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
  • F15B9/00—Servomotors with follow-up action, e.g. obtained by feed-back control, i.e. in which the position of the actuated member conforms with that of the controlling member
  • F15B9/02—Servomotors with follow-up action, e.g. obtained by feed-back control, i.e. in which the position of the actuated member conforms with that of the controlling member with servomotors of the reciprocatable or oscillatable type
  • F15B9/08—Servomotors with follow-up action, e.g. obtained by feed-back control, i.e. in which the position of the actuated member conforms with that of the controlling member with servomotors of the reciprocatable or oscillatable type controlled by valves affecting the fluid feed or the fluid outlet of the servomotor
  • F15B9/09—Servomotors with follow-up action, e.g. obtained by feed-back control, i.e. in which the position of the actuated member conforms with that of the controlling member with servomotors of the reciprocatable or oscillatable type controlled by valves affecting the fluid feed or the fluid outlet of the servomotor with electrical control means
• • 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
  • F15B11/006—Hydraulic "Wheatstone bridge" circuits, i.e. with four nodes, P-A-T-B, and on-off or proportional valves in each link
• • 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
  • F15B21/00—Common features of fluid actuator systems; Fluid-pressure actuator systems or details thereof, not covered by any other group of this subclass
  • F15B21/08—Servomotor systems incorporating electrically operated control means
• • 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
  • F15B2211/30—Directional control
  • F15B2211/305—Directional control characterised by the type of valves
  • F15B2211/3056—Assemblies of multiple valves
  • F15B2211/30565—Assemblies of multiple valves having multiple valves for a single output member, e.g. for creating higher valve function by use of multiple valves like two 2/2-valves replacing a 5/3-valve
  • F15B2211/30575—Assemblies of multiple valves having multiple valves for a single output member, e.g. for creating higher valve function by use of multiple valves like two 2/2-valves replacing a 5/3-valve in a Wheatstone Bridge arrangement (also half bridges)
• • 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
  • F15B2211/31—Directional control characterised by the positions of the valve element
  • F15B2211/3105—Neutral or centre positions
  • F15B2211/3116—Neutral or centre positions the pump port being open in the centre position, e.g. so-called open centre
• • 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
  • F15B2211/315—Directional control characterised by the connections of the valve or valves in the circuit
  • F15B2211/31505—Directional control characterised by the connections of the valve or valves in the circuit being connected to a pressure source and a return line
  • F15B2211/31511—Directional control characterised by the connections of the valve or valves in the circuit being connected to a pressure source and a return line having a single pressure source
• • 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
  • F15B2211/315—Directional control characterised by the connections of the valve or valves in the circuit
  • F15B2211/3157—Directional control characterised by the connections of the valve or valves in the circuit being connected to a pressure source, an output member and a return line
  • F15B2211/31576—Directional control characterised by the connections of the valve or valves in the circuit being connected to a pressure source, an output member and a return line having a single pressure source and a single 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
  • F15B2211/30—Directional control
  • F15B2211/32—Directional control characterised by the type of actuation
  • F15B2211/327—Directional control characterised by the type of actuation electrically or electronically
  • F15B2211/328—Directional control characterised by the type of actuation electrically or electronically with signal modulation, e.g. pulse width modulation [PWM]
• • 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
  • F15B2211/415—Flow control characterised by the connections of the flow control means in the circuit
  • F15B2211/41554—Flow control characterised by the connections of the flow control means in the circuit being connected to a return line and a directional 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
  • F15B2211/60—Circuit components or control therefor
  • F15B2211/63—Electronic controllers
  • F15B2211/6303—Electronic controllers using input signals
  • F15B2211/6336—Electronic controllers using input signals representing a state of the output member, e.g. position, speed or acceleration
• • 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
  • F15B2211/60—Circuit components or control therefor
  • F15B2211/63—Electronic controllers
  • F15B2211/6303—Electronic controllers using input signals
  • F15B2211/6346—Electronic controllers using input signals representing a state of input means, e.g. joystick position
• • 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
  • F15B2211/765—Control of position or angle of the 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
  • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
  • F15B2211/765—Control of position or angle of the output member
  • F15B2211/7656—Control of position or angle of the output member with continuous position control

Definitions

• the invention relates to a hydraulic actuating unit with a positioning motor which is arranged in a diagonal of a bridge circuit having four electromagnetic valves, the other diagonal being arranged between a pressure source and a pressure sink.
• Such an actuating unit is known from DE 39 01 475 Al.
• a normally-open and a normally-closed electromagnetic valve are connected in series.
• the positioning motor is in the form of a double-acting piston which is additionally loaded on each side by a spring.
• US 4 416 187 discloses a servo system with four valves, which are illustrated in the normally-closed state. These valves are in the form of pulse-controlled electromagnetic valves.
• the invention is based on the problem of providing a hydraulic actuating unit with a rapid response behaviour.
• Normally-open electromagnetic valves are electro ⁇ magnetic valves which remain open in the no-current or unenergized state. They are not moved into their closed position until they are energized or a current is supplied to them.
• normally-open electro ⁇ magnetic valves in the unenergized state there is a permanent flow of fluid from the pressure source to the pressure sink. Since this flow of fluid is distributed uniformly over the two double branches of the bridge circuit, the pressure on each side of the piston of the positioning motor is the same. If the fluid flow in one double branch of the bridge is changed by actuating one or more valves, the pressure on the corresponding side of the piston of the positioning motor also changes automatically, and the piston is correspondingly displaced, until equilibrium is established again.
• a throttling device is arranged between the pressure sink and the electromagnetic valves adjacent to the pressure sink.
• the connecting line from the electromagnetic valves to the pressure sink for example, a tank, can in some cases assume considerable lengths.
• the tank connections of further hydraulic units are often fed into these tank lines so that in combination with the throttling caused by the long line lengths there is also a risk of pressure peaks occurring (water hammer) .
• pressure peaks are moderated by the throttling device to such an extent that they are unable to have an adverse affect on the position of the positioning motor.
• the throttling device is formed by a throttle common to both electromagnetic valves. This measure ensures in a simple manner that the flow path on each side of the positioning motor can be kept substantially equal. No additional matching of the throttles to one another needs to be undertaken.
• a non-return valve arrangement opening in the direction towards the pressure sink can be arranged between the pressure sink and the electromagnetic valves adjacent to the pressure sink.
• Such a non-return valve arrangement which can also be in the form of a non-return valve common to both electromagnetic valves, not only damps the pressure peaks but with greater reliability keeps them away from the electromagnetic valves.
• the positioning motor is preferably connected to a position sensor, which is in signal connection with a control unit which activates the electromagnetic valves, the electromagnetic valves, the position sensor and the control unit being received in a hermetically sealed unit which is connected by way of a hydraulic interface to the positioning motor.
• Electrical, mechanical and hydraulic components can thus on the one hand be kept strictly separate from one another, but on the other hand can be combined to afford a conveniently operable control.
• the positioning motor is preferably directly connected to an activation device of a hydraulic pump.
• a rapid response is desirable, in order to be able to follow the pressure and volume requirement of a hydraulic system supplied by the pump as rapidly as possible.
• this also has the advantage of saving energy.
• the rapid response and the relatively large forces that can be generated using four normally-open electromagnetic valves means that the activation can be effected directly at the pump without further servo elements being required. Avoiding further auxiliary elements in turn improves the stability, since with fewer elements fewer deviations and thus also fewer potential errors are to be feared.
• each additional element causes an increased time delay, which can quickly lead to instability in the case of control loops. Moreover, such a control is naturally more expensive.
• the pump preferably forms the pressure source.
• the pump therefore itself delivers the output for its adjustment. In this manner, routes can be kept short, with the result that energy losses can be kept low and the response behaviour can be improved.
• the hydraulic interface is mounted directly on the pump.
• the sealed unit can therefore be assembled together with the pump as a modular item.
• two bridge circuits are provided, the diagonals of which between pressure source and pressure sink are connected parallel to one another and the diagonals of which containing the positioning motor likewise being connected parallel to one another.
• each bridge circuit Preferably, provision is made for each bridge circuit to have its own throttling and non-return valve arrangement. This allows the bridges to be well isolated from one another, that is to say, allows a largely independent control.
• the two bridge circuits are identical with one another. In this manner several bridge circuits can be connected in parallel without too much consideration having to be given to their dimensions.
• the bridges are largely equally loaded and deteriorate to a correspondingly uniform extent.
• Fig. 1 shows a first embodiment of a hydraulic actuating unit
• Fig. 2 is a diagrammatic view of the actuating unit from the outside
• Fig. 3 shows a second embodiment of the hydraulic actuating unit.
• a hydraulic actuating unit 1 comprises a positioning motor 2 which is arranged in one diagonal of a hydraulic bridge circuit 3.
• the other diagonal of the bridge circuit 3 lies between a pressure source in the form of a pump 4 and a pressure sink in the form of a tank 5.
• the hydraulic bridge circuit 3 has four branches. In each branch there is a respective electromagnetic valve 6, 7, 8, 9. All the electromagnetic valves 6, 7, 8, 9 are normally-open, that is to say, they are open in the no-current or unenergized state and do not close until a current is applied.
• the signal wave-form of a corresponding control current is illustrated diagrammatically by respective square-wave pulse trains, that is to say, the valves are pulse- controlled.
• This pulse train is supplied from a control unit 11 by way of a control line 10 which has four paths each for actuating a respective electromagnetic valve 6, 7, 8, 9.
• the control unit 11 is connected on one side to an electrical adjusting device 12. That device produces a desired value for the positioning motor 2. On the other side, the control unit 11 is in signal connection with a position sensor 13.
• the position sensor 12 produces an actual value for the setting of the positioning motor 2.
• a diagrammatically shown arm 14 is connected to a piston 17 of the positioning motor 2.
• a throttle 16 damps any pressure surges that might occur between the tank 5 and the bridge circuit 3. Pressure surges are therefore kept away from the two electromagnetic valves 8, 9 adjacent to the tank 5.
• a non-return valve opening in the direction towards the tank 5 could be used in place of the throttle 16.
• the pump 4 produces a flow of liquid through the two double branches, each of which is provided with the electromagnetic valves 6, 8 and 7, 9 respectively. Since the two double branches are substantially of identical construction, on both sides of the piston 17 of the positioning motor 2 the pressure is also equal. By throttling one of the electromagnetic valves 6, 7, 8, 9 or even by throttling two diagonally opposite valves 6, 9 or 7, 8, the pressure conditions on the two sides of the piston 17 of the positioning motor 2 can be changed so that the piston 17 of the positioning motor 2, and with its also the arm, is displaced.
• normally-open electromagnetic valves 6, 7, 8, 9 a relatively precise adjustment of the setting of the piston 17 of the positioning motor 2 can be achieved.
• normally-open electromagnetic valves it is primarily the magnetic forces that determine the degree of opening with small flows. But with small flows the forces acting from the outside on the electromagnetic valves, that is to say, by way of the fluid, are greatest. Because of the small air gaps the valves are less sensitive to these disruptions than in the case of the large air gaps occurring with normally-closed valves in the same open position.
• Fig. 2 shows the use of such an actuating unit on a pump 4.
• the pump can be the same one as that acting as pressure source for the actuating unit.
• the electromagnetic valves 6, 7, 8, 9 are combined in a hermetically sealed unit 18 which is connected to the pump 4 by way of a hydraulic interface 19.
• the position sensor 13 can also be arranged in the electronics module.
• the use of the illustrated actuating unit in a pump 4 is advantageous. With pump actuation there is in principle always an adequate flow quantity present. Since the valves are open, this flow can be produced without particularly large losses. Certain internal losses cannot be avoided, of course. These internal losses are compensated, however, by the pump's responding substantially more quickly so that it pumps more closely to the requirement of an attached hydraulic system and therefore keeps the losses there small.
• Fig. 3 shows a further construction.
• identical parts have been provided with identical reference numbers.
• a further bridge circuit which can be of more or less identical construction. To distinguish between them the corresponding reference numbers have therefore been marked a and b.
• Two position sensors 13a and 13b are also provided. With the construction illustrated, the system is more tolerant of errors because it has built-in redundancy. If, for example, one bridge circuit should fail because of malfunction of a valve, the system can still continue to function even if with poorer results. The actuation of the piston 17 is effected more slowly.
• a rapid response can be achieved even with relatively large units.
• relatively large positioning motors 2 can also be operated without difficulty.
• an improved control concept can be achieved with the two parallel bridges.
• the individual electromagnetic valves are actuated, as illustrated diagrammatically, by pulse trains.
• the pulse duty factor of these pulse trains is normally dependent on the magnitude of the error, that is, on the size of the deviation of the desired value preset by the adjusting device 12 with respect to the actual value detected by the position sensors 13a, 13b.
• the piston 17 of the positioning motor 2 is displaced only when the difference between the desired value and the actual value is less than a preset tolerance or reference value.
• This reference value can be made smaller for one bridge circuit 3a than for the other bridge circuit 3b. If the positional or setting error is greater than the reference value of the two bridge circuits 3a, 3b, the two bridge circuits are used to compensate for the error. If, on the other hand, the error is greater than the reference value of one bridge circuit 3b, but smaller than the reference value of the bridge circuit 3a, only the bridge circuit 3b is used to reduce the error.
• the pump 4 can alternatively be replaced by any other pressure source, for example, a low-pressure pump or a pressure accumulator.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Fluid Mechanics (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Analytical Chemistry (AREA)
• Fluid-Pressure Circuits (AREA)
• Servomotors (AREA)

Priority Applications (2)

Applications Claiming Priority (2)

Publications (1)

Family

ID=6527138

Family Applications (1)

Country Status (3)

Cited By (6)

Families Citing this family (7)

Citations (2)

Family Cites Families (4)

• 1994
  • 1994-09-01 DE DE4431103A patent/DE4431103C2/de not_active Expired - Fee Related
• 1995
  • 1995-08-28 DE DE69521724T patent/DE69521724D1/de not_active Expired - Lifetime
  • 1995-08-28 EP EP95929784A patent/EP0828946B1/de not_active Expired - Lifetime
  • 1995-08-28 WO PCT/DK1995/000345 patent/WO1996007029A1/en active IP Right Grant

Patent Citations (2)

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