State of the art
The invention is based on a control device for a
hydraulic volume flow according to the preamble of the claim
From the DE 196 34 319 A1
or the DE 41 40 604 A1
already a generic type control device with a check valve is known, in which a seat valve body is arranged. The poppet valve body cooperates with a housing-fixed main valve seat. In the seat valve body, a pilot valve body is arranged, which cooperates with a valve seat in the seat valve body. The seat valve body is pressed by the action of pressure in a pressure space on one of its end faces in the main valve seat.
In the control device according to the DE 196 34 319
is the pressure chamber on the outside of the seat valve body column located connected to a working cylinder. To open the shut-off valve, the pilot valve body is turned on at the beginning of an opening process by a proportional solenoid so far that the pressure chamber is completely relieved of pressure. After unlocking the check valve of the seat valve body is moved by the proportional solenoid mechanically against the force of a spring.
In the control device of the DE 41 40 604 A1
the pressure chamber is connected via a throttle of defined flow cross-section with a working cylinder. By means of a variable throttle point whose opening cross-section is controlled by the pilot valve body, the pressure in the pressure chamber and thus the position of the seat valve body in the check valve can be determined by means of a proportional magnet. The position of the seat valve body in the check valve determines the volume flow of the hydraulic fluid from the working cylinder in a return line.
in the known control devices, for example, an abrasive metal chip
blocked the valve seat, then the pilot valve can also at a
Control signal for
not complete anymore
There remains a small pilot volume flow of hydraulic fluid,
so that the pressure
slightly falls in the pressure room
and so that the main control valve opens slightly. By this leakage
conditionally, the working cylinder slowly loses hydraulic fluid, and
the working piston descends into the working cylinder. At a working cylinder
for the lifting fork
of a forklift causes this hydraulic leakage,
slowly lower the fork. This is undesirable because the fork lift itself
should not move without control current specification.
Advantages of the invention
The invention is based on a control device for a
Volume flow of a hydraulic fluid at least one loaded working fluid
with at least one check valve, which has a main valve and one with
an inlet and outlet connected pressure chamber for receiving under
Having pressurized hydraulic means for controlling the main valve,
wherein the pressure in the pressure chamber controllable by a pilot valve
It is suggested that the
Pressure chamber drainage side by means of at least one other valve shut off
is. Locks this further valve from the pressure chamber, so can
in a leakage of the pilot valve described above, no hydraulic fluid
drain from the pressure chamber.
In the pressure room, therefore, the pressure prevails with him over the
Feed connected loaded hydraulic circuit before. In this case
becomes the main valve body
pressed against the main valve seat
and the main valve blocks the flow of hydraulic fluid
from. The additional valve thus offers the advantage of a redundant safety shutdown.
When switching off the control current, the pilot valve is closed, simultaneously
the other valve is closed, so that the pilot control flow
redundantly interrupted by two different valves, and the
Main valve body
is pressed into its main valve seat due to the build-up in the pressure chamber load pressure.
Even if not complete
closed pilot valve, a flow and, for example
in a forklift, a movement under load can be avoided.
an advantageous embodiment of the invention, the main valve
a main valve body
which interacts with a main valve seat. Training
the main valve as a seat valve has the advantage that the flow
the hydraulic means with the valve closed in the simplest way
is interrupted without losses
due to leakage. The intension of the invention, a drain of
Hydraulic fluid from the cylinder and thus a shift
the working piston completely
to prevent, is thus best achieved.
Preferably, the pilot valve has a pilot valve body, which is displaceable by a plunger of a proportional solenoid. By means of a proportional magnet can be implemented in a cost effective manner, an electrical signal in a travel of a pilot valve body. The pilot valve body in turn adjusts the position of a main valve body, which can control much larger volume flows of hydraulic fluid. in the de-energized state of the proportional solenoid pushes a return spring the pilot valve body in a the drain of the pressure chamber blocking position. The pressure in the pressure chamber causes - as described above - the main valve body, also to block the flow of hydraulic fluid. In the absence of drive current of the main valve body is pressed firmly into its seat due to the hydraulic pressure in the pressure chamber.
is the pilot valve body
in a bore of the main valve body for controlling a pilot flow rate
displaceable. The check valve can be very compact in this way
be built. Preferably, the pilot valve is on the drain side
arranged the pressure chamber. When opening
of the pilot valve body takes
the pressure in the pressure chamber and thus in the closing direction
acting force. After all
the latter falls below the condition caused by the hydraulic pressure of the load
Counterforce in opening direction.
The main valve body
is pushed in the direction of the pilot valve body and gives the
Main valve seat free. By this succession of the main valve body is
the pilot flow volume again smaller because the relative displacement
between main valve body
and pilot valve body
becomes smaller. The pressure in the pressure chamber becomes larger again, and
the main valve body
shifts again in the closing direction. Ultimately
a stable balance. Due to this compact design
Hydraulic lines between pressure chamber and pilot valve body short
being held. Pressure fluctuations are thus due to the
largely avoided. The other valve is thus lower pressure fluctuations
exposed and can be dimensioned cheaper
an advantageous embodiment of the invention is the other
Valve arranged between pressure chamber and pilot valve. This offers
the advantage that the
more valve on the static part of the check valve in easier
Way, and the pilot flow rate and
the main control volume flow are merged immediately after the valve seats
Would be that
another valve arranged after the pilot valve, would be a
own, complicated discharge of the pilot flow volume from the
Locking valve to the other valve needed.
the other valve is a seat valve. A seat valve stands out
by its simple structure, but it is - more advantageous
Way designed as a solenoid valve - his
Determination quite fair, in the de-energized state, the pilot flow rate
an advantageous embodiment of the invention, the check valve
and the other valve over
firmly connected. A composite unit of check valve
and further valve is distinguished by its easy assembly and disassembly.
The hydraulic connections run inside the housing. Separate hydraulic connection lines,
which are cost-intensive and pose potential leakages,
eliminated in this way.
the check valve and the other valve are arranged coaxially with each other.
the other valve directly to the pressure chamber. This arrangement
offers the advantage that the
Hydraulic connection between pressure chamber and further valve only off
a short hole exists.
is at least part of the further valve in a bore in
arranged the check valve. The additional valve can thus save space
in the case
the check valve are integrated and in a simple manner, for example via a
Screw connection to be connected to this. This shows that
the check valve, a hydraulic connection between the other
Valve and the pilot valve on. This will be - as above
already executed - separate
Hydraulic connection lines, which are cost-intensive and potential
Leakage pose, saved.
the other valve is electrically controlled and electrically parallel
switched to a hydraulic pressure switch valve. The hydraulic fluid is
in the operating state to the piston stroke in the working cylinder of a pressure supply pump
put under pressure. With an inlet pressure balance, the pressure
switched on the Hyrauliksystem. The inlet pressure balance in turn
is actuated by the hydraulic pressure switch valve. The returning hydraulic fluid
is collected in a tank before it comes from the pressure supply pump
is returned to the hydraulic system. The hydraulic pressure switch valve
When it is de-energized relieves a spring chamber of the inlet pressure compensator.
the pressure supply pump of the hydraulic system even when switched on
Actuator depressurizes the hydraulic fluid to the tank. That's all
Load movements requiring hydraulic pressure are excluded. Im not energized
State of Hydraulikdruckschaltaltventils are all in this way
switched off by working piston in working cylinders.
By the pilot valve and the invention further valve all lowering movements of working piston in working cylinders are interrupted with the safety of a redundant system in the de-energized state. The parallel connection of the hydraulic pressure switching valve on the one hand and the other valve on the other hand thus offers the advantage that in the disconnected, de-energized state, no movement is possible. A correspondingly operated hydraulic implement, such as a forklift, persists in motionlessness. There are no uncontrolled, unwanted movements instead.
the other valve is a 2/2 seat valve. This offers the advantage
a simple, inexpensive
Design and fulfilled
nevertheless its purpose.
Advantages are shown in the following description of the drawing.
In the drawing is an embodiment
represented the invention. The drawing, the description and the
numerous features in combination. The skilled person will become the characteristics
individually consider and summarize to meaningful further combinations.
Description of the embodiment
1 shows a control device for a volume flow 10 . 22 a hydraulic means of a working cylinder 12 , about with a pump 28 and via a 3/2-way valve 30 lifted a load and controlled via a check valve can be lowered. The check valve has a main valve body 14 that with a main valve seat 16 interacts and via one of a proportional solenoid 18 actuatable pilot valve body 20 is controllable. The pilot valve body 20 is over a preloaded spring 34 in the closing direction 24 in his valve seat 36 in the main valve body 14 pressed. The feather 34 relies on one end 46 on a heel 54 inside a case 52 and acts on a second end 50 about one on the pilot valve body 20 attached spring plate 56 on the pilot valve body 20 in the closing direction 24 ,
Should a load with the working cylinder 12 be lowered, the proportional magnet 18 activated. One with the armature of the proportional magnet 18 connected plunger 32 shifts the pilot valve body 20 against the spring 34 , which is further biased. The pilot valve body 20 moves out of the valve seat 36 in the main valve body 14 in the opening direction 26 , so that a pilot flow volume 22 via a throttle point 38 , a feed 48 , a pressure room 40 , about one with the pressure room 40 connecting another valve 60 , two connection channels 58 . 62 and finally a fine control 66 and the valve seat 36 can drain into a return not shown. At the same time, the pressure in the pressure chamber becomes 40 reduced, with a force in the closing direction 24 on a surface 42 of the main valve body 14 acts. Exceeds the on a surface 44 acting pressure force in the opening direction 26 in the closing direction 24 acting pressure force, shifts the main valve body 14 in the opening direction 26 until an equilibrium position is reached. The load is over the working cylinder 12 lowered at a certain speed.
According to the invention, the pilot volume flow described above 22 through the other valve 60 shut off. If the pilot flow volume 22 interrupted, arises in the pressure room 40 the prevailing pressure in the loaded cylinder, as above the throttle point 38 builds up a pressure difference only with flowing hydraulic fluid. The pressure in the pressure chamber 40 causes a force in the closing direction 24 on a surface 42 of the main valve body 14 , This exceeds the one on a surface 44 acting pressure force in the opening direction 26 , because on both surfaces 42 . 44 when the other valve is sealed off, the same pressure acts and the force in the closing direction 24 receiving surface 42 is larger. The main valve body 14 So it's stuck in the main valve seat 16 pressed. The main valve blocks and the flow through the main valve 10 will be interrupted.
The other valve 60 is switched so that it is energized in the operating state and thus open. On the other hand, if the control device is switched off, this is the additional valve 60 de-energized and thus closed. A feather 68 pushes a valve cone 70 the further valve 60 in a valve seat 72 , In the undisturbed case of the normally closed control system locks the pilot valve, then follows the main valve body 14 as a result of the build-up in the pressure chamber closing force the pilot valve body 20 until he is in the main valve seat 16 comes to rest, and the main valve locks. But if the pilot valve blocked by any reason, for example by a Abriebspan from the hydraulic system, the pilot valve can not completely lock, and thus could without the other valve 60 the main valve also the volume flow 10 do not lock. In this accident, a load would be lowered, for example, in a forklift, the lifting fork, as from the associated working cylinder 12 Hydraulic fluid flows. This is extremely undesirable in a disconnected implement, as an uncontrolled movement of the possibly unguarded implement can cause personal injury and property damage. Due to the shut-off working device, respectively when de-energized control system, additionally blocking another valve 60 The safety of being able to exclude an unintentional movement of the disconnected implement, significantly increased.