speed limit needs. Up to this delivery rate, the speed of the hydraulic consumer can be adjusted by means of the pump speed. The pump only pumps more pressure medium if additional hydraulic consumers have to be supplied.

In the embodiment according to claim 5, the respective direction of movement of the hydraulic consumer is selected by means of the directional control valve. The quantity control device is effective in every direction of movement of the hydraulic consumer.

In the embodiment according to claim 6, the quantity control device is accommodated in a single working pressure line. Nevertheless, the speed of movement of the hydro consumer is limited in both directions of movement.

A structurally simple, compact and functionally reliable embodiment of the lowering brake valve emerges from claim 8. The two pressure compensator control orifices are designed so that they are open together in the normal position and regulate in the flow direction they monitor from the open position towards their shut-off position. This avoids unnecessary flow losses at low speed of the hydro consumer.

The features of claim 9 contribute to the structural simplicity of the lowering brake valve.

In the embodiment according to claim 10 is structurally simple for each flow direction the same Volume control reached. The common control spring is space-saving. The lowering brake valve has only a few individual parts.

With regard to smooth control movements of the control piston, the embodiment according to claim 11 is useful.

In the embodiment according to claim 12, the union nut has a double function, since on the one hand it secures the measuring orifice and on the other hand it forms the stop for the control spring.

An alternative embodiment is set out in claim 13. Different speeds can be set for both flow directions, which can be changed independently of each other.

In the embodiment according to claim 14, the passages are housed in a space-saving manner. Nevertheless, the control behavior is clean.

The embodiment according to claim 15 is particularly space-saving. The lowering brake valve integrated into the screw-in housing represents a structural unit that can be screwed into the working pressure line or a channel of the hydraulic consumer.

Fig. 1

eine hydraulische Steuervorrichtung als Blockschaltbild,

Fig. 2

einen Längsschnitt durch eine Mengenregelvorrichtung bzw. ein Senkbremsventil, das in Fig. 1 symbolisch dargestellt ist, in der Normalstellung,

Fig. 3

die linke Hälfte eines Längsschnitts des Senkbremsventils von Fig. 2 in einer Regelstellung, und

Fig. 4

die rechte Hälfte eines Längsschnittes desselben Senkbremsventils in einer anderen Regelstellung.

Embodiments of the subject matter of the invention are explained with the aid of the drawing. Show it:

Fig. 1

a hydraulic control device as a block diagram,

Fig. 2

2 shows a longitudinal section through a quantity control device or a lowering brake valve, which is shown symbolically in FIG. 1, in the normal position,

Fig. 3

the left half of a longitudinal section of the lowering brake valve of Fig. 2 in a control position, and

Fig. 4

the right half of a longitudinal section of the same counterbalance valve in a different control position.

A hydraulic control device S according to Fig. 1, e.g. of a lifting device, such as a forklift truck or forklift truck, has a pump P which sucks from a tank T and feeds a pump line 1. A tank line 2 leads to the tank. A safety pressure relief valve 3 is provided between the pump line and the tank line 1, 2. The pump P can be a speed-controlled pump, the delivery rate of which is proportional to the pump speed. A hydro consumer V, e.g. a double-acting hydraulic cylinder 5, with a piston-side and a piston rod-side working chamber 6, 7 is connected via working pressure lines 3, 4 to a directional control valve W (4/3-way control valve with blocked zero position), with which the direction of movement of the hydraulic consumer 5 can be adjusted.

In the working pressure line 3 is a quantity control device M, additionally in the form of a Two-way lowering brake valve Z, provided.

In addition, a further hydraulic consumer V1 is connected to the pump line 1 or the tank line 2 via a working pressure line 8 and a further directional control valve W1.

In a lifting device, the hydraulic consumer V can be used for swivel adjustment, e.g. a lifting fork, be provided in both directions, while the hydraulic consumer V1 is used for another function of the lifting device.

The bidirectional lowering brake valve Z has a (in the present case fixed) orifice 9 and a pressure compensator orifice arrangement 10, which via a pilot line 11 with the pressure prevailing in the working pressure line 3 between the chamber 7 and the orifice 9 and in the opposite direction a pilot line 12 can be acted upon by the pressure prevailing between the measuring orifice 9 and the pressure compensator orifice arrangement 10. A control spring 13 (or two) serves to center the pressure compensator orifice arrangement 10 in an open normal position.

2 shows the construction of the quantity control device M or the bidirectional lowering brake valve Z. It is a screw-in valve, the screw-in housing G of which is screwed with an external thread section 15 into an internal thread section 14 of the working pressure line 3. It is conceivable to design the valve with a conventional block-shaped housing and to provide connections for the working pressure line 3.

In the housing G, an axial bore forms a housing chamber 16, in which a control piston 17 designed as a hollow cup piston is guided in a sealed, displaceable manner with a guide section 18. At the open piston end 19, the orifice 9 is fixed in the form of an aperture ring 36 with an aperture bore 37. The piston crown designated 20 contains at least one throttle passage 21 to a control chamber part 22 of the housing chamber 16. At the lower end of the screw-in housing G, a screw-in tool engagement point 23 is provided.

Radial bores 24 distributed in the circumferential direction are provided in the wall of the control piston 17 and form a pair of first and second control edges 25, 26 spaced apart in the direction of displacement of the control piston 17. A circumferential groove 27 open to the control piston 17 is formed in the wall of the housing chamber 16, the groove flanks of which also form a pair of first and second control edges 29, 28. In the circumferential groove 27 open oblique bores 30 which lead to the outer circumference of the screw-in housing G adjoining the external thread section 15.

A control spring 13 surrounds the control piston end 19 and is fixed with prestress via abutment parts 35 between stops 33 and 34 on the control piston 17 and between abutments 32 and 31 of the screw-in housing. The abutment 32 is formed by a screw-in ring 40 with which the control piston 17 and the control spring 13 are secured in the screw-in housing G. The stop 33 is formed by a union nut 38, with which the orifice plate 9 is fixed interchangeably with another orifice plate with a differently sized orifice hole 37. The union nut 38 has a passage 39 which is also shaped as a turning aid.

In the position of FIG. 2, pressure medium can pass in the working pressure line 3 in any direction of flow, as long as the amount of pressure medium only generates a pressure difference across the measuring orifice 9 which is less than the force of the control spring 13. In this position, the speed of the hydraulic consumer V in FIG. 1 is increased or decreased by means of the speed of the pump P. The respective direction of movement is set with the directional control valve W.

The control spring 13 serves to maintain the normal position of the control piston 17 shown in FIG. 2. The pressure difference occurring via the measuring orifice acts on the action area of the control piston 17 defined by the guide section 18, which acts downward on the pressure acting in FIG. 2 above the measuring orifice 9 , while the pressure below the orifice 9 acts through the passage 21 in the control chamber part 22 in the direction of displacement upwards.

If the piston rod of the hydraulic cylinder 5 in FIG. 1 is pushed out (FIG. 3, flow direction 41), the higher pressure upstream of the measuring orifice 9 acts on the control piston 17 downwards, while the lower pressure downstream of the measuring orifice 9 via the passage 21 in the control chamber part 22 the control piston 17 acted upwards. With the pressure in the control chamber part 22, the control spring 13 also counteracts the higher pressure upstream of the measuring orifice 9. The control piston 17 is shifted downward (FIG. 3). The control edges 25 and 29 cooperate crosswise and regulate the continuous amount of pressure medium by a predetermined pressure difference across the measuring orifice 9 to adhere to and keep the speed of adjustment of the hydraulic cylinder 5 constant. If the pressure rises upstream of the orifice plate, then the control piston 17 is shifted further downward and the quantity passing between the control edges 25 and 29 is further regulated until the pressure difference across the orifice plate 9 is again at its predetermined value. The speed of the hydraulic cylinder 5 still does not change. In this control game of the control piston 17, the stop 34 of the control piston 17 is released from the lower spring end of the control spring 13 supported on the spring abutment 31, while the upper stop 33 compresses the control spring, the upper end of which springs from the spring abutment 32.

If the directional control valve W is changed over in order to reverse the direction of movement of the hydraulic consumer V, the lowering brake valve Z is flowed through in the opposite flow direction 42. The then higher pressure upstream of the orifice 9 acts through the passage 21 in the control chamber part 22 on the pressure surface of the control piston 17, while the lower pressure downstream of the orifice 9 acts in the opposite direction on the control piston 17. The control piston 17 is adjusted upwards in FIG. 4. The cross-cooperating control edges 26, 28 regulate the amount of pressure medium until the pressure difference across the measuring orifice 9 again corresponds to the predetermined value, the speed of movement of the hydraulic consumer V being limited in the new adjustment direction. If the pressure increases upstream of the orifice plate 9, the passage between the control edges 26, 28 is further narrowed so that the pressure difference across the orifice plate 9 is maintained and the speed of the hydraulic consumer does not increase. In contrast, the pressure downstream of the orifice 9 increases, for example because the load on the hydraulic consumer V increases, then the control piston 17 in Fig. 4 is adjusted downward, so that the control edges 26, 28 move away from one another and allow a larger amount of pressure medium to pass through the pressure difference across the orifice 9 and the speed of the hydraulic consumer hold. In this control game of the control piston 17 (FIG. 4), the control spring 13 is compressed between the spring abutment 32 and the stop 34, while it is released from the stop 33 and from the spring pivot bearing 31.

Instead of a control spring 13 common to both flow directions 41, 42, it is possible to have two separate control springs 13 act on the control piston 17. These can be biased differently or have different spring stiffnesses in order to bring about different control behavior for the two flow directions to be monitored. Both with a common control spring 13 and with two separate control springs, structural measures can be taken in order to be able to change the preload as desired. The installation position of the bidirectional lowering brake valve Z in relation to the hydraulic consumer is irrelevant. The orifice 9 could also be arranged separately from the control piston 17.

Claims (15)

Quantity control device (S) for the high-pressure hydraulics, with which in a hydraulic circuit the pressure medium flow to and from a hydraulic consumer (V) of at least one hydraulic consumer (V, V₁) connectable to a pressure source (P) independently of pressure and / or Changes in load can be limited, with a measuring orifice (9), which is assigned a pressure compensator orifice (25-29) that sets the pressure difference specified by the measuring orifice (9) for each flow direction, and with at least one line branching off the hydraulic circuit, (1, 2) characterized in that the orifice plate (9) with the two pressure compensator control orifices (25-29) in a bidirectional lowering brake valve (Z) with an exclusive two-way flow control function for each flow direction (41, 42) is structurally combined in a section of a working pressure line (S) are arranged, and that the branching line (1,2) on the side facing away from the hydraulic consumer (V) of the bidirectional lowering brake valve (Z) vo is seen. Flow control device according to claim 1, characterized in that at least one further hydraulic consumer (V₁) and / or a safety pressure relief valve (3) is (are) connected to the branching line (1, 2). Quantity control device according to claims 1 and 2, characterized in that the hydraulic consumer (V) monitored with the bidirectional lowering brake valve (Z) is subordinate to the hydraulic consumer (V₁) connected to the branching line. Flow control device according to at least one of Claims 1 to 3, characterized in that the working pressure lines (3, 4) are connected to a speed-controlled pump (P), the delivery rate of which is proportional to the pump speed. Quantity control device according to at least one of claims 1 to 4, characterized in that a directional control valve (W) for adjusting the direction of movement of the hydraulic consumer (V) is arranged between the pump (P) and the bidirectional lowering brake valve (Z). Quantity control device according to at least one of Claims 1 to 5, characterized in that the hydraulic consumer (V) is a double-acting hydraulic cylinder (5) which has a working chamber (6,7) on the piston side and on the piston rod side, that both chambers (6,7 ) via working pressure lines (3,4) and the directional control valve (W), preferably a 4/3-way control valve with blocked zero position, can optionally be connected to a pump line (1) and a tank line (2), and that the bidirectional lowering brake valve (Z) is arranged in the working pressure line (3) leading from the piston rod-side chamber (7) to the directional control valve (W). Lowering brake valve (Z) for limiting the maximum speed of movement of a hydraulic consumer (V) regardless of load or pressure fluctuations, with a measuring orifice (9) and a pressure balance regulating orifice (25-29) that adjusts the pressure difference across the measuring orifice (9), suitable for a Flow direction a two-way flow regulator in a working pressure line of the Form hydraulic consumer, characterized in that the metering orifice (9) forms a second two-way flow regulator in the same working pressure line (3) with a second pressure compensator orifice (25, 26, 28, 29) for the other flow direction, and in that the two Two-way flow controllers are combined in a bidirectional lowering brake valve (Z) and alternately limit the movement speeds of the hydraulic consumer (V5) in both directions of movement. Lowering brake valve according to Claim 7, characterized in that a hollow control piston (17) is sealed in a housing chamber (16) which can be flowed through on one side via the measuring orifice (9) and can be displaced in any direction of flow (41, 42) against the force of a control spring (13) is guided that the control piston (17) in the housing chamber (16) has an action surface in one direction of displacement of the control piston (17) with the pressure on one side of the orifice plate (9) and in the other direction of displacement with the pressure on the other Side of the measuring orifice (9) can be acted upon, and that flow passages (24) in the control piston (17) and in the wall of the housing chamber (16) have two pairs of first and second control edges (25, 26, 28) spaced apart in the direction of displacement of the control piston (17) , 29), of which, depending on the direction of flow, the first or the second cooperate alternately and crosswise as a control orifice. Lowering brake valve according to claim 8, characterized in that the control piston (17) is designed as a pot piston with an external guide section (18), that the pot piston in the piston head (20) has a passage (21) to a control chamber part (22) of the housing chamber (16) and in the piston head (20) facing away from the piston end (19) has the measuring orifice (9), preferably as an exchangeable orifice ring (36). Lowering brake valve according to claim 8, characterized in that a common control spring (13) is provided for both directions of displacement of the control piston (17), which spring tension, preferably adjustable, between axially spaced stops (33, 34) of the control piston (17) and axially spaced Abutments (31, 32) of the housing chamber (16) are clamped in such a way that, depending on the direction of displacement of the control piston (17), one spring end that stands out from one abutment is supported on the stop and the other spring end that stands out from the other stop is supported on the other abutment. Lowering brake valve according to claim 11, characterized in that sleeve-like spring abutment parts (35) are provided in both spring ends. Lowering brake valve according to claims 9 to 11, characterized in that the measuring orifice (9) on the open piston end (19) is interchangeably fixed by means of a continuous union nut (38) which at the same time forms the one stop (33) for the control spring (13). Lowering brake valve according to claims 8 and 9, characterized in that a separate, pre-tensioned control spring is provided for each direction of displacement of the control piston (17), and that, preferably, the pre-tension or stiffness of one control spring can be changed independently of the pre-tension or stiffness of the other control spring is. Lowering brake valve according to claim 8, characterized in that the flow passages (24) in the control piston (17) are radial bores distributed in the circumferential direction, and in that the flow passages provided in the wall of the housing chamber, for example in the form of inclined bores (30), into a to the control piston ( 17) open peripheral groove (29), the groove flanks of which form a pair of control edges consisting of first and second control edges (29, 28). Lowering brake valve according to at least one of claims 7 to 14, characterized in that the housing chamber (16) is provided in a screw-in housing (G) which has an external thread section (15) between the flow passages (30) and a housing part assigned to the freely inflatable piston end (19) ) and an axially accessible rotary handle (23).

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