DE29923204U1 - Hydraulic directional valve - Google Patents

Description

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Description: Hydraulic directional control valve

The invention relates to a hydraulic directional control valve, the control piston (main piston 3) of which can be adjusted against the force of a spring (main spring 18) by the plunger of a magnet (12) from its first position (closed position) to its second position (open position) according to the preamble of claim 1.

This valve is well known.

In one position of the valve piston (closed position), the pressure chamber (7) into which the pump connection (P) opens is closed off from the consumer chamber, while the consumer chamber with the consumer is open to the return chamber (20) and the tank connection (R), so that the consumer is relieved of pressure. In the open position, the consumer is connected to the pump connection, while the pressure chamber is closed off from the return chamber and the tank.

This valve is particularly suitable as a pilot valve for a hydraulic valve that is hydraulically operated.

The object of the invention is to design this valve in such a way that it is suitable as a pilot valve with the smallest possible size and has a positive overlap with regard to the closure of the consumer chamber with respect to the return flow and the opening of the consumer chamber with respect to the pressure chamber. The solution according to claim 1 has the advantage that the valve housing does not have to provide any connections between the return flow channel and the consumer channel. The valve can therefore be accommodated in particular in a valve cartridge (claim 4). This provides a simple possibility of adjusting the overlap and the opening width of the connection between consumer and return flow, so that the damping of the movement of the main valve can be adjusted in this way.

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In order to avoid the hydraulic forces being insufficient to safely lift the tappet piston from the main piston and to establish the return connection between the consumer connection (control connection of the main valve) and the return, according to claim 2 the tappet piston is pressed into its open position by a safety spring against the force of the magnet, such that in the closed position of the main piston the central channel is open.

Claim 3 provides a secure, leak-free closure between the pressure chamber and the consumer chamber (8).

The manufacturing advantages of the design according to claim 4 are combined with a good adjustment option for the overlap and the opening width of the connection between consumer and return.

The closure end of the main piston protruding into the consumer chamber is preferably designed as a cone pair according to claim 5.

The design according to claim 6 and claim 7 has the advantage that the pressure chamber is sealed against the consumer chamber and control connection without leakage. Hydraulic directional control valves that are used as pilot valves and are controlled electromagnetically must offer a high safety standard in many areas of application (e.g. in lifting equipment or in mining).

The design and development of an electro-hydraulic directional control valve according to claim 8 has the advantage that faults in the magnet or the valve are detected immediately and in advance. For this purpose, a current control device is integrated into the control device of the magnet. The current control device is preferably located on or in the area of the magnet. The current control device has an electronic memory. Characteristic values are stored in the memory which ideally characterize the current consumption of the magnet during the switching process when switching to one of the switching positions. The actual course of the current consumed by the magnet when the valve is switched to the switching position and/or when the magnet is switched off is measured and at least significant points of the actual course or the entire actual course are compared with the corresponding points of the target course or with the target course and signaled. The error message is signaled on the valve itself, in particular by an optical signal (claim 9).

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The advantage of the design according to claim 11 is that not every deviation is signaled, but it can be determined beforehand by testing which deviations are within the permissible functional tolerances. It is essential for the function of a pilot valve that, on the one hand, sufficient holding forces act on the valve piston in order to position the piston securely in its intended switching position. On the other hand, however, the power consumption should be minimized. In an electrohydraulic pilot valve or directional control valve, this is achieved by the design or further development according to claim 12. In addition, the current control device can measure the current flow of the magnet during the switching process and detect when the switching position is reached. After the current drops at the end of the switching process, the current is increased again to essentially the greatest level reached during the switching process and then reduced to the level required to hold the switching position. With this design, this also happens with directional control valves that have several switching stages one behind the other in the switching path. This ensures that the valve piston reaches its switching position safely and with sufficient holding power. It also prevents the magnet from being subjected to current to the point of saturation, which would place an excessive load on it, particularly overheating it. The power consumption and in particular the current peaks are limited to the necessary level.

(In the following, embodiments of the invention are described with reference to the drawing.)

Show it:

Fig.1: a hydraulically controlled directional control valve, which is controlled by an electro-hydraulic

3/2 pilot valve is operated;
Fig.2: the electro-hydraulic pilot valve;
Fig.3: the current consumption when switching the pilot valve

The main valve, electro-hydraulic control valve 15, has an electromagnetically controlled pilot valve. The pilot valve has a valve housing (outer housing 1) which is fitted into a valve body (pilot valve 14, only visible in Fig. 1).

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can be installed. An essentially hollow-cylindrical valve housing is screwed into the outer housing 1 and can be sealed in zones by means of external seals 22 and 23. The main piston, valve piston 3, is guided in the cartridge 2 at one end and is sealed against the end chamber of the cartridge by seal 16. The end chamber forms the return chamber 20, which is connected to the return line R of the valve leading to the tank.

In the front side of the outer housing 1, which faces away from the return chamber 20, a tappet piston 4 is slidably mounted and sealed to the outside by a seal 17. The tappet piston 4 projects into the control chamber 8, which is formed in this area of the outer housing 1 and in the cartridge 2. The control chamber 8 is closed off from the pump connection chamber 7 by an inner collar which forms a seat 5. In the area of the seat 5, the main piston 3 has a seat collar 6 which interacts with the seat 5 of the cartridge and forms the closure between one side of the consumer chamber, control chamber 8, and the other side, the pump connection chamber 7. The pump connection chamber 7 is delimited on the other side by the seal 16, which on the other hand delimits the return chamber 20. The main piston 3 has a connecting channel (central channel 21) which connects the return chamber 20 on the one hand and the control chamber 8 on the other. The tappet piston 4 projects with its free end into the consumer chamber, control chamber 8.

In the consumer chamber, control chamber 8, the closing end 9 of the valve piston and the tappet piston 4 interact by combining an inner and an outer cone. In the case shown, the seat end 10 of the main piston 3 is designed as an outer cone 9 and the facing end 10 of the tappet piston 4 is designed as an inner cone 10. The control chamber 8 can thus be connected to or separated from the return chamber 20.

The tappet 11 of the tappet piston 4 interacts with the tappet of the magnet 12 (not shown), which is controlled by the electrical control connection 13. The main piston 3 is pressed with its seat collar 6 against the seat 5 by the main spring 18, which is supported on the front side of the pump connection chamber 7 in the area of the seal 16. The cross-sectional areas of the seat 5/6 and the piston end of the

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Main pistons 3 at the other end of the pressure chamber 7 are essentially identical, so that the main piston is pressure balanced and is pressed against the seat 5 only by the main spring 18.

The tappet piston can be loaded by a safety spring 19 in the sense of lifting it from the seat end 9 of the main piston 3. For this purpose, the safety spring 19 is supported on the one hand on the inner collar 5 of the cartridge and on the other hand on a collar of the tappet piston 4.

About the function:

In the rest position, the pressure chamber 7 is closed off from the control chamber 8 by the main spring 18 pressing the main piston 3 with the seat collar 6 against the seat 5. Since the plunger piston is not loaded by the magnetic plunger, the safety spring 19 presses the plunger piston 4 against the front side of the control chamber 8 or against a stop (not shown) of the magnetic plunger. The control chamber 8 is connected to the return chamber 20 via the central channel 21 and is therefore relieved of pressure. The main valve is thus in its initial position. When the magnet 12 is activated (Fig. 3, point 31), it initially draws a current which increases strongly when the spring force of the safety spring is overcome (point 32) and then increases somewhat less strongly until it stops at the seat end of the main piston 3. The current reaches a first current peak (point 33). When the control chamber is closed off from the return chamber by the plunger piston with seat end 10 striking the closing end 9 of the main piston, the current drops sharply (point 34). The main piston 3 is now displaced against the main spring 18. This causes the current to rise again and reaches a second current peak (point 35) when the seat 5/6 begins to open. When the main piston 3 moves against its stop on the front side of the return chamber 20, the current drops sharply again (point 36). The current is now increased again to a value that essentially corresponds to the highest of the previously described values (point 37). This ensures that the main piston has safely reached its second switching position. In the second switching position, the control chamber is connected to the pressure chamber and closed off from the return chamber. This closes the valve slide.

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controlled and adjusted by the control pressure of the pressure chamber. The current is now reduced to a holding current (from point 38) which, according to experience, generates a sufficient magnetic counterforce to the force of the main spring 18. This ensures that the magnet is only slightly loaded during the holding time, in which it works against the spring force of the main spring, i.e.: as low as previously determined to be sufficient by calculation and testing.

The control device 25 contains a memory in which limit values and limit ranges are stored for one or more of the points 31 - 38, but in particular for the peak values. These limit values/limit ranges have been determined beforehand by testing and represent the target values and the permissible limits. This means that as long as the current occurring during the switching process does not exceed these limit values, it can be assumed that the valve and all its parts are performing their function properly. However, if the current exceeds maximum values or falls below minimum values, this is a sign that the valve is faulty, e.g. it is stuck due to chips or has become leaky due to wear.

If the control system detects a deviation of the actual values from the stored target values or an exceedance of the limit ranges, a warning signal is issued. In mining or other large-scale plants, it can be advantageous to signal this warning signal to the central control station. For the optical monitoring of a hydraulic system, however, it can be advantageous if the warning signal also appears on the valve, e.g. as a red light.

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Reference symbols

1. Valve housing, outer housing

2. Valve housing cartridge

3. Main piston valve piston

4. Tappet piston

5. Seat, inner waistband

6. Seat waistband

7. Pressure chamber, pump connection chamber

8. Consumer Chamber, Control Room

9. Sitting, closing end

10. Seated, internal cone

11. Tappet

12. Magnet

13. Control connection, electrical

14. Pilot valve

15. Main valve, electro-hydraulic control valve

16. Seal

17. Seal

18. Mainspring

19. Safety spring

20. Return chamber

21. Connecting channel central channel

22. Seals

23. Seals

24. Attacks

25. Current control device

Claims (13)

1. Hydraulic directional control valve,
whose control piston (main piston 3 ) can be adjusted against the force of a spring (main spring 18 ) by the plunger of a magnet ( 12 ) from its first position (closed position) to its second position (open position),
and the other features:
in the closed position, the pressure chamber ( 7 ) with the pump connection (P) is closed relative to the consumer chamber ( 8 ) and the consumer chamber with the consumer (A) is open relative to the return chamber ( 20 ) and the tank connection (R);
in the open position, the consumer chamber ( 8 ) is closed off from the return chamber ( 20 );
with the characteristic features:
the consumer chamber ( 8 ) and the return chamber ( 20 ) are arranged at the opposite ends of the main piston ( 3 ), namely the consumer chamber ( 8 ) on the side facing the magnet and the return chamber ( 20 ) on the side facing away from it;
the main piston is penetrated by a central channel ( 21 ) which connects the consumer chamber ( 8 ) and the return chamber ( 20 ) with each other;
the magnetic tappet acts on a tappet piston which can be displaced in the valve housing coaxially to the main piston and which has a seat end facing the main piston ( 3 ), through which it closes the central channel when it comes into contact with the main piston. 2. Directional control valve according to claim 1 or 2 with the characterizing features:
the tappet piston is pressed into its opening position by a safety spring ( 19 ) against the force of the magnet, such that the central channel ( 21 ) is open in the closed position of the main piston. 3. Directional control valve according to claim 1 or 2 with the characterizing features:
the piston collar, by which the pressure connection and the pressure chamber ( 7 ) are closed off from the consumer chamber ( 8 ) and the consumer connection of the valve in the closed position of the valve piston, is designed as a seat cone which cooperates with a corresponding seat ( 5 ) of the valve housing in the closed position of the valve piston. 4. Directional control valve according to one of claims 1 to 3 with the characterizing features:
the valve housing consists of an outer housing ( 1 ), on the front side of which the magnet is mounted, and an inner housing (cartridge 2 );
Preferably, the cartridge ( 2 ) is mounted displaceably, in particular screwably, in the outer housing, and the plunger piston ( 4 ) is movable in the direction of the opening of the central channel ( 21 ) until it abuts against the front side of the outer housing or the magnet. 5. Directional control valve according to one of claims 1 to 4 with the characterizing features:
the end (closing end 9 ) of the main piston ( 3 ) which projects into the consumer chamber ( 8 ) is conical and cooperates with the seat end ( 10 ) of the tappet piston provided with an inner cone to close the central channel. 6. Directional control valve according to one of claims 1 to 4 with the characterizing features:
the main spring ( 18 ) is supported on the one hand on the piston collar ( 6 ) of the main piston ( 3 ) and on the other hand on the front side of the pressure chamber ( 7 ). 7. Directional control valve according to one of claims 1 to 5 with the characterizing features:
the size of the seat surface on the seat collar ( 6 ) or seat ( 5 ) corresponds essentially to the cross-section (seal 16 ) of the main piston ( 3 ) in the valve housing (cartridge 2 ) which is sealed against the pressure chamber ( 7 ) and the return chamber ( 20 ), so that the main piston is essentially pressure-balanced. 8. Hydraulic directional control valve
with the following features:
the valve piston ( 3 ) is moved by a magnet (12) into a switching position (opening position) predetermined by a stop;
in particular according to the preamble of claim 1 and in particular according to one of the preceding claims
marked by:
a current control device ( 25 ) in which the course of the current consumed by the magnet is measured and evaluated when the valve is switched to the switching position and/or when the magnet is switched off. 9. Hydraulic directional control valve according to claim 8 with the characterizing features:
During the evaluation, at least significant points of the actual curve or the entire actual curve are compared with the corresponding points of the target curve or with the target curve and deviations are signaled as error messages. 10. Hydraulic directional control valve according to claim 9 with the characterizing features:
The error message is signaled on the valve itself, in particular by an optical or acoustic signal. 11. Hydraulic directional control valve according to claim 8 or 9 with the characterizing features:
In the current control device ( 25 ), the deviations which are to be signalled as error messages are stored as limit values. 12. Hydraulic directional control valve according to one of claims 8 to 11 with the characterizing features:
The current control device measures the current flow of the magnet during the switching process and detects when the switching position is reached;
The current is then increased again essentially to the level reached up to that point and then reduced to the level required to hold the switch position. 13. Hydraulic directional control valve according to claim 11 with the characterizing features:
the valve piston can be switched in several consecutive switching stages;
After reaching the last switching stage, the current is increased again essentially to the highest level reached up to that point and then reduced to the level required to maintain the last switching stage.