DE4334167A1 - Hydraulic system for loading a hydraulic consumer with a regulated consumer pressure and choke valve in particular for use in such a hydraulic system - Google Patents

Abstract

The invention relates to a hydraulic system for loading a hydraulic consumer with a regulated consumer pressure. This hydraulic system has a hydraulic pump, by which pressure medium can be drawn from a tank and the delivery volume of which can be adjusted by an actuator for regulating the consumer pressure. The actuator can be connected to the pressure side of the hydraulic pump. Connected between the hydraulic pump and the consumer is a retaining valve which opens at a minimum pressure sufficient to adjust the delivery volume of the hydraulic pump. Finally, a choke valve is connected between the consumer-side outlet of the retaining valve and the tank. So that leakage through the choke valve is not too great on the one hand and rapid pressure reduction is possible on the other hand even at a low consumer pressure, the effective opening cross-section of the choke valve is preferably infinitely variable between a maximum value at a consumer pressure corresponding to the tank pressure and the value 0 at a consumer pressure lying above the minimum pressure. In addition, the invention relates to a choke valve with a choke housing and a choke body which is adjustable rectilinearly in the choke housing and can be acted upon in the opening direction by a spring and in the closing direction by a closing force which can be produced by a pressure applied to the choke inlet. Such a choke valve is ... especially for use in a ... according to the invention ... Original abstract incomplete.

Description

The invention is based on a hydraulic system that the Features from the preamble of claim 1 and that serves a hydraulic consumer with a regulated To apply consumer pressure. The regulated Ver user pressure can also be smaller than the signal pressure, the to adjust the delivery volume to the hydraulic one System belonging hydraulic pump is necessary.

A hydraulic system of this type is not pre-published published DE patent application P 42 11 551 already described been. After that is between the hydraulic pump and the consumer switched a damming valve, which is used to adjust the Delivery volume of the hydraulic pump opens sufficient minimum pressure. This ensures that between the pressure side off gear of the hydraulic pump and the accumulation valve to adjust the Hydraulic pump necessary signal pressure prevails. Via the dam valve the minimum pressure builds on the lower consumer pressure from. The minimum pressure can be exactly the maximum necessary position pressure, but it can also be selected higher. For Regulation of a consumer pressure lower than the min residual pressure is also a throttled connection between the consumer outlet of the accumulation valve and the tank necessary. Is the consumer pressure to be regulated higher than that Minimum pressure, this connection is advantageously ver closed to avoid leakage. Accordingly, at the hydraulic system according to the mentioned patent application in the connection between the consumer side output of the Damming valve and the tank arranged a ball valve, the ball acting as a closing body in the opening direction of egg ner helical compression spring and in the closing direction of the ver  user pressure is applied. The ball seat valve is in the Principle of a switching valve that is open as long as the Ver user pressure is less than the minimum pressure, and then closes when the consumer pressure reaches the minimum pressure. It can thus be said that if the pressure is below the minimum pressure no consumer pressure between the consumer side Outlet of the accumulation valve and the tank connect to a certain throttle cross-section exists while this connection is closed when the consumer pressure is equal to or greater is greater than the minimum pressure.

It has been shown that at a high level below the minimum pressure lying consumer pressure the leakage through the throttle cross-section to the tank is quite large if you cross the throttle cut big chooses. On the other hand, a lower one can of the minimum pressure is only relatively long sam can be reduced if the throttle cross-section is small elects.

The invention has for its object a hydraulic Sy stem with the features from the preamble of claim 1 so to further develop that with consumer pressure to be regulated, which is below the minimum pressure, the leakage is only slight and at a low pressure below the minimum pressure Consumer pressure this can be reduced quickly.

This object is achieved according to the invention for a hydraulic system with the features from the preamble of claim 1 thereby solved that the effective opening cross section of the throttle valve between a maximum value at the tank pressure the consumer pressure and the value zero at a value above the min consumer pressure, preferably infinitely variable is changeable. Due to the large opening cross section at nied consumer pressures below the minimum pressure such a consumer pressure can also be reduced quickly, although the pressure difference across the throttle valve is small. At higher consumer pressures and thus greater pressure differences  The limit over the throttle valve is its opening cross-section small, so that the leakage despite the larger pressure difference is not too big and always because of the larger pressure difference rapid pressure reduction is still possible.

Advantageous embodiments of a hydraulic system according to the invention systems can be found in subclaims 2 to 11.

A good resolving power of the throttle valve with simple Production of its parts is obtained according to claim 2 by that the throttle valve has an adjustable throttle body with egg has a locking cone. In particular, according to claim 3 Throttle valve is a needle valve with a pilot hole in the the adjustable throttle body designed as a needle is.

In principle, it is conceivable to change the opening cross section of the Change throttle valve in that the throttle body through Twisting a set screw z. B. by means of an electric motor is axially displaceable in the two opposite directions. However, a solution appears to be simpler in which, according to claim 4 an adjustable throttle body of the throttle valve in opening direction is acted upon by a spring. In the closing direction can then z. B. act a proportional magnet, the stroke of which is easy controlled by the voltage applied to the winding can.

However, the adjustable throttle is preferred Body of the throttle valve in the closing direction from the consumer pressurizable. Depending on the amount of Ver user pressure in a different position of the throttle body Balance between that of the spring in the opening direction exerted force and that of the consumer pressure on an effective area che of the throttle body generated closing force, so that ever according to the level of the consumer pressure, another public transport cross section of the throttle valve. Does the Ver pressure, the effective opening cross-section becomes small  ner, the consumer pressure decreases, so the effective opening cross-section larger.

It is beneficial if there is a change in consumer pressure only damped on the throttle body in the closing direction acting force affects. Therefore, is vorese according to claim 6 hen that a rear pressure chamber in which the adjustable pressure in the closing direction there is a damping cross-section with the consumer side input of the throttle valve is connected.

A rear pressure chamber of the throttle valve is more advantageous as an axial bore in the throttle body connected to the consumer side input of the throttle valve. The hole can be made so narrow along its entire length be that the damping cross section is formed. Think However, it is also possible to use a single short throttle point in the Hole or in a transverse bore leading into the bore watch. In this way, the damping cross-section may be easier to manufacture, since not with a long, very thin one Drill must be worked.

The spring that the adjustable throttle body in opening direction tion is preferably applied outside of the Throttle leading flow path arranged so that they the Can not influence flow.

According to claim 10 it is provided that a rectilinearly adjustable rer closing body of the throttle valve from the pressure medium in the direction the movement to open the throttle valve can be flowed against. On in this way it is particularly easy to establish a connection between between the inlet of the throttle valve and the consumer side Output of the dam valve z. B. through a single hole in the Dros to manufacture sel housing. With a reverse flow of the Throttle valve would be the connection through the Throttle body or through the throttle body may more complicated.  

A training according to claim 10 is particularly favorable if the throttle valve into an existing pressure limitation valve is integrated, then the closing body of the Druckbe limit valve serves as a throttle body, in which normally little space is available. The training also offers according to claim 10, the possibility according to claim 11 the ver user-side input of the throttle valve via a through axial bore in the adjustable throttle body with a to connect the rear pressure chamber and thereby also a damper to form the cross section.

The invention also relates to a throttle valve, in particular in a hydraulic system according to one of the preceding Claims can be used and its throttle cross section in Interplay between an Fe acting in the opening direction derkraft and a pressure force acting in the closing direction ver is changeable.

Advantageous embodiments of a throttle valve according to claim 12 can be found in claims 13 to 18.

An embodiment of a hydraulic according to the invention Systems with a throttle valve according to the invention is in the Drawings shown. Using the figures in these drawings the invention will now be explained in more detail.

Show it

Fig. 1 shows the switching arrangement of the hydraulic system with a dam valve and the output side of the dam valve is connected pressure relief valve and throttle valve and

Fig. 2 shows a section through a valve arrangement in which the dam valve, the pressure relief valve and the throttle valve according to FIG. 1 are integrated into one another.

The hydraulic system according to FIG. 1 includes a hydraulic pump 10 as the pressure source, the delivery volume of which is adjustable and which can suck in pressure medium from a tank 12 via a suction line 11 and feeds it into a pressure line 13 . In the hydraulic pump, it can e.g. B. to act of such an axial piston inclined disc type, the swash plate via a Stellzy cylinder 14 is adjustable against the force of a spring. The pressure chamber of the actuating cylinder 14 can be connected by a control valve 15 , which can be actuated from a rest position by an electromagnet 16 against a return spring, via a control line 17 to the pressure line 13 and via a control line 18 to the tank 12 . To adjust the delivery volume of the Hy dropumpe 10 in the direction of smaller delivery volume, the Stellzy cylinder 14 must be subjected to a certain signal pressure, the z. B. is in the range of about 20 bar. Without this pressure in the pressure line 13 , the delivery volume of the hydraulic pump 10 can not be reduced, but is set to a maximum value.

The pressure line 13 leads to the inlet of a damming valve 25 , the sen valve member 26 by a compression spring 27 in the closing direction and the pressure prevailing in the pressure line 13 in the opening direction is acted upon. The accumulation valve 25 is closed below a minimum pressure, which may correspond to the signal pressure for the adjustment of the delivery volume of the hydraulic pump 10 or may be slightly above this pressure. When the minimum pressure is reached, it begins to open. The compression spring 27 can be a very soft spring, so that the pressure difference between the beginning of the opening and the complete opening of the damper valve 25 is very small.

On the output side, the dam valve is connected via a line 28 to a consumer unit 29 , which, for. B. can be a rotating Hy dromotor or a hydraulic cylinder including a directional valve.

On the line 28 , that is, at the consumer-side outlet of the accumulation valve 25 , a pressure relief valve 30 and a throttle valve 31 with their inputs are connected in parallel to one another. At their outputs, the two valves 30 and 31 are connected to the tank 12 . The throttle valve 31 has a throttle body 32 which is acted upon in the opening direction by a compression spring 33 and in the closing direction via a control line 34 by the consumer pressure prevailing in line 28 . Through a throttle cross-section 35 in line 34 , changes in consumer pressure only have a dampened effect on the pressure acting on the throttle body. The effective opening cross section of the throttle valve 31 has a maximum value when the pressure in the line 28 corresponds to the tank pressure. The opening cross section is zero, so the throttle valve is completely closed when the consumer pressure in line 28 is just as large or slightly larger than the minimum pressure that opens the dam valve 25 . Between the value zero and the maximum value, the opening cross-section is infinitely variable depending on the consumer pressure.

The pressure in the consumer line 28 is detected by a pressure sensor 36 , which has an electrical output signal which depends in a characteristic quantity on the level of the pressure in the line 28 . A control signal for the electromagnet 16 of the control valve 15 is generated from the electrical signal of the pressure sensor 36 in a control electronics 37 . The Fördervo lumen of the hydraulic pump 10 is adjusted taking into account the speed of the pump so that the desired pressure in the line 28 is set due to the flow rate. This pressure can also be less than the signal pressure for the adjustment of the delivery volume or less than the minimum pressure set on the dam valve 25 . If this is the case, the pressure drop across the dam valve 25 corresponds exactly to the pressure difference between the minimum pressure and the pressure to be regulated. The variable opening cross section of the throttle valve 31 ensures that the leakage through the throttle valve 31 is low when the consumer pressure is below the minimum pressure. The opening cross section is then only small. At a small below the minimum pressure Ver consumer pressure, the opening cross section of the throttle valve 31 is large, so that the pressure in the line 28 can be quickly reduced to whoever. The leakage is still only small because of the small consumer pressure, the pressure difference across the throttle valve 31 is also small.

Corresponds to the pressure to be regulated in line 28 to the minimum pressure or is greater than this, the dam valve 25 is open and in lines 13 and 28 there is the same pressure level.

The dam valve 25 , the pressure relief valve 30 and the throttle valve 31 are integrated according to FIG. 2 in a single valve unit with a common housing 45 . This housing be sits a bore 46 which is introduced into the housing from one side of the housing 45 and which is extended on the opposite side of the housing through a smaller diameter bore 47 and is open to the outside. The bore 47 forms the pump-side inlet of the dam valve 25 . Immediately above the step 48 formed between the two bores 46 and 47 , a connecting bore 49 opens radially into the bore 46 and forms the consumer-side outlet of the damming valve 25 and at the same time part of the line 28 . At a distance above the Anschlußboh tion 49 and the opposite ends in a tion to the Boh 46 running around the annular channel 50, another connecting bore 51, which is provided for connection to the provided in Fig. 1 by the reference numeral 12 tank.

In the bore 46 is open to the bore 47 and on the other side closed by a bottom 52 sleeve 53 is screwed, which is at a distance from the step 48 between the two bores 46 and 47 , at its inner end two diametrically opposite Has slots 54 and is provided at the level of the ring channel 50 with individual radial bores 55 through which a connection between the ring channel 50 and the inner space 56 of the sleeve 53 is created. The connection bore 51 or the ring channel 50 is through a first, arranged between the housing 45 and the sleeve 53 seal 57 to the lower part of the bore 46 and the connection bore 49 and through a second seal 58 arranged between the housing 45 and the sleeve 53 sealed the upper part of the bore 46 .

The dam valve 25 includes a closing body 65 , on which three parts, namely a frustoconical closing part 66 , a neck 67 and a piston part 68 can be distinguished. With the piston part 68 of the closing body is inserted into the guide sleeve 53, 65 and in the extent to the radial holes 55 towards ver pushed until the locking part 66, whose diameter is larger than the inner diameter of the sleeve 53 abuts against the end face of the sleeve. A seal 69 on the piston part 68 , which bears against the inside of the sleeve 53 , seals the two chambers of the interior 56 located on opposite sides of the piston part 68 from one another. The neck 67 of the closing body 65 is perforated by two cross-shaped radial bores 70 which in the center have a connection to an axial bore 71 leading through the piston part 68 into the neck 67 .

The closing body 65 interacts with its closing part 66 with a valve seat on the step 68 between the two bores 46 and 47 . At the same time, it serves on the outer edge of the Axialboh tion 71 itself as a valve seat for a further closing body 72 , which belongs to the pressure relief valve 30 and of the compression spring 27 located in the interior 56 of the sleeve 53 and supported on the bottom 52 with a truncated cone in the axis al bore 71 and is pressed against the closing body 65 . The compression spring 27 thus presses the closing body 65 against the housing 45 and is the dam valve 25 and the pressure relief valve 30 in common. It is designed so that the closing body 65 of the damper valve 25 lifts off its seat at the minimum pressure already mentioned. The seating area between the closing body 65 and the closing body 72 is significantly smaller than the seating area between the closing body 65 and the housing 45 selects ge, so that a much higher pressure than the minimum pressure, for. B. a pressure of 150 bar, is necessary to ben the closing body 72 from the then abutting the sleeve 53 closing body 65 .

Through the closing body 72 axially extends a double stepped bore 75 , the bore portion 76 with the largest diameter water is closed to the outside by a screw 77 . In the bore 75 a Na del 78 belonging to the throttle valve 31 is inserted, the diameter of which corresponds to the diameter of a central bore section 79 of the bore 75 and which has a cone tapering towards its front end with an edge on the one with the smallest diameter and to the axial bore 71 in the closing body 65 of the damming valve 25 open bore section 80 of the bore 75 defines an opening cross-section, the size of which depends on the position of the needle 78 relative to the closing body 72 . Through a bore 81 in the closing body 72, which extends approximately radially, the bore section 79 is connected to the tank connection 51 . The bore 61 opens in any position of the needle 78 in the region of its cone in the bore portion 79 , so it is closed by the needle 78 in no position. At the step between the two drilling sections 76 and 79 , a compression spring 82 is supported , which acts on the stopper ring 83, the needle 78 in the sense of an increase in the opening cross section of the throttle 31 .

The needle 78 is seen with a continuous axial bore 84 ver, so that between the bore body 76 of the closing body 72 , the locking screw 77 and the needle 78 limited pressure chamber 85 and the axial bore 71 in the closing body 65 there is a connection and in the axial bore 71 of the closing body 65 and the pressure prevailing in the connecting bore 49 can also build up in the pressure chamber 85 . The diameter of the bore 84 is chosen so that this bore represents a damping distance and changes in the pressure in the connection bore 49 propagate only damped into the pressure chamber 85 . If one disregards the cross section of the bore 84 , the pressure in the pressure chamber 85 acts on the needle 78 within a surface which corresponds to the cross section of the bore section 79 of the bore 75 . The pressure in the axial bore 71 acts within egg ner surface on the needle 78 , which corresponds to the cross section of the Bohrungsab section 80 . Corresponding to the differential area between the cross sections of the two mentioned bore sections, the pressure in the pressure chamber 85 generates a force which impacts the needle 78 in the direction of a reduction in the throttle cross section. Depending on the level of the pressure in the connection bore 49 and thus the pressure in the pressure chamber 85 , a balance between the spring force and the pressure force will occur in another position of the needle 78 , so that the opening cross section of the throttle 31 depends on the pressure in the connection bore 49 . The higher this pressure, the smaller the opening cross section.

It is now assumed that there is tank pressure in the connection bore 49 and the pressure in the bore 47 , that is to say at the inlet of the damming valve 25 and thus in the pressure line denoted by 13 in FIG. 1, is less than the minimum pressure of z. B. 20 bar, which is necessary to open the dam valve 25 . The Stauven til 25 is still closed. The pressure relief valve 30 is also closed. The throttle valve 31 has its largest opening cross-section, the needle 78 being pressed by the compression spring 82 against the locking screw 77 . Individual, not shown projections on the locking screw 77 or on the needle 78 ensures that a pressure can build up behind the Na del 78 . The largest opening cross-section is selected so that practically the entire pressure difference between the connection bore 49 and the connection bore 51 drops over the opening cross-section between the cone of the Na del 78 and the edge at the bore section 80 . After switching on the hydraulic pump 10 , the pressure at the inlet of the accumulation valve 47 increases very quickly to the minimum pressure, so that the accumulation valve 25 begins to open and a pressure builds up in the connection bore 49 , the pressure to be regulated being below the minimum pressure . With the pressure building up in the connection bore 49 , the pressure in the pressure chamber 85 also increases and pushes the needle 78 forward, the opening cross section of the throttle 31 being reduced. As soon as the desired pressure to be regulated is reached, the hydraulic pump 10 pivots back and only promotes so much Druckmit tel quantity that the control pressure is maintained. The dif ference between the minimum pressure and the control pressure drops via the dam valve, the closing body 65 of which does not abut the sleeve 53 in this case, but occupies an intermediate position between the seat on the housing 45 and the sleeve 53 .

If a control pressure that is higher than the minimum pressure is desired, the delivery rate of the hydraulic pump 10 is increased. As soon as the pressure in the connection 49 reaches the minimum pressure, the dam valve 25 is fully opened. The closing body 65 lies against the sleeve 53 . The needle 78 has reached the minimum pressure on the edge between the bore sections 79 and 80 of the bore 75 because the compression spring 82 is selected so that precisely at this pressure its force is overcome by the pressure force. The throttle 30 is now closed.

Only when the pressure in the connection bore 49 becomes so high that it generates such a force on the seat surface of the closing body 65 for the closing body 72 that the force of the spring 27 is overcome, does the pressure limiting valve 30 open, so that the pressure in the Connection bore 49 can no longer grow.

Claims (18)

1. Hydraulic system for acting on a hydraulic consumer ( 29 ) with a controlled consumer pressure with a hydraulic pump ( 10 ) from the pressure medium from a tank ( 12 ) can be sucked in and its delivery volume through an actuator connected to the pressure side of the hydraulic pump ( 10 ) ( 14 ) for regulating the consumer pressure is adjustable, with a between the hydraulic pump ( 10 ) and the consumer ( 29 ) switched damming valve ( 25 ), which opens at a sufficient pressure for adjusting the delivery volume of the hydraulic pump ( 10 ) and with one throttle valve ( 31 ) connected between the consumer-side outlet ( 49 ) of the accumulation valve ( 25 ) and the tank ( 12 ), characterized in that the effective opening cross section of the throttle valve ( 31 ) between a maximum value at a consumer pressure corresponding to the tank pressure and the value 0 at a consumer pressure above the minimum pressure, preferably continuously variable is. 2. Hydraulic system according to claim 1, characterized in that the throttle valve ( 31 ) has an adjustable throttle body ( 78 ) with a cone. 3. Hydraulic system according to claim 2, characterized in that the throttle valve ( 31 ) is a needle valve and has a guide bore ( 79 ) in which the adjustable throttle body designed as a needle ( 78 ) is guided. 4. Hydraulic system according to claim 1, 2 or 3, characterized in that an adjustable throttle body ( 78 ) of the throttle valve ( 31 ) is opened in the opening direction by a spring ( 82 ) be. 5. Hydraulic system according to claim 4, characterized in that the adjustable throttle body ( 78 ) can be acted upon by the consumer pressure in the closing direction. 6. Hydraulic system according to claim 5, characterized in that the adjustable throttle body ( 78 ) can be acted upon in the closing direction by a pressure which prevails in a rear pressure chamber ( 85 ) which has a cross-section of damping ( 84 ) with the consumer side Input ( 80 ) of the throttle valve ( 31 ) is connected. 7. Hydraulic system according to claim 5 or 6, characterized in that the throttle body ( 78 ) has an axially extending bore ( 84 ) via which a rear pressure chamber ( 85 ) with the consumer-side input ( 80 ) of the throttle valve ( 31 ) is. 8. Hydraulic system according to one of claims 4 to 7, characterized in that the adjustable throttle body ( 78 ) acting in the opening direction spring ( 82 ) outside of the flow path through the throttle valve ( 31 ) is arranged. 9. Hydraulic system according to claim 8, characterized in that the spring ( 82 ) in a rear, by an active surface of the adjustable throttle body ( 78 ) limited pressure chamber ( 85 ) is arranged. 10. Hydraulic system according to one of the preceding claims, characterized in that the throttle valve ( 31 ) has a linear throttle body ( 78 ) which can be flowed against by the pressure medium in the direction of the movement for opening the throttle valve ( 31 ). 11. Hydraulic system according to claim 10, characterized in that the adjustable throttle body ( 78 ) has a continuous axial bore ( 84 ) through which the consumer-side input ( 80 ) of the throttle valve ( 31 ) with a rear pressure chamber ( 85 ) connected is. 12. Throttle valve, in particular for use in a hydraulic system according to one of the preceding claims, characterized in that a throttle body ( 78 ) is provided which is rectilinearly adjustable relative to a throttle housing ( 72 ) and which is in the opening direction by a spring ( 82 ) and in the closing direction device can be acted upon by a closing force which can be generated on an active surface of the throttle body ( 78 ) by the pressure at the throttle inlet ( 80 ). 13. Throttle valve according to claim 12, characterized in that the throttle body ( 78 ) is guided in a receptacle ( 75 ) of the housing outside the pressure medium path and that at the rear end of the throttle body ( 78 ), the selkante with a Dros of the throttle housing ( 72 ) the throttle cross-section form the front end of the throttle body ( 78 ), a pressure chamber ( 85 ) is located, which is connected to the throttle input ( 80 ) in connection. 14. Throttle valve according to claim 13, characterized in that the pressure chamber ( 85 ) with the throttle input ( 80 ) is connected via a damping cross section ( 84 ). 15. Throttle valve according to claim 13 or 14, characterized in that the throttle input ( 80 ), seen from the rear end of the throttle body ( 78 ), beyond the throttle edge of the throttle housing ( 72 ). 16. Throttle valve according to claim 13, 14 or 15, characterized in that the connection between the pressure chamber ( 85 ) and the throttle input ( 80 ) is made via the throttle body ( 78 ). 17. Throttle valve according to claim 15 and 16, characterized in that the connection is formed by an axially through the throttle body ( 78 ) passing bore ( 84 ). 18. Throttle valve according to one of claims 13 to 17, characterized in that the throttle housing ( 72 ) is formed by the closing body ( 72 ) of a pressure relief valve ( 30 ).