DE2439030A1 - Two stage hydraulic flow regulating valve - flow sensing valve located in output line provides feedback compensating signals for flapper auxiliary control pistons - Google Patents

Abstract

Precise flow regulation utilises a two-stage hydraulic valve with a high response flow output sensing stage. The reference flow input is preset using a torque motor driving a flap valve. Outputs from the flap stage provide control signals for the second stage spool valve. One output from the second stage is coupled directly to a flow sensing device. Flow across the sensor to an output line is transmitted over a sharp-edged orifice formed by the annular gap between a disc and the bore. Two valve lands at either end are spring biased in the null position and are responsive to pressure through bleed holes. The input and output of the sensor provide feedback signals to two compensating cylinders operating on the flap input stage. Any flow variation due to supply pressure fluctuation or load provides a negative feedback to the flapper.

Description

Two-stage flow rate control valve device The invention relates to valve devices in which the flow rate of a flowing pressure medium is controlled to a load in dependence on an input signal.

In numerous applications, a valve device is required, which makes it possible to determine the flow rate of a pressure medium that is fed to a load should be to regulate exactly in accordance with an input signal regardless of fluctuations in the system pressure and / or changes in the pressure back-up caused by the load is caused. Various systems of this type are so far with more or less Successfully built, one of these systems is for example in the US patent 3,561,488. This is done by the input signal a The flow rate of a control pressure medium is specified, and the system then acts as follows: that the working medium flow rate is proportional to it. With other systems, as described, for example, in U.S. Patents 3,126,031 and 3,282,168 are, feedback loops are provided, which depend on the actual, for Load flowing pressure medium are actuated. While all of these known systems work satisfactorily for certain use cases, they are all limited in their dynamic range in which they work to satisfaction. Numerous known systems control the flow rate in the range between 100 and 96 the nominal flow rate down to 10% with sufficient accuracy, which is a dynamic range of 10 t means 1. Through special dimensions and very careful manufacture this range can be extended to 20: 1 or even larger. It exists however, today the requirement that such valve systems have precise control the flow rate over a dynamic range of 75 or 100 t 1. A however, none of the known systems is capable of such a dynamic range, with one exception some very complex to control satisfactorily. It is therefore the aim of the invention to provide such an improved valve system.

The invention is therefore based on the object of a valve system to create that is able to control the flow rate of a print medium to a load as a function of an input signal via a greatly expanded precisely control dynamic range.

Briefly, this object is achieved according to the invention with a valve system solved, which is a two-stage system and has a feedback loop, caused by the pressure drop at a new type of current sensor in one of the output lines is controlled. The sensor is essentially a variable flow opening, which is designed so that at flow rates below a certain size the sensor has an opening with a small, solid cross-section, while with flow rates above this certain value the area of the flow opening with the flow rate increases. As a result, the pressure drop across the sensor and the control function exerted by it increase rapidly with increasing flow rate in the lower part of the flow, in which Usually the scheme is difficult to implement while approaching the fields larger flow rate is much gentler. So can be a great dynamic Control the area very effectively.

For a better understanding of the invention, it will now be referred to in conjunction with the drawing based on some exemplary embodiments described. 1 shows a schematic cross section through a device containing the invention Valve system; FIGS. 2 and 3 are graphic representations for explaining the invention; 4 shows a schematic cross-sectional illustration of a further embodiment the second stage valve; 5 shows a schematic cross section of a modified one Shape of flow sensor; Fig. 6 is a graphic illustration for explaining the Operation of the flow sensor according to FIG. 5; and FIG. 7 shows a schematic cross section, which shows the first valve stage in a modified form.

First, FIG. 1 is considered, wherein the valve of the first Stage is designated as a whole with 11. This first stage valve consists of a valve housing 12, in which there is a recess 13, welde from the top in Fig. 1 extends into the housing and through a passage 14 is connected to the sump 15.

A torque motor 16 with an actuating arm 17 is mounted on the housing 12 placed, which protrudes into the recess 13.

The lower end of the Stellaris is designed as a finger or flap 18. In the valve of the first stage nozzles 21 and 22 are inserted into the recess 13 protrude and stand on both sides of the flap 18. The nozzles 21 and 22 are above Lines 23 and 24 and throttles 25 and 26 with a source 27 for control pressure medium tied together. In the drawing, the pressure medium source 27 is shown as lying two separate pressure medium sources on both sides of the valve, however this is only due to the schematic representation; the pressure medium sources 27 on either side of the first stage control valve are considered to be a single one to understand. With the line 23 in the area between the nozzle A and the throttle 25 a control line 28 is connected, and in the same way is a control line 29 is connected to the line 24 in the area between the nozzle 22 and the throttle 26.

The first stage in the manner described is a common folding the nozzle control valve. An input signal supplied to the torque motor 16 moves the cap 18 from its central position to one side closer to the nozzles 21 or 22 and away from the other accordingly, so that this creates a pressure difference is generated between the lines 23 and 24 upstream of the nozzles, this Control pressure difference between lines 28 and 29 prevails. Direction and size of the control differential pressure depend on the sense of direction and the size of the input signal to the torque motor 16 dependent.

In the housing 12 of the first stage 11, however, are still a first and a second cylinder 31, 32 incorporated, which are open to the recess 13. In this cylinder 31 and 32 pistons 33 and 34 are used with rounded Press the ends against the actuating arm 17 of the torque motor 16 from two sides. the Cylinders 31 and 32 are hydraulically connected to feedback lines 35 and 36, the purpose of which is described below.

The second stage of the valve system is in its entirety with 41 and has a valve housing 42 into which a hollow cylinder chamber 43 is incorporated, in which a total of 44 designated piston arrangement is used which has a central collar 45 and outer collars 46 and 47. the Collars 45 and 46 are connected to each other by a connecting rod 48, what in the same way for the collars 45 and 47 with a corresponding connecting rod 49 applies. The overall length of the piston assembly 44 is considerably shorter than that Length of the hollow cylinder chamber 43, so that end spaces 51 and 52 to opposite Ends of the cylinder are created which are connected to the control lines 28 and 29 are in connection.

The housing 42 is also provided with a central recess 53, the preferably one from the outside into the housing at a right angle to the cylinder chamber 43 is drilled hole, which the cylinder chamber approximately in their Middle cuts. The bore goes a little beyond the cylinder chamber, such as this is shown in the drawing. The recess 53 is fluidly with a pressure medium source 54z - connected for a pressure medium of the second stage - <seldhes is under pressure P5; its width in the direction of the axis of the cylinder chamber 43 is essentially equal to the width of the middle collar 45, so that in the neutral position or reference position, which is shown in the drawing, the central collar 45 straight covers recess 53 with little or no overlap. In which In the particular embodiment shown here, the width is simple the diameter of the drilled hole, which is practically the same or just slightly is smaller than the length of the central collar 45. This central collar is in the axial direction seen in the center a circumferential annular groove 45 'formed so that the pressure medium source 54 is also in communication with the other end of the bore 53, which without this Ring groove would be blocked.

The housing 42 is also equipped with a further recess 55, which also from the outside into the housing at right angles to the cylinder chamber 43, this is introduced to enforce a little. In the neutral position of the Parts as shown in the drawing fill the right-hand edge the recess 55 practically with the right-hand side Boundary surface of the collar 46 together, while the left-hand edge of the recess 55 is does not extend completely to the left boundary wall of the annular collar 46.

An identical recess 567 which is also perpendicular to the cylinder chamber drilled hole is located in the housing 42 to the left of the central recess 53, wherein the left delimiting edge practically with the left end face of the annular collar 47 collapses in its neutral position. The right edge of the recess 56 extends However, not up to the right end face of the annular collar 47. The two recesses 55 and 56 are connected to the pressure medium sump 57. The coils 46 and 47 have annular grooves 46 'and 47' similar to the annular groove 45, which are located approximately in the longitudinal center of the recesses 55 and 56 are when the piston 44 is in the neutral position according to Drawing stands. Each of the recesses 53, 55 and 56 could itself have a groove be equipped on its inner wall, which then creates the ring grooves in the collars can be omitted.

However, the illustrated embodiment is currently preferred.

The housing 42 also has radially extending outlet channels 58 and 59, which can be simple bores, the former of which in the area of the connecting part 48 opens into the hollow cylinder 43, while the second opens into the cylinder 43 in the area of the connecting section 49.

The passage channels 58 and 59 are connected to fluid lines 61 and 62 connected, which lead to a load that is about a hydraulic Motor 64 can be.

The line 61 consists of a first section 61 ', which directly adjoins the valve of the second stage 41, and a second section 61'1, which is connected to the hydraulic motor 64. In this line 61, a flow sensor is inserted between the sections 61 'and 61 ", which is shown in FIG its entirety is designated by 66.

This flow sensor 66 also has a housing 67, the one Hollow cylinder chamber 68 has. The housing 67 is provided with two recesses 69 and 70, which are open towards the interior of the hollow cylinder 68 and are spaced apart from one another to have.

The recesses can have a wide variety of shapes, but are preferably shaped as a kind of annular groove, as shown in the drawing here Case shows. The housing 67 also has a passage 72, which the partial line 61i of the line 61 connects to the first recess 69. Another passage channel 73 in the housing 67 connects the second recess 70 with the second part 61 " the line 61.

In the hollow cylinder chamber 68, a piston is inserted, the total is designated 74 and has annular collars 75 and 76 at its ends. Furthermore carries the piston has a substantially circular disc 77 in its center, which connected to the two end collars 75 and 76 by connecting rods 78 and 79, respectively is. The total length of the piston assembly 74 is considerably smaller than that of the Zjlinderkam-.

mer 68, so that at the two ends end cavities 81 and 82 develop. In these end cavities springs 83 and 84 are inserted, which the piston assembly Press 74 into the neutral or reference position shown in the drawing, if no pressure medium flows to load 64. The end collars 75 and 76 have openings 86 and 87 in the axial direction, thus connecting the end chamber 81, 82 with the central space of the hollow cylinder 68 consists. The already mentioned feedback lines 35 and 36 are connected to one another via the flow sensor 66.

More precisely, the feedback line 35 is connected to the section 61 ' of the flow line 61 and the feedback line 36 to the section 61 ″ of the Line 61 connected. In this arrangement, lines 35 and 36 can be any Feel the pressure difference at the sensor 66, which then serves as a feedback signal.

The central portion 77 of the piston assembly 74 is diameter formed, which is sufficiently smaller than the inner diameter of the cylinder chamber 68 so that between the periphery of the central portion 77 and the inner surface of the cylinder chamber a ring opening remains. In one implemented valve, the cylinder chamber had an inside diameter of approx. 11 mm and a gap width of just under 0.2 mm between the middle part 77 and the inner surface of the cylinder chamber, which is considered to be satisfactory was felt. The part 77 preferably has a sharp ring edge that it completely surrounds.

The term sharp "indicates an edge with a small edge radius of less than 0.1 mm. The purpose of such sharpen Edge is that the ring opening 88 acts as a sharply delimited opening, so that the amount of pressure medium that flows through is relatively dependent on fluctuations in temperature reacts in the pressure medium.

To describe the mode of operation it is assumed that an input signal is given to the torque motor and with such a sense of direction, that the flap 18 is moved to the left in the drawing. This shift increases the pressure in the control line 28 and decreases it in the control line 29, whereby the piston 44 is displaced to the right from the neutral position, so that Pressure medium from the pressure medium source 54 into the channel 58 and the line 61 flow can, while the amount of liquid from the line 62 into the channel 59 and from there can flow into the sump 57.

It should be noted that there are no return springs on the piston 44 act to shift this back approximately into the neutral position, so that as long as there is a differential pressure between the control lines 28 and 29, the piston 44.sich constantly moving. The flowing pressure medium in line 61 now flows up its way to the load 64 through the ring opening 88 and thus generates a pressure drop at the flow meter 66, which prevails between the lines 35 and 36 and which is returned to the cylinders 31 and 32, which acts on the pistons 33 and 34 will. With the assumed sense of direction of the input signal, the pressure is in the line 35 higher than that in line 36 so that the piston 33 pushes the actuating arm 17 to the right, that is, in the opposite direction to that caused by the input signal given direction. The pressure drop across the flow sensor is very short 66 sufficiently large so that the flap 18 is returned to its neutral position in which the differential control pressures in lines 28 and 29 are equal to each other so that the piston 44 comes to rest and the fluid in an amount flows to load 64, which is determined by the size of the input signal.

When checking the effect and mode of operation of the flow sensor 66 to an even more precise extent it can be seen that the pressure medium flow from the passage channel 72, which passes through the ring opening 88 and then the passage 73, the middle part 77 shifts to the left. The cross-sectional area remains for low values of the input signal of the ring opening 88 through which the pressure medium flows, constant. When the input signal and so that the flow rate increases, the body 77 shifts to the left and thus arrives at the edge of the recess 70. At that moment, it increases with further The cross-section of the ring opening increases in the flow rate.

Fig. 2 shows how the amount of pressure medium depends on the input signal changed in the lower ranges, assuming that the load is only one generates little or no backwater. At very low values of the input signal, in which the cross-sectional area of the ring opening remains constant, it has been found that the pressure medium flow rate to the load is approximately linear with the input signal increases, which the first section 91 of the curve shown shows. Also is recognizable that this section of the curve is fairly flat, which means that relatively large changes in the input signal are necessary to small changes cause the pressure medium flow rate. That means a very good tax option the amount of fluid flowing at these low values, i.e. in areas in which the control or regulation of most valves is very arduous. When the input signal rises and thus the amount of pressure medium flowing reaches a point at which section 77 reaches the marginal edge of recess 70, in which then the cross-section of the ring opening increases and the curve a knee as shown at 92. at this point the slope of the curve increases sharply and becomes much steeper, as shown in section 93. In one embodiment of the invention, the knee 92 was at a flow rate of less than 1% of the total possible flow rate determined, if only slightly - or none at all Back pressure originated from the load 64.

FIG. 7 represents a continuation of the curve from FIG. 2 and shows the change in the amount of fluid flowing when the input signal changes the entire upper range, still assuming that from the load no back pressure goes out. This portion 94 of the curve shows that the flow rate over this upper range again changes approximately linearly.

The curves of Figures 2 and 3 are tests on a model under conditions Taken with little or no load. Further attempts on the same model but showed that the flow rate of the pressure medium between idle the Load and full load only very slightly over a dynamic range of approximately 70% changed. Further tests on the same model also showed that the system completely insensitive to changes in the feed pressure over a comparable large dynamic range was.

It now continues with the consideration of the operation of the Gesaitsysteas, recalling that the input signal was assumed of the torque motor an original displacement of the flap 18 to the left Had consequence, whereupon the piston 44 was shifted to the right, and that the feedback signal above the pistons 33 and 34 return the flap 18 to its neutral position reset while the piston 44 remained displaced. When the input signal is taken away is removed, the force that had moved the flap 18 to the left is also removed, so that the piston 33 moves the flap 18 to the right for a moment, whereby the pressure in the.

Control line 29 rises above the control line 28 and the Piston 44 is thereby pushed into its neutral position. This decreases of course the amount of flow through the flow sensor 66 so that the feedback signal becomes smaller, and the system is quickly stabilized, with the flap 18 and the piston 44 are again in their neutral starting position and no Pressure medium flows more to the load. The piston 74 is also in its neutral position relocated back, 'as the drawing shows. An input signal of reverse The sense of direction would result in the same adjustment sequence, with the pressure medium then flows to the load in reverse.

In Fig. 1, the second stage of the valve is shown so that it is tightly closed in the middle. However, the principle of the invention is also Applicable when a centrally open valve is used in the second stage, as shown in FIG. This valve is soft Parts denoted by the same reference numerals, and only the collar 95 in FIG Mitte has one major difference, namely its size and its Position with respect to the central recess 53 in the neutral position is such that the both sides of the valve over the central annular collar 95 in the hollow cylinder chamber 43 have a connection. The outer annular collars 96 and 97 are also of such a size and are so arranged relative to the recesses 55 and 56 in the neutral position, that also in this neutral position, the side recesses 55 and 56 with the Interior of the cylinder chamber 43 have connection. So it is the modified one Embodiment around a valve with an open center through which the pressure medium source 54 over both edges of the middle annular collar 95 pressure medium to the sump 57 continuously flows so that the pressure in the neutral position in the channels 58 and 59 is the same is. The use of such a centrally open valve is in some applications advantageous. The operation of the system of such a valve is that of that described The valve arrangement from FIG. 1 is essentially the same.

5 is now to be considered, the one modified Represents flow sensor. through here are the parts that are the same as with the flow sensor according to Fig. 1, provided with the same reference numerals. One and only The difference is the middle section 98 of the exemplary embodiment in FIG. 5, the one Has the shape of a cylinder like the collar of a valve piston and which closes with it Sliding fit in section 99 of the cylinder chamber surface of the cylinder chamber 68 is seated, which section is located between the recesses 69 and 70.

In such an exemplary embodiment, a defined one results Threshold value of the input signal that must first be fed to the system, before any pressure medium can flow to the load. With increasing input signal shifts the differential pressure at the sensor, which occurs between lines 72 and 73, the part 98 against the force of the springs 83 and 84; however, no pressure medium flows to the load before the one end edge of the part 98 is not the corresponding end edge of the Has reached recess 69 or 70.

Then pressure medium flows to the load according to a non-linear function depending on the input signal, as shown by curve 100 in FIG. 6 is.

Even if the valve of the first stage in Fig. 1, as a flap valve is shown, other types of valves can also be used in the first stage, such as about a cylinder.

and piston valve with open center or closed center. A suitable first stage valve with an open Center as a cylinder piston valve is shown in FIG. The valve is designated by 101 in its entirety and has a housing 102 which has formed a hollow cylinder space 103 as well also through channels 104, 105 and 106, which establish the connection of a DruckmitUlquelle 27 (schematically drawn in two places, but only available once) Via throttle points 107 and 108 and the cylinder chamber 103 to a pressure medium sump 15. Pistons 111 and 112 are inserted into the cylinder chamber 103, their neutral position is shown in the figure, in which they the passageways 104 and 106 in part cover, while the passage 105 always remains fully open. The torque motor 16, which may be the same as that of FIG. 1, shifts to an input signal Stelltinger 18, which protrudes between the pistons 111 and 112. With approaches 113 and 114 on the pistons 111 and 112, the latter act on the adjusting finger 18. The end chambers of the hollow cylinder 103 at the mutually remote ends of the pistons 111 and 112 are connected to the feedback lines 35 and 36. The control lines 28 and 29 are bits of passageways 104 and 106 between the throttle areas 107 and 108 and the cylinder chamber 103 in communication.

Presses when the torque motor responds to an input signal the adjusting finger 18 the pistons 111 and 112 in one direction or the other, what from the sense of direction of the Depends on the input signal, and it pushes it, where the area size with which the pistons 111 and 112 the passageways 104 and 106 cover, is differentially reduced so that upstream differential control pressures appearing in the control lines 28 and 29 and the second stage control the valve assembly. In the case of the arrangement according to Fig.

1 presses the back coupling signal, which is generated by the pressures in the Lines 35 and 36 are formed, the pistons 111 and 112 in opposite directions the direction of displacement by the torque motor 16 back to its in the drawing Neutral starting position shown.

Claims (13)

PATENT PROOFS 1. Valve device with a pressurized working medium, a return line, a load, first and second in communication with the load standing line for the pressure medium, one controlled by an input signal first stage for generating a differential control pressure in a first and a second control line, a second stage that reacts to the control pressures and the flow rate of the pressure medium from the pressure medium source through one of the lines controls to the load as well as from the load through the other line to the sump, an in one of the lines used flow rate sensor, the a feedback signal generated, which indicates the direction and size of the flowing pressure medium quantity, and means which, as a function of the feedback signal, provide a further control make the first stage, characterized in that the flow rate sensor (66) a piston arrangement (74) held in the neutral position under the action of a spring has, which is displaceable depending on the amount of pressure medium flowing through and generates a differential pressure representative of the feedback signal. 2. Valve device according to claim 1, characterized in that the first stage (11) is a flap valve with a first and a second nozzle (21, 22), through which working medium under pressure against opposite sides the flap (18) is directed, a torque motor (16) depending on the input signal moves the flap (18) towards one nozzle and away from the other, whereby the Pressure upstream of the nozzles is changed differentially to generate a differential control pressure and which includes means which, depending on the feedback signal, the flap (18) in the opposite direction to the adjustment by the torque motor (16). 3. Valve device according to claim 2, characterized in that a first and a second feedback line (35, 36) across the flow rate sensor (66) are connected to each other and the pressure difference at the flow rate sensor represents the feedback signal, and that those dependent on the feedback signal Means have a first and a second piston (31, 32) which of opposite sides due to the pressure in the first and two feedback lines (35, 36) are pressed against the flap- (18). 4. Valve device according to claim 1, characterized in that the second stage (41) is a four-way closed center valve. 5. Valve device according to claim 1, characterized in that the second stage is a four-way valve with an open center. 6. Valve device according to claim 1, characterized in that the first stage is a cylinder piston valve (101). 7. Valve device according to claim 1, characterized in that the first stage has a pressure medium source (27) and a return line (15), and a housing (12) which has a hollow cylinder chamber (103) and a plurality of passageways (104, 105, 106) to the pressure medium from the pressure medium source (27) to direct the hollow cylinder chamber (103) to the sump (15), in the hollow cylinder chamber (103) a first and a second piston (111, 112) are inserted, the specific Cover passageways (104, 106) with a variable area, a torque motor (16) is present, which moves the piston (111 112) on an input signal and so the cover area of the specific passageways (104, 106) changed, whereby the pressure upstream of the determined passageways (104, 106) changes, and so that a differential control pressure is generated, and that on the feedback signal there the pistons (111, 112) in the opposite direction to the adjustment by the torque motor (16) are charged. 8. valve device, characterized by a valve body (67), in which a substantially cylindrical chamber (68) is incorporated and with A first and a second recess (69, 70) in the inner surface of the cylinder chamber are spaced apart, which first and second passage channels (72, 73), the first and second, respectively Connect recess (69, 70) to the outside of the valve, a piston (74) in the cylinder chamber (68) is inserted, which has a first and a second annular collar (75, 76) at both ends and also a substantially cylindrical one Disc (77) in the middle section, which is connected via rod-like connecting pieces (78, 79) connected to the collars (75, 76) that between the opposite sides the respective ring collars (75, 76) are connected and springs (83, 84) push the piston (74) into a neutral position in which the first and second Ring collar (75, 76) outside of the first and second recesses (69, 70) close the ends of the cylinder markers come to rest while the middle disk is moving (77) is located almost in the middle between the recesses, whereby the connection of the Sensor in a pressure medium system is such that pressure medium from one of the passageways by the sensor flows to the other passage and thereby a displacement of the piston (74) from the neutral position, while the resulting differential pressure between the passages (72, 73) a measure of the amount of pressure medium flowing through is. 9. Valve system according to claim 8, characterized in that the springs between the end-side annular collars (75, 76) of the piston (74) and the opposing ones End faces of the hollow cylinder space (68) are used. 10. Valve system according to claim 9, characterized in that in the outer annular collars (75, 76) axially parallel passage channels (86, 87) for a pressure medium compensation flow are formed. 11. Valve system according to claim 9, characterized in that the Middle part (77) has a diameter which is sufficiently smaller than the inner diameter the cylinder chamber (68) is, so that an annular opening (88) of a certain size between Perimeter of Mitbiteils (77) and inner surface of the cylinder wall (68) is present. 12. Valve system according to claim 11, characterized in that the Middle part (77) has a sharply formed circumferential edge. 13. Valve system according to claim 8, characterized in that the Central part (98) of the piston arrangement (74) has an essentially cylindrical jacket surface of such a diameter that the 5il with a sliding fit in the inner surface the hollow cylinder chamber (68) fits.