EP2029815B1 - Method for the positionally correct orientation of working equipment which is arranged in a tiltable manner on a lifting frame, which can be raised and lowered, of a working machine - Google Patents

Description

The invention relates to a method for the positional alignment of tiltable arranged on a lifting and lowering mast of a working machine working equipment, wherein the working equipment is moved by means of a tilt cylinder relative to the mast, wherein the working equipment is connected via a Gelenkhebelmechanimus with the piston rod of the tilt cylinder, said the tilting cylinder is supplied with hydraulic oil of a hydraulic pump for the working hydraulics via a directly actuated control slide, and secondary consumers of the working machine are supplied with hydraulic oil by at least one further hydraulic pump.
Furthermore, the invention relates to a work machine with a liftable and lowerable mast and with respect to the mast tiltable arranged by a tilting work equipment, the working equipment is connected via a toggle mechanism with the piston rod of the tilting cylinder and the tilting cylinder via a directly operated spool with a hydraulic pump for the working hydraulics is connected, and wherein at least one further hydraulic pump is provided, wherein the further hydraulic pump is connected via a switching valve simultaneously with the two hydraulic ports of the tilting cylinder, wherein the switching valve is actuated via a control device.
Mobile machines, especially wheel loaders, have work equipment, which are mounted on the frame of the machine by means of a lifting and lowering mast. For a speedy workflow, it is expedient that the work equipment (especially when working with a bucket) after emptying the same in a raised position of the mast after lowering it automatically returns to a position at ground support, which without readjustment by the driver continued work, ie a new recording of material in favorable angular position of Shovel bottom, so approximately parallel to the ground, allows. Depending on the given conditions, it is advantageous to be able to preset the blade bottom in the direction of a certain positive or negative angle of attack. Wheel loaders of a certain size, such as at a starting weight from 7 t, today usually have a hydraulic pilot control for the spool on the lifting and Schaufelkippwerk and occasionally also additional functions are served. In such equipped with a feedforward control for the spool wheel loaders, it is known to provide Rückführautomatiken which bring after activation, the bucket back to the neutral position, ie that position in which it will impinge parallel or with a desired angle to the ground. For this purpose, intervenes in the feedforward control for the tilting function of the blade triggering hydraulic circuit to allow the automatic return in the desired manner in function. The intervention in the pilot control also offers the advantage that only a small flow of oil can be controlled at low pressures.

Such low oil flows offer the advantage that the switching times of the therefore only small nominal sizes having solenoid valves are low. However, the valve piston to be guided by spring force into its middle position after reaching the corresponding angular position of the blade has a certain positioning time. Since the tilting cylinder or cylinders are acted upon during this switch-off by the hydraulic pump for the working hydraulics and their flow is dependent on the prevailing in this period speed of the drive motor, thereby conditions a different wake of the tilt cylinder after a shutdown signal, which causes the When the ground level is reached, the bucket does not appear parallel to the ground (or at the specified desired angle of attack). This disadvantageous for the loading blade position is either acceptable or it can be achieved by additional measures a largely independent of the engine speed blade position, such as in DE 44 37 300 C2 described.

These above-described known Rückführautomatiken are thus suitable only for work machines having a hydraulic pilot control for the spool. However, wheel loaders of lower weight classes up to about 6 tons are often directly controlled, i. The control lever actuated by the driver acts via a deflection linkage directly on the pistons of the spool valve. Thus, in such work machines, there is no hydraulic pilot control for the spool that would allow for an implementation of known automatic recirculation actuators. In work machines, especially wheel loaders of this type, therefore, the kinematics systems for lifting and tilting are mainly designed so that the blade is completely dumped in the upper Hubrahmenstellung and impinges when lowering the hoist with its bottom approximately parallel to the ground on this. However, this only applies when lowering from the uppermost Hubrahmenstellung. If the bucket is lowered in a maximum tilted position from a lower lifting height, there are strong deviations from the parallelism.

A serious disadvantage arises in such a design of the kinematics system when working with a forklift fork. Since the tilt angle of the blade for a favorable material absorption from the bottom layer increases at least in the first stroke range, the angular position of the forklift fork will also take such a course, so that the driver has to correct when lifting continuously to keep the forklift tines in an approximately ground-parallel position , Dangerous conditions arise, however, when with Bodenparalleler zinc position a load, e.g. picking up a loaded pallet from medium lifting height, such as during unloading of trucks or railway carriages, and then lowering it. In this case, unless carefully controlled by the driver, the tines incline increasingly forward, so that the charge can slide off these.

As wheel loaders of this weight class are increasingly being used to a large extent for stacking work, the design of the kinematics systems today is that the forklift fork over the entire stroke range is performed in parallel. But this has the consequence that when using a Loading bucket this, when the lifting frame is lowered with completely dumped bucket, the bucket then strongly tilted forward with the blade blade or with mounted teeth with these on the ground. Thus, there is a need for a Rückführautomatik for machines with directly operated spool.

In a directly controlled spool, however, the tilt piston for the tilting mechanism can not be used for the blade return, because this would have to move independently of the control lever, which holds the driver in the hand. This would be possible only by a complex separation of the control linkage from the spool with inserted insertion of an adjusting cylinder or the like. Already for reasons of space, this option is largely eliminated, since the Umlenkgestänge is often mounted directly on the spool housing. Therefore, the required for a Rückführautomatik flow would have to be taken directly between the pump for the working hydraulics and the spool, which would require a valve of large nominal size on the one hand, but on the other hand would not allow the driver to operate the lifting function during the automatic Rückkippvorganges. After automatic termination of the Rückkippvorganges then the pump current would act on the sink side of the lifting cylinder abruptly, causing the lowering behavior changed to a hard-to-recognize time for the driver. Such a solution is therefore eliminated.

A work machine with the features of the preamble of claim 3 is made US-A-535620 known. In this work machine, an additional hydraulic pump is provided, which alone serves to actuate the tilt cylinder, which is correspondingly expensive.

The object of the invention is to provide as simple as possible, possibly also retrofitted Rückführautomatik for the tilting work equipment a working machine with a directly operated spool valve for the tilting cylinder.

This object is achieved in a method of the type described in the present invention, that after actuation of a trigger element by the driver, the two hydraulic connections of the cylinder designed as a differential cylinder tilting cylinder via a switch actuated by a control valve are simultaneously connected to the hydraulic pump for the auxiliary consumers and thereby the tilt cylinder is moved in the direction of the neutral position of the working equipment, wherein the position of the tilting cylinder is determined and monitored by the control device of the changeover valve, and that the control device of the changeover valve on reaching the predetermined neutral position of the tilting cylinder switches the changeover valve in a position in which the two hydraulic connections of the Tilting cylinders are shut off by the hydraulic pump for the auxiliary consumers.

According to the invention, it is thus provided that for the realization of the automatic return system not the flow of the pump is used for the working hydraulics, but the flow rate of the pump for the secondary consumers. This can e.g. either be removed in front of the hydraulic motor for the fan of the oil cooler, wherein during the short period of Rückkippvorganges then the fan in the usually existing freewheeling circuit runs and experiences only a slight speed drop, or even after the fan. In this case, the fan motor is then acted upon at its outlet opening with the pressure required for the tipping back of the blade, which, however, can be absorbed by the fan motor.

The supply of the oil to the tilting cylinder via a laid in the direction of the hydraulic pump for the auxiliary consumer electromagnetic switching valve. This switching valve has a circuit diagram that when switching on the feedback mechanism via the trigger element (switch) directs the flow of oil to the two ports of the tilt cylinder so that it is acted upon by the principle of a differential cylinder, ie the extension speed of the piston rod is released from that of her , determined by the flow rate of the pump to be filled volume.

In the usual area ratio of piston rod to cylinder of about 1: 4 corresponding to a relative to the cylinder diameter about half the piston rod diameter, the piston rod is extended at a certain flow four times as fast as in the application of the cylinder only on the piston side. Since the flow rate of the hydraulic pump used for the secondary consumers is only about half as large as the flow rate of the hydraulic pump for the working hydraulics, thus the piston rod is extended at about twice the speed compared to the use of the pump for the working hydraulics. Thus, even after triggering of the automatic feedback system in the case of lifting frame positions below the maximum height, it is still achieved that the working equipment (for example a blade) already strikes the ground in its ground-parallel end position. Especially with wheel loaders of the aforementioned weight class (up to about 6 t), this is for a speedy workflow of great advantage in which often material is poured only on a heap, the lifting frame does not need to be raised to its uppermost position.

The position of the tilting cylinder is determined and monitored by the control device of the changeover valve and the control device of the changeover valve switches on reaching the predetermined neutral position of the tilting cylinder, the changeover valve in a position in which the two hydraulic connections of the tilting cylinder are shut off by the hydraulic pump for the auxiliary consumers. In this way, an exact alignment of the work equipment is ensured in the predetermined neutral position.

As a switching valve, a 4/2-way valve is preferably used.

To solve the problem initially set, the invention also provides a working machine with the features of claim 3.

In a particularly preferred embodiment it is provided that in the hydraulic line between the switching valve and the hydraulic port on the Piston rod side of the tilt cylinder a check valve is provided. This check valve ensures proper operation even if the driver at the same time actuates the control slide in the direction of tilting when the automatic return mechanism.

The above-described solution also makes it possible, in the case of working machines, in particular loaders with directly actuated slide valves, to have a blade return automatic of simple construction, which nevertheless still has advantages over the previous systems with control slides with hydraulic pilot control:
Thus, high adjustment speeds are achieved as a result of the differential circuit of the tilt cylinder, so that when loading, for example, trucks, in which the front blade area immersed in wheel loaders of the aforementioned magnitude below the upper edge of the truck,
the waiting time after triggering of the automatic feedback system is low and the loader can return due to the rapidly tilted blade. This high adjustment speed allows even when emptying the blade at not completely raised lifting frame a ground-parallel impact of the blade during the lowering process.

Due to the differential circuit of the tilt cylinder with an approximately four-fold increase in speed, the pump can be used for the auxiliary consumers with a smaller displacement than the pump for the working hydraulics to achieve compared to previous systems still superior and meet all operating requirements increasing the adjustment speed. Thus, all components forming the system can be kept small due to the lower flow rate.

The desired end position of the working equipment (e.g., bucket) is approached with high repeatability even at different engine speeds and thus different flow rates of the pump, since the shutdown takes place only via a small valve size solenoid valve. Such solenoid valves have shutdown times of less than 50 ms. In contrast, in conventional systems, in which the Kippwerkkolben the spool over the feedforward takes over the shutdown of the return operation, the end position of the blade from the currently prevailing engine speed greatly influenced, since the actuating time of a here also existing solenoid valve still added to the tilting piston, which a Is multiple of that of the solenoid valve. To compensate for this, additional devices are required in known systems.

In the solution according to the invention, neither in the event of unintentional triggering of the automatic feedback system nor in the event of overloads Set critical or unforeseeable operating conditions for the driver. This also applies to an actuation of the tilting mechanism of the spool in any adjustment during the course of the automatic return operation. Equipping during final assembly of the machine or retrofitting after delivery is easy to carry out, all existing components on the working machine remain unchanged. It only need to be connected in addition to the easy-to-install electrical-electronic elements for signaling hydraulic lines small nominal diameter.

Fig. 1

einen Hydraulikschaltplan für einen nicht im Einzelnen dargestellten Radlader und in den

Fig. 2 bis 6

die einzelnen Betriebszustände des die Rückführautomatik betreffenden Teils des Hydraulikschaltplanes nach Fig. 1.

The invention is explained in more detail below by way of example with reference to the drawing. This shows in

Fig. 1

a hydraulic circuit diagram for a non-illustrated wheel loader and in the

Fig. 2 to 6

the individual operating states of the part of the hydraulic circuit diagram relating to the automatic return system Fig. 1 ,

From a wheel loader, not shown, a mast 1 is shown schematically. This mast 1 can be raised and lowered at a pivot point 2 and mounted on a wheel loader frame, not shown. At the lower end of the mast 1 a working equipment is articulated at a point of articulation 3, which is formed in the embodiment in the form of a blade 4. This blade 4 is about a hinge mechanism 5, 6 by means of a generally designated 7 tilting cylinder relative to the mast 1 about the pivot point 3 pivotally.

The tilting cylinder 7 has a piston rod 8 and a piston 9 and is opposite to the piston rod 8 End in a pivot point 10 also hinged to the frame of the wheel loader.

At the end region of the piston rod 8 situated outside the tilt cylinder, a support rod 11 is fastened which carries at its free end a control lug 12 which forms part of a tilt cylinder position determination device. On the tilting cylinder 7 itself, a component designed as a proximity switch 13 in this example is arranged as a second part of the tilting cylinder position determining device, which is in operative connection with an electronic control device 15 via an electrical signal line 14, the function of which will be explained in more detail below. Of course, the tilt cylinder position determination device can also be realized in other ways. It is essential that it is able to detect that position of the tilt cylinder 8, which is the predetermined in Fig. 1 shown neutral position of the blade 4 relative to the ground 16 corresponds.

The working machine, in this case the wheel loader, has a drive motor, for example a diesel engine 17, which drives three hydraulic units, namely a preferably adjustable hydrostatic drive 18, a hydraulic pump 19 for the working hydraulics of the wheel loader and at least one further hydraulic pump 20 for secondary consumers. In this case, hydraulic oil is conveyed from the hydraulic aggregates 18, 19, 20 out of a tank, generally designated 21, or conveyed back into it.

The hydraulic pump 19 for the working hydraulics is used inter alia for a normal operation of the blade 4 by the driver via the tilting cylinder 7. For this purpose, the pump 19 is connected via a hydraulic line 22 to a control slide 23 which can be actuated directly by the driver by means of control levers 24 is. The spool valve 23 is connected via a hydraulic line 25 to the piston side 26 and via a hydraulic line 27 to the annular space 28 of the tilting cylinder 7. Further, a line 29 is provided to the tank 21.

The hydraulic pump 20 for the auxiliary consumers is used, for example, to supply or drive a fan motor 30 of a fan 31. The hydraulic pump 20 is connected via two hydraulic lines 32 and 33 to the fan motor 30, wherein between the two hydraulic lines 32 and 33, an electromagnetic 4/2 -Wegeventil 34 is arranged. In the in Fig. 2 shown rest position of the valve 34, the fan motor 30 is connected to the hydraulic pump 20. A pressure relief valve 42 secures the hydraulic pump 20 from.

The solenoid valve 34 also has two ports 35, 36, wherein the terminal 35, a hydraulic line 37 is connected, which is in communication with the annular space 28 of the tilting cylinder 7, wherein in this line, a check valve 38 is arranged. To the terminal 36, a hydraulic line 39 is connected, which is in communication with the piston side 26 of the tilting cylinder 7.

The electromagnetic 4/2-way valve 34 is connected via an electrical signal line 40 to the control device 15, which in turn is in turn connected to a trigger element 41 designed as a switch.

If the driver wants to trigger the return mechanism, he actuates the switch or the trigger element 41, whereby the control device 15, the 4/2-way valve 34 in the switching position according to Fig. 1 3 brings, in which both the oil flow of the hydraulic pump 20 and the displaced from the annular space 28 of the tilting cylinder 7, via the terminal 35 flowing oil flow together via the port 36 of Piston side 26 of the tilting cylinder 7 are supplied, so that the tilting cylinder 7 is acted upon by the principle of a differential cylinder, ie the extension speed of the piston rod 8 is determined by the released by the flow of the hydraulic pump 20 to be filled volume. In this position of the solenoid valve 34, the fan motor 30 is decoupled from the hydraulic pump 20.

The piston rod 8 of the tilting cylinder 7 is extended as long as the hydraulic pump 20 and thus guided the blade 4 in neutral position until it is determined by the Kippzylinderpositionsbestimmungseinrichtung 12, 13 that the predetermined desired maximum extension position of the piston rod 8 and thus the desired neutral position of the blade. 4 is reached. Via the signal line 14, a corresponding signal is output to the control device 15, which the 4/2-way valve 34 in the in Fig. 2 shown rest position brings, so that a further oil flow to the tilting cylinder 7 is excluded from the hydraulic pump 20.

In the Fig. 2 to 6 now the individual operating states of the automatic feedback are shown.

According to Fig. 2 the automatic feedback system is not switched on. The solenoid valve 34 switches the flow rate of the hydraulic pump 20 to free passage to the secondary consumer (s) (eg, fan motor 30). The terminals 35, 36 of the tilt cylinder 7 are locked by the solenoid valve 34, so that upon actuation of the tilt cylinder 7 via the spool 23 by the driver (via the control lever 24) no mutual interference is given.

In the in Fig. 3 As shown, the automatic return system has been switched on by the driver via the triggering element 41. The flow of the hydraulic pump 20 flows together with the displaced from the annular space 28 of the tilt cylinder 7 oil the piston side 26 of the tilt cylinder 7 to. Due to the connection made in the solenoid valve 34 both sides of the cylinder prevails in this also the same pressure. The output to the outside via the piston rod 8 corresponds to the product of the hydraulic pressure and the piston rod surface. The tilting mechanism of the spool valve 23 is not actuated, so that the oil of the hydraulic pump 19 for the working hydraulics largely flows without pressure into the tank 21. Upon reaching the bottom-parallel position corresponding blade position, determined by the Kippzylinderpositionsbestimmungseinrichtung 12, 13, the solenoid valve 34 turns off again and it follows the wiring diagram Fig. 2 ,

In the presentation according to Fig. 4 the tilting cylinder 7 is additionally applied in the direction of "tilting" by the driver during the automatic Rückkippvorganges. The piston rod 8 continues to drive, however, the differential action of the tilting cylinder 7 is repealed, since the annular space 28 of the tilting cylinder 7 is connected via the spool 23 to the tank 21. In this case, the check valve 38 in the hydraulic line 37 prevents the flow rates of the two hydraulic pumps 19 and 20 can not flow to the annulus 28 of the tilt cylinder 7, but as intended only to the piston side 26. The displaced from the annulus 28 oil flow is directly into the tank 21st directed. After reaching the bottom parallel position corresponding cylinder position, the solenoid valve 34 switches off again and there is again a circuit diagram for the automatic return Fig. 2 , but where, if the driver continues to keep the tilting mechanism switched over to the control slide 23 to "tilt", the blade 4 continues to move in this direction.

In the in Fig. 5 the situation shown is the tilt cylinder 7 during the automatic tipping by the driver additionally applied in the direction of "dumping". Although such a procedure in a loader has no practical meaning, but should be made to the fact that then a Auskippvorgang, as the driver obviously wanted done. Through the opening of the return flow channel in the control slide 23, both oil flows are conducted from the piston side 26 of the tilt cylinder 7 into the tank 21, while the hydraulic pump 19 for the working hydraulics promotes into the annular space 28, which, however, again via the check valve 38 and the solenoid valve 34 the piston side 26 of the tilting cylinder 7 is in communication. As a result of the weight of the implement and in dependence on the flow resistance in the lines, the spool 23 and the solenoid valve 34, the speed of the retracting piston rod 38 determined. In any case, the blade 4 moves in the direction specified by the driver Auskipprichtung.

At the in Fig. 6 the situation shown acts on the blade 4, a larger load F in the direction of "dumping", which exceeds the holding force due to the differential circuit of the tilt cylinder 7 after activating the Rückführautomatik. This may be the case if, due to the sticking of larger amounts of material, the blade 4 has only partially emptied or if, when working with a tree or pipe clamp, the driver in forward inclined position of the blade 4 while still holding the load unintentionally the switch 41st operated for the Rückführautomatik. Then, although the tilting cylinder 7 tends to retract, however, the check valve 38 prevents the pressure built up on the piston side 26 of the tilting cylinder 7 from propagating into the annular space 28. It can be a hydraulic holding force of the tilt cylinder 7 in the size of the product of the piston surface and the pressure of Adjust the relief valve 42 so that the external load can be held in position. In this case, the hydraulic pump 20 promotes the secondary consumers via the pressure relief valve 42 in the tank. If the driver then actuates the function "tilting" via the spool valve 23, the annular space 28 of the tilting cylinder 7 is released via the return passage in the spool valve 23 and the piston rod 8 extends in the desired direction.

Claims (5)

1. Method for the positionally correct orientation of working equipment (4) arranged on a liftable and lowerable lifting frame (1) of a working machine in a tiltable manner, wherein the working equipment (4) is moved relative to the lifting frame (1) by means of a tilting cylinder (7), wherein the working equipment (4) is connected to the piston rod (8) of the tilting cylinder (7) by means of an articulated lever mechanism (5, 6), wherein the tilting cylinder (7) is supplied with hydraulic oil from a hydraulic pump (19) for the working hydraulic system by a direct-operated control valve (23), and wherein secondary consumers of the working machine are supplied with hydraulic oil from at least one other hydraulic pump (20),
   wherein
   following operation of a triggering element (41) by the driver, the two hydraulic connections (25, 27) of the tilting cylinder (7) designed as a differential cylinder are also connected to the hydraulic pump (20) for the secondary consumers by a switch-over valve (34) activated by a control device (15) thereby moving the tilting cylinder (7) in the direction of the neutral position of the working equipment (4), wherein the position of the tilting cylinder (7) is determined and monitored by the control device (15) of the switch-over valve (34), and wherein, on reaching the pre-set neutral position of the tilting cylinder (7), the control device (15) of the switch-over valve (34) switches the switch-over valve (34) into a position in which the two hydraulic connections (25, 27) of the tilting cylinder (7) are shut off from the hydraulic pump (20) for the secondary consumers.
2. Method according to claim 1,
   characterised in that
   a 4/2-way directional control valve is used as switch-over valve (34).
3. Working machine with a liftable and lowerable lifting frame (1) and working equipment (4) arranged in a tiltable manner relative to the lifting frame (1) by means of a tilting cylinder (7), wherein the working equipment (4) is connected to the piston rod (8) of the tilting cylinder (7) by means of an articulated lever mechanism (5, 6) and the tilting cylinder (7) is connected to a hydraulic pump (18) for the working hydraulic system by means of a direct-operated control valve (23), and wherein at least one further hydraulic pump (20) is provided, wherein the further hydraulic pump (20) is connected to the two hydraulic connections (25, 27) of the tilting cylinder (7) by means of a switch-over valve (34), wherein the switch-over valve (34) can be actuated by a triggering element (41) by means of a control device (15), wherein the tilting cylinder (7) is designed as a differential cylinder,
   characterised in that
   the further hydraulic pump (20) is provided for secondary consumers, and that the further hydraulic pump (20) is also connected to the two hydraulic connections (25, 27) of the tilting cylinder (7) by means of the switch-over valve (34),
   wherein the tilting cylinder (7) is provided with a device for detecting (12, 13) the position of the tilting cylinder which is connected to the control device (15).
4. Working machine according to claim 3,
   characterised in that
   the switch-over valve (34) is configured as a 4/2-way directional control valve.
5. Working machine according to claim 3 or 4,
   characterised in that
   a non-return valve (38) is provided in the hydraulics line (37) between the switch-over valve (34) and the hydraulic connection (27) on the piston rod side (28) of the tilting cylinder (7).

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