Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
  • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
  • F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
  • F15B11/02—Systems essentially incorporating special features for controlling the speed or actuating force of an output member
  • F15B11/028—Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the actuating force
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
  • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
  • F15B2211/00—Circuits for servomotor systems
  • F15B2211/20—Fluid pressure source, e.g. accumulator or variable axial piston pump
  • F15B2211/205—Systems with pumps
  • F15B2211/2053—Type of pump
  • F15B2211/20538—Type of pump constant capacity
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
  • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
  • F15B2211/00—Circuits for servomotor systems
  • F15B2211/30—Directional control
  • F15B2211/305—Directional control characterised by the type of valves
  • F15B2211/30505—Non-return valves, i.e. check valves
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
  • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
  • F15B2211/00—Circuits for servomotor systems
  • F15B2211/40—Flow control
  • F15B2211/405—Flow control characterised by the type of flow control means or valve
  • F15B2211/40507—Flow control characterised by the type of flow control means or valve with constant throttles or orifices
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
  • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
  • F15B2211/00—Circuits for servomotor systems
  • F15B2211/40—Flow control
  • F15B2211/405—Flow control characterised by the type of flow control means or valve
  • F15B2211/40515—Flow control characterised by the type of flow control means or valve with variable throttles or orifices
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
  • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
  • F15B2211/00—Circuits for servomotor systems
  • F15B2211/40—Flow control
  • F15B2211/41—Flow control characterised by the positions of the valve element
  • F15B2211/411—Flow control characterised by the positions of the valve element the positions being discrete
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
  • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
  • F15B2211/00—Circuits for servomotor systems
  • F15B2211/40—Flow control
  • F15B2211/415—Flow control characterised by the connections of the flow control means in the circuit
  • F15B2211/41572—Flow control characterised by the connections of the flow control means in the circuit being connected to a pressure source and an output member
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
  • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
  • F15B2211/00—Circuits for servomotor systems
  • F15B2211/40—Flow control
  • F15B2211/42—Flow control characterised by the type of actuation
  • F15B2211/426—Flow control characterised by the type of actuation electrically or electronically
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
  • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
  • F15B2211/00—Circuits for servomotor systems
  • F15B2211/40—Flow control
  • F15B2211/45—Control of bleed-off flow, e.g. control of bypass flow to the return line
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
  • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
  • F15B2211/00—Circuits for servomotor systems
  • F15B2211/40—Flow control
  • F15B2211/46—Control of flow in the return line, i.e. meter-out control
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
  • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
  • F15B2211/00—Circuits for servomotor systems
  • F15B2211/40—Flow control
  • F15B2211/47—Flow control in one direction only
  • F15B2211/473—Flow control in one direction only without restriction in the reverse direction
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
  • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
  • F15B2211/00—Circuits for servomotor systems
  • F15B2211/50—Pressure control
  • F15B2211/505—Pressure control characterised by the type of pressure control means
  • F15B2211/50563—Pressure control characterised by the type of pressure control means the pressure control means controlling a differential pressure
  • F15B2211/50572—Pressure control characterised by the type of pressure control means the pressure control means controlling a differential pressure using a pressure compensating valve for controlling the pressure difference across a flow control valve
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
  • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
  • F15B2211/00—Circuits for servomotor systems
  • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
  • F15B2211/705—Output members, e.g. hydraulic motors or cylinders or control therefor characterised by the type of output members or actuators
  • F15B2211/7051—Linear output members
  • F15B2211/7052—Single-acting output members

Definitions

• Hydraulic device for controlling the pressure medium flow
• the invention relates to a hydraulic device for controlling the flow of pressure medium to or from a single-acting cylinder loaded with a load, with a pump which conveys pressure medium from a tank to the single-acting cylinder, with a valve arrangement arranged between the pump and the single-acting cylinder, which together with a switching valve that returns pressure medium to the tank in the one switching position, controls the pressure medium flow to and from the single-acting cylinder, in particular for controlling the lifting mechanism of a mobile machine.
• Such a device for controlling the pressure medium flow to or from a single-acting cylinder loaded with a load is known from DE 40 30 952 AI. Details of the load acting on the single-acting cylinder are not given in this document.
• An electrically controlled shut-off valve is arranged between a constant pump and a single-acting cylinder. This check valve forms a valve arrangement with two connections, one in the
• Flow direction of the pressure medium works as a check valve and which allows a continuous fine control of the pressure medium flow in the other flow direction.
• the check valve and an additional switching valve which is also electrically controlled, control the pressure medium flow to and from the cylinder.
• the switching valve connects the constant pump with the check valve in a first switching position. In the other switching position of the switching valve, it also connects the constant pump to the tank. In the first switching position of the switching valve, pressure medium flows from the constant pump via the valve arrangement which acts as a check valve in this flow direction. The connection from the constant pump to the tank is blocked.
• the piston of the cylinder is at maximum speed according to the volume flow of the constant pump and the Dimensions of the cylinder extended and the load on the cylinder raised.
• pressure medium delivered by the constant pump flows back directly to the tank.
• pressure medium displaced from the cylinder is also supplied to the tank. If the check valve is not activated, the check valve locks. Then no pressure medium flows out of the cylinder and the load is held. If the check valve and the switching valve are actuated, pressure medium flows from the cylinder via the check valve and the switching valve to the tank. A fine control of the pressure medium flow flowing back to the tank via the shut-off valve takes place via the level of the electrical control signal supplied to the shut-off valve. In contrast to lowering the load, it is not possible to control the speed when lifting the load.
• Tool for fine positioning e.g. B. when coupling to the hoist or when decoupling from the hoist.
• Such a control can be implemented more cost-effectively with switching valves than with proportional valves.
• the vehicle moves at the fast speed close to the desired position and then fine positioning at the slow speed carried out.
• the constant pump is designed so that it promotes the pressure medium flow required for fast lifting of the load.
• the pressure medium flow (consumer flow) fed to the single-acting cylinder is equal to the pressure medium flow (pump flow) delivered by the constant pump.
• the consumer current is smaller than the pump current in accordance with the lower adjustment speed.
• the reduction in the consumer flow required for slowly lifting the load takes place by means of an appropriately dimensioned throttle in the valve arrangement arranged between the pump and the consumer.
• the difference between the pump flow and the consumer flow is returned to the tank via a pressure limiting valve.
• the pump pressure rises up to the limiting pressure of the pressure limiting valve. Since the pressure relief valve primarily serves as a safety valve, the set pressure is greater than the highest operational pressure. The pump pressure thus rises to a higher value during slow lifting than with fast lifting, where the pump pressure is only slightly above the load pressure.
• the consumer current depends on the cross-sectional area of the throttle and the pressure drop across the throttle.
• the pressure drop across the throttle is the difference between the pressure limit of the pressure relief valve and the load pressure.
• the invention has for its object to provide a device of the type mentioned, which allows a slow lifting of the load and in which the piston of the single-acting
• Cylinders during slow lifting regardless of the load with which the piston is loaded extends at a constant speed.
• the pump flow bypassing the valve arrangement is divided upstream of the throttle into two partial flows, of which the smaller than constant pressure medium flow flows via the throttle and the larger one, which results from the difference between the pump flow and the constant pressure medium flow, via the pressure compensator Tank flows back.
• the pressure compensator keeps the pressure difference across the throttle and thus also the pressure medium flow flowing through the throttle constant. In one switching position of the switching valve, this pressure medium flow is fed to the single-acting cylinder, and the piston of the single-acting cylinder slowly raises the load. In the other switching position of the switching valve, the constant
• Pressure medium flow which has flowed through the throttle, supplied to the tank. Since only the smaller partial flow flows through the switching valve, the switching valve only needs to be dimensioned for this partial flow and not for the sum of the pump flow and the consumer flow, which is displaced from the chamber of the single-acting cylinder when the load is quickly lowered . A switching valve of smaller size can therefore be used.
• the pump pressure is set according to the pressure drop across the throttle.
• a blocking position of the valve arrangement makes it possible to bypass the valve arrangement when the load is slowly raised.
• the pressure drop at the switching valve arrangement can be bypassed if necessary
• FIG. 1 shows a first hydraulic device according to the invention in a schematic representation
• Figure 2 shows a second hydraulic device according to the invention in a schematic representation
• Figure 3 shows a third hydraulic device according to the invention in a schematic representation.
• a pump 1 conveys pressure medium from a tank 2 to a single-acting cylinder 3, to which a load 4 is applied.
• the load 4 is shown in Figures 1 to 3 as an arrow indicating the direction of action of the load 4.
• Pump 1 is a constant pump.
• the pressure medium flow it pumps, the pump flow, is constant.
• the pump current is selected in accordance with the consumer flow required for quickly lifting the load 4.
• An electrically controlled valve arrangement 5 is arranged between the pump 1 and the cylinder 3.
• the series connection of a throttle 6 and a check valve 7 is arranged parallel to this valve arrangement.
• a line 8 connects the throttle 6 with the check valve 7.
• the line 8 and the tank 2 are arranged with an electrically controlled switching valve 9, which connects the line 8 with the tank 2 in the shown rest position and interrupts the connection between the line 8 and the tank 2 in its working position.
• a pressure compensator 10 keeps the pressure difference across the throttle 6 constant.
• the pressure difference across the throttle 6 is referred to below as ⁇ p Dl .
• a constant pressure medium flow thus flows via the throttle 6, the size of which is determined by the cross-sectional area of the throttle 6 and the pressure difference ⁇ p Dl across the throttle 6.
• the constant pressure medium flow flowing through the throttle 6 is referred to below as the throttle flow. Its size is selected in accordance with the speed desired for slowly lifting the load 4.
• the pressure compensator 10 forms, together with the throttle 6, a 3-way flow control valve.
• the pump pressure is denoted by p p
• the pressure in line 8 by p.
• p- p - ⁇ p D1 .
• the pressure difference .DELTA.p D1 is approximately 3 bar, that is to say substantially smaller than the load pressure p.sub. ⁇ , which is of the order of 100 bar.
• the electrically controlled valve arrangement 5, together with the electrically controlled switching valve 9, controls the pressure medium flow from the pump 1 to the cylinder 3 and from the cylinder 3 to the tank 2.
• the valve arrangement 5 has two pressure medium connections, one of which with the pump 1 and the other is connected to the cylinder 3. Without electrical control, the valve arrangement 5 blocks in both flow directions.
• the valve arrangement 5 behaves like a check valve acted on in the blocking direction.
• To lift the load the valve arrangement 5 is controlled so that the entire pump current flows into the cylinder 3.
• the valve arrangement 5 behaves like an in Check valve pressurized flow direction.
• To lower the load the valve arrangement 5 and the switching valve 9 are activated such that the pressure medium can flow from the cylinder 3 to the tank 2.
• the rate of descent of the load 4 can be reduced by throttling the flow cross section of the valve arrangement 5.
• the device-related structure of the valve arrangement 5 is of minor importance.
• the valve arrangement 5 is shown in the figures as a series connection of three electrically controlled switching valves 11, 12 and 13. If the switching valve 11 is activated, it allows a pressure medium flow in both flow directions. In the rest position shown in the figures, it blocks in both directions of flow. Leak-free locking is not required, however.
• the switching valve 12 allows a pressure medium flow in both flow directions. In its working position, it throttles the flow cross section for pressure medium flowing back to tank 2.
• the switching valve 13, which is shown in the rest position in the figures, is a non-return valve which prevents pressure medium from flowing back from the cylinder 3 in its rest position. In its working position, the switching valve 13 allows an unrestricted return flow of pressure medium from the cylinder 3. A restricted flow of pressure medium from the pump 1 via the valve arrangement 5 to the cylinder 3 is not provided.
• the switching valves 9 and 11 to 13 are initially not activated; they are in the rest position shown in FIG. 1.
• the output of the pump 1 is connected to the tank 2 via the throttle 6.
• the pump flow flows back to the tank 2 in two partial flows.
• the larger partial flow flows directly to tank 2 via pressure compensator 10, while the smaller throttle flow flows to tank 2 via switching valve 9.
• the pump pressure p p is adjusted so that it is equal to the pressure difference ⁇ p D1 across the throttle 6. Because of the low pump pressure p, in this position of the switching valves 9 and 11 to 13 there is only a small power loss.
• the load is held, ie neither pressure medium flows to nor from the cylinder 3.
• the check valve 7 prevents pressure medium flowing from the cylinder 3 to the tank 2 via the line 8.
• the switching valves 9 and 11 are switched to the working position, the switching valves 12 and 13 remain in the rest position.
• the pump pressure p is set such that it is greater than the load pressure by the pressure drop at the valve arrangement 5 p is.
• the switching valves 11 and 13 are switched to the working position, the switching valves 9 and 12 remain in the rest position.
• the pressure medium displaced from the single-acting cylinder 3 initially flows through the Valve arrangement 5 and then together with the pump flow to tank 2.
• the total flow of the pressure medium is divided into two partial flows.
• the constant throttle flow flows to tank 2 via throttle 6 and switching valve 9, while the remaining pressure medium flow flows directly to tank 2 via pressure compensator 10.
• the pump pressure p p is adjusted so that it is equal to the pressure difference ⁇ p 1 at the throttle 6. Since only a small, constant partial flow flows through the switching valve 9 to the tank 2, an inexpensive valve of small size can be used.
• the switching valves 11, 12 and 13 are switched into the working position, the switching valve 9 remains in the rest position. Because of the throttle which is active in the operating position of the switching valve 12, only a consumer flow, which flows together with the pump flow to the tank 2, flows through the valve arrangement 5 in comparison to the pressure medium flow which flows when the load is rapidly lowered. The total flow is again divided into two partial flows.
• the constant throttle flow to tank 2 flows via throttle 6 and switching valve 9, while the remaining pressure medium flow flows directly to tank 2 via pressure compensator 10.
• the pump pressure p is adjusted so that it is equal to the pressure difference ⁇ p ßl at the throttle 6.
• the valve arrangement 5 can also be realized in a different way.
• the switching valves 12 and 13 can be replaced by the check valve known from DE 40 30 952 AI. It is also conceivable to replace the valve arrangement 5 by a single valve which comprises several functions.
• valve arrangement 5 blocks the pressure medium flow from the pump 1 to the cylinder 3 in a first switching position or switching position combination, and a check valve function for a in a second switching position or switching position combination allows the load 4 to be lifted quickly, allows the load 4 to be lowered rapidly in a third switch position or switch position combination and has a throttle for slowly lowering the load in a fourth switch position or switch position combination.
• the hydraulic device shown in FIG. 2 contains a pressure relief valve 14 and a further throttle 15.
• the pressure relief valve 14 is arranged between the throttle 6 and the switching valve 9. It limits the pressure p during fast lifting as well as slow lifting of load 4. and thus also the pump pressure p p greater by the constant pressure difference ⁇ p D1 when the load 4 z. B. drives against a stop and the single-acting cylinder 3 can no longer accommodate any other pressure medium. Since, when the pressure limiting valve 14 responds, only a part of the pump flow flows through the pressure limiting valve 14, while the larger partial flow is already discharged to the tank 2 via the pressure compensator 10, the pressure limiting valve 14 - as well as the switching valve 9 - can - A valve of small size can be used.
• the cross-sectional area of the throttle 15 is equal to or greater than the cross-sectional area of the throttle 6.
• the pressure difference labeled ⁇ p D2 is then equal to or less than the pressure difference ⁇ p D - across the throttle 6.
• the hydraulic device shown in FIG. 3 contains in addition to the hydraulic device shown in FIG A pressure relief valve 16 and a further throttle 17 are set up.
• a line 18 connects the check valve 7 to the throttle 17.
• the pressure in line 18 is denoted by p_. It is limited by the pressure relief valve 16 to an adjustable value that is greater than the largest operationally occurring load pressure p L.
• the pressure difference across the throttle 17 is denoted by ⁇ p D3 .
• a switching valve 19 is inserted between the throttle 6 and the check valve 7 in the line 8.
• the switching valve 19 is an electrically controlled switching valve with three useful connections and two switching positions. Since it has the same function as the switching valve 9 in FIGS. 1 and 2, it can replace the switching valve 9 in FIGS. 1 and 2. Likewise, the switching valve 9 shown in FIGS. 1 and 2 can be used in FIG. 3 instead of the switching valve 19.
• the switching valve 19 connects the line 8 with the tank 2 in the rest position, in the working position it blocks the connection between the line 8 and the tank 2.
• the pressure relief valve 16 limits the load pressure p L , that is, the pressure in the piston chamber of the cylinder 3, when the pressure medium in the piston chamber, for. B. due to solar radiation, or when additional forces act on the piston of the cylinder 3 through a body that falls on the raised hoist.
• the pressure relief valve 16 limits the pump pressure p to a value which is greater than the response pressure of the pressure relief valve 16 by ⁇ p D1 .
• the pressure relief valve 16 therefore only needs to be dimensioned for the pressure medium flow flowing through the throttle 6.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Fluid Mechanics (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Fluid-Pressure Circuits (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=7784006

Family Applications (1)

Country Status (6)

Families Citing this family (12)

Family Cites Families (13)

• 1996
  • 1996-12-21 WO PCT/DE1996/002504 patent/WO1997028373A1/de not_active Application Discontinuation
  • 1996-12-21 EP EP96945908A patent/EP0877863A1/de not_active Withdrawn
  • 1996-12-21 PL PL96328159A patent/PL328159A1/xx unknown
  • 1996-12-21 US US09/101,581 patent/US6065386A/en not_active Expired - Fee Related
  • 1996-12-21 CZ CZ19982211A patent/CZ286074B6/cs not_active IP Right Cessation
  • 1996-12-21 DE DE19653810A patent/DE19653810A1/de not_active Withdrawn

Non-Patent Citations (1)

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