DE19719228A1 - Hydraulic control device for load-independent control of a double-acting engine - Google Patents

Description

State of the art

The invention is based on a hydraulic Control device for load pressure independent control of a double acting motor according to the in the preamble of Claim 1 specified genus.

Such a hydraulic control device is already used load pressure compensated control of a double acting Motors known from DE 36 34 728 C2, two of which Directional control valves for parallel actuation of the assigned Motors from a common variable displacement pump with pressure medium are supplied, the controller with a control line a shuttle valve chain with the maximum load pressure of the two motors is applied. Here is with everyone Directional control valve the pressure compensator used for load pressure compensation downstream of a metering orifice on the control slide, the Pressure compensator also used for direction control Piston sections of the control spool is connected upstream. Of the Throttle valve in the downstream pressure compensator is in Opening direction from the pressure downstream of the orifice plate and in Closing direction of the highest load pressure and the Control pressure difference applied by the control spring. With  this arrangement can be a so-called Achieve oil flow sharing like many Use cases is required. Flows in here Parallel operation of two or more directional valves and not sufficient pump oil flow, i.e. in the event of an insufficient supply, less oil evenly over all orifices. The Pressure differences at the respective orifices are shown smaller and less oil flows to the engines. The oil flow through the directional valves increases in relation to the predetermined target values. So it is principally around a valve arrangement for dividing the pump flow into individual partial flows flowing to each motor, whereby also with different loads on the motors The division ratio remains constant and thus the movements be maintained without the standstill of the highly loaded engine comes. Despite the beneficial This hydraulic control device has oil flow distribution but the disadvantage of lack of security. So you can Load pressure is not sufficiently safe when the pump pressure drops hold when the pressure in the control circuit, for example Leakage or line break drops. He can also Key slide in the pressure compensator one Check valve function not fast enough perceive as it is via control circuits with shuttle valve chains is controlled. Furthermore, the directional valve has no second Individual orifice plate to measure the oil flow to the engine limit regardless of the slide deflection. From Another disadvantage is that the directional valve is not a fourth Has switching position for an open gear. Furthermore it is unfavorable that for the formation of the control circuit in Arranged inside the control slide connecting lines need to be relieved to the tank. This leads to a complex, expensive construction of the Spool.  

Furthermore, DE 40 26 720 A1 is a hydraulic one Control device for load pressure independent control of a Double-acting motor is known in which a pressure compensator upstream of that formed on the spool Orifice plate is switched. This directional valve can be used with a check valve separated from the pressure compensator Meet security requirements, with discharge a cross channel between the check valve and orifice plate controlled via a piston section of the control slide which is also designed as a full slide valve. Also points the directional control valve has a second individual orifice Limit the oil flow to. With this directional valve with the The orifice plate of the upstream pressure compensator becomes its Throttle slide in the closing direction from the pressure upstream of the Orifice plate on the control slide and in the opening direction from Pressure downstream of the orifice plate, i.e. plus the load pressure acted upon by the force of a spring. The pressure compensator holds thus the pressure difference across the measuring throttle on the directional valve constant even with different load pressure, so that too the associated flow rate remains constant and the am Directional valve set working speed is kept constant. A disadvantage of this Control device is that it is not a supply dependent Allows oil flow sharing. Be with such Directional control valves for several motors in parallel operation is controlled, the motor with the lowest is first Load pressure supplied with a pressure medium stream during the remaining rest of the volume flow to the other motors is directed. This changes the ratio of Distribution of volume flows, which is not constant here remains. Especially in the case of undersupply, this can lead to that the function of the least loaded engine remains in parallel, while the high-loaded one actuated engine stops, which in many Use cases is not desirable.

Advantages of the invention

The hydraulic control device according to the invention load-independent control of a double-acting Motors with the characterizing features of claim 1 on the other hand the advantage that it is at a supply-dependent oil flow distribution a higher degree Offers security and an extended usability. So can be arranged separately from the pressure compensator of the check valve in connection with the control of the Pressure relief in the cross channel directly above the Control spool achieve that the load pressure with falling Pump pressure can be kept safer and faster. This also applies if the pressure in the control circuit Leakage or line break decreases. The lines be formed as simply as possible in the control circuit, whereby Connecting lines in the spool itself are not required, see above that this as a simple, inexpensive building Full slide can be executed. Furthermore, can this design, the directional control valve with a fourth Equip switching position for an open gear, the with the load pressure line connected to the pump is relieved. Further With this directional valve, a second individual Integrate orifice plate, which the oil flow to the engine limited regardless of the deflection of the spool. Overall, the control device enables a relative simple and compact design. More beneficial Refinements result from the subclaims, the Description as well as the drawing.

drawing

An embodiment of the invention is shown in the drawing and explained in more detail in the following description. In the drawings Fig. 1 shows a longitudinal section through a hydraulic control device with a directional control valve and kcmbinierter pressure balance in a simplified illustration, Fig. 2 as a detail of a shuttle valve of a control circuit according to II-II in Fig. 1, and Figure 3 is a schematic representation of a control block for. two double-acting motors with two control devices according to FIG. 1.

Description of the embodiments

Fig. 1 shows a longitudinal section through a hydraulic control device 10 for the load pressure independent control of a double-acting motor. In the control device 10 , the actual directional valve 11 in load-sensing execution and the associated pressure compensator 12 are arranged in a common housing 13 .

The housing 13 has a longitudinal bore 14 extending between the two end faces, in which a total of seven chambers 15 to 21 are formed by annular extensions, of which the five adjacent chambers 15 to 19 serve to control the direction of the pressure medium flow, while the two outer chambers 20 , 21 are assigned to a metering orifice 22 , which is used to control the speed of the motor. Of the five adjacent chambers 15 to 19 , the middle chamber serves as an inlet chamber 17 , while the two chambers lying next to it form a first motor chamber 16 and a second motor chamber 18 , which are connected to a motor connection 23 or 24 . In addition to each motor chamber 16 , 18 there is a return chamber 15 and 19 , respectively, which are connected in a manner not shown to a return connection in the housing 13 . Of the two orifice chambers 20 , 21 , the first orifice chamber 20 located next to the second return chamber 19 serves as an outlet-side orifice chamber and the other as an inlet-side second orifice chamber 21 .

In the longitudinal bore 14 , a control slide 25 is guided tightly and slidably. The control slide 25 is divided into six piston sections 27 to 32 by annular grooves. The three piston sections 27 , 28 , 29 lying side by side are equipped with control edges and are used for directional control. An adjoining fourth piston section 30 , which lies in the drawn neutral position of the control slide 25 in the outlet-side measuring orifice chamber 20 , serves primarily to relieve a control circuit. The adjoining fifth piston section 31 is part of the measuring orifice 22 and, with its control edges, determines the size of the volume flow to the engine and thus its speed when the control slide is deflected into both working positions. The outer, sixth piston section 32 protrudes from the longitudinal bore 14 so that an actuating device, not shown, can act on it. At its opposite end, the control slide 25 projects with the first piston section 27 into a double-acting return device 33 , the type of which is known per se and which centers the control slide in its neutral position 34 , from which it can be deflected in two working positions 35 and 36 . Furthermore, the control slide 25 has a fourth switching position 37 , which is designed as an open position.

As FIG. 1 also shows, a second bore 39 is arranged in the housing 13 below the longitudinal bore 14 and a third bore 41 below it, all of which run parallel to the longitudinal bore 14 . The second bore 39 is formed like a blind hole and accommodates a check valve 42 with its spherical closing member 43 in its interior. In contrast, the third, multiply offset bore 41 runs between the two end faces of the housing 13 and, in addition to the pressure compensator 12, also accommodates a second individual measuring aperture 44 . To make this possible, the outlet-side measuring orifice chamber 20 has an extension 45 , which extends perpendicular to the control slide 25 and intersects the third bore 41 . In addition to this extension 45 , a circulation chamber 46 also extends perpendicularly to the longitudinal slide 25 in the housing 13 , into the end of which the second bore 39 opens into the slide-near end, while the end which is remote from the longitudinal slide 25 penetrates the third bore 41 . In this way, a wall of the housing 13 extending between the extension 45 and the circulation chamber 46 forms an annular web 47 which serves both as a control edge for the second measuring orifice 44 and for a throttle slide 48 of the pressure compensator 12 . The throttle slide 48 is designed as a hollow slide with a blind hole 49 and a radial bore 51 so that it connects the circulation chamber 46 with the outlet-side orifice chamber 20 in a throttled manner in the starting position centered by the control spring 52 . When the throttle slide 48 assumes its working position during operation, this connection is controlled via the radial bore 51 . The throttle slide 48 is acted on its right end face by the pressure in the extension 45 in the opening direction, that is, against the force of the spring 52 . The force of the control spring 52 and the maximum load pressure in the spring chamber 53 act on the throttle slide 48 in the closing direction and are fed from a control circuit via a control opening 54 .

As further shown in FIG. 1, a pressure tap opening 55 is located in the second bore 39 in the area between the check valve 42 protecting the inlet chamber 17 and the circulation chamber 46 , via which the maximum load pressure of the connected motor is tapped. As FIG. 2 shows in more detail, this pressure signal from the pressure tap opening 55 in the directional control valve 11 is compared in a shuttle valve 56 with another pressure signal from a second directional control valve 70 and the selected maximum load pressure signal is forwarded via a control channel 57 . Shuttle valve 56 and control channel 57 form parts of a control circuit 58 known per se, in which the maximum load pressure is selected in a manner known per se via shuttle valve chains and used for a load-sensing control.

While the supply-side Meßblendenkammer 21 connected to an inlet conduit 61, which connects the two flange surfaces of the housing 13 together, the drain-side Meßblendenkammer 20 communicates via a transverse passage 62 with the inlet chamber 17 in conjunction, wherein, in this transverse channel 62 in succession, the individual-metering orifice 44 the pressure compensator 12 and the separate check valve 42 are switched. The throttle slide 48 is thus downstream of the orifice 22 and is acted upon by control pressures such that a supply-dependent oil flow distribution is achieved with it.

Fig. 3 shows a schematic representation of a control block, wherein in addition to the first control means 10, a similar, second control means 70 are flanged together such that at least two double-acting motors are operated in parallel. The control devices 10 , 70 are connected between a connection plate 71 and an end plate 73 and connected in parallel to the continuous inlet channel 61 . The inlet channel 61 is supplied with pressure medium from a pressure medium supply unit 73 , the maximum load pressure being returned via the control circuit 58 . For this purpose, the shuttle valves 56 in both control devices 10 , 70 form a valve chain, via which the respective maximum load pressure is selected or the control circuit 58 is relieved.

The mode of operation of the control device 10 is explained as follows, the basic function of such load-sensing valves being assumed to be known per se. In the mutually identical, parallel-connected control devices 10, 70 is the pressure compensator 12 of the metering orifice 20 arranged downstream in each case and is also located upstream of the directional control edges by way valve. 11 The LS pressure tap, that is, the pressure tap opening 55 in the directional control valve 11 tapping the load pressure, is located between the pressure compensator 12 and the check valve 42 , so that the respective pressure signal is given to the control circuit 58 via the shuttle valve 56 . The highest load pressure selected in the control circuit 58 is passed on the one hand to the pump 73 and on the other hand into the spring spaces 53 of the pressure compensators 12 , this load pressure signal reaching the spring spaces 53 via control lines and the control openings 54 . On the opposite end face, the throttle slide 48 is acted upon by the pressure downstream of the measuring orifice 22 in the opening direction. This type of connection and the pressurization of the throttle slide 48 enables a supply-dependent oil flow distribution when the two control devices 10 , 70 are actuated in parallel.

Is shown in more detail in the neutral position 34, as shown in FIG. 1 and FIG. 3, the hanging on the Druckabgriffsöffnung 55 control circuit 58 through the circulation chamber 46 be controlled radial bore 51 and the blind bore 59 in the throttle slide 48, the extension 45, the discharge-side measuring orifice chamber 20 and the open control edge on the fourth piston section 30 to the second return chamber 19 are relieved. This also regulates the pump 73 to a low outlet pressure. This relief of the LS pressure line via the pressure compensator 12 and the control slide 25 is particularly simple and enables the control slide 25 to be designed as a full slide, which thus has no internal connecting bores. The same type of relief can also be achieved if the control slide 25 assumes its fourth switching position 37 for free movement.

If the control device 10 is actuated on its own and thereby deflected into one of the working positions 35 or 36 , control of the connected motor which is independent of the load pressure can be achieved. The volume flow arriving from the pressure medium supply unit 73 via the inlet channel 61 flows via the activated measuring orifice 22 and the downstream pressure compensator 12 and the check valve 42 into the inlet chamber 17 and further back to the engine or from the engine in the return. Before the throttle slide 48 in the pressure compensator 12 opens, it controls the relief connection via the radial bore 51 . Likewise, the control edge on the fourth piston section 30 closes the connection to the return chamber 19 before the measuring orifice 22 opens. In this way there is no loss of oil to the return. The pressure compensator 12 keeps the pressure drop across the measuring orifice 22 constant in a manner known per se, so that the speed of the motor is proportional to the deflection of the control slide 25 and is controlled independently of load pressure fluctuations. If the function of the pressure compensator 12 is impaired by leakage or a jamming shuttle valve, the check valve 42 can in any case close and prevent oil from flowing from the load in the direction of the pump connection. Regardless of the pressure conditions in the spring chamber 53 of the pressure compensator 12 , a load on the motor is securely held when the pump pressure drops. The check valve 42 designed as a seat valve ensures low leakage.

If both control devices 10 , 70 are actuated in parallel, this results in a supply-dependent oil flow distribution, which is also referred to as so-called social behavior.

The highest load pressure occurring on one of the motors is thus applied to all pressure compensators 12 of the control devices 10 and 70 . Thus, the throttle slide 48 of both pressure compensators 12 are set such that their end faces facing the respective measuring orifice 22 always have the same pressure even under different loads on the motors, so that the orifices 22 are flowed through by constant amounts of pressure medium in relation to one another. In principle, it is a valve arrangement for dividing the pump flow into individual partial flows flowing to each motor, the division ratio remaining constant even with different loads on the motors and the desired speed thus being maintained. If, in this parallel actuation of both control devices 10 , 70, there is not a sufficient pump oil flow, so that there is an undersupply, correspondingly less oil flows uniformly over all measuring orifices 22 . This is ensured by the downstream pressure compensator 12 , which always regulates the pressure to the highest load pressure plus the control pressure difference. The pressure differences at the orifice plates 22 become smaller and less oil flows to the engines. The oil flow through the directional control valves 11 decreases in relation to the predetermined target values.

The directional control valve 11 also has a fourth switching position, this free position 37 being achieved by pressing the control slide 25 into the housing 13 . In this release position, both motor connections 23 , 24 are connected to the return chambers 15 and 19 , and the LS pressure line is also relieved.

With the second individual orifice 44 , which is connected between the orifice 22 on the control slide 25 and the pressure compensator 12 , the volume flow can be limited independently of the stroke of the control slide 25 for the directional control valve 11 , as is known per se.

The design of the control device 10 with a pressure compensator 12 connected downstream of the measuring orifice 22 on the control slide 25 , with the check valve 42 separated from the pressure compensator 12 and with the relief of the LS pressure line 55 via the throttle slide 48 and the control slide 25 for the return, the control slide 25 is designed as a full slide valve, represents a particularly advantageous combination.

Of course, are shown on the embodiment shown Changes possible without departing from the spirit of the invention to deviate.

Claims (12)

1.Hydraulic control device for load pressure-independent control of a double-acting engine with a directional control valve, the housing of which accommodates a control slide in a longitudinal bore, which has piston sections serving to control the speed and direction of the engine, of which the piston section serving as a measuring orifice for speed control is connected to the control slide via a The cross channel on the housing side is connected to the piston sections for the direction control on the control spool, which are arranged separately, whereby in this cross channel a volume flow controlling 2-way pressure is switched, the throttle slide in the closing direction of a spring and a maximum load pressure and in the opening direction of the pressure in Cross channel downstream of the orifice and upstream of the pressure compensator and with a pressure tap opening for a control circuit, which is located downstream of the throttle valve in the cross channel and which via a relief device g on the piston valve to a return chamber can be relieved, characterized in that in the transverse channel ( 62 ) downstream of the pressure compensator ( 12 ) and upstream of the piston valve ( 25 ) a check valve ( 42 ) separate from the throttle valve ( 48 ) is connected, so that the pressure tap opening ( 55 ) upstream from the check valve ( 42 ), the relief device has a piston section ( 30 ) on the piston slide ( 25 ) which controls the connection between an outlet-side measuring orifice chamber ( 20 ) and the adjacent return chamber ( 19 ) and that the throttle slide ( 48 ) in its initial position ( 74 ) creates a throttled connection ( 51 , 49 ) between the pressure tap opening ( 55 ) and this orifice chamber ( 20 ) and blocks this connection ( 51 , 49 ) in its working positions ( 75 ). 2. Hydraulic control device according to claim 1, characterized in that in the transverse channel ( 62 ) downstream of the metering orifice ( 22 ) and upstream of the pressure compensator ( 20 ) a second individual metering orifice ( 44 ) is connected, which is in particular adjustable. 3. Hydraulic control device according to claim 1 or 2, characterized in that the piston slide ( 25 ) in addition to a neutral ( 34 ) and two working positions ( 35 , 36 ) has a fourth switching position ( 37 ) for free movement. 4. Hydraulic control device according to one of claims 1 to 3, characterized in that the control slide ( 25 ) is designed as a full slide without connecting lines for working or control pressure medium in its interior. 5. Hydraulic control device according to one of claims 1 to 4, characterized in that the housing ( 13 ) has two parallel to the longitudinal bore ( 14 ) for the control slide ( 25 ) bores ( 39 , 41 ), all of which lie in one plane and of which the second, middle bore ( 39 ) receives the check valve ( 42 ), while in the other, third bore ( 41 ) the pressure compensator ( 12 ) and the individual orifice plate ( 44 ) are arranged. 6. Hydraulic control device according to claim 5, characterized in that the central bore ( 39 ) is formed like a blind hole and protrudes with its inner end in a perpendicular to the longitudinal axis of the control slide ( 25 ) extending circulation chamber ( 46 ) which the third bore ( 41 ) penetrates. 7. Hydraulic control device according to claim 6, characterized in that the downstream orifice chamber ( 20 ) has a perpendicular to the spool ( 25 ) extending extension ( 45 ) which is substantially parallel to the circulation chamber ( 46 ) and the third bore ( 41 ) penetrates while the upstream orifice chamber ( 21 ) is connected to an inlet channel ( 61 ). 8. Hydraulic control device according to one of claims 1 to 7, characterized in that the orifice ( 22 ) associated orifice chambers ( 20 , 21 ) in the longitudinal bore ( 14 ) laterally next to the five working chambers ( 15 to 19 ) for direction control in the housing ( 13 ) are arranged. 9. Hydraulic control device according to one of claims 1 to 8, characterized in that the throttle slide ( 48 ) is designed as a hollow slide with blind hole ( 49 ) and for the relief control of the pressure tap opening ( 55 ) has a position-dependent override radial bore ( 51 ). 10. Hydraulic control device according to one of claims 6 to 9, characterized in that in the housing ( 13 ) between the circulation chamber ( 46 ) and the outlet-side measuring orifice chamber ( 20 ) wall in the third bore ( 41 ) forms an annular web ( 47 ) which forms the housing-side control edges for the throttle slide ( 48 ) and the individual metering orifice ( 44 ). 11. Hydraulic control device according to claim 10, characterized in that the ring web ( 47 ) lies approximately in the same radial plane as the discharge-controlling piston section ( 30 ) on the piston slide ( 25 ) in its neutral position ( 34 ). 12. Hydraulic control device according to one of claims 1 to 11, characterized in that the throttle slide ( 48 ) between its starting position ( 74 ) and its working positions ( 75 ) has a blocking position ( 76 ) in which the throttled connection ( 51 ) is controlled and the transverse channel ( 62 ) has not yet been opened.