EP1003939B1 - Hydraulic control device for a mobile machine, especially for a wheel loader - Google Patents

Description

The invention is based on a hydraulic control arrangement, for a mobile machine, especially for a wheel loader is used and the characteristics from the Preamble of claim 1.

According to the preamble of claim 1, there is already one hydraulic control arrangement known from document US-A-5034892. From DE 39 09 205 C1 it is known the pitch vibrations of wheel loaders, especially when the loading shovel is full and higher driving speed occur with a damping system to dampen the component of the hydraulic Control arrangement of the wheel loader is. For vibration damping are the generally two hydraulic lift cylinders for Lifting and lowering the loading bucket via a check valve on one Hydraulic accumulator can be connected via a hydraulic pump a filling line, which is in front of the directional control valve block from the Pump line branches, can be charged. The between the shut-off valve arranged on the hydraulic accumulator and the lift cylinders is closed as long as the shovel is working and can be opened by the driver or automatically, as soon as pitch vibrations occur while driving or as soon as the driving speed above a certain value, e.g. over 6 km / h lies.

The branch of the filling line in front of the directional control valve block brings with it that the hydraulic accumulator is not only one Actuation of the directional valve assigned to the lift cylinders, but when actuating any directional valve that leads to a Pressure build-up in the pump line leads, is charged. For example, can also operate the hydraulic steering the steering machine belonging to the working machine to an inflow lead from pressure medium to the hydraulic accumulator. Then it is the check valve is still open, so an uncontrolled movement can occur the lift cylinder take place.

Another damping system against pitching vibrations, that too Part of the hydraulic control arrangement of a work machine is known from DE 41 29 509 C2. It branches the filling line from a work line, which between the Lift cylinders and the directional valve assigned to them runs. The check valve arranged in the filling line is pressure-controlled and can differ from that in the work line Load pressure of the lift cylinder against the storage pressure, of which a rear control chamber on the valve member of the check valve is acted upon, and against the strength of a weak Pressure spring can be opened. So the memory pressure is only slightly smaller than that during a work cycle occurring maximum load pressure of the lift cylinder. The rear control area is used to dampen the pitching vibrations the check valve is relieved to the tank via a pilot valve, so that the check valve opens and pressure medium freely between the hydraulic accumulator and the lift cylinders pushed back and forth can be.

It is also known in a hydraulic control arrangement with a hydraulic cylinder and with a directional valve with which the Pressure medium paths between a pressure chamber of the hydraulic cylinder, a pressure medium source and a tank are controllable unlockable check valve to be provided with which the pressure chamber is largely leak-free shut off when the directional valve is in its rest position. At the inflow of Pressure medium to the pressure chamber opens the check valve in its forward direction. For the discharge of pressure medium the pressure chamber, it must be unlocked, what of a second to a second pressure chamber of the hydraulic cylinder leading working line can happen from.

A pressure rupture valve can also be used in a pressure chamber of a hydraulic cylinder be upstream, usually immediately sits on the hydraulic cylinder. A pipe rupture safety valve is designed so that the pressure chamber has a pressure medium check valve opening towards the pressure chamber without further ado can flow. For the discharge of pressure medium from the pressure chamber becomes a bypass to the check valve more or less wide open. Such as. known from DE 32 39 930 C2, a control piston is adjusted proportionally. He can to the pipe rupture valve from the above The same pilot pressure is applied to the document, with which the directional valve moves in one direction is controlled.

The invention has for its object a hydraulic Control arrangement with the features from the preamble of the claim 1 evolve so that the pressure chamber of a hydraulic cylinder can be blocked off, but that nevertheless connection necessary for damping pitching vibrations can be produced to a hydraulic accumulator.

This task is accomplished with a hydraulic control arrangement with the features from the preamble of claim 1 the characterizing part of claim 1 solved in that an unlockable check valve is available, which the Pressure chamber of the hydraulic cylinder is connected upstream and towards it opens when you actuate the directional valve in the sense the discharge of pressure medium from the pressure chamber to the tank and upon actuation of the control valve in the sense of manufacture a fluidic connection between the pressure chamber and the hydraulic accumulator can be controlled. That way you can Pressure chamber connected to the hydraulic cylinder and hydraulic accumulator even if one leads to the hydraulic accumulator branch line between the directional valve and the check valve to a working line leading from the directional valve to the hydraulic cylinder is connected so that the check valve also with respect this branch line perform its blocking function can. Under an unlockable check valve is common also a bypassable check valve, e.g. at Pipe rupture safety valves are present, understood.

Advantageous configurations of a hydraulic system according to the invention Tax arrangement can be found in the subclaims.

According to claim 2, three control lines are provided, wherein the third control line, to the unlocking means of the check valve are connected via switching means when actuated of the directional valve with a first control line and at an actuation of the control valve with a second control line is connected. Basically there are also electrical ones Control lines, electrical control signals and electrical Switching means conceivable.

However, the check valve can very often be unlocked hydraulically. An advantageous embodiment with regard to a hydraulic Unlockable check valve is specified in claim 3.

If the directional control valve can be operated hydraulically, then is a Pilot oil circuit with a pilot oil source available which according to claim 6 expediently also the control oil for the unlocking of the check valve is removed. Usually are used for hydraulic actuation of the directional valve on the Pilot valves working on the basis of pressure reducing valves uses an inlet connection and an outlet connection and one connected to a control room on the directional valve Own exit. There is a constant maximum in the inlet connection Pilot pressure. In the exit is depending on the adjustment of a pressure reducing valve compared to the maximum Pilot pressure reduced pressure with which the Directional control valve is applied. Depending on the amount of pressure on The directional valve becomes different at the outlet of a pressure reducing valve adjusted proportionally. It is expedient now the second control line to the part of the pilot oil circuit connected in which the maximum pilot pressure prevails.

A pilot oil circuit is not necessary if according to claim 7 the control chamber of the check valve via the second Control line can be connected to the hydraulic accumulator. Operational namely the hydraulic accumulator up to the load pressure, primarily until a maximum pressure is always reached by highest occurred in the pressure chamber of the hydraulic cylinder Load pressure charged so that when the control chamber is connected of the check valve with the hydraulic accumulator one for opening sufficient pressure force is available stands.

This ensures with great certainty that at non-actuated directional valve and non-actuated control valve no pilot pressure builds up in the control chamber of the shut-off valve, there is a changeover valve according to claim 8, via in a first switch position, which it is when not activated Control valve occupies the second control line with tank connected is. As a changeover valve that is the third control line in the sense of a maximum pressure selection either with the first Control line or connects to the second control line, can then use a simple hydraulic shuttle valve become.

Several embodiments of a hydraulic according to the invention Control arrangement are shown in the drawings. Based on these exemplary embodiments, the invention will now be closer explained.

Figur 1

das erste Ausführungsbeispiel, bei dem eine Steuerkammer eines entsperrbaren Rückschlagventils aus dem Vorsteuerkreislauf zur Betätigung des Wegeventils über ein Umschaltventil und ein Wechselventil mit Druck beaufschlagbar ist,

Figur 2

die zweite Ausführung, bei der die Druckbeaufschlagung des Steuerraums am Rückschlagventil vom Hydrospeicher aus erfolgt und

Figur 3

die dritte Ausführung, bei der eine erste Steuerleitung oder eine zweite Steuerleitung über ein elektrisch betätigbares Umschaltventil mit einer zur Steuerkammer des entsperrbaren Rückschlagventils führenden dritten Steuerleitung verbindbar ist.

Show it

Figure 1

the first embodiment, in which a control chamber of an unlockable check valve from the pilot circuit for actuating the directional valve can be pressurized via a changeover valve and a shuttle valve,

Figure 2

the second version, in which the control chamber is pressurized at the check valve from the hydraulic accumulator and

Figure 3

the third embodiment, in which a first control line or a second control line can be connected via an electrically actuated changeover valve to a third control line leading to the control chamber of the unlockable check valve.

The hydraulic control arrangements shown are each for wheel loaders, tractors, telescopic handlers or other machines provided and comprise a control block 10 with several Directional control valves, in particular with a directional control valve 11, the can take a spring-centered position and with the two hydraulic cylinders designed as differential cylinders 12 can be controlled with which e.g. the boom of a wheel loader can be raised and lowered. The directional valve 11 has a first working connection 13, of which a first working line 14 to the bottom pressure chambers 15 of the hydraulic cylinders 12 leads. A second working line 16 runs between a second working connection 17 of the directional valve 11 and the piston rod-side pressure chambers 18 of the hydraulic cylinders 12. Via a pressure connection and a tank connection the two working connections 13 and 17 with a pressure medium source and connected to a tank 27.

A filling line 20 branches off from the working line 14 leads to a hydraulic accumulator 21 via a check valve 22. The Check valve 22 is designed as a 2-way cartridge valve and has a movable valve member 23. This is a step piston the one with the face of the smaller one in diameter Piston section in the manner of a seat valve on a Seat cone can sit on. On the said face the valve member 23 from the prevailing in the working line 14 Pressure, that is, the load pressure of the two hydraulic cylinders 12 in the opening direction applied. On the ring surface between the Both piston sections of the valve member 23 act via one Terminal 61 of a plate 26 in which the valve member 23rd the accumulator pressure is in the opening direction. In the closing direction the valve member 23 from one to the rear Control room 24 prevailing pressure and a compression spring 25 applied, which is equivalent to a pressure of about 3 to 4 bar is.

On the plate 26 with the 2-way cartridge valve 22 are two further valves built. The first valve 30 is a 3/2-way valve with a first input 31, which with the between the working line 14 and the check valve 22 section the filling line 20 is connected, and with a second Input 32, which is connected to the hydraulic accumulator 21. An output 33 of the directional control valve 30 is dependent on Load pressure in the working line 14 either with the input 31 or connectable to the input 32. It works in the sense a connection of the output 33 to the input 32 a adjustable compression spring 34 on the not shown Valve member of the valve 30. In the sense of a connection of the Output 33 with the input 31, the valve member of the Pressure in the inlet 31, i.e. from the load pressure of the hydraulic cylinders 12 applied.

A control channel 41 leads from the outlet 33 of the directional control valve 30 a port P of a control valve 42, which is a 4/2-way valve is. Its valve member takes effect a compression spring 43 a rest position in the passage exists between the port P and a port A, which with the control chamber 24 of the check valve 22 is connected. On Tank connection T and another connection B of the control valve 42 are locked in its rest position. The tank connection is through the housing of the various valves Channels with a leakage connection Y of the plate 26 connected. The port B of the control valve 42 is connected to the rear control space of a second located in the plate 26 located 2-way cartridge valve 45 connected through which pressure chambers 18 of the hydraulic cylinder 12 on the piston rod side a tank port T of the plate 26 can be connected. The valve member of the control valve 42 may be an electromagnet 44 are brought into a switching position in which the port P shut off and the two ports A and B connected to the terminal T.

So that the bottom pressure chambers 15 of the hydraulic cylinder 12 in the rest position of the directional valve 11 shut off without leakage oil are these pressure rooms in the work management 14 located unlockable check valve 50 upstream, that opens to the pressure rooms. The check valve 50 can be unlocked hydraulically. To do this is at a tax chamber 51 a control line 52 connected to the versions according to Figures 1 and 2 with the output of a shuttle valve 53 is connected. The control line 52 is the third control line within the meaning of the claims. Between the one input of the shuttle valve 53 and the working line 16, which to the piston rod side pressure chambers 18 of the Hydraulic cylinder 12 leads, extends a control line 54, which is the first control line in the sense of the claims. Another control line 55, the second control line in For the purposes of the claims, runs according to the explanations Figures 1 and 2 between the second input of the shuttle valve 53 and a connection 56 of a 3/2-way valve 57, the movable valve member under the action of a compression spring 58 assumes a rest position in which the connection 56 with a tank port T is connected, and an electromagnet 59 can be brought into a position in which the Port 56 is connected to a pressure port P.

In the embodiment according to FIG. 1, the directional valve 11 is the Control blocks 10 can be actuated hydraulically in proportion, wherein the pilot pressures with the help of a hydraulic pilot device 65 generated and via control lines 66 to the directional control valve 11 are given. The control oil supply is used Control oil pump 67, from which a pressure line 68 to the pilot control unit 65 leads. Through a pressure relief valve 69 is in pressure line 68 a pressure of e.g. Maintain 30 bar. This is the maximum pilot pressure with which the directional valve 11 can be applied. The pressure port P of the Switch valve 57 is connected to the pressure line 68.

Should the piston rods of the hydraulic cylinders 12 be extended the directional valve is actuated in such a direction, that the working line 14 pressure medium from a hydraulic pump can flow. The check valve 50 opens and the Piston rods extend, the hydraulic cylinders in the pressure chambers 15 12 as well as in the working line 14 by the Load moved by the hydraulic cylinders more specific Load pressure prevails. As long as the load pressure in the work line 14 below that on the compression spring 34 of the directional valve 30 set pressure remains, this switches the memory pressure via the control valve 42 to the rear control chamber 24 of the check valve 22 through. The load pressure now opens that Check valve 22 whenever it is at least the Force of the compression spring 25 equivalent small pressure difference is above the store pressure. It can then overpressure the filling line 20 get into the hydraulic accumulator 21, so that this one can be seen from the force of the weak compression spring 25 down, always on the largest during a work cycle occurred load pressure in the working line 14 charged is. It should be noted that the check valve 50 can be equipped with a closing spring. The Pressure in the line section of the working line 14 between the directional control valve 11 and the check valve is then one the force of this closing spring is equivalent to a small pressure difference greater than the pressure in the pressure chambers 15 of the hydraulic cylinders 12. Do you make the equivalent pressure differences of the Closing spring and the compression spring 25 of the valve 22 are the same large, the pressure in the hydraulic accumulator 21 is equal to the largest pressure occurred in the pressure rooms 15. If the load pressure able to overcome the force of the compression spring 34 at the valve 30, the check valve 22 remains closed. Because after one Switching of the valve 30 is in the rear control room 24 of the check valve 22 of the load pressure, so that in association with the compression spring 25, the check valve 22 is held securely. The pressure in the hydraulic accumulator 21 can therefore be that at the compression spring 34 of the valve 30 do not exceed the set value. For safety reasons, however, there is also a pressure relief valve 60 provided, the input with the hydraulic accumulator 21 is connected.

In the working line 16 and in the piston rod side Pressure chambers 18 of the hydraulic cylinders 12 prevail during the extension the piston rods a pressure close to the tank pressure.

It is assumed that the loading bucket of a wheel loader is loaded and driven to an unloading point with the wheel loader. Arbitrarily by the driver when pitching vibrations occur, or automatically at a certain speed the mobile work machine, e.g. at a speed of 6 km / h, the solenoid 44 of the control valve 42 and the electromagnet 59 of the changeover valve 57 energized so that these two valves from those shown in Figure 1 Rest positions in the other switching position switch. Now the rear control chamber 24 of the check valve 22 via the control valve 42 to the Y port Plate 26 connected and thus relieved to tank 27.

The valve member 23 of the check valve 22 is the storage pressure and lifted from its seat by the pressure in the working line 14. The control line 55 is via the changeover valve 57 connected to the pressure line 68, so that at one input of the shuttle valve 53 a pressure in the amount of the maximum Pilot pressure pending. This pressure is there on the other Input of the shuttle valve 53 There is tank pressure from the shuttle valve on the control line 52 and from there into the control chamber Given the unlockable check valve 50. This opens, so that an open connection between the hydraulic accumulator 21 and the pressure chambers 15 of the hydraulic cylinders 12 consists. Because the memory pressure during the work cycle corresponds to the maximum pressure reached when opening the last opening valve 22 or 50 no sagging of the piston rods the hydraulic cylinder 12, but at most one the bucket is lifted slightly. It may be that while of the working cycle load pressures occur which the valve 30 switch and therefore the charge level of the Hydro accumulator does not follow. However, these load pressures occur only in special situations, e.g. when tearing one off Object anchored in the ground or when driving the loading shovel against a stop, but are not through the weight of the loading shovel and the cargo determines that only works when driving the wheel loader. The state of charge of the Hydraulic accumulator 21 is therefore always sufficient around the loading shovel to keep at the level of this when opening the valve 22 or the valve 50 occupies.

About this also by switching the control valve 42 opened valve 45 can pressure fluid from the piston rod side Pressure chambers 18 of the hydraulic cylinder 12 displaced into the tank become. Refill can be done using refill valves, which are assigned to the directional valve 11. So that can Volume changes of the pressure spaces 18 are compensated for during the open connection of the pressure chambers 15 to the hydraulic accumulator 21 occur.

The embodiment according to FIG. 2 is largely the same as that according to Figure 1, so that only the differences in the following discussed, but otherwise to the description of the execution is referred to Figure 1. There is now a hydraulic one Line 75 between the pressure port P of the changeover valve 57 and a connector 60 of the plate 26, the intern is connected to a second terminal 61 which in the Connection between the check valve and the hydraulic accumulator 21 lies. At the pressure port P of the switching valve 57 is therefore the memory pressure. Because the hydraulic accumulator during the work cycle always with the limitation mentioned above the highest occurred in the pressure chambers 15 of the hydraulic cylinders 12 Load pressure is charged at random or automatic actuation of the changeover valve 57, which takes place together with the actuation of the control valve 42, the accumulator pressure is available to the check valve 50 to unlock. The directional control valve 10 can as be hydraulically actuated in the embodiment according to FIG. However, it is also an electrical or mechanical one Operation possible. A pilot oil circuit is not necessary.

The embodiment according to FIG. 3 is also correct with regard to the Control block 10, the hydraulic cylinders 12, the hydraulic accumulator 21, the valves 22, 30, 42, 45 and 50 with the designs according to Figures 1 and 2 match. With the embodiment according to FIG. 2 there is further agreement in that the check valve 50 to unlock from the hydraulic accumulator 21 with Pressure is applied. However, it is now the shuttle valve 53 according to Figure 2 replaced by a changeover valve 75, the under assumes a rest position due to the action of a compression spring 76, in which the third control line 52 with the first Control line 54 is connected. The valve 75 can by a Electromagnet 77, the same with the electromagnet 44 of the control valve 42 is driven into a second Switch position in which the third control line 52 is connected to the second control line 55 which leads directly to connection 60 of plate 26. A relief the control line 55 to the tank is therefore in execution not provided according to Figure 3, but could also be there e.g. be made possible by a further changeover valve.

Claims (9)

1. A hydraulic control arrangement for a mobile working machine, in particular for a wheel loader, having at least one hydraulic cylinder (12) with the aid of which a working tool can be moved, having a directional control valve (11) for controlling the pressure-fluid channels between a pressure chamber (15) of the hydraulic cylinder (12), a pressure-fluid source and a tank (27), having a hydraulic accumulator (21) which can be connected to the pressure-fluid source via a filling line (20), and having a control valve (42) with which a connection between the hydraulic accumulator (21) and the pressure chamber (15) of the hydraulic cylinder (12) can be controlled to open and close, characterized by a pilot-operated shut-off valve (50) which is connected upstream of the pressure chamber (15) and opens toward it and can be controlled to open when the directional control valve (11) is actuated to allow pressure fluid to flow off from the pressure chamber (15) to the tank (27) and when the control valve (42) is actuated to establish a fluid connection between the pressure chamber (15) and the hydraulic accumulator (21).
2. A hydraulic control arrangement according to Claim 1, characterized in that, when the directional control valve (11) is actuated, the shut-off valve (50) can be supplied with a control signal via a first control line (54) and, when the control valve (42) is actuated, can be supplied with a control signal via a second control line (55), and by the fact that there are switch-over means (53, 75) which, as a function of the actuation of the control valve (42), connect a third control line (52) running between them and the release means (51) of the shut-off valve (50) to the first control line (54) or the second control line (55).
3. A hydraulic control arrangement according to Claim 2, characterized in that the shut-off valve (50) is hydraulically releasable and has a control chamber (51) to which the hydraulic third control line (52) leads, in that there is a switch-over valve (53, 75) which can be actuated by means of the control valve (42), and in that the third control line (52) is connected to the hydraulic first control line (54) in one control position of the switch-over valve (53, 75) and when the directional control valve (11) is actuated to allow pressure fluid to flow off from the pressure chamber (15) of the hydraulic cylinder (12); and is connected to the hydraulic second control line (55) in the other control position of the switch-over valve (53, 75).
4. A hydraulic control arrangement according to Claim 3, characterized in that the first control line (54) is connected to a second pressure chamber (18) of the hydraulic cylinder (12).
5. A hydraulic control arrangement according to Claim 3, characterized in that the directiorial control valve can be actuated hydraulically by applying a pilot pressure to it and that the pilot pressure is also present in the first control line.
6. A hydraulic control arrangement according to any of Claims 3 to 5, characterized in that there is a pilot oil circuit with a pilot oil source (67) and the directional control valve (11) can be actuated hydraulically by the inflow of pilot oil from the pilot oil circuit, and that the shut-off valve (50) can be released by inflow of pilot oil from the pilot oil circuit via the second control line (55).
7. A hydraulic control arrangement according to any of Claims 3 to 5, characterized in that the control chamber (51) of the shut-off valve (50) can be connected to the hydraulic accumulator (21) via the second control line (55).
8. A hydraulic control arrangement according to Claim 6 or 7, characterized in that there is a switch-over valve (57), and that the second control line (55) is connected to the tank (27) in a first control position of the switch-over valve (57) and to a pressure-fluid source (21, 67) in a second control position of the switch-over valve (57).
9. A hydraulic control arrangement according to Claim 8, characterized in that there is a shuttle valve, (53) which acts in such a way as to select the maximum of the pressures in the first control line (54) and the second control line (55) and in each case connects that line of these two control lines (54, 55) in which the higher pressure occurs to the third control line (52).

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