WO2013087156A2

WO2013087156A2 - Pressure limiting valve and closed hydraulic circuit having a pressure limiting valve

Info

Publication number: WO2013087156A2
Application number: PCT/EP2012/004996
Authority: WO
Inventors: Hakan Camurdan; Robert Wanner; Jürgen GINTER; Dirk Van Aalst; Markus GEPRÄGS
Original assignee: Robert Bosch Gmbh
Priority date: 2011-12-14
Filing date: 2012-12-04
Publication date: 2013-06-20
Also published as: WO2013087156A3; DE102011121052A1

Abstract

Disclosed is a pressure limiting valve arrangement having a pressure limiting valve, preferably a low-pressure limiting valve, having a valve body, onto the first control surface of which a system pressure to be limited is applied in the opening direction, e.g. via a first control line or via a first control connection. In addition, the pressure limiting valve has a spring via which the valve body is pressurised in the closing direction. According to the invention, the valve body has a second control surface onto which system pressure can be applied via a second control line or a second control connection. The system pressure can also act on the second control surface to a reduced or throttled extent. A closed hydraulic circuit with two working lines, into which a feed pump can convey a substitute pressurising agent to make up a shortfall via a supply line, is also disclosed. The supply line can be relieved with various response pressures via a pressure limiting valve arrangement of the type described above.

Description

Pressure relief valve and closed hydraulic circuit with a pressure relief valve

description

The invention relates to a pressure relief valve according to the preamble of

Patent claim 1 and a closed hydraulic circuit with such a pressure relief valve.

Pressure relief valves are connected to hydraulic systems to limit their system pressure. For this purpose, the system pressure acts via a control line in the opening direction on a valve body, while against a spring acts on the valve body in the closing direction with a force. When the system pressure exceeds the pressure equivalent of the spring force, the valve body is moved to an open position, and the system relieved via the pressure relief valve.

The document DE 196 40 545 A1 and the document DE 10 2004 057 740 B4 each show a pressure relief valve which serves to limit the pressure of a feed line. About the feed line pressure medium in a low pressure leading working line of a closed hydraulic circuit is promoted by a feed pump, which serves as a substitute pressure means for a shortage of the circle.

In the publication DE 10 2004 057 740 B4, a control pressure is additionally tapped from the supply line via a control line, which is used to adjust a

Variable displacement pump of the closed circuit is used. Furthermore, one is

Pressure cutting device, which limits the pressure in the control line. The pressure cut device relieves the control line to a tank when the pressure of the high pressure working line exceeds the pressure equivalent of the spring force. Since this reduction of the control pressure leads to a pivoting back of the variable displacement pump, which promotes the working line leading to high pressure, the pressure in the high-pressure leading working line is indirectly limited via the pressure cutting device. A disadvantage of said pressure relief valves that their set pressure is always defined by the spring and therefore is not changeable.

Furthermore, pressure limiting valves are known from the prior art whose spring force is variable, whereby the response pressure of the pressure limiting valve can be adjusted in a predetermined interval.

On the other hand, the object of the invention is to provide a pressure limiting valve in which the possibilities of changing the response pressure is widened and improved.

This object is achieved by a pressure limiting valve arrangement having the features of patent claim 1

In DE 10 2004 057 740 B4, in addition to the conventional pressure limiting valve, a feed pressure reduction device is shown, via which the feed line can be connected to the suction side of the constant feed pump in order to reduce the pressure build-up in the feed line. This feed pressure lowering device is transitionally, e.g. activated when starting an internal combustion engine, which also drives the feed pump in addition to the variable. This serves to relieve the

Starter.

The closed hydraulic circuit according to the invention with feed pump and feed pressure line is the object of the pressure protection and the

Reduce pressure drop of the supply pressure line device technology.

This problem is solved by a closed hydraulic circuit with the

Features of claim 12.

The pressure limiting valve arrangement according to the invention has a pressure limiting valve-preferably a low-pressure limiting valve-which has a valve body whose first control surface-for example via a first control line or via a first control line Control connection - is acted upon in the opening direction with a system pressure to be limited. With a spring, the valve body is acted upon in the closing direction.

Furthermore, the valve body has a second control surface, which can be actuated via a second control line or a second control connection with system pressure. In this way, the set pressure of the pressure limiting valve arrangement according to the invention or of its pressure limiting valve can be changed over between two different values which are clearly spaced apart from one another.

The system pressure may be reduced at the second control surface. If this pressure reduction is optional, a third set pressure can be set. If this pressure reduction is variable, the response pressure can be selected within an interval spaced from the first response pressure.

Further advantageous embodiments of the invention are in the dependent

Claims described.

According to a first basic variant, the second control surface acts against the spring in the opening direction of the valve body. This can be reduced by pressurization of the second control surface of the response pressure of the pressure relief valve assembly according to the invention or its pressure relief valve over the prior art.

According to a second basic variant, the second control surface acts together with the spring in the closing direction of the valve body. This can be increased by pressurizing the second control surface of the set pressure.

In a device-technically simple embodiment, a switching valve designed as a 2/2-way valve is arranged in the second control line, or the second control connection is preceded by such a switching valve. Over a nozzle could then be relieved the second control surface.

Preferably, the second control line is shut off in a biased by a spring basic position (normally closed), and in a by an electric magnet activated switching position open. This is set in the de-energized state of the switching valve in the first basic variant, an increased response pressure and the second basic variant, a reduced set pressure of the pressure relief valve assembly according to the invention.

In the second control line may alternatively be arranged as a 3/2-way valve switching valve, or the second control terminal is such

Switching valve upstream.

The second control surface is relieved in the one switching position of the switching valve via the valve to a tank and acted upon in the other switching position with the pressure at the inlet of the pressure relief valve. The one switching position can be activated by an electromagnet switching position or the biased by a spring basic position. This is in the de-energized state of the switching valve in a first basic variant, a reduced set pressure and the second principal variant, an elevated set pressure of the invention

Pressure limiting valve arrangement set.

In a particularly preferred refinement, a pressure reducing valve designed as a proportionally adjustable 3/2 way valve is arranged in the second control line, or the second control connection is preceded by a pressure reducing valve designed as a 3/2 directional control valve. Thus, the second control pressure, which - based on the system pressure - applied to the second control terminal, can be variably reduced. Thus, the response pressure can be selected within an interval spaced apart from the first response pressure.

It is preferred if a valve body of the pressure reducing valve in a biased by a spring basic position relieves the second control surface to a tank, and if the valve body of the pressure reducing valve is movable by an adjustable electromagnet in switching positions, whereby the second control line controlled against the force of the spring becomes. This results in a control engineering stabilization of the pressure reducing valve when connected to the second control line between the pressure reducing valve and the

Pressure control valve is connected to a further control line, via which the valve body of the pressure reducing valve is acted upon in the direction of its basic position.

In a particularly preferred embodiment, the valve body of the pressure relief valve is guided displaceably in a valve sleeve, wherein a radially expanded conical portion of the valve body of the pressure limiting valve is biased by the spring against a valve seat forming a circumferential edge of the valve sleeve. In this case, the first control surface is arranged on an inner region of the conical section and bounded by the valve seat on its outer periphery. According to the first basic variant of the pressure limiting valve arrangement according to the invention, an end face of the valve body of the pressure limiting valve remote from the conical section forms the second control surface.

In a preferred embodiment, the pressure limiting valve arrangement or the pressure limiting valve according to the invention is a screw-in valve. For this purpose, the valve bush has a screw thread on its outer circumference.

On the outer circumference of the valve sleeve adjacent to the screw thread, a housing of the pressure reducing valve may be attached. Then, three radial holes or three hole stars are arranged in the contact area of the housing of the pressure reducing valve in the valve sleeve. These form, firstly, a connection of the pressure reducing valve with a arranged in a longitudinal bore of the valve sleeve second control chamber and secondly, a connection of the pressure reducing valve with the system pressure to be limited and third, a connection of the pressure reducing valve with a tank relieved spring chamber of the pressure relief valve.

The closed hydraulic circuit according to the invention has two working lines into which replacement pressure means for a shortage can be conveyed from a feed pump-preferably from an internal gear pump-via a feed line. The feed line can be relieved via a pressure relief valve arrangement described above. In normal operation, this pressure relief valve arrangement can be used for increased response pressure and in idle or in load-reduced operation to be set to reduced set pressure. Thus, when the hydraulic circuit is transitionally operated at idle or load reduced, the power consumption of the feed pump is reduced to save energy.

In a preferred development of the hydraulic circuit, an adjustment unit of a variable displacement pump is connected to the supply line via an adjustment pressure line. Thus, the necessary for adjusting the variable adjustment pressure is generated by the feed pump.

In a particularly preferred application of the above-described hydraulic circuit, this is in a vehicle - e.g. Concrete mixer - or provided in a mobile work machine. The vehicle or the work machine has an internal combustion engine, to which the variable displacement pump of the circuit is coupled. A Versteilmotor the circle is connected to a temporary or transitional operated auxiliary unit -. coupled to a mixing drum - the vehicle or the work machine. In this application, the hydraulic circuit energy can be saved by the fact that the pressure limiting valve arrangement is set to the reduced set pressure in load-free or low-load mitlaufendem additional unit. Thus, the power consumption of the feed pump and thus the

Internal combustion engine reduced.

In the following, various embodiments of the invention will be described in detail with reference to FIGS.

Show it

1 shows a circuit diagram of a first embodiment of the pressure limiting valve arrangement according to the invention.

FIG. 2 shows a circuit diagram of a second exemplary embodiment of the pressure limiting valve arrangement according to the invention,

FIG. 3 shows a circuit diagram of a third exemplary embodiment of the pressure limiting valve arrangement according to the invention, FIG. 4 shows a circuit diagram of a fourth exemplary embodiment of the pressure limiting valve arrangement according to the invention,

Figure 5 shows the first embodiment of the Druckbegrenzungsven- tilanordnung invention in a sectional perspective view and

6 shows a part of an embodiment of a closed hydraulic circuit according to the invention with the first embodiment of the Druckbegrenzungsven- tilanordnung according to Figure 1 or 5.

FIG. 1 shows a circuit diagram of a first exemplary embodiment of the pressure limiting valve arrangement 1 according to the invention. It is connected to a hydraulic system whose system pressure is to be monitored or limited. Of the hydraulic system, only one line 4 is partially shown. This opens into a pressure relief valve 3, the valve body 2 is biased by a spring 6 (in Figure 1) to the left in the closing direction. In the manner known from the prior art, the system pressure prevailing in the line 4 counteracts in the opening direction. For this purpose, the system pressure prevailing at the inlet of the pressure limiting valve 3 acts via a first control line 12 and via a first control chamber 8 on a first control surface 10 of the valve body 2.

According to the invention a second control line with the sections 14a and 14b is provided which connects the system pressure leading line 4 with a second control chamber 16. The second control chamber 16 is bounded by a second control surface 18, which is arranged on the valve body 2 and acts on this in the closing direction with a second control pressure. In this case, in the second control line 14a, 14b designed as a 3/2-way valve pressure reducing valve 20 is arranged. It has a valve body 22 which is biased by a spring 24 in the closing direction. Furthermore, the valve body 22 is acted upon via a further control line 25 from the outlet pressure of the pressure reducing valve 20 and thus from the second control pressure of the pressure limiting valve 3 in the closing direction. The counteracts an adjustable solenoid 26 in the opening direction. With the pressure reducing valve 20, the system pressure prevailing in the line 4 and in the first section of the second control line 14a can be reduced so as to produce a variable further in the opening direction of the pressure limiting valve. valve 3 to generate effective control force. Thus, the response pressure of the first embodiment of the pressure relief valve arrangement 1 according to the invention can be reduced steplessly as a function of energization of the electromagnet 26.

FIG. 2 shows a circuit diagram of a second exemplary embodiment of the pressure-limiting valve arrangement 101 according to the invention. This is simpler in terms of device technology compared with the first exemplary embodiment according to FIG. 1 and is reduced in scope of functions. For this purpose, instead of the pressure reducing valve 20 of the first exemplary embodiment, a 3/2-way switching valve 120 is provided in the second control line 14a, 14b. The other technical characteristics correspond to the first one

Embodiment of Figure 1.

In a (shown in Figure 2) biased by a spring 124 basic position of the switching valve 120, the portion 14a of the second control line 14a, 14b is shut off. The portion 14b of the second control line is relieved in the basic position of the switching valve 120 to the tank, whereby the second control surface 18 does not transmit an assisting opening force to the valve body 2 of the pressure limiting valve 3. Therefore, in the basic position of the 3/2-way switching valve 120, the set pressure of

Druckbegrenzungsventiis 3 comparatively high, while it is lowered by energizing an electromagnet 126 of the 3/2-way switching valve 120. For this purpose, the directional control valve 20 switches into an open position, whereby the voltage applied in the line 4 system pressure via the second control line 14a, 14b also abuts against the second control surface 18 and thus supports an opening movement of the valve body 2 of the pressure limiting valve 3.

The first and the second embodiment of the Druckbegren- tion valve arrangement 1 according to the invention; 101 are constructed according to the first basic variant of the pressure limiting valve arrangement according to the invention, in which the second control pressure via the second control surface 18 facilitates an opening movement of the pressure limiting valve 3. In this first basic variant applies in the de-energized state of the valve 20; 120: FFeder - Pi * A- | - ^► PNDI ~ FFeder Ai

In the first basic variant applies in the energized state of the valve 20; 120:

FFeder = Pl * Ai + p ₂ * A ₂

FFeder = Pl * + p ₂ * A * = ^ * (Pl + p ₂ * i)

F _F erer / Ai = Pl + p ₂ * I

With:

A ₂ = size of the second control surface 18

Ai = size of the first control surface 10

i = A ₂ / A †

Pi = first control pressure

p ₂ = second control pressure

If e.g. both control surfaces 10, 18 are the same size, and if in the first embodiment, the second control pressure is not reduced by the pressure reducing valve 20 or when the second embodiment, the switching valve 120 is opened, results in halving the response pressure of the pressure relief valve assembly 1, 101st

Figure 3 shows a third embodiment and Figure 4 shows a fourth embodiment of the pressure relief valve assembly 201 according to the invention; 301, wherein the second control pressure according to the second basic variant via the second control pressure line 14a, 14b acts on a valve body 202 of the pressure relief valve 203 in the closing direction. In this case, the second control pressure acts in the second control chamber 216 together with a spring 206 against the pressure of the first control chamber 208. In the third embodiment according to Figure 3 and in the fourth embodiment shown in FIG 4, the prevailing in the line 4 to be limited system pressure on the first control line 12th guided to the first control surface 210 and acts there in the opening direction. In the third exemplary embodiment according to FIG. 3, a 3/2-way switching valve 220 is provided in the second control line 14a, 14b and pressurizes the second control surface 218 with system pressure in a basic position (shown in FIG. 3) and biased by a spring 124. In a switched by an electromagnet 126 switching position, the second control surface 218 is relieved via a tank line T to the tank.

In the fourth exemplary embodiment of the pressure limiting valve arrangement 301 according to the invention according to FIG. 4, the pressure reducing valve 20 described with reference to FIG. 1 is arranged in the second control line 14a, 14b. Thus, starting from the system pressure prevailing in the line 4, the second control pressure acting in the closing direction can be reduced steplessly.

In the second basic variant applies in the de-energized state of the 3/2-way switching valve 220 according to Figure 3 and in the energized state of the pressure reducing valve 20 according to Figure 4:

FFeder = Pl * P2 ^* A ₂

Fpeder = Pi * Ai ^* i - p ₂ ^* Ai = Ai ^* (p _! ^* I - p ₂ )

F _F erer / Ai = Pi ^* i-p ₂

with i = A ₂ / Ai

In the second basic variant applies in the energized state of the 3/2-way switching valve 220 according to Figure 3 and in the de-energized state of the pressure reducing valve 20 according to Figure 4:

FFeder = Pi * Α · | - »P D2 ⁼ Fpeder Ai

FIG. 5 shows the first exemplary embodiment of the pressure limiting valve arrangement 1 according to the invention in a sectional perspective view. The Pressure relief valve 3 has a valve sleeve 28 which is screwed via an external screw thread 30 in a housing 32 of a hydraulic device not shown in detail. The hydraulic device may be a connection plate or a pump. In the line 4 of the hydraulic device is to be monitored or limited system pressure. In the valve sleeve 28, the valve body 2 is guided displaceably. He has at his (in Figure 5) right end portion a

Cone portion 34, which is radially opposite a substantially circular cylindrical

Main section is expanded. The cone portion 34 forms with a peripheral edge of the valve sleeve 28 a valve seat 36 and is biased via a valve disc 38 of the spring 6 (in Figure 5 to the left) in the closing direction.

The line 4 and the cone portion 34 are connected to each other via the first control line 12 and the first control chamber 8. In this case, the first control line 12 extends radially in the valve sleeve 28, while the first control chamber 8 is formed by a pressure chamber which includes the valve body 2 in sections.

The (in Figure 5) left end face of the valve body 2 serves as a second control surface 18, which is acted upon via a radial bore 14b and the second control chamber 16 with the second control pressure. The second control pressure can be regulated by the pressure reducing valve 20. For this purpose, a housing 40 of the pressure reducing valve 20 comprises a protruding from the housing 32 end portion of the valve sleeve 28 and connects in this way the pressure reducing valve 20 via the radial bore 14b with the second control chamber 16. Furthermore, the pressure reducing valve 20 via radial bores and longitudinal bores 14a with the line 4 in connection. Also via radial bores and longitudinal bores T is the pressure reducing valve 20 in conjunction with a spring chamber 42 of the pressure relief valve. The spring chamber 42 is relieved via a further tank channel T to the tank.

Figure 6 shows a part of an embodiment of a closed hydraulic circuit according to the invention. The circle is provided on a concrete mixer vehicle and serves for the temporary drive of a mixing drum (not shown). For this purpose, the circle has a variable displacement pump 44, from the two working lines 46, 48th a (not shown) Versteilmotor is driven. The Versteilmotor serves to drive the mixing drum.

The variable displacement pump 44 is driven by an internal combustion engine (not shown), wherein a feed pump 50 designed as a fixed displacement pump is also driven by a rigid mechanical coupling. This promotes from a tank via a feed line 52 and one of two check valves 54 replacement pressure medium in the respective low pressure leading working line 46, 48th

From the feed line 52 branches off an adjusting pressure line 56, which via a

Proportional valve 58 is connected to a double-acting adjusting 60 of the variable displacement pump 44.

The feed line 52 can be relieved via the pressure relief valve assembly 1 according to Figures 1 and 5 at different response pressures.

In a first operating state of the hydraulic circuit according to the invention, the mixing drum is driven under load, wherein the feed pump 50 and the feed line 52 are secured at the elevated pressure level. This is achieved by the basic position of the pressure reducing valve 20 (cf., explanations to FIG. 1), the second control surface 18 being relieved of pressure.

In a second operating state of the hydraulic circuit according to the invention with reduced power, the pressure reducing valve 20 is energized, whereby the set pressure of the pressure relief valve 3 is significantly reduced. Thus, the pressure of the feed line 52 and the load of the feed pump 50 is reduced, resulting in a discharge of the (not shown) internal combustion engine.

Notwithstanding the embodiment shown in Figure 6, the other embodiments of the pressure relief valve assembly according to Figures 2 to 4 instead of the pressure limiting valve assembly of Figure 1 can be connected to the feed line 52. Disclosed is a pressure limiting valve arrangement with a pressure limiting valve - preferably low pressure limiting valve - which has a valve body, the first control surface - for example, via a first control line or via a first control terminal - is acted upon in the opening direction with a system pressure to be limited. Furthermore, the pressure relief valve has a spring, via which the valve body is acted upon in the closing direction. The valve body has a second control surface, which can be pressurized via a second control line or a second control connection with system pressure. The system pressure may also be reduced or throttled at the second control surface.

Disclosed is still a closed hydraulic circuit with two working lines, in which can be supported by a feed pump via a feed line replacement pressure means for a shortfall. The supply line can be relieved via a pressure relief valve arrangement described above with different response pressures.

Claims

claims

A pressure limiting valve arrangement (1; 101; 201; 301) having a

A pressure limiting valve (3; 203) having a valve body (2; 202), the first control surface (10; 210) of which is subjected to a system pressure to be limited in the opening direction, and a spring (6; 206) via which the valve body (2; 2, 202) is acted upon in the closing direction, characterized in that the valve body (2; 202) has a second control surface (18; 218) which can be pressurized with system pressure via a second control line (14a, 14b) or a second control connection.

2. Pressure relief valve arrangement according to claim 1, wherein the second

Control surface (18) in the opening direction of the valve body (2) acts.

3. Pressure limiting valve arrangement according to claim 1, wherein the second

Control surface (218) acts in the closing direction of the valve body (202).

4. Pressure limiting valve arrangement according to one of the preceding claims, wherein in the second control line designed as a 2/2-way valve switching valve is arranged or wherein the second control port is designed as a 2/2-way valve switching valve upstream.

5. Pressure limiting valve arrangement according to one of claims 1 to 3, wherein in the second control line (14a, 14b) designed as a 3/2-way valve switching valve (120, 220) is arranged, or wherein the second control port as a 3/2-way valve trained switching valve (120, 220) is connected upstream.

6. Pressure relief valve arrangement according to one of claims 1 to 3, wherein in the second control line (14 a, 14 b) designed as a proportionally adjustable 3/2-way valve pressure reducing valve (20) is arranged, or wherein the second

Control connection designed as a 3/2-way valve pressure reducing valve (20) is connected upstream.

7. A pressure relief valve assembly according to claim 6, wherein a valve body (22) of the pressure reducing valve (20) relieves the second control surface (18; 218) to a tank in a biased by a spring (24) basic position, and wherein the valve body (22) of the pressure reducing valve (20) of an adjustable electromagnet (26) is movable in switching positions, via which the second control line (14a, 14b) against the force of the spring (24) aufsteuerbar.

8. Pressure limiting valve arrangement according to claim 7, wherein the second

Control line (14b) between the pressure reducing valve (20) and the pressure limiting valve (3; 203), a further control line (25) is connected, via which the valve body (22) of the pressure reducing valve (20) is acted upon in the direction of its basic position.

9. Pressure limiting valve arrangement at least according to claims 2 and 6, wherein the valve body (2) of the pressure limiting valve (3) in a valve sleeve (28) is displaceably guided, and wherein a radially expanded cone portion (34) of the valve body (2) of the pressure relief valve (3 ) is biased against a valve seat (36) forming peripheral edge of the valve sleeve (28) via the spring (6), and wherein the first control surface (10) on the cone portion (34) is arranged and bounded by the valve seat (36), and one being removed from the cone portion (34)

arranged end face of the valve body (2) of the pressure limiting valve (3) forms the second control surface (18).

10. Pressure limiting valve arrangement according to claim 9, wherein the

Valve bush (28) on its outer circumference has a screw thread (30).

11. Pressure relief valve assembly according to claim 10, wherein on the outer circumference of the valve sleeve (28) adjacent to the screw thread (30) a housing (40) of the pressure reducing valve (20) is fixed, and wherein in the contact region of the housing (40) of the pressure reducing valve (20) in the Valve sleeve (28) has three radial bores (14 b) or three bore stars (14 b) are provided, which connects the

Pressure reducing valve (20) with one in a longitudinal bore of the valve sleeve

arranged second control chamber (16) and a connection of the Pressure reducing valve (20) with the system pressure to be limited and a connection of the pressure reducing valve (20) with a tank relieved spring chamber (42) of the pressure limiting valve (3) form.

A closed hydraulic circuit with two working lines (46, 48) into which replacement pressure medium can be conveyed by a feed pump (50) via a feed line (52), having a pressure relief valve arrangement (1; 101; 201; 301) according to any one of

previous claims.

13. A circuit according to claim 12 with a variable displacement pump (44), wherein of the

Supply line (52) branches off an adjusting pressure line (56), which with a

Adjustment unit (58, 60) of the variable displacement pump (44) is connected.