EP0837275B1 - Solenoid actuated relief valve for electro-hydraulic lifting devices - Google Patents

Description

The invention relates to a solenoid operated drain valve according to the preamble of Claim 1.

In practice, a concept of the lifting module is used for small, inexpensive lift trucks known, according to which the discharge control of the pressure medium by a Black / white drain valve is performed as it is from data sheet D 7490/1 from March 1996 by Heilmeier & Weinlein, 81673 Munich. Two different connections of the drain valve are possible. In the first case locks the drain valve when the magnet is de-energized. The control of the lifting movement takes place about the pump. The lowering movement is controlled by means of the drain valve, which is brought into the open position by the current-applied magnet. For the lowering function, the pilot valve is opened completely, so that the Load pressure with the control chamber relieved via a differential area on the closing element the closing element lifts in the opening direction over the entire opening stroke. in the the second case is the drain valve when the magnet is de-energized in the open position. There is a two-position switching valve between the consumer and the branch to the drain valve intended. The lifting and lowering movements are by means of both valves controlled. When lifting is in the load holding position Two-position switching valve the drain valve by energizing the magnet in the closed position is set and the lifting speed is controlled by the pump. To lower the drain valve to the closed position and the two-position switching valve in the drain position before the drain valve in the open position is switched. Regardless of the wiring principle, the Black / white drain valve when lowering does not control the ramp function as it is for Forklift is desired. The in the first case as a closing spring and in the second case as The opening spring for the pilot valve is soft in both cases, i.e. it has a spring characteristic with no appreciable increase. Furthermore, the nozzle and the passage of the pilot valve for quick response of the Drain valve as large as possible and, for example, designed with regard to the minimum drain quantity. The locking element works exclusively with a seat function with the Main valve seat together to absolute in the closed position of the drain valve To ensure tightness. This tightness is necessary to ensure that the load pressure is maintained for a long time.

In the case of more complex lifting modules for larger and more expensive forklifts, there is an interconnection principle according to DE-C2-42 39 321 known, in which the drain control via a Two-way current regulator takes place, which is designed to be stack-tight. It is at Lowering movements are given a ramp function, however, the construction effort considerable for this, so that this lifting module in small and inexpensive lift trucks is not used for cost reasons.

A valve known from GB-A-2 041 169 is an electromagnetic valve and Faucet to be closed, in which a pressure shock when closing and high Mechanical loads when opening are avoided by using a hydraulic Damping for the opening and closing movement is provided. This is accomplished due to the cross-section of the overflow channels, which change depending on the stroke open the control chamber of the pilot valve. One with the actuating magnet (Black / white magnet) provided spring is only for resetting of the armature, which the magnet cannot move in this direction. The magnet enables no setting of intermediate positions for quantity control. Further the valve is not a tight seat valve, as is the case in high-pressure hydraulics for lifting modules is needed. The stroke-dependent change in cross-section of the overflow channels is used to control the flow rate in such a way that an initially rapid opening stroke gradually slows down and an initially rapid closing stroke gradually to be slowed down. A ramp function cannot be achieved with the known valve.

Further prior art is contained in US-A-3 977 649, FR-A-1 110 895 and US-A-5 205 531.

The invention has for its object a drain valve of the type mentioned to create a structurally simple and inexpensive ramp function for controlling the lowering movements. It is aimed at, despite the ramp function is the proven and simple construction principle of the previous one Maintain black and white drain valves. Furthermore, a clean one Ramp function when lowering allowable drain valve can be created that too is usable for larger and more complex forklift trucks, for example with a lifting module according to DE-C2-42 39 321.

The object is achieved according to the invention with the features of claim 1 solved.

Surprisingly, the replacement of the previously used soft spring results by a hard spring and by integrating the quantity adjustment device clean ramp function for controlling the lowering movement. The concept of Black and white drain valve can be maintained with very little modification, i.e. the components of the black / white drain valve can largely to be used. The magnet is capable of depending on its current application exactly predeterminable and exactly reproducible opening positions of the pilot valve to which the closing element regulates itself automatically adapts with game movements. The black / white function is replaced by a Control function of the drain valve, the amount setting device one for Ramp function provides important volume regulation of the pressure medium to be drained. The ramp function is given when opening and closing the drain valve. The manufacturing cost is low, so that the drain valve is particularly suitable for small and inexpensive forklift is usable, which is an enormous price pressure subject. The necessary forklift tightness or absolute tightness to hold the Load pressure remains. The one previously used for the black / white drain valve concept Magnet can be easily modified so that its force characteristic curve becomes the characteristic curve fits the hard spring.

According to claim 2, the passage of the pilot valve or the Throttle size of the upstream throttle reduced. With that one becomes achieved milder response. However, this is for the desired ramp function advantageous. The throttle and the passage can be the same size and should not be larger than 0.6 mm in practice. The throttle is expedient however smaller than the passageway. In practice, for example, a throttle is used a diameter of 0.4 mm in front of a passage with approx. 0.5 mm. Thereby a jerk and a jerk when lowering can be largely avoided.

According to claim 3, the hard spring acts on the closing member in the closing direction of the pilot valve which is opened in the opening direction by the movable armature of the magnet is adjustable.

Alternatively, according to claim 4, the closing member by the hard spring in the opening direction of the pilot valve biased. In both cases (claims 3 and 4) positions of the ram can be precisely predicted and reproduced adjust by means of the magnet, the closing element moving with play adapts to the respective position of the plunger.

The embodiment according to claim 5 is structurally simple and reliable there is an absolutely tight closed position on the seat edge of the tapered surface. When the conical surface is initially lifted off the seat edge, pressure medium flows via the pilot valve and the gap between the spool bore portion and the slide approach before increasing the opening stroke of the closing element a kind of aperture control takes place. Only shortly before the full opening position or in the fully open position there is an essentially unregulated pressure medium flow. The volume control over the stroke of the closing element can be constructively pre-determine their identifier.

According to claim 6, the gap is in the range of conventional slide fits.

An embodiment which is favorable in terms of production technology emerges from claim 7.

The embodiment according to claim 8 is simpler in terms of production, in which a desirable low coverage for barely noticeable jerks is achieved.

According to claim 9, the coverage should be as small as possible.

According to claim 10, the ramp function using as many as possible Components of the black / white drain valve reached what the manufacturing cost the drain valve for the ramp function is influenced favorably. It is possible at the Black and white drain valve to replace only the spring and the closing member, and the Modify magnets slightly to achieve the ramp function.

A rigid or hard spring with a steep characteristic curve used according to the invention is for example, a spring characterized by a force of 13N or more per mm Travel, while a soft spring with a flat characteristic, for example is characterized by a force of 8N or less per mm of travel.

Fig. 1

ein Blockschaltbild einer ersten Ausführungsform eines Hubmoduls,

Fig. 2

ein Blockschaltbild einer zweiten Ausführungsform eines Hubmoduls,

Fig. 3

einen Teil eines vergrößerten Längsschnitts eines Ablaßventils entsprechend der ersten Ausführungsform gemäß Fig. 1,

Fig. 4

einen Teil eines vergrößerten Längsschnitts eines Ablaßventils der Ausführungsform der Fig. 2,

Fig.5 + 6

Detailschnitte zu zwei Varianten, und

Fig. 7

ein Federkennliniendiagramm.

Embodiments of the subject matter of the invention are explained with the aid of the drawing. Show it:

Fig. 1

2 shows a block diagram of a first embodiment of a lifting module,

Fig. 2

2 shows a block diagram of a second embodiment of a lifting module,

Fig. 3

1 shows a part of an enlarged longitudinal section of a drain valve according to the first embodiment according to FIG. 1,

Fig. 4

1 shows a part of an enlarged longitudinal section of a drain valve of the embodiment in FIG. 2,

Fig. 5 + 6

Detailed cuts to two variants, and

Fig. 7

a spring characteristic diagram.

A lifting module H according to FIG. 1 for a forklift truck, in the lifting movements of one Load by means of a cylinder Z in speed and extent by means of a pump P are controlled, a pump P driven by a motor M points to the cylinder Z running working line 1. The pump P draws in from a tank T, in the one branching off from the working line 1 drain line 5 with two sections 5a and 5b opens. Another drain line 3 contains a system pressure relief valve 4. Between the drain lines 3 and 5 is in the working line 1 in the direction check valve 2 blocking the pump P. Between the sections 5a, 5b of the drain line 5, a solenoid-operated drain valve V is provided, namely - as indicated by the parallel lines - a regulating drain valve V. In the symbolic representation of FIG. 1 is a closing element of the Drain valve V indicated by 7, which is shown by a spring 8 in the direction of the Closed position and adjustable by a magnet 6 in a through position is. The magnet 6 can be excited according to an arrow 9 with a variable current with which a ramp function is controlled.

In Fig. 1, the drain valve V is in the closed position when the magnet 6 is de-energized. With the ramp function, you can sensitively move from a standstill when lowering control a gradual increase in speed of the load and a gradual one Decrease in speed to a standstill, essentially without noticeable Starting or stopping jerk.

According to FIG. 2, in contrast to the embodiment according to FIG. 1, there is between one Branch 10 of the drain line 5 and the cylinder Z a two-position switching valve V2 provided by a switching magnet 11 from the shut-off position in the The through position can be switched (black / white valve V2). The solenoid-operated shut-off valve V ', which is also a control valve, holds when the magnet 6 is de-energized, the through position (shown in FIG. 7) and is applied to the magnet 6 with a variable current (arrow 9) Regulation of the pressure medium quantity to be drained in several positions or continuously adjusted to the closed position.

The construction of the drain valve V for the circuit shown in FIG. 1 goes 3. A stepped bore 12 is provided in a housing 11 the sections 5a and 5b of the drain line 5 intersects. With A is the load pressure side indicated, while B represents the discharge side to the tank T. In the stepped bore 12 a sleeve-like insert 13 is positioned between the sections 5a and 5b a main valve seat S with a sharp (or possibly chamfered) seat edge 14 contains. A cylindrical slide bore section adjoins the seat edge on the discharge side B. 15 on. Several unthrottled passages lead to load pressure side A. 17. The insert 13 is by means of a screw-in body 18 in the stepped bore 12 fixed, which carries the magnet 6. A magnet 19 is contained in the magnet 6, that for adjusting a movable armature 20 (upwards in FIG. 3) with variable Electricity can be applied. The armature 20 has a bore 21 into which a hard spring 22 engages, which is held in a stationary core of the magnet 6 is (spring abutment 23), and a plunger 24 in the bore 21 with bias acted down.

The plunger 24 has a head part 25, on which the spring 22 rests, and which in the 3 shown in the closed position of the drain valve V on a shoulder 39 of the movable Anchor 20 sits. The lower end of the plunger 24 is approximately conical designs and forms a closing member 26 of a pilot valve C. The pilot valve C monitors the connection between a control chamber 27 at the top of one Closing element G and the discharge side B and has a passage 29 in the closing element G on, which is designed as a cylindrical throttle bore. If applicable a weak closing spring 40 for the closing element G in the control chamber 27 contain. A larger axial bore 30 connects to the passage 29. Between a throttle 28 is provided on the load pressure side A and the control chamber 27, for example in the form of a radial bore. The throttle 28 is for example approx. 0.4 mm in size, while the passage 29 is approx. 0.5 mm in size.

The closing element G works as a seat valve by means of a conical surface 31 with the seat edge 14 of the main valve seat S together. In this area there is also a quantity setting device E provided from the slide bore section 15 in Extension of the main valve seat S in the insert 13 and from a cylindrical Slide extension 32 in the extension of the conical surface 31 of the closing element G. and will be explained with reference to FIG. 6. The spring 22 is a hard spring, i.e. she has a characteristic (Fig. 7, 36b) with a considerable drop in the spring force F over the Deformation path s. In the known black / white drain valve according to the state In technology, the spring provided at this point is a soft spring with a Characteristic curve 37b with a flat course (indicated by dash-dotted lines). The magnet 6 is in its force characteristic is matched to the spring characteristic 36b of the hard spring 22 in FIG. 3, to set exactly reproducible different positions of the plunger 24 to be able to.

Function for FIGS. 1 and 3:

When the magnet 6 is de-energized, the hard spring 22 keeps the pilot valve C closed. In the control chamber 27, the load pressure on the load pressure side A prevails on one Area of the closing element G, which is larger than the area of the main valve seat S. The load pressure holds the closing element G in the closed position shown, in the absolute Tightness is given, as with the pilot valve C. Is used to initiate a Lowering the magnet 6 then acted on with a certain current the plunger 24 is pulled up into an intermediate position in which the closing member 26 emerges from the passage 29. The pressure in the control chamber 27 is reduced, so that the load pressure lifts the closing member G from the main valve seat S. The slide approach 32 initially cooperates with the slide bore section 15 initially allow a small amount of pressure medium to flow off, in addition to the Quantity of pressure medium that flows out through the open pilot valve C. The closing element G performs a game movement in which a state of equilibrium is established, in which the pilot valve depending on possible load pressure fluctuations C throttles just so far that a certain opening position or Game movement of the closing element G results in a predetermined amount of pressure medium flows out to the tank T. Is by amplifying the current for the magnet 6 the tappet 24 is positioned further up, then the closing element G follows accordingly, until finally the overlap between the slide section 32 and the slide bore section 15 is canceled, and pressure medium flows out stronger. With a further increase in the current for the magnet, the closing element can be Finally adjust G to the full open position. Will the electricity again reduced, then the closing element G throttles again. Will the current switched off, then the stiff or hard spring 22 initially closes the pilot valve C, before the load pressure subsequently closes the closing element G into the closed position adjusted, the plunger 24 follows this closing movement. It can be based on this Way a ramp function with only gradually increasing amount or with only gradually decrease the amount to the tank.

4, the armature 20 of the magnet 6 presses the plunger 24 when it is excited downward. The hard spring 22 is supported on a stationary abutment 23 'in one stationary anchor part 20 'and acts on the head part 25 of the plunger 24 in Direction upward with a biasing force to open the pilot valve C. This means that when the magnet 6 is de-energized, the load pressure in section 5 a Lifting element G lifts from the main valve seat S to the full open position (in 4, the full through position of the closing element G is not shown). The Magnet 6 is modified compared to FIG. 3 so that it is energized the plunger 24 adjusted downward in the closing direction of the pilot valve C, though if necessary, by means of an auxiliary tappet 24. The further construction of the drain valve V ' corresponds to that described in Fig. 3, i.e. also the size and characteristic of the Magnet 6 is approximately the same.

In both embodiments, the magnet 6 or the hard spring 23 is designed that he or she in the closed position results from the area of the passage 29 Force on the plunger 24 can overcome without noticeable jump. This Closing force results from the fact that the plunger 24 in the magnet 6 on all sides with the Pressure in the control chamber 27 is applied.

Function to Figs. 2 and 4:

When the magnet 6 is de-energized, the closing element G takes its open position a, since the hard spring 22 has placed the plunger 24 in the upper end position. Will the Magnet 6 is subjected to a preselected current, then the plunger 24 is countered the force of the hard spring 22 with the closing member 26 in the passage 29 of the Closing element G adjusted. The control pressure in the control chamber 27 increases. The Closing element G is in the direction of its closed position on the main valve seat S adjusted. The quantity of pressure medium flowing out via the main valve seat S is throttled. The closing element G can perform game movements in order to Pilot valve C to open or close more or less. When increasing the Current for the magnet 6, the plunger 24 is adjusted further down. the follows the closing element G towards its closed position, briefly to also act on the quantity setting device E before the final closed position starts. At maximum current on the magnet 6, the closing element G takes the final Closed position, in which the conical surface 31 sealing on the seat edge 14 seated. If the current applied to the magnet is then reduced again, then is the outflowing over the initial opening stroke of the closing element G. Pressure medium amount through the cooperation between the spool portion 32 and the slide bore section 15 (Fig. 3) regulated. It can be based on this Control the lowering movement of the load with a ramp function.

5, the conical surface 31 of the closing element G is directly through the Slide piston extension 32 extended. The slide bore section 15 begins in a distance from the seat edge 14, which is predetermined by an extension 33. Between the slide piston section 32 and the slide bore section 15 there is an overlap Ü in the closed position (FIG. 5), which is expedient can be less than 10% of the total opening stroke of the closing element G. The overlap Ü is defined, for example, by the step-like transition between the widening 33 and the slide bore section 15 and a lower one End edge 34 of the spool portion 32. It lies in this area Gap 35 in front, which is dimensioned in the manner of conventional slide fits, e.g. with 0.1 mm. Since the conical surface 31 lies in an outside of the slide piston section 32 Area cooperating with the seat edge 14, the conical surface 31 and the slide piston section 32 simply manufacture.

6 is the conical surface 31 of the closing element G for manufacturing reasons transferred into the slide piston section 32 via a fillet-like constriction 38, the one with a direct axial extension of the seat edge 14 Slide bore section 15 cooperates. The overlap Ü can do something to be taller. The gap 35 is dimensioned as specified.

7 is the characteristic curve 36a for the hard spring 22 of the embodiment of FIG. 4 indicated, in comparison to the spring characteristic 37a one usually in a black and white drain valve of this design uses a soft spring.

In itself, the same type of magnet 6 can be used in both cases necessary modifications are simple. It is favorable to have one in the drain valve V, V ' To use magnet 6, which is slightly stronger than the same size commonly used for the known black and white sense valve to in the drain valve V, V 'for the ramp function to match the hard spring. The reason for the soft spring in the known black / white drain valve is that the spring in a circuit in which the drain valve when the magnet is de-energized is closed, and is to ensure the resetting of the masses while this spring with the connection in which the drain valve is open when the magnet is de-energized, should only set the pressure at which the drain valve is opened without the Disrupt the closing stroke. The drain valve V, V 'with the ramp function has the hard one Spring 22, however, the additional task, in cooperation with the magnet 6th Different positions of the plunger can be reproducibly set in steps or continuously allow.

Claims (10)

1. Solenoid-operated outlet valve (V, V') for an electrohydraulic lifting module (H), in particular for a lifting stacker, having a closing element (G) which has an associated main valve seat (S) in the closing direction and to which the outlet pressure can be applied in the opening direction and to which a variable difference between the outlet pressure and the control pressure derived from the load pressure can be applied in the closing direction, having a pilot control valve (C) which can be operated by means of the magnet (6) and is arranged in a control chamber (27) for the closing element, for controlling the magnitude of the control pressure, having a restrictor (28) upstream of the control chamber, and having a closing element (26), which can be moved against a spring (22) by the magnet, for the pilot control valve, in which case the closing element can be acted on by the magnet against the spring, which acts either in the closing movement direction or in the opening movement direction, characterized in that, for a ramp function of the outlet valve (V, V'), the spring is a spring (22) with a steep characteristic (36a, 36b), and in that the closing element (G) and the main valve seat (S) form a quantity adjustment apparatus (E) which is dependent on the travel.
2. Outlet valve according to Claim 1, characterized in that the passage through the restrictor (28) is at most as large as the passage (29) through the pilot control valve (C), whose size corresponds at most to a hole with a diameter of 0.6 mm.
3. Outlet valve according to Claim 1, characterized in that the hard spring (22) applies a bias load to a plunger (24) having an approximately conical tip in the closing direction of the pilot control valve (C), in that the passage (29) through the pilot control valve (C) is an axial hole in the closing element (E) and in that the magnet (6) contains a moving armature (20) which can be caused to act on the plunger (24) in the opening direction of the pilot control valve (C).
4. Outlet valve according to Claim 1, characterized in that the hard spring (22) applies a bias load to a plunger (24) having an approximately conical tip in the opening direction of the pilot control valve (C), in that the passage (29) is an axial hole in the closing element (E) and in that the moving armature (20) of the magnet (6) acts on the plunger (24, 24') in the closing direction of the pilot control valve (C).
5. Outlet valve according to Claim 1, characterized in that the quantity adjustment apparatus (E) which is dependent on travel, comprises a conical surface (31), a cylindrical slide attachment (32) which enters the main valve seat (S), and a, possibly chamfered, seat edge (14), as well as a cylindrical slide hole section (15) which runs from the seat edge (14) to the side of the outlet pressure and interacts - by means of the slide attachment (32) with a gap (35) - at least over an initial travel range from the closed position of the closing element (G).
6. Outlet valve according to Claim 5, characterized in that the gap (35) size is equivalent to that of a normal sliding fit, for example about 0.1 mm.
7. Outlet valve according to Claim 5, characterized in that the slide hole section (15) is a direct extension of the seat edge (14), and in that a circumferential constriction (38) is provided between the conical surface (31) and the slide attachment (32) on the closing element (G).
8. Outlet valve according to Claim 5, characterized in that the slide hole section (15) starts at an axial distance from the seat edge (14) and has a smaller internal diameter than the seat edge (14), and in that the conical surface (31) runs directly as far as the slide attachment (32), whose external diameter is smaller than the internal diameter of the seat edge (14) and of the slide hole section (15).
9. Outlet valve according to Claim 5, characterized in that an axial cover (Ü) is provided between the slide section (32) and the slide hole section (15) in the closed position of the closing element (G) and, preferably, amounts to less than 10% of the total opening travel of the closing element (G).
10. Outlet valve according to at least one of the preceding claims, characterized in that said outlet valve is formed from a black/white outlet valve with its valve components and installation of a hard spring (22) instead of a soft spring, by means of the quantity adjustment apparatus (E), possibly by means of a reduction in the size of the passage (29) in the pilot control valve (C) and by means of the magnet (6) having a characteristic which is matched to the characteristic (26a, 26b) of the hard spring (22) and having a quantity control response which is proportional to the current applied to the magnet (6).

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