DE102011109505A1 - Hydraulic directional valve e.g. pressure maintenance valve, for controlling pressure medium flow path, has detent device formed such that detent device is triggered if pressure medium volumetric flow in pressure medium flow path is zero - Google Patents

Abstract

The valve (46) has a detent device (66) over which a valve slide (58) of the valve is locked in a function position. The detent device is formed such that the detent device is triggered if pressure medium volumetric flow in a pressure medium flow path is zero. The detent device has a piston (84) for locking the valve slide. The piston has two piston surfaces (90, 92) turned away from each other. Upstream pressure in a locking direction of the detent device acts on one of the piston surfaces. Downstream pressure in a release direction acts on the other piston surface.

Description

The invention relates to a hydraulic directional control valve with a latching device according to the preamble of patent claim 1.

In such directional valves, it is known from the prior art to provide a neutral start fuse. This is to ensure that the main spool without pump pressure (especially in a parked supply machine) is not in a locked functional position, so that no unexpected function or movement of a hydraulic consumer controlled by the directional valve takes place in the next construction of pump pressure (especially when recruited supply machine) ,

Furthermore, it is known from the prior art to provide a kickout device in such hydraulic directional control valves, via which the main spool valve is released when a pump pressure is exceeded from a latched functional position. This can be z. B. be necessary when reaching a stop of a cylinder supplied by the directional control valve. The released main spool can then return to a spring-centered neutral position.

In the DE 195 28 974 A1 is a directional control valve with a locking device for fixing a valve spool disclosed. The latching device in this case has a latching element which can be prestressed via a latching spring into a latching position against a valve slide of the directional control valve. The detent spring is supported on a locking piston. The locking piston can in this case be moved by a kickout piston in the direction of relaxation of the detent spring. The Kickout piston is clamped with a spring against a valve seat. Contrary to the spring force of the kickout piston can be acted upon by a system pressure. If the system pressure exceeds a predetermined value, then the kickout piston lifts off from its valve seat and thereby moves the locking piston connected to it, as a result of which the spring force of the detent spring acting on the detent element is reduced and thus the latching of the valve slide is released. A neutral start fuse is not disclosed in this document.

The document DE 39 23 743 also discloses a directional control valve with a latching device. The directional control valve has a neutral start safety device and a kickout device. For neutral start protection, a piston held by the pump pressure against a spring is provided in the valve slide of the directional control valve. If the pump pressure falls below a predetermined value, the piston is displaced by the spring force of the spring into a release position in which the latching device is released by the piston. The Kickout device also has a piston in the form of a ball, which is arranged in the valve spool of the directional control valve. The piston is biased by a spring against a piston seat and acted upon by a consumer pressure against the effective direction of the spring force. If the consumer pressure exceeds a predetermined value, the piston is displaced counter to the spring force into a release position in which the latching device is triggered.

The publication DE 10 2008 022 509 A1 represents a further embodiment of a directional control valve with a latching device. The respective latching is generated by a pin which is biased by a kickout piston of a kickout device against a valve spool of the directional control valve. The pin dips radially from the outside into different grooves of the valve slide. The kickout piston, in turn, is biased by a spring against the pin, with the spring resting against a neutral start piston. The neutral start piston is displaced in an existing pump pressure in a clamping direction of the spring. A decrease in the pump pressure causes the neutral start piston moves in a relaxation direction of the spring, the latch then dissolves at a certain minimum pump pressure, whereby a neutral start safeguard is implemented. The kickout piston is subjected to a load pressure in the release direction of the pin. From a predetermined maximum load pressure of the pin is then relieved to the extent that the catch detaches.

The document EP 0 394 860 shows a directional control valve with a latching device with a permanent latching, a load pressure-dependent latching and a Nichtarretiermodus is possible. Here, an axial bore is provided in a directional valve spool, in which a locking piston of a locking part is received, are movable over the engagement body through the peripheral wall of the directional control valve slide in corresponding grooves of the valve housing. The control of the locking piston via a valve slide a kickout device via which the locking piston can be acted upon by a system pressure to produce the latching engagement. When a predetermined system pressure is exceeded, a connection to a tank is opened via the valve slide of the kickout device, so that the pressure applied to the locking piston pressure is reduced and the locking engagement is released. The triggering force of the kickout device can be adjusted via an adjusting device by an operator. That is, in the known valve arrangement can be selected by appropriate adjustment of the triggering force a constant latching, a kickout (kickout) when exceeding a predetermined system pressure and a cancellation of the detent by setting a minimum release force.

A disadvantage of the described directional control valves is the extremely complex construction of the neutral start safeguard and the kickout device. Furthermore, it is disadvantageous that the pressures at which the kickout device and the neutral start fuse are triggered must be adjusted.

In contrast, the invention has the object to provide a device simply constructed way valve with a locking device in which an adaptation of a neutral start fuse and a kickout device to certain pressures is not necessary.

The object is achieved by a hydraulic directional control valve according to the features of patent claim 1.

According to the invention, a hydraulic directional control valve, in particular a load-sensing SB23 directional control valve, has a latching device, wherein a pressure medium flow path is controlled by the directional control valve. The latching device is used to lock a valve spool of the directional control valve in at least one functional position or switching position. The latching device is designed such that a triggering takes place when no pressure medium volume flow in the pressure fluid flow path longer exists. This is especially the case when a supply machine is turned off or a maximum load pressure is reached, for example, when a consumer connected to the directional control valve reaches its stop in the form of a hydraulic cylinder. Thus, the latching device, regardless of predetermined load pressures, as in the above-described prior art, can be triggered and thus can be made extremely simple.

In a further embodiment of the invention, the pressure medium volume flow via a metering orifice of a load-sensing control is flowable. A pressure difference across the metering orifice is then used to control the load device. If no pressure medium volume flow is present, the pressure difference across the measuring diaphragm is essentially zero.

The latching device preferably has a piston which serves for latching the valve spool. The piston can then be controlled as a function of the pressure difference across the metering orifice.

The piston advantageously has two piston surfaces which are arranged such that a pressure on one piston surface in a locking direction and a pressure on the other piston surface act in a release direction of the latch. A pressure upstream of the metering orifice and on the second piston surface a pressure downstream of the metering orifice preferably act on the first piston surface. From the pressure difference, a latching force is formed on the piston. If the pressure difference due to a non-existent pressure medium volume flow is about zero, then the piston is relieved and the locking device triggered.

The piston may have a circular cylindrical cross section, in which case the same size piston surfaces are formed on its end faces.

About the piston is advantageously a latching element with a latching force for locking the valve spool acted upon. The valve slide has for this purpose in particular a latching recess into which the latching element can be latched.

The latching element can be acted upon device technology extremely easy on the second piston surface of the piston, wherein the pressure acting in the triggering direction, with a detent force.

For releasing the latching element upon actuation of the valve slide, the latching recess is configured such that an actuating force acting on the valve slide acts on the latching element against the latching force.

The latching recess is for example an easy to manufacture annular groove with an approximately semicircular cross-section.

The locking element can simply be mounted radially displaceable in a bore of the valve housing of the directional valve to the valve slide. The bore then opens advantageously on the one hand in a valve slide leading slide bore and the other in a cylinder bore leading to the cylinder, in which the piston bounds with its piston surfaces two cylinder chambers.

For each functional position of the valve slide, at least one latching element, which can be acted upon by a piston, is advantageously provided. The at least one locking elements of the functional positions are arranged offset to one another in the longitudinal direction of the valve slide.

Thus, the valve spool is evenly loaded, at least two evenly distributed around the valve spool around arranged locking elements for latching the valve spool in a functional position are provided.

In a further embodiment of the invention, the latching device has a latching element which can be acted upon by a piston with a latching force via a spring. The piston in this case has a repellent from the spring piston surface which limits a pressure chamber. The piston is above the pressure chamber, with an existing one Pressure medium volume flow, acted upon by a system pressure. Advantageously, it is pressed by the system pressure against a housing-fixed stop, so that there is a certain bias of the spring. Advantageously, the pressure chamber is connected via a valve whose position depends on the pressure medium volume flow, in the absence of pressure medium volume flow to a tank. The valve may be, for example, a pressure compensator of a load-sensing control or a check valve. The valve can be a simple 2/2-way valve when the system pressure is applied to the piston via a throttle. Without such a throttle would be a 3/2-way valve appropriate in one switching position, the connection of the pressure chamber to the fluid path with system pressure open and the connection to tank is closed and in the other switching position, the connection to the tank is open and shut off to the fluid path with system pressure.

Other advantageous developments of the invention are the subject of further subclaims.

Preferred embodiments of the invention will be explained in more detail with reference to drawings described below.

Show it

1 a longitudinal sectional view of a directional control valve from the prior art and

2 a longitudinal sectional view of two inventive directional control valves according to a first and second embodiment.

In the 1 is a directional valve in a longitudinal sectional view 1 disclosed in the prior art. This will be briefly explained below for a better understanding of the invention. This directional control valve is an SB23 directional control valve, as disclosed, for example, in the Applicant's leaflet RD 66 130 / 03.09.

The directional valve 1 serves as a control device for load pressure independent control of consumers connected to this. The directional valve 1 is an individual pressure scale in series 2 assigned. The directional valve 1 and the individual pressure balance 2 are in a common housing designed as a valve disc 4 arranged axially parallel to each other.

In the case 4 is a pressure connection 6 formed, from which pressure medium via a throttle cross-section 8th is flowable, that of a control edge 10 a pressure compensator piston 12 the individual pressure balance 2 is formed. Downstream of the throttle cross-section 8th is a current regulator 14 arranged with an adjustable aperture for limiting the maximum pressure medium volume flow. After the current regulator 14 is in the case 4 a connection channel 16 formed in a measuring aperture chamber 18 empties. The measuring aperture chamber 18 is about one on a valve spool 20 trained measuring aperture 22 with another measuring aperture chamber 24 connectable. The valve spool 20 is in a slide bore 26 slidably guided and serves to control a Druckmittetverbindung between the pressure port 6 and two work connections 28 and 30 , The second orifice chamber 24 is downstream with one in the housing 4 trained inlet channel 32 connected. This is above the valve spool 20 with one of the working connections 28 respectively. 30 fluidically connectable. In the inlet channel 32 is a check valve 34 arranged, which serves to maintain a load pressure, for example, in case of disturbances, a secure holding a load of a to the working connections 28 . 30 connected consumer. From the inlet channel 32 branches between the measuring aperture chamber 24 and the check valve 34 a control channel 36 via which the pressure compensator piston of the individual pressure compensator 2 with the pressure in the second orifice chamber 24 can be acted upon. Furthermore, in the housing 4 two drain connections 38 . 40 provided for the pressure relief of the working connections 28 and 30 and the second orifice chamber 24 serve.

The valve spool 20 is via a double-acting rear-heating device 42 in the in the 1 shown neutral position held. For locking the valve spool 20 is a known from the prior art locking device 44 intended.

In the 2 are two directional valves according to the invention 46 and 48 shown in a highly simplified longitudinal sectional view. These can be SB23 directional valves, as used in the 1 are shown, but these have a different locking device.

The directional valves 46 and 48 each have a designed as a valve disc housing 50 respectively. 52 in each case a slide bore 54 respectively. 56 is provided. There is one in each of these 2 greatly simplified valve slide 58 respectively. 60 guided smoothly. The directional valves 46 and 48 are arranged axially parallel to each other and lie with their housings 50 and 52 over connecting surfaces 62 respectively. 64 to each other.

The directional valves 46 and 48 are identical, so for a more detailed explanation of the subject invention in the 2 upper directional valve 46 is used in the following.

The directional valve 46 has a locking device 66 with the valve slide 58 in two Switched positions can be locked. The locking device 66 indicates for each latched switching position of the valve spool 58 two approximately diametrically arranged spherical detent elements 68 . 70 respectively. 72 . 74 on each for latching in one of the valve spool 58 trained annular groove 76 are submersible. This has an approximately semicircular cross-section, the minimum width of the annular groove 76 equal to or greater than the diameter of the spherical locking elements 68 to 74 is.

Since the the locking elements 68 to 74 For locking associated devices are substantially the same, is for a more accurate representation of the locking device 66 for the sake of simplicity, the following in the 2 upper left device with the locking element 68 explained. The locking element 68 is in a radially to the slide bore 54 extending through bore 78 slidably mounted.

The hole 78 opens on the one hand in the slide bore 54 and on the other in a coaxial with the bore 78 in the case 50 introduced cylinder bore 80 , This has a larger diameter than the bore 78 and flows into an outer surface of the housing 50 , this being the case of the interface 62 repellent interface 82 of the housing 50 is. In the cylinder bore 80 is a piston having an approximately circular cylindrical cross-section 84 guided smoothly. This subdivides the cylinder bore 80 in two cylinder chambers 86 respectively. 88 , The cylinder space 86 is here by one of the valve spool 58 groundbreaking piston surface 90 of the piston 84 and the cylinder space 88 from one to the valve spool 58 indicative piston surface 92 limited, the piston surfaces 90 and 92 have substantially the same size. The piston surface 90 and 92 of the piston 84 are above the cylinder chambers 86 and 88 each acted upon with a pressure. The cylinder bore 80 is by suitable sealant 96 sealed to the outside.

To control the locking device 66 by a pressure difference is that of the piston surface 90 limited cylinder space 86 via connecting means, not shown, hydraulically connected to an upstream portion of a metering orifice, while the other cylinder space 88 hydraulically connected to a downstream area of the metering orifice. The metering orifice is, for example, a metering orifice formed on the valve slide, as used, for example, in the directional control valve from the prior art 1 with reference number 22 is shown. This will cause the piston 84 over its piston surface 90 with a pressure upstream of the metering orifice and across its piston surface 92 subjected to a pressure downstream of the metering orifice. If a pressure medium volume flow flows over the metering orifice, a pressure difference arises over it, whereby the pressure upstream is greater than the pressure downstream. As a result, then the latching element 68 groundbreaking piston surface 90 of the piston 84 subjected to a higher pressure than the piston surface 92 , This has the consequence that on the piston 84 a resulting compressive force in a locking direction, ie, in the direction of the locking element 68 acts. This is then from the piston 84 over the piston surface 92 with the resulting pressure force or latching force against an outer circumferential surface 94 of the valve spool 58 pressed. Is the valve spool 58 now arranged in its first switching position, in which case the annular groove 76 in the area of the left locking elements 68 and 70 is arranged, then these through the over the piston 84 applied latching force in the annular groove 76 emotional. For locking the valve spool 58 in its second switching position dive the locking elements 72 and 74 in the ring groove 76 a, if these opposite the locking elements 72 and 74 is arranged. Due to the spherical configuration of the locking elements 70 to 74 These act as a kind of ball bearing when the valve spool 58 is shifted in its switching positions, whereby a friction between the locking elements 70 to 74 and the valve spool 58 is extremely low.

The locking device 66 triggers when the pressure difference across the metering orifice is substantially zero, that is, when no pressure medium flow rate flows more through the metering orifice. As a result, the pressures on the piston surfaces 90 and 92 of the piston 84 are substantially the same, whereby a resultant compressive force is substantially zero. The locking elements 68 to 74 are thus essentially powerless. Is the valve spool 58 then with a restoring device, for example as in the 1 with the reference number 42 is shown connected, then the locking elements by a on the valve spool 58 acting actuating force from the annular groove 76 moves and the valve spool 58 for example, moved to its neutral position. Due to the semicircular cross section of the annular groove 76 of the valve spool 58 are formed oblique flanks over which the locking elements 68 to 74 from the valve spool 58 be acted upon in the radial direction with the actuating force.

At a neutral start is at the beginning of the pressure medium flow rate zero, which is why a pressure difference across the orifice is also zero and the piston 84 relieved of pressure. As a result, the locking elements are at neutral start 68 to 74 not subjected to a detent force.

Likewise, a pressure differential across the metering orifice is substantially zero, if one with the directional control valve 46 controlled consumer, such as a hydraulic cylinder, reaches its end position or system pressure for another reason such is high that a pressure relief valve is open and thus a pressure medium flow no longer flows through the orifice, but to a tank. Due to the non-existent pressure fluid flow then the locking device 66 triggered.

With the locking device 66 Thus, an extremely simple neutral start safeguard and a kick-out device are implemented. The locking device 66 has, compared to the prior art, the advantage that no pressures must be predetermined, in which the locking device 66 triggers. Furthermore, the locking device 66 advantageously, an extremely small number of components.

In the case of an under supply to the directional control valve 46 connected consumer, in which the power supplied by the consumer hydraulic pumps is no longer sufficient to maintain a desired pressure medium flow rate, a pressure difference can be reversed on the metering orifice, whereby the latching device 66 is triggered. In order to avoid triggering in case of insufficient supply, it is also conceivable here the valve slide 58 about an additional locking device to lock, which is designed such that is not tripped in case of undersupply.

It can be provided a Freigang- or floating position, in which the valve spool 58 in addition to working positions and a neutral position is displaced. In this floating position, for example, as in the 1 , two working ports connected to a tank, which also no pressure medium flow rate flows through the orifice plate and the locking device 66 is triggered. In order to enable latching in this floating position, it is conceivable to provide an additional latching device, which is designed such that it does not trigger in the floating position.

Alternatively, the locking force on the locking elements 68 to 74 also over wedge elements of the pistons 84 is transferred to this, whereby, for example, a non-radial arrangement of the piston 84 is possible.

The pistons 84 For example, are designed so that at a pressure difference across the metering orifice of 6 bar, a sufficiently high locking force on the locking elements 68 to 72 acts. The piston surfaces 90 . 92 of the piston 84 For this purpose, preferably have a diameter of about 7.5 mm. The latching force is then sufficient to the valve spool 58 with two locking elements 68 . 70 or 72 . 74 to lock.

Due to the diametrical arrangement of the locking elements 68 . 70 respectively. 72 . 74 is the valve spool 58 advantageously loaded from opposite sides with a latching force.

For switching on and off the locking device 66 is conceivable, the pressure fluid connection between the cylinder chambers 86 and to control the area upstream of the metering orifice via a switching valve. As a switching valve, for example, an electrically operated 2/2-way valve can be used.

In the following, a second embodiment will be briefly explained, which as an alternative with dashed lines in 2 is drawn. In the second embodiment, the cylinder space 86 not like in the first embodiment 2 connected to the region upstream of the metering orifice, but it is this via a connecting channel with a system pressure port via a throttle 96 connected. The other cylinder room 88 is depressurized to a return. Thus, the piston 84 in the second embodiment via its the pressure chamber 86 limiting piston area 90 acted upon by the system pressure, causing the locking element 68 a detent force acts. To implement a neutral start fuse and a kickout device is a valve 98 provided, which is connected hydraulically parallel to the throttle to the connecting channel. This has a valve spool whose position depends on the pressure medium volume flow. The valve is designed such that when the pressure medium volume flow is zero, a connection between the cylinder chamber 86 and a tank is turned on.

The valve is, for example, the check valve or the individual pressure compensator from the prior art 1 , The position of the pressure compensator piston 12 the individual pressure balance 2 out 1 is a measure of the pressure fluid flow through the directional control valve 46 respectively. 48 , If there is no more pressure fluid flow, the pressure compensator piston will become 12 moved to his basic position. The pressure compensator piston 12 or the individual pressure balance 2 are then configured such that in this basic position of the cylinder chamber 86 connected to the tank.

If the valve is a check valve, see reference number 34 according to 1 , is formed, then a position of the valve body of the check valve is a measure of the size of the pressure medium volume flow. If this is zero, then the valve body lies on its valve seat. The check valve is then designed such that there is a pressure medium connection between the cylinder space in this position 86 and the tank opens.

In the embodiments is conceivable between the piston 84 and the locking element 68 to provide a detent spring. The piston is displaced by the system pressure to a housing-fixed stop, resulting in a certain voltage of the detent spring, which generates the detent force. When pressure relief of the piston, the detent spring can push back the piston until it is at least as relaxed that the latching is not maintained.

Disclosed is a hydraulic directional control valve for controlling a Druckmittelströmungspfads with a locking device. A valve spool of the valve can be latched via the latching device. This is designed such that it is controlled in dependence of a pressure medium volume flow. The latching device triggers when the pressure medium volume flow is essentially zero.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 19528974 A1 [0004]
• DE 3923743 [0005]
• DE 102008022509 A1 [0006]
• EP 0394860 [0007]

Claims (15)

Hydraulic directional control valve for controlling a pressure medium flow path with a latching device ( 66 ), via which a valve slide ( 58 ) of the directional valve ( 46 ) is lockable in at least one functional position, characterized in that the latching device ( 66 ) is designed such that it triggers when a pressure medium volume flow in the pressure medium flow path is substantially zero. Hydraulic directional control valve according to claim 1, wherein according to a load-sensing control with a measuring diaphragm ( 22 ) is equipped for setting a pressure medium volume flow to a hydraulic consumer and a pressure difference across the orifice plate for controlling the locking device ( 66 ) is used. Hydraulic directional control valve according to claim 1 or 2, wherein the latching device ( 66 ) a piston ( 84 ), which for locking the valve spool ( 58 ) serves. Hydraulic directional control valve according to claim 3, wherein the piston ( 84 ) two mutually repellent piston surfaces ( 90 . 92 ), wherein on the first piston surface ( 90 ) a pressure taken upstream of the metering orifice in a locking direction of the latching device ( 66 ) acts and on the second piston surface ( 92 ) a pressure downstream of the metering orifice acts in a triggering direction. Hydraulic directional control valve according to claim 4, wherein the piston surfaces are the same size. Hydraulic directional control valve according to one of the claims 3 to 5, wherein over the piston ( 84 ) a latching element ( 68 . 70 . 72 . 74 ) with a latching force for locking the valve spool ( 58 ) can be acted upon. Hydraulic directional control valve according to claim 6, wherein the valve spool ( 58 ) a latching recess ( 76 ), in which the locking element ( 68 . 70 . 72 . 74 ) is latched. Hydraulic directional control valve according to claim 7, wherein the latching recess ( 76 ) of the valve spool ( 58 ) is designed such that one on the valve spool ( 58 ) acting actuating force on the locking element ( 68 . 70 . 72 . 74 ) in a direction opposite to the direction of the latching force acts. Hydraulic directional control valve according to claim 6, 7 or 8, wherein the, in particular spherical, latching element ( 68 . 70 . 72 . 74 ) of the piston ( 84 ) with the second piston surface ( 92 ) can be acted upon. Hydraulic directional control valve according to one of the claims 7 to 9, wherein the latching recess ( 76 ) is an annular groove with an approximately semicircular cross-section. Hydraulic directional control valve according to one of the claims 6 to 10, wherein the latching element ( 68 . 70 . 72 . 74 ) in a bore ( 78 ) of a valve housing ( 50 ) of the directional valve ( 46 ), wherein the bore ( 78 ) between a valve slide leading slide bore ( 54 ) and a cylinder bore leading to the piston ( 80 ) is trained. Hydraulic directional control valve according to one of the claims 6 to 11, wherein for each functional position of the valve spool ( 58 ) at least one each from a piston ( 84 ) acted upon locking element ( 68 . 70 ; 72 . 74 ) is provided, wherein the at least one latching elements ( 68 . 70 ; 72 . 74 ) of the functional positions in the longitudinal direction of the valve spool ( 58 ) are offset from each other. Hydraulic directional control valve according to one of the claims 6 to 12, wherein in each case at least two around the valve spool ( 58 ) evenly distributed around locking elements ( 68 . 70 ; 72 . 74 ) for latching the valve spool ( 58 ) are provided in a functional position. Hydraulic directional control valve according to claim 1, wherein the latching device has a latching element which is acted upon by a piston, in particular via a detent spring, with a latching force, wherein the piston delimiting a pressure chamber with a piston surface acting in Verrastungsrichtung and wherein the piston via the pressure chamber at a existing pressure medium volume flow can be acted upon by a system pressure and wherein the pressure chamber via a valve whose position depends on the pressure medium volume flow, is connected to non-existing pressure medium volume flow to a tank. Hydraulic directional control valve according to claim 14, wherein the valve is a pressure compensator of a load-sensing control or a check valve.

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