EP1426499A1 - Method and apparatus for end stroke dampening in hydraulic actuators of mobile working machines - Google Patents

Abstract

The end of stroke damping system may be used for a mobile digging machine with two hydraulic cylinders (10,11). It has a control circuit (15) connected to position (17) and velocity sensors (16) on cylinders and closes throttle valves near the end of the stroke of each piston (18). End switches may be connected to a timer (19) in the control circuit. Three hydraulic pumps (1-3) draw hydraulic fluid from a tank (14) and pass it through three control valves (4-6).

Description

The present invention relates to a method and a device for damping movement of hydraulic cylinders of mobile machines, in particular Hydraulic excavators, whereby reaching is achieved by means of a position detection device a pre-end position of the hydraulic cylinder is detected before it is reached the end positions of the hydraulic cylinder reduces its speed of movement and the hydraulic cylinder to the respective end position at a reduced speed is driven. For this purpose there is a flow control element for throttling the inlet and / or the flow of the hydraulic cylinder provided by a Control device is activated accordingly when the pre-end position is reached, in order to throttle the volume flow that flows into and out of the hydraulic cylinder flows.

The damping of movement or end position switch-off of hydraulic cylinders ensures ensure that the speed of the hydraulic cylinder shortly before reaching the mechanical End stop is reduced to excessive mechanical stress of the steel components due to mass forces caused by the sudden deceleration to avoid and increase comfort during work. For one Such motion damping have been hydraulic as well as electrical solutions Shutdowns suggested.

Figure 7 shows a hydraulic solution. As shown therein, the drive takes place of hydraulic cylinders of earth-working machines such as hydraulic excavators and the like regularly via a hydraulic pump 1 and a downstream one Directional control valve 4. In the hydraulic cylinder 10 are in the end area of the piston and rod Geometric changes 13 attached, which changed when entering the Geometry 12 of the cylinder housing pressure build-up of the returning fluid cause.

The speed of the cylinder is determined by the delivery rate of the hydraulic pump 1 determined in the inlet to the cylinder. A damping effect only arises if the quantity in the feed to the cylinder is reduced. A reduction can can only be achieved by either the controller R of the pump 1 or a pressure relief valve 7 connected in the hydraulic circuit responds. The response of the pump regulator or the pressure relief valve is determined by the inlet pressure reached, which means that the dynamic pressure on the discharge side accordingly the ratio of the hydraulic cylinder must increase. The The pressure regulator of the pump or the pressure relief valve responds depending on Machine size between 300 and 350 bar pressure, so that on the inlet side of the Hydraulic cylinder a back pressure of 600 to 700 bar is required.

The dynamic pressure is reduced by throttling at the annular gap and special throttle cross sections reached, the throttling effect at the annular gap strongly dependent on the manufacturing tolerances and the viscosity of the fluid. Because of these deviations of geometry and fluid parameters the probability is high that either the dynamic pressure is not sufficient to activate the regulating elements, or that the dynamic pressure rises so high that the strength of the cylinder housing is at risk.

Because of these shortcomings, an electrical shutdown of the Inlet and outlet proposed. For systems with electro-hydraulic pilot control offers an electrical shutdown, with one limit switch per direction of movement of the cylinder is provided. Shortly before the end position of the A corresponding limit switch is passed over the cylinder, with the signal of which the Control device switches off the corresponding directional valve. It does so braking of the movement depending on the switching speed of the directional valve.

With this solution, however, what is stopped regularly too early or too late on the one hand means that the kinematics is not fully used or at least the mechanical end stop of the hydraulic cylinder at too high a speed is achieved. In the event of an uncontrolled shutdown, pressure peaks also occur on the outlet side and lack of filling on the inlet side, which leads to increased Load the lines and hydraulic components.

The present invention is therefore based on the object of an improved Method and an improved device for damping the movement of hydraulic cylinders to create the disadvantages of Avoid prior art and further develop the latter in an advantageous manner. Preferably, the mechanical end stop should be driven too high Speed safely avoided while still maintaining the kinematics of the hydraulic cylinder be fully exploited.

According to the invention, this object is achieved by a method according to the patent claim 1 and a device according to claim 7 solved. Preferred configurations the invention are the subject of the dependent claims.

According to the invention, a speed detection device is therefore provided, which the speed of movement of the hydraulic cylinder before reaching the respective end position recorded. The control device, which is the flow control element controls for throttling the inflow or outflow comprises a delay device, with the help of which the start time of the throttling depending on the detected movement speed is changed.

The flow control element is therefore dependent on the detected speed of movement of the hydraulic cylinder actuated sooner or later, so that the movement damping or speed reduction of the hydraulic cylinder sooner or later starts. The movement damping can in particular be related to the speed of movement be adjusted so that on the one hand reaching the mechanical End stop occurs, on the other hand reaching the end stop but only at the desired minimum speed.

In order to adapt the motion damping to the recorded speed, basically the throttle speed of the flow element, i.e. the speed, with which the volume flow is shut down can be changed. In order to allow simple control, however, is a further development of the invention preferably provided that the throttle speed of the flow control member regardless of the detected movement speed of the hydraulic cylinder is specified. The adjustment of the motion damping becomes alone thereby achieved that the start time of the throttling or the actuation time of the flow control element as a function of the detected speed is moved. However, it is quite possible here if several are used Flow control elements the actuation times of the control elements different to shift, so that there is a different damping characteristic overall results. However, here too, for each of the tax bodies Throttle speed per se are kept the same.

The start of damping is expedient with decreasing movement speed of the hydraulic cylinder is delayed, i.e. pushed back in time.

The adaptation of the starting time of the damping to the speed of movement can basically be done in different ways. To the control arrangement however, to keep it simple, is in the development of the invention Control device designed such that a fixed start time then always is specified if the detected movement speed is greater than or equal to is a predetermined limit speed, i.e. So that of the piston position detection device detected final position with a limit speed or at an even greater speed. In this case the damping initiated immediately. Is the movement speed recorded in the pre-end position however, below the limit speed, the starting time damping delayed by a certain period of time. The timespan, around the start of the damping or the time of actuation of the flow control member can be moved by the control device can be set variably. The control device preferably changes the Time span by which the damping is shifted, proportional to the detected one Speed when reaching the pre-end position.

In a further development of the invention, the speed detection device can have two end signal generators arranged one behind the other, which shortly before reaching the end position of the piston are run over, and a time recording device comprise the time span between the signals of the two end signal generators detected. The signal of the time recording device that the said period of time reproduces between the signals of the two end signals, forms the speed signal, that the control device of the control of the flow control member based sets.

The time span recorded, the crossing of the two arranged one behind the other End signal generator lasts, is then in a comparison device of the control device compared with a predetermined period of time. If the difference is negative, i.e. the recorded time is less than the specified time, the fixed earliest possible starting time of the damping determined by the control device. is the difference is positive, i.e. the recorded time is greater than the specified time, the Amount of the difference between the delay in the start of damping. In particular the starting time can be determined by the amount of the difference be moved backwards.

The speed detection device or its end signal generator can basically arranged at different locations and assigned to the hydraulic cylinder his. To create a simple arrangement and for both end positions only one pair of end signal transmitters can be provided on the piston rod of the hydraulic cylinder and / or a detection sensor coupled to it first and second markings can be provided, each one of the two end positions or pre-end positions of the piston. Both marks can are detected by a correspondingly arranged pair of end signal transmitters. It is accordingly only one detection device for detecting both end positions or only one detection device for detecting the speed Reaching both end positions provided.

The detection devices can preferably be integrated in the hydraulic cylinder be arranged in particular in the region of the collar of the hydraulic cylinder through which the piston rod exits.

According to a particularly advantageous embodiment of the invention, one of Hydraulic cylinder separate, but with this coupled detection transmitter provided be that moves according to the movement of the hydraulic cylinder. In particular, a rotary turntable can be provided here, the two Has markings of the aforementioned type. The position of the markings can be detected by appropriate end signal transmitters.

Fig. 1:

eine schematische Darstellung eines hydraulischen Antriebssystems für zwei Hydraulikzylinder eines Hydraulikbaggers mit einer Vorrichtung zur Bewegungsdämpfung nach einer vorteilhaften Ausführung der vorliegenden Erfindung, wobei das Antriebssystem als Dreipumpensystem dargestellt ist,

Fig. 2:

ein Stromzeitdiagramm, das den Verlauf des Ansteuerstroms für die Wegeventile des hydraulischen Antriebs aus Fig. 1 zur Erreichung der gewünschten Bewegungsdämpfung zeigt,

Fig. 3:

die Anordnung der Endsignalgeber zur Erfassung einer Vorendstellung und Geschwindigkeit des Kolbens des Hydraulikzylinders nach einer Ausführung der Erfindung, bei der vier Endsignalgeber vorgesehen sind, die eine Markierung an der Kolbenstange erfassen,

Fig. 4:

eine schematische Darstellung einer mit der Kolbenstange des Hydraulikzylinders gekoppelten Detektionsscheibe sowie die zugehörige Anordnung der Endsignalgeber einer Erfassungseinrichtung zur Erfassung der Vorendstellung und der Geschwindigkeit des Hydraulikzylinders für beide Bewegungsrichtungen,

Fig. 5:

eine schematische Darstellung einer in den Hydraulikzylinder integrierten Einrichtung zur Erfassung der Kolbenstellung und der Kolbengeschwindigkeit,

Fig. 6:

eine schematische Darstellung einer in den Hydraulikzylinder integrierten Einrichtung zur Erfassung der Vorendstellung und der Geschwindigkeit des Kolbens des Hydraulikzylinders nach einer weiteren Ausführung der Erfindung, und

Fig. 7:

eine schematische Darstellung eines hydraulischen Einpumpenantriebs eines Hydraulikzylinders mit hydraulischer Bewegungsdämpfung nach dem Stand der Technik.

The invention is explained in more detail below on the basis of preferred exemplary embodiments and associated drawings. The drawings show:

Fig. 1:

1 shows a schematic representation of a hydraulic drive system for two hydraulic cylinders of a hydraulic excavator with a device for damping movement according to an advantageous embodiment of the present invention, the drive system being shown as a three-pump system,

Fig. 2:

1 shows a current-time diagram which shows the course of the control current for the directional control valves of the hydraulic drive from FIG. 1 in order to achieve the desired movement damping,

Fig. 3:

the arrangement of the end signal transmitters for detecting a pre-end position and speed of the piston of the hydraulic cylinder according to an embodiment of the invention, in which four end signal transmitters are provided which detect a marking on the piston rod,

Fig. 4:

1 shows a schematic illustration of a detection disk coupled to the piston rod of the hydraulic cylinder and the associated arrangement of the end signal transmitters of a detection device for detecting the pre-end position and the speed of the hydraulic cylinder for both directions of movement,

Fig. 5:

1 shows a schematic representation of a device integrated in the hydraulic cylinder for detecting the piston position and the piston speed,

Fig. 6:

is a schematic representation of a device integrated in the hydraulic cylinder for detecting the pre-end position and the speed of the piston of the hydraulic cylinder according to a further embodiment of the invention, and

Fig. 7:

is a schematic representation of a hydraulic pump drive of a hydraulic cylinder with hydraulic motion damping according to the prior art.

As Figure 1 shows, the hydraulic cylinders 10 and 11, for example, the Lifting cylinders of a hydraulic excavator can be driven by a hydraulic drive, of the three hydraulic pumps 1, 2 and 3, each with one Regulator R can be regulated. The three hydraulic pumps 1, 2 and 3 are over one directional control valve 4, 5 and 6 each connected to the hydraulic cylinders 10 and 11, which are also connected in parallel to each other. Through the directional valves 4, 5 and 6 the inlets and outlets of the hydraulic cylinders 10 and 11 separated from the respective pumps 1, 2 and 3 and blocked or with the pump are brought into flow connection, the flow direction is reversible so that the hydraulic cylinders are extended and retracted can be. Upstream of the directional valves 4, 5 and 6 are in the by the pumps 1, 2 and 3 outgoing pressure lines pressure relief valves 7, 8 and 9 switched over the hydraulic fluid can be drained into the tank 14. The directional valves too 4, 5 and 6 are connected to the tank 14 via corresponding lines in the closed position, the fluid delivered by the pump and, if appropriate Switch position fluid returning from the hydraulic cylinders to run the tank.

The directional control valves 4, 5 and 6 are controlled by an electronic control device 15 driven to control the movement of the hydraulic cylinders 10 and 11.

The movement of the hydraulic cylinders 10 and 11 is on the one hand by a position detection device 17 monitors the approach of the piston rod to the indicates both end positions, in particular reaching a pre-end position indicates. On the other hand, by means of a speed detection device 16 detects the speed of the piston rod of the hydraulic cylinders 10 and 11, if they reach the above end position.

The speed detection and the detection of the pre-end position can be done in different ways. Figure 3 shows a speed detection device 16 in its simplest form. The speed is measured in each of the pre-end positions of the piston of the hydraulic cylinder by means of two limit switches S ₁ and S ₂ or S ₃ and S ₄ . A marking is attached to the piston rod 18, which is detected by the limit switches S ₁ to S ₄ when the piston rod is moved past it. The limit switches can be mechanical switches or inductive sensors. The limit switches S ₁ to S ₄ are assigned a time recording device 19 in the control device 15, which determines the time span that the successively arranged limit switches S ₁ and S ₂ or S ₃ and S ₄ take. The time it takes to drive over a pair of limit switches is a measure of the piston speed when the pre-end position is reached.

FIG. 4 shows a simplified solution of a speed detection device 16. Here, the limit switches S ₁ and S _{2 are} not arranged directly on the hydraulic cylinder or are not assigned directly to the piston rod 18, but are attached to the pivot point of corresponding equipment parts which are relative to one another by the hydraulic cylinders 10 and 11 be moved. For example, the rotary detection disc 20 with a moving part such. B. on the spoon with the bearing block of a hydraulic excavator or be formed by part of the bearing block. The limit switches in the form of inductive sensors S ₁ and S ₂ can with the counterpart, for. B. the arm of the hydraulic excavator. The markings 21, 22 are attached to the detection disk 20 such that they reach the limit switches S ₁ and S ₂ when the hydraulic cylinder reaches one of its pre-end positions.

Another preferred embodiment of a speed detection device 16 is shown in FIG. 5. In this embodiment, the path of the piston is detected via markings on the cylinder rod or piston rod 18 and corresponding limit switches or sensors S ₁ and S ₂ over the complete path of the piston. The sensors S ₁ and S ₂ are located in the unpressurized area of the piston rod bearing. Such a relative measuring system is expediently provided with a reference zero which is passed over at least once each time the machine is started.

For the present movement damping, the configuration of the position and speed detection device 16 or 17 shown in FIG. 6 is preferred in comparison thereto. The path of the piston rod 18 is only detected in the region of the two end positions, which is completely sufficient for hydraulic cylinders in which only the Motion damping according to the invention should take place. The limit switches S ₁ and S ₂ are in turn integrated into the hydraulic cylinder in the region of the piston rod bearing and detect markings on the piston rod 18 which are provided in their end regions. If the markings 21 or 22 reach the limit switches or end signal transmitters S ₁ and S ₂ , they emit a signal so that, in the manner described above, on the one hand the reaching of the pre-end position of the piston is indicated and on the other hand the speed of the piston is detected or can be determined.

The control device 15 shown in Figure 1 actuates the directional control valves 4, 5 and 6 Reaching the pre-end positions depending on the speed recorded as follows:

As FIG. 2 shows, a movement of the hydraulic cylinders 10 and 11 is initiated by the control of the directional valves 4, 5 and 6 at point P1. The control current is first increased to a 10% value such as 10, so that the start of movement of the hydraulic cylinders can be assumed in point 2. The pressure build-up and the acceleration of the hydraulic cylinders 10 and 11 take place along the control ramp between points P2 and P3. The hydraulic cylinders reach their maximum speed at 90% control current I ₉₀ , which is reached in point P3 of the diagram in FIG. From there, the maximum current Imax is reached in point P4, so that the hydraulic pistons run at full speed.

If the piston is moved accordingly to one of its end positions, the first end signal generator S ₁ is first run over in the direction of movement. In the diagram point P5 according to FIG. 2, the hydraulic cylinder is still driven at full speed, the first end signal generator S ₁ emitting its signal. Depending on the equipment component, a control piston of one of the directional control valves 4 or several control pistons of several directional control valves 4 and 5 is abruptly deactivated, so that the corresponding control current for these directional control valves suddenly drops from point P5 to point P6, ie to zero. The control pistons follow the current according to their dynamic properties.

The remaining control pistons continue to be driven with the full control current Imax until the second end signal generator S _{2 is also} run over and emits its corresponding signal. In the time recording device 19 of the control device 15, the time t _{K is} determined which was required to drive over both end signal generators S ₁ and S ₂ . A comparison and difference formation device 23 in the control device 15 compares the detected value t _{K of} the time period, which is a measure of the speed of the hydraulic cylinder, with a predetermined value t _S. If the detected time t _{K is} less than or equal to the value t _S , the damping process takes place along the line between the points P7, P8, P9, P10, P11, P12. This means that the recorded piston speed was greater than or equal to a limit speed. The damping process is initiated immediately.

However, if the detected time t _K is greater than the predetermined value t _S , the damping takes place with a time delay, specifically along the line between the points P7 ', P8', P9 ', P10', P11 'and P12'. The time offset t _F is selected by the control device 15 proportional to the time exceeding t _S , ie proportional to the amount by which the detected time t _{K is} greater than the predetermined time t _S.

The non-delayed damping process along the line between the points P7 and P12 and the time-delayed damping process along the line between points P7 'to P12' can be described as follows:

First, the control current for the remaining directional control valves 6 to n, ie for the directional control valves that were not immediately retracted when the first end signal generator S _{1 was} overrun, is reduced to the grade rule I _S. As a result of the jump, the control pistons of the directional control valves are suddenly brought into a position from which a braking effect occurs on the outlet side of the hydraulic cylinders 10 and 11.

Braking then takes place along the damping ramp from point P8 to Point P9 or from point P8 'to point P9'. Depending on the number of remaining A piston continues to run along the damping ramp up to the Points P11 or P11 ', where it is then switched off, i.e. the current will reduced to zero, as indicated by points P12 or P12 '.

The remaining control piston of the one way valve is driven along a control ramp from point P9 to point P10 or P9 'and P10', where it then reaches the outlet current I _A at point P10. With the outlet flow it is possible to reach the end position with full cylinder force.

The cut-off is initiated at point P13 by releasing the hand control. The current runs along the jump ramp from point P13 to point P14 and is then turned off along the line from point P14 to point P15.

It is understood that the damping process in the opposite direction after the same Scheme expires. The detection and direction detection takes place in reverse Direction.

If instead of the three pumps 1, 2 and 3 only one pump is used to feed the hydraulic cylinders, it goes without saying that the control piston of the corresponding directional control valve is not yet switched off when the first end signal generator S ₁ is passed over. The overall procedure then takes place as a function of the speed from when the second end signal generator S _{2 is passed} . Basically, n pumps can be used.

Claims (14)

1. Method for damping the movement of hydraulic cylinders (10, 11) of mobile work machines, in particular hydraulic excavators, in which, before reaching one of the end positions of the hydraulic cylinder (10, 11), its movement speed is reduced and the hydraulic cylinder (10, 11) is moved into the respective end position at a reduced speed , In order to reduce the speed by means of a flow control element (4, 5, 6), the inflow and / or outflow of the hydraulic cylinder (10, 11) is throttled, characterized in that the speed of movement of the hydraulic cylinder (10, 11) is recorded before the respective end position is reached and the starting time (P7, P7 ') of the throttling is changed as a function of the detected movement speed.
2. Method according to the preceding claim, wherein the throttle speed of the flow control member (4, 5, 6) regardless of the detected Movement speed of the hydraulic cylinder (10, 11) is specified.
3. Method according to one of the preceding claims, wherein the beginning of damping (P7, P7 ') with decreasing detected movement speed is delayed.
4. Method according to one of the preceding claims, wherein a fixed start time (P7) is specified if the detected movement speed is greater than or equal to a predetermined limit speed, and wherein the start time (P7 ') by a time period (t _F ) with respect to the fixed start time ( P7) is decelerated when the detected movement speed is less than the predetermined limit speed.
5. Method according to the preceding claim, wherein the time period (t _F ) changes as a function of the detected movement speed, preferably selected proportionally to the detected movement speed.
6. Method according to one of the preceding claims, wherein two end signal generators (S ₁ , S ₂ ) arranged one behind the other are passed before reaching the respective end positions, the time period (t _K ) between the passage of the two end signal generators (S ₁ , S ₂ ) is detected a time difference (δt) is determined from the detected time period (t _K ) and a predetermined time period (t _S ) and a delay (t _F ) of the starting time (P7 ') of the damping is determined according to the time difference (δt).
7. Device for damping the movement of hydraulic cylinders of mobile machines, in particular hydraulic excavators, according to the method according to one of the preceding claims, with a position detection device (17) for detecting a pre-end position of the hydraulic cylinder (10, 11), a flow control element (4, 5, 6) for throttling the Inlet and / or outlet of the hydraulic cylinder (10, 11), and a control device (15) for controlling the flow control member (4, 5, 6) when reaching the pre-end position, characterized in that a speed detection device (16) for detecting the speed of movement of the Hydraulic cylinder is provided when the pre-end position is reached and the control device (15) has a delay device for delaying the activation of the flow control member (4, 5, 6) as a function of the detected movement speed.
8. Apparatus according to the preceding claim, wherein the speed detection device (16) has two end signal transmitters (S ₁ , S ₂ ) arranged one behind the other and a time detection device (19) is provided which measures the time period (t _K ) between the signals of the two end signal transmitters (S ₁ and S ₂ ) recorded.
9. Device according to the preceding claim, wherein one of the end signal transmitters (S ₁ , S ₂ ) simultaneously forms the position detection device (17).
10. Device according to one of the preceding claims, wherein on the piston rod (18) of the hydraulic cylinder (10, 11) and / or a coupled thereto Detector (20) first and second markings (21, 22) are provided are, which each correspond to one of the two end positions and which both from the position detection device (17) and / or the speed detection device (16) can be recorded.
11. Device according to one of the preceding claims, wherein the speed detection device (16) in the hydraulic cylinder (10, 11) is integrated.
12. Device according to one of the preceding claims, wherein the speed detection device (16) separate from the hydraulic cylinder (10, 11) and is assigned to a detection transmitter (20).
13. Device according to one of the preceding claims, wherein the control device (15) a comparison device (23) for comparing the detected time period (t _K ) with a predetermined time period (t _S ) and for forming the difference between the two time periods (t _K , t _S ) and the delay device has a delay generator which, depending on the determined difference, preferably proportional to it, specifies the delay (t _F ) of the activation of the flow control member (4, 5, 6).
14. Device according to one of the preceding claims, wherein the position detection device (17) a hinge point of two components of the of the Hydraulic cylinder (10, 11) is assigned to the driven movement train and the position of the two components relative to one another.

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