DE102009058406A1 - Charge detection system - Google Patents

Abstract

Disclosed is a load detection circuit with a load detection valve, which is acted upon at its two control sides with the pressure in the chambers of a cylinder as a consumer, depending on whether a pulling or pushing load acts on a cylinder rod of the cylinder, a corresponding load on one of the two control sides - (Over-) pressure is applied, whereby one of two tensile or compressive load indicating outputs of the load detection valve is acted upon by the pressure representing the net load as the reference pressure.

Description

The present invention relates to a load detection circuit having a load detection valve for detecting and converting a load pressure prevailing at a load into a (reference) pressure usable for controlling a hydraulic system.

For the control of a hydraulic system, it is generally necessary to detect the load applied to a hydraulic load and to generate a control signal representing it. This signal in turn serves as a reference pressure signal for controlling / regulating hydraulic system own components such as a hydraulic pump, control valves, etc.

Different solutions for detecting the load applied to a load and for providing a load-representative pressure signal are known from the prior art.

As a solution example here is the stepped piston according to the 4 called. Such a stepped piston has an equal area ratio as the example designed as a hydraulic cylinder consumer and is connected in parallel to the consumer. Accordingly, the stepped piston undergoes load application of a load comparable to the consumer deflection depending on the spring stiffness / spring hardness, with which the stepped piston is clamped, from which then a statement about the load acting on the consumer net load can be taken.

Another solution example shows the 5 from which a preferably designed as a hydraulic cylinder consumer can be removed, at the annular and piston chamber each have a pressure sensor is connected. Depending on the pressure load within the ring and piston chambers, both sensors generate an electrical signal that is fed to an electronic control unit which calculates the net pull / pressure load from this and provides a representative (electrical) pressure signal.

From the above description of the generally known prior art, it follows that in a conventional load detection, an electrical signal is generated as a reference pressure signal. When such a signal is to be used, for example, to actuate a hydraulic-mechanical valve, the electrical reference pressure signal must first be converted back into a hydraulic signal by means of a further valve. This is expensive and requires appropriate space for the arrangement of the necessary valves. Also, not every control, in particular in mobile hydraulics, has corresponding control electronics. Incidentally, the same applies to stationary hydraulic drives.

It is also known from the prior art to control hydraulic components of a hydraulic system exclusively on the basis of hydraulic control signals (without the interposition of electronics). As an example, the so-called load-sensing may be mentioned here, according to which both the pressure and the volume flow of a hydraulic pump are adapted to the conditions demanded by a consumer.

Specifically, in a load-sensing hydraulic system, the controlled variable is the pressure drop across a consumer control valve (proportional valve) of the hydraulic system. On the basis of this pressure gradient in the case of an actuation of the consumer, a pressure regulating valve is displaced, via which a hydraulic actuating cylinder of a variable displacement pump is actuated. However, in this arrangement, only the quantity of pressure medium supply requested by the consumer can be used as an absolute reference value for regulating the variable displacement pump.

In view of this problem, it is the object of the present invention to produce a hydraulic signal without the use of electronics, which represents a quantitative and qualitative measure of the load on a consumer.

This object is achieved by a load detection circuit with a load detection valve (load detection piston) having the features of patent claim 1. Advantageous embodiments of the invention are the subject of the dependent claims.

Essentially, the essence of the invention consists in that the instantaneous load pressure at a consumer is converted directly into a (reference) pressure which distinguishes a tensile / compressive load. This pressure can then be used for load-dependent control of a hydraulic system. More specifically, a load detection valve (pressure valve) is provided, which is acted upon at its two control sides with the pressure in both chambers of a cylinder as a consumer. Depending on whether a pulling or pushing load acts on a cylinder rod, a corresponding load (over) pressure (in particular a load pressure or a load overpressure) is applied to one of the two control sides, as a result of which the load detection valve receives one of its two, traction or overpressures Pressure load indicating outputs with a pressure representing the net load (reference pressure) acted upon.

It is advantageous if a first control side of the load detection valve has a ( pressure-chamber-shaped) piston chamber pressure portion fluidly connected to a piston chamber of the cylinder and having a piston chamber pressure fluid isolated (pressure chamber-shaped) Zuglastleitungsabschnitt which is connectable to an annular chamber of the cylinder. Further, a second control side of the load detection valve has a (pressure-chamber-shaped) annular chamber pressure section connected to the annular chamber of the cylinder and a fluid-isolated (pressure chamber-shaped) pressure load line section connectable to the piston chamber of the cylinder.

Preferably, the load detection valve has a valve piston which, depending on the current pressure situation on the two control sides (pressure difference), is displaceable from a neutral position blocking all valve connections to a second switching position, in which the piston chamber pressure section of the first control side is connected to the pressure load line section of the second control side and ( or) is displaceable in a third switching position, in which the annular chamber pressure portion of the second control side is connected to the Zuglastleitungsabschnitt the first control side.

In this way it is possible, depending on whether the piston chamber is under pressure in the case of a compressive load or the annular chamber in the case of a tensile load, this pressure in the associated pressure measuring chamber, namely the pressure load line section or Zuglastleitungsabschnitt as a representative (reference) pressure tap and hydraulic regulation.

Preferably, the piston chamber pressure portion of the first control side and the pressure load line portion of the second control side, the same pressure application area on the valve piston, which is different from the also same pressure application surface of the annular chamber pressure portion of the second control side and the Zuglastleitungsabschnitts the first control side. In this way, the load detection valve can be matched to the geometric conditions of the cylinder, so that, for example, a pressure bias of the cylinder piston from the load detection valve is not displayed. However, it should be noted that, for example, in the case of a synchronous cylinder, all of the above-mentioned pressure application surfaces can be the same.

The invention will be explained below with reference to preferred embodiments with reference to the accompanying drawings.

1 shows a hydraulic circuit for load detection by means of a load detection valve (pressure valve) according to a first preferred embodiment of the invention,

2 shows a longitudinal section of the load detection valve according to the 1 .

3 shows a hydraulic circuit for load detection by means of a load detection valve (pressure valve) according to a second preferred embodiment of the invention,

4 shows a stepped piston for load detection according to a prior art and

5 shows a pressure sensor arrangement for load detection according to the prior art.

In the 1 a hydraulic circuit with respect to the detection of a load acting on a cylinder by means of a load detection valve according to the invention is shown schematically.

As a result, a cylinder has 1 an annular chamber 1a and a piston chamber 1b , the fluid-tight from an axially movable (cylinder) piston 2 are separated. The piston chamber 1b is via a piston chamber line 4 and the annular chamber 1a is via an annular chamber line 6 to a not further shown hydraulic system for actuating the cylinder 1 connected. Parallel to the cylinder 1 is a load detection valve 8th to the piston chamber line 4 and the annular chamber conduit 6 connected.

Specifically, the load detection valve has 8th , in the form of a proportional pressure valve, has two input ports 10 . 12 and three output terminals 14 . 16 . 18 , of which a first output terminal 14 a tank connection is. Furthermore, the load detection valve has 8th a first and second control page 20 . 22 , which are each biased by a spring and to the two control pressures separately (spatially separated) can be applied. This is the first tax page 20 a (chamber-shaped) piston chamber pressure section 24 , via a first control line to the piston chamber line 4 connected. The second control page 22 has a (chamber-shaped) annular chamber pressure section 26 , via a second control line to the annular chamber line 6 connected. Both control lines are additionally equipped with one input connection each 10 . 12 of the load detection valve 8th connected and act on these with the piston chamber pressure or the annular chamber pressure.

The load detection valve 8th has an axially continuously displaceable valve piston 28 , in the design position, ie in neutral position (center position of the valve piston, caused by the bilateral uniform spring preload), the two input terminals 10 . 12 and the three output ports 14 - 18 of the valve 8th locks. In a first maximum position, in which the valve piston 28 when pressurizing / increasing the pressure of Piston chamber pressure section 24 the first tax page 20 is movable, connects the valve piston 28 the pressure applied to the piston chamber pressure input port 10 with a second output terminal 16 to which a pressure load line 30 connected. In this first maximum position is one to the third output terminal 18 connected train load line 32 with the tank connection 14 of the valve 8th connected. In a second maximum position, in which the valve piston 28 upon pressurization / pressure increase of the annular chamber pressure section 26 the second control page 22 is movable, connects the valve piston 28 the pressure applied to the annular chamber pressure input port 12 with the third output terminal 18 to which the train load line 32 connected. In this second maximum position is the to the second output terminal 16 connected pressure load line 30 with the tank connection 14 of the valve 8th connected.

Finally, the pressure load line 30 with a (chamber-shaped) pressure load section 34 the second control page 22 of the load detection valve 8th connected and the train load line 32 with a (chamber-shaped) tensile load section 36 the first tax page 20 of the load detection valve 8th connected. The pressure load section 34 and the tensile load section 36 are fluid-tight from the annular chamber pressure section 26 or piston chamber pressure section 24 each separately.

With regard to the structural design of the load detection valve according to the invention 8th will be referred to below 2 Referenced.

As in longitudinal section according to the 2 can be seen, there is the load detection valve according to the invention 8th from a preferably two-part valve housing 38 , in which a longitudinal bore is formed. In the longitudinal bore is the valve piston 28 used axially displaceable.

On the in 2 left side of the valve 8th is between the corresponding piston face and the valve body 38 a chamber is formed, which the Zuglastabschnitt 36 the first tax page 20 forms. In this chamber, the one biasing spring is used, which is the valve piston 28 according to the 2 pushes to the right. The valve piston 28 has in its middle section a radially projecting heel 40 on his the train load section 36 facing side flank another chamber with the housing 38 forms, which the piston chamber pressure section 24 the first tax page 20 represents. On the the piston chamber pressure section 24 opposite side edge of the paragraph 40 This forms with the housing 38 a third chamber, which the pressure load section 34 the second control page 22 represents. Finally, the forms in the 2 right end of the valve piston 28 with the housing 38 a fourth chamber, the annular chamber pressure section 26 the second control page 22 represents. Also in this chamber, a spring is used, the valve piston in a according to the 2 left direction pushes.

Like from the 2 can also be seen, are the attack surfaces on the respective end faces of the valve piston 28 (in the chambers 26 . 36 ) are equal to each other but different from those of said side flanks on the radial piston shoulder 40 (in the chambers 24 . 34 ), which in turn are equal to each other. The reason for this is that the respective attack surfaces (control window) on the valve piston 28 on the pressurizing surfaces of the cylinder piston 2 have to be coordinated, for example, in a pressure-loaded cylinder piston 2 (at rest) a pressure force equilibrium on the valve piston 28 to get the valve piston 28 holds in neutral position, so that the bias on the cylinder piston is not displayed / detected. It should be noted that the pressurizing surface of the cylinder piston 2 smaller on the annular chamber side than on the piston chamber side.

Further, in the valve piston 28 a blind hole 42 introduced, which is closed on the open side by means of a blanking plug. In this blind hole 42 opens a first radial bore 44 connected to the piston chamber pressure section 24 the first tax page 20 is fluid-connectable and a second radial bore 46 that with the pressure load section 34 the second control page 22 is fluid-connectable when the valve piston 28 according to the 2 is moved to the right. Finally, in the valve housing 38 a fluid channel 48 incorporated, which at its one end in the Zuglastabschnitt 36 the first tax page 20 opens and at its other end with the annular chamber pressure section 26 the second control page 22 is fluid-connectable when the valve piston 28 according to the 2 is moved to the left.

• – D. h. befindet sich der Ventilkolben 28 in einer Mittelposition gemäß der 2 (Konstruktionslage), dann sind alle Anschlüsse gesperrt.
• – Wird der Ventilkolben 28 nach links verschoben, dann wird die Kammer 34 über die Bohrungen 42 und 44 mit dem Tankanschluss 14 verbunden. Gleichzeitig wird die Kammer 36 über an der rechten Stirnseite des Kolbens 28 angedeutete Längsnuten sowie den Fluidkanal 48 mit der Kammer 26 verbunden.
• – Wird schließlich der Ventilkolben 28 gemäß der 2 nach rechts verschoben, dann erhält die Kammer 34 über die Bohrungen 42 und 44 eine Verbindung mit der Kammer 24. Gleichzeitig wird die Kammer 36 über an der linken Stirnseite des Kolbens 28 angedeutete Längsnuten mit dem Tankanschluss 14 verbunden.

Incidentally, in 2 the tank connection 14 indicated, between the Zuglastabschnitt 36 the first tax page 20 and the piston chamber pressure section 24 the first tax page 20 is placed and during a displacement of the valve piston 28 rightly (according to the 2 ) with the tensile load section 32 or during a displacement of the valve piston 28 to the left (according to the 2 ) with the pressure load section 30 the second control page 22 about the blind hole 42 in the valve piston 28 is connected.

• - D. h. is the valve piston 28 in a middle position according to 2 (Construction position), then all connections are blocked.
• - Will the valve piston 28 moved to the left, then the chamber 34 over the holes 42 and 44 with the tank connection 14 connected. At the same time the chamber 36 over at the right end of the piston 28 indicated longitudinal grooves and the fluid channel 48 with the chamber 26 connected.
• - Finally, the valve piston 28 according to the 2 moved to the right, then receives the chamber 34 over the holes 42 and 44 a connection with the chamber 24 , At the same time the chamber 36 over at the left end of the piston 28 indicated longitudinal grooves with the tank connection 14 connected.

The operation of the load detection valve according to the first preferred embodiment can be described as follows:
Lies on the cylinder 1 a load, this results in a pressure in one of the two cylinder chambers 1a . 1b , This pressure is also due to the load detection valve 8th over the piston chamber line 4 and / or the annular chamber conduit 6 and ensures that the valve piston 28 is deflected in a corresponding direction. Depending on the load situation, the connection opens from the respectively pressurized cylinder chamber to the train load line section 36 the first tax page 20 or to the pressure load line section 34 the second control page 22 , At the same time the other part of the currently pressurized control side with the tank connection 14 connected. This increases the pressure of the tensile load section 36 or pressure load section 34 the opposite just not pressurized control side, which represent the actual pressure measuring chambers, to the valve piston 28 is in balance due to the applied pressures and the connection between the loaded cylinder chamber and the associated pressure measuring chamber is closed again. The springs arranged on both sides ensure in the pressure-balanced state for a centering of the valve piston 28 in its neutral position.

In this process, it receives to the second and third output terminals 16 . 18 of the valve 8th connected pressure load line 30 or the train load line 32 a pressure signal corresponding to the pressure in the tensile load section 36 or the pressure load section 34 , which represents the (reference) pressure representing the load of the load.

As a further functional example that case is considered, after which the cylinder piston 2 is pressure-clamped:
Assume that the cylinder area ratio between the annular chamber side and the piston chamber side is i = 2. Will the cylinder piston 2 biased on the annular chamber side with a pressure of, for example, 20 bar, prevails on the piston chamber side, a back pressure of 10 bar to the cylinder piston 2 to keep in balance. It is also assumed that a pressure load FDL is applied to the cylinder rod, which pressure is in the piston chamber 1b of 100 bar corresponds. Thus prevails in the equilibrium state in the piston chamber 1b an actual pressure of 110 bar.

The pressures within the two cylinder chambers make the valve piston 28 according to the 2 shifted to the right, thereby opening a connection between the piston chamber pressure section 24 the first tax page 20 and the pressure load section 34 as a pressure measuring chamber of the second control side 22 , Since the pressure application surfaces of the piston chamber pressure section 24 and the print load section 34 are the same size, the force application surface in the annular chamber pressure section 26 however, to the annular chamber 1a of the cylinder 1 is adjusted (that is smaller), in which a 20 bar piston biasing pressure prevails, now the pressure increases in the pressure load section 34 at 100 bar. In this case, a pressure balance prevails over the load detection valve 8th , wherein the valve piston 28 is pushed back by the spring preload in neutral position. The in the pressure load section 30 tapped 100 bar correspond to the net pressure load acting on the piston rod. It is both quantitatively in terms of pressure level as well as qualitatively implemented as a compressive load in a reference pressure.

If the load pressure on the load sinks, the pressure in the corresponding pressure measuring chamber will cause it 34 that the valve piston 28 is deflected in the opposite direction. This opens a connection from the pressure measuring chamber 34 the second control page 22 (ie from the print load section 34 ) to the tank connection 14 , As a result, the pressure builds up in the pressure load section 34 and thus in the pressure load line 30 as long as, until again a state of equilibrium on the valve piston 28 is reached. Thus, the load can be tapped at any time in the form of a pressure. This signal can then be used in the hydraulic control for various tasks. In the 3 a second embodiment of the invention is shown, which will be discussed below only to the differences from the first embodiment described above. Incidentally, the second embodiment corresponds to the first.

From the dargstellten arrangement of the tank connection 14 In the first embodiment of the invention, it can be seen that in the case of a readjustment of a load change on the hydraulic cylinder 1 Depending on the situation, hydraulic fluid from the tank connection 14 of the load detection valve 8th flows (for example, when the load is reduced or when the load changes). Since the outflowing hydraulic fluid comes from the cylinder chambers, the consumer was slowly moving in the direction of the load.

To avoid this, is in the tank line or at the tank connection 14 according to the second embodiment of the invention, a variable (adjustable) aperture 50 , For example, a 2/2-way valve interposed. With this valve 50 is it possible to use the load detection valve 8th only to be left in operation as long as it is needed for further control measures. In the remaining time the tank connection remains 14 locked, so that load changes do not lead to an unwanted movement of the load.

LIST OF REFERENCE NUMBERS

1

cylinder

1a

annular chamber

1b

piston chamber

2

cylinder piston

4

Piston chamber line

6

Annulus line

8th

Load detection valve

10, 12

input terminals

14-18

output terminals

20

First tax page

22

Second tax page

24

Piston chamber jerk section

26

Annulus pressure section

28

plunger

30

Pressure load line

32

Zuglastleitung

34

Pressure load section

36

Zuglastabschnitt

38

valve housing

40

piston paragraph

42

Blind hole

44

First radial bore

46

Second radial bore

48

fluid channel

50

Variable aperture

Claims (7)

Load detection circuit with a load detection valve ( 8th ), which at its two control sides ( 20 . 22 ) with the pressure in both chambers of a cylinder ( 1 ) is applied as a consumer, depending on whether a pulling or pushing load a cylinder rod of the cylinder ( 1 ), on one of the two control pages ( 20 . 22 ) a corresponding load (over) pressure is applied, whereby one of two tensile or compressive load indicating outputs ( 16 . 18 ) of the load detection valve ( 8th ) is applied with the pressure representing the net load as the reference pressure. Load detection circuit according to claim 1, characterized in that a first control side ( 20 ) of the load detection valve ( 8th ) a piston chamber pressure section ( 24 ), which is equipped with a piston chamber ( 1b ) of the cylinder ( 1 ) is fluidly connected and a Zuglastabschnitt ( 36 ), which has an annular chamber ( 1a ) of the cylinder ( 1 ) and that a second control page ( 22 ) of the load detection valve ( 8th ) an annular chamber pressure section ( 26 ), which with the annular chamber ( 1a ) of the cylinder ( 1 ) and a pressure load section ( 34 ), which with the piston chamber ( 1b ) of the cylinder ( 1 ) is connectable. Load detection circuit according to claim 2, characterized in that the load detection valve ( 8th ) a valve piston ( 28 ), depending on the pressure gradient over the two control pages ( 20 . 22 ) from one of all valve connections ( 10 - 18 ) locking neutral position is displaceable in a second switching position, in which the piston chamber pressure section ( 24 ) of the first control page ( 20 ) with the pressure load section ( 34 ) the second control page ( 22 ) and is displaceable in a third switching position, in which the annular chamber pressure section ( 26 ) the second control page ( 22 ) with the tensile loading section ( 36 ) of the first control page ( 20 ) connected is. Load detection circuit according to claim 3, characterized in that the load detection valve ( 8th ) a tank connection ( 14 ), which in the second switching position of the valve piston ( 28 ) with the tensile loading section ( 36 ) of the first control page ( 20 ) and in the third switching position of the valve piston ( 28 ) with the pressure load section ( 34 ) the second control page ( 22 ) is connected. Load detection circuit according to one of the preceding claims 2 to 4, characterized in that the piston chamber pressure section ( 24 ) of the first control page ( 20 ) and the pressure load section ( 34 ) the second control page ( 22 ) the same pressure application surface on the valve piston ( 28 ), which is different from the likewise same pressure application surface of the annular chamber pressure section ( 26 ) the second control page ( 22 ) and the tensile load section ( 36 ) of the first control page ( 20 ). Load detection circuit according to one of the preceding claims, characterized by a preferably variable diaphragm ( 50 ) at the tank connection ( 14 ) of the load detection valve ( 8th ) is arranged. Load detection circuit according to claim 6, characterized in that the aperture is a 2/2-way valve. Load detection circuit according to one of the preceding claims, characterized in that the load detection valve ( 8th ) is a proportional valve.

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