DE2313300A1 - VALVE SYSTEM - Google Patents

Description

Hamburg, March 7, 1973 133 173 07

Priority: March 23, 1972, USA. Pat.Anm.Nro 237255

Applicant:

Caterpillar Tractor Go.

Peoria, 111, U.S.A,

Valve system

The invention relates to valves, and more particularly relates to a modulating pilot valve.

The use of pilot or pilot valves for the Controlling the operation of main control valves has been since Known for some time · Pilot valves allow! remote control and, a reduction in the time required for actuation actuation force required by control valves · A remote control can be advantageous through a pilot control can be implemented inexpensively because only small volumes and pressures are required for a pilot system *

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For the same reasons, also the required operating force "be reduced considerably ₀ It's" example evident that hydraulic "operated machines that are required for large liquid volumes and pressures, require the use of very large control valves for the actuation of a considerable force is necessary · At the same time are "considerable loading ,. movements required in order to be able to carry out the control function of such machines. " These factors make pilot control particularly desirable in control systems of hydraulically operated machines. This is particularly true for machines that require high pressures and large volumes to operate.

In hydraulic excavators, there is a particularly great need for effective pilot control of the hydraulic system. This need is particular because of the extremely high pressures and volumes of fluid normally used or required to operate this system urgent · A pilot control is particularly desirable with such tools because of the very high cost, which is attributable to the fact that the control valves are arranged very close to the driver's cab in order to enable operation. typical joint systems too ^; allow · Such an arrangement of the control valves wuide-very expensive pipes and other accessories and

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require a complex arrangement of the pipe systems

üin pilot operation is therefore desirable in such machines because of the numerous and frequently repeated control movements that the operator makes during normal operation such machines must perform «, a pilot control can

the forces which the operator himself has to exert in order to operate or control the system are considerable Reduce o The operator becomes tired less quickly and remains for a decent operating time the machine is fresh

However, currently known pilot control systems have the disadvantage that they only partly for use in hydraulic excavators are suitable _e The known pilot control systems allow the operator an accurate control and they do not give the required for such machines or at least desired sense of control · Due to the nature For the work to be carried out with it, an excavator must be suitable for executing movements with widely differing speeds and in very broad power ranges should work.

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enable the hydraulic fluids to be calibrated *

Numerous valve designs for modulating or adjusting the control fluid are known. Prior art designs are described, for example, in US Patents 2,971,536 of February 14, 1961, 3,477,225 of November 11, 1969, and 3,486,418 of December 30, 1969 3,556,155 of Jan. 19, 1971 "These patents illustrate the path of the prior art to a modulation control of a main control valve or a hydraulic motor, however, _β the problem differs in each Pailο

Although the method for a modulated control of hydraulic motors often occurs. a pilot control for control valves are applicable and vice versa, occur at the tunable Pilot control identifies particular problems that are missing in engine control systems «For example, the depends on the power required to drive a motor depends on the respective load, while the power required to move the The force required by the main control valve is normally dependent on its position in relation to its center position istο The pilot valve is adjusted in order to Adjust main control valve * while control valve is operating so that movement, not adjustment or adjustment of the motor is achieved *

Additional problems associated with pilot control systems are caused by the fact that the in-

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direct connection between the operating lever operated manually by an operator and the main control valve led to a loss of the sense of control of the tool. The typical result of this lack of control The feeling for the tool control is an erratic and unpredictable movement of the tool ο The operation of the Machine is therefore often random, dangerous and uneconomical

The main aim of the invention is therefore to provide a pilot control valve which has the above disadvantages of the prior art avoids «, the invention further aims to create a pilot valve which works in such a way that precise control of a control valve is achieved «

According to the invention, a pilot valve is also created, which suitable modulation or tuning- Has means which act in such a way that precise and correct control is achieved via a main control valve »

Another purpose of the invention is to provide a modulation or tuning device for a pilot valve which operates to provide an accurate increase in control pressure for actuation of the main control valve is reached *

A pilot valve according to the invention for actuating a The main control valve has a throttle device for modulating the control fluid in order to accelerate

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actuation of the main control valve at each end of the modulation or tuning range of the main valve and an extended tuning range for an effective to achieve the same and precise control of the main control valve by an operator < > The throttle device for modulating the control fluid leads to according to the invention to exact rates of increase of the control pressure in order to have a complete and precise control of the To reach the position of the main control valve *

Further advantages and features of the invention result from the claims and the following description of the drawings, in which the invention on the basis of an exemplary embodiment and is shown with the aid of function diagrams, for example «Show:

1 is a schematic sectional illustration of a preferred embodiment of an inventive Pilot valve,

Fig. 2 is a graphical representation of the versus the control movement applied tool speed and

3 shows a graphic representation of the working movement of the valve slide depending on the pilot or pilot pressure,

Figo 1 shows a preferred embodiment of one according to the invention Valve arrangement with a pilot or pilot valve generally designated 10. The one shown

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Embodiment of this valve has a housing 12 with two essentially parallel, cylindrical bores 14 and 14S i * ¹ which each identically constructed control slide 16 and 16 'are arranged so as to be able to move back and forth through an inlet channel 18 which crosses both bores supplied from a pump 20 the pressurized fluid which is passed through the spool valve at different outlets "two overcurrent or Eückströmkanäle 22 and 24, can via which! fluid flow back to a collection container 26 ₉ intersect the two bores 14 and 14 'on opposite Sides of the inlet channel pilot or pilot channels 28, 30 and 28 ^f , 30 'are each connected to one of the bores 14 or «14' in order to establish a connection to a main control valve for the pilot control fluid. Because the two control spools are designed in the same way, only one is described in detail below · The corresponding parts of the other control spool have the same reference numerals with an additional apostrophe »

Each of the distributor slides 16 has annular incisions 32 and 34 'between which a central shoulder 36 is formed »Two further incisions 38 and 40 are arranged outside of the aforementioned incisions, whereby paragraphs 42 and 44 are formed «These sections, in conjunction with a number, still control

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openings to be described the liquid flow from the Inlet to the pilot channels and the return channels »tuning— or regulating means in the form of a number of metering slots and openings are for regulation or modulation of the control fluid provided in order to achieve a uniformly graduated or multi-stage actuation of the To reach the control valve

The dosing means consist of a first opening 46 which is a fixed, non-adjustable connection between the annular incision 32 and the outer surface of the shoulder. 36 produces, and from a second invariable metering opening 48, which formed a connection between the annular incision 34 and the outer diameter of the shoulder 36. Furthermore, transverse slots 50 and are provided in order to make the openings 46 and 48 effective immediately after the control slide is in a predetermined position ₉ in which the edge of the slot enters the inlet channel. "Variable openings 54 and 56 work in parallel with the unchangeable openings described above." The grooves or slots 54 and 56 are formed such that immediately after the fixed openings 46 and 48 have reached their full effectiveness, timing or control begins such that connections between the inlet duct 18 and the outlet ducts 28 and 30 immediately a

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reach a certain minimum level and from this minimum level gradually up to the full opening of the pilot valve gain weight"

Two more metering orifices or channels 58 and 60 are arranged in series with the aforementioned metering orifices and each steep a connection between the inner recesses 32 and 34 and the outer cuts 38 and 40 forth _o These channels provide a pilot outlet for the Control lines 28 and 30 when the valve 16 is in its neutral position. Thus, at least during part of the time in which there is a connection between the inlet 18 and the control channels 28 and 30 via the inlet openings, a pressure drop occurs. The channels 59 and 60 are active when the outer cuts 38 and 40 are in communication with the outlet channels 22 and 24, but they are ineffective abruptly once cut off the connection between ä one of these incisions and the outlet channel by the displacement or movement of the incisions isto

Because of the critical alignment required for the openings and channels of the distributor slide 16, suitable means are provided to prevent the slide from rotating is held in a bore 66, for example by means of an end screw 68, _e

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Furthermore, suitable means for centering the slide are provided, which are preferably as shown are designed, but also any other customary May have shape. However, the centering must be adjusted in a suitable manner so that they are matched to other tuning or setting functions of the valve and thus to achieve the invention contribute to the desired new and beneficial effect In the preferred embodiment, for example, a first spring for centering the And a second spring then comes into effect at a certain point just before the Control or coordination effect began

The gate control valve described above is in the illustrated embodiment for the control or the Operation of a connected main control valve 72 is provided. The pilot valve is connected to pressure chambers 78 and 80 of the main control valve via control lines 76 and 76 connected «The pressure in chambers 78 and 80 acts on the ends of a control valve 82 to bring it into selected To move control positions »

The illustrated valve, instead of which any other suitable valve could be used _9, has a neutral center position and delivers when it moves from this center position to one side or the other

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is adjusted, pressure fluid for the operation of a double-sided drive machine in one direction each β This typical main control valve has the usual means for regulating the control fluid e The valve slide also has the usual insensitivity range to achieve a suitable seal of the valve rod _o The insensitivity range is a dead one Zone, which can be defined as the movement of the valve that occurs before any valve action occurs

The operation of the pilot valve of the present invention can best be seen in conjunction with the diagrams are explained in Mg. 2 and 3, which also show important features and advantages of the invention.

In Mgο 2, the solid line is the usual one Valves in general required operating stroke »i.e. the movement of the operating lever, shown in percent» A coordination or modulation of the speed of the controlled device or tool over the full speed range from O - 1OO # occurs only approximately in the middle third of the adjustment range of the control lever. As the solid line shows, it must conventional valve from O to about 33 # (point A) its entire adjustment range can be moved before any movement of the controlled device or tool occurs. The control range then extends from 33 #? where the loading

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movement of the controlled device begins, up to about 66 $ (point Β) of the actuation stroke of the operating lever, where the controlled device speed reached the full value of $ 100 The movement from that point to 100 $ of the actuation stroke (point C) takes place again in the dead zone, which is usually required around the flow path over the spool of impurities to keep clear and thus to ensure an undisturbed flow «

The use of a pilot valve according to the invention is shown by the dashed line, which shows that the dead zone at the beginning of the actuation stroke only extends to about $ 15-18 (point D), and that the control range extends from this point to about $ 80-85 (point E) of the entire adjustment range The use of a pilot valve according to the invention thus leads to an advantageous Reduction of the dead zone of the operating stroke of the operating lever and at the same time an expansion of the control range to about 65 $ of the entire actuation stroke ο

figο 3 serves to illustrate the dashed lines shown Working movement of the control slide of the pilot control valve in comparison with the one shown in solid lines Working movement of the control spool of the main control valve, each of which is opposed to the pilot control pressure.

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carry- are, »The illustration clearly shows the by the ratio or multiplication reached by the pilot spool the movement of the main control spool «A comparison of the two diagrams clearly shows the advantages of a pilot system constructed according to the invention o each other corresponding points are marked with the same letters in both diagrams »

The cross-sections 50 and 52 in the spool, see i * ig «are connected via the openings 46 and 48 with the incisions 32 and 34 in order to conduct pilot control pressure to the channels 28 and 30 when the spool moves from its neutral rest position will. The cross-slots allow the fixed ports 46 and 48 are almost instantly effective at a very small adjusting movement of the slider * The required path is in the illustrated embodiment, for example, 0 _o 031 ^lf, about (0.79 mm) _e represented by the The throttling caused by the second opening 58 or 60, depending on the currently effective space of the first opening 46 or 48, leads to the setting of the pilot pressure built up.The two openings connected in series enable precise control of the pilot pressure and guide from the time at which the opening of the transverse slot begins 50 or 52 (point i ¹ ) to full opening (point D) to a high rate of increase in pilot pressure

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to point D and as a result leads to a pilot pressure which is sufficient to move the main control valve from 0 to point L, where the modulation of the main control flow begins. Point D in FIG. 3 corresponds to this. Beginning of the effective control range of the control lever of the pilot valve at about 16 $ of the entire adjustment range, see Fig. Control slide in the Hegel area between points L and M to be reached. Point M corresponds to the end of the control range of the control lever of the pilot control valve, see point E in FIG. 2 _O From point Gr to point H of the stroke of the pilot control slide, see FIG. 3, the second opening 58 or 60, see FIG. 1 This leads to an increase in the rate of pressure increase from point G- to the maximum pressure of the pilot system at point H, through which the main control slide is moved from point M to its extreme position, see point N ₀ This high rate of pressure increase during the described movement of the pilot control slide leads to the advantageous result that only about 16 $ of the entire actuation stroke of the operating lever from point E to point 0 in FIG. 2 is to be carried out in order to move the main control slide in the dead zone to be carried out between points M and Έ

The physical characteristics of the pilot valve

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be apparent from the following discussion of when moving the valve rod and the Ventilsehieber movement over the entire adjustment of about 0.312 "operations sequentially (7" 92 am) occurring · The beginning of the adjustment of the control slide in any sighting of O to about 0.031 ^M ( 0.79 pretty) is a dead zone »which is necessary for sealing and reduces the flow requirements and tolerances of the pilot system to a minimum« The effect of the unchangeable openings with the bores 46 and 48 begins at point P at about 0.031 " (0.79) mm · The full effect is reached at about 0.062 ^M (1.58 mm) at point D of the working movement of the valve operating, where the pilot line pressure is about 40 PSI (2.8 kg / cm ² ). Further movement of the pilot spool to about 0.07 "(1.78 mm) results in a pilot pressure of about 50 PSI (3» 5 kg / cm), and the control spool has moved from 0 at point J to about 0.22 ^M ( 5.6 mm) moved at point L.

When the pilot valve is from about 0.07 to 0.250 " (1.78 to 6.35 mm), that is to the point G-, moves, takes the effective space of the first opening because the variable openings in 3? form of the slot space 54 or 56 come to the tree of the bore 46 or 48 so that the pilot pressure proportional to the slide movement to one Maximum value of about 175 PSI (12 kg / cm) at point G increases «The rate of increase of the pilot pressure between the Points D and G- is less than the increase between the

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Points ϊ ¹ and D and thus leads to a wide controlled tuning · or regulation range »The second invariable channel 58 is blocked at about 0.250" (6.35 mm) at point G of the slide movement, and the pilot pressure then rises very quickly to the maximum system pressure of about 325 PSI (23 kg / cm ² ) at point H ₀

The solid line in ELgο 3 shows the movement of the main control spool for the pilot pressure ranges described _above . 4 kg / em) to initiate spool movement from point J and only about 21 PSI (1.47 kg / cm) to reach point K at about 0.156 "(3» 96 mm) of spool travel © at this point, the main valve spool comes to the second, also referred to as the control spring Peder in contact _o A pilot pressure of about 50 PSI) 3 »5 kg / cm) is' required to this Each in connection with the centering extent compress, until point L is reached at approximately 0.219 "(5.55 mm) of the main slide travel, in which the tuning or modulation range begins point D, i.e. in a position that is considerably less than 1/3 of the entire adjustment range of 0.312 "(7.92 mm)« The control slide of the main control valve requires

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Change 175 PSI (12 kg / cm) actuation pressure to reach point M with a shift of about 0.476 "(12.6 mm), which is at the end of the tuning range» This pressure occurs at about 0.250 "(6.35 mm ) at point G of the actuation path of the pilot slide. Moving the main control spool over the full adjustment range up to approximately 0.688 "(17.48 mm) at point N requires an actuation pressure of approximately 275 PSI (19 kg / cm). The actuation pressure increases at approximately 0.250" (6.35 mm) Adjustment of the pilot slide quickly to 325 PSI (23 kg / cm ² ) at point H and remains at this value up to point I at about 0.31 "(7.9 mm) so that the distance between points H and I again is considerably less than 1/3 of the total adjustment range of the pilot slide *

The relative position of the pilot slide and the main control slide as well as the pilot pressure for the movement of the main control slide for a given position can be determined for any position simply by drawing vertical and horizontal lines between the curves and the coordinates of the representation in ÄLg _e 3 are projected. Then there is a horizontal line to the right up

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projected to the point of intersection with the curve of the main control slide shown in solid lines * The vertical projection of this point hits the horizontal axis at approx. 0.26 "(6.6 mm). 2.54 ¹ ^ ¹¹¹ ) the main control slide is adjusted by 0.26 "(6.6 mm)." By projecting the horizontal line between the two curves onto the vertical axis, the main control slide is moved by 0.26 "(6.6 mm) a pilot pressure equal to about 70 PSI (4-9 kg / cm).

The present invention thus shows an advantageous pilot valve arrangement with means for a graduated and modulated control, for an expansion of the tuning or control range of the main control valve and for a reduction of the dead zone in this area. Control valve through positions in the ineffective or dead zone up to a point, including the modulations or ^: control begins. Slide valve is achieved «At the end of the control range there is a rapid increase in pressure in order to quickly move the main control valve into its fully open position ·

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Claims (1)

PATSNTANSP RüO H E 1 · / valve system with a main control slide for control the inflow of hydraulic fluid for the operation of a hydraulic motor and with a hydraulic fluid source connected pilot valve, which feeds the hydraulic fluid to the main control spool, characterized in that the pilot valve (10) has a tuning device assigned to its control movement. device has for a modulated control of the pressure fluid, for an accelerated movement by a Impairment area of the main control spool (82) and for substantially proportional movement of the main spool through a tuning range ο Valve system according to claim 1, characterized in that that the tuning means for establishing an effective fluid communication from a pilot inlet (18) to a pilot control channel (28, 30) extends in the axial direction from an annular incision (32, 34) in a shoulder (36) of the pilot control slide (16) extending slot (54, 56), and that a passage channel (46, 48) led from the incision to a transverse slot (50, 52) of the control slide 3ο valve system according to claim 1, characterized in that that the tuning device has a fixed opening (46, 48) and a device for a movement of the - 20 309840/0365 -J ₀ - Control slide (16) has essentially immediate establishment of a connection with this opening O 4ο valve system according to claim 3, characterized in that that the connecting device consists of one in the control slide provided transverse slot (50, 52) consists » 5ο valve system according to claim 3 »characterized in that that, a slot (54, 56) of variable depth for the production a connection acting in parallel with the invariable opening (46, 48) is provided 6ο valve system according to claim 3 * characterized in that to reduce the pressure in the connection to a pilot control channel (28, 30) under the pressure of the pressure fluid source (20, 26) one with the invariable opening (46, 48) in series horizontal opening (58, 60) is provided _o 7 * valve system according to claim 1, characterized in that that the tuning device has a first invariable effective at the beginning of the movement of the pilot control slide JOpening (46, 48) for connecting the pressure to the pilot control channel (28, 30) has that one of the first Opening, variable opening (54 »56) that acts in parallel to enlarge the connection space for the hydraulic fluid is provided with further movement of the control slide, and that another with the first - 21 309840/0 3 85 Opening in series acting opening (58, 60) for reducing the pilot control pressure below the pressure of the pressure fluid source is provided _o 8ο Pilot system based on one or more of the previous ones Claims, characterized in that the pilot valve (10) is provided in a housing (12) cylindrical bore (14) has that inlet and return flow channels (18, 22, 24) and a pilot control channel (28, 30) with this bore in connection that for controlling the connections between these channels a control slide (16) is arranged to be movable to and fro in the bore, and that the control slide a tuning device for generating differential pressure changes in the pilot control channel carries " 9 · Valve system according to claims 5 and 8, characterized in that the space or depth variable slot (54 »56) for producing a connection in the Control slide (16) of the pilot control valve is formed 10. Valve system according to claim 6 and 8, characterized in that that to reduce the pressure in the pilot control channel (28p 30) to a level below the pressure in Inlet channel (18) is an opening in series with the invariable opening (46, 48) (58, 60) is provided - 22 309840/0365 11ο valve system according to claim 9 »characterized that the parallel connection between the inlet channel (18) and the pilot control channel (28, 30) is arranged is 12ο valve system according to claim 8, characterized in that that the inlet channel (18) is connected centrally to the bore (14) that on each side of the inlet channel a return channel (22, 24) is connected to the bore that a pilot control channel (28, 30) is connected to the bore between the inlet channel and one of the two return flow channels, and that the control slide (16) for controlling the connections between these channels is a mitbig arranged Shoulder (36) and two annular incisions (32, 34) formed on both sides of the shoulder having" 13 «Valve system according to claim 12, characterized in that that the tuning device has a first invariable opening (46, 48) for producing one at the beginning of the Movement of the control slide & L6) in each direction immediately effective connection between the inlet (18) and a pilot control channel (28, 30) that extends from the shoulder (36) .to the annular Incision (32, 34) has a slot (54, 56) extending parallel with the invariable Opening (46., 48) acts and an expanded - 23 - '309840/0366. connection path between the inlet (18) and the control channel (28, 30) with further movement of the slide (16) and that a second invariable opening (58, 60) is in series with the first and established an effective connection between the control channel (28, 30) and the return flow channel (22, 24) 14ο valve system according to claim 3 and 13, characterized j that a transverse slot (50, 52) in the shoulder (36) for the production of the sudden connection is formed, and that means are provided which the second opening when reaching the full Block effectiveness of the annular incision (32, 34) «. 309840/0365